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Last Updated :2024/11/17

研究者情報

マスター

アカウント（マスター）

  • 氏名

    圦本　尚義(ユリモト　ヒサヨシ), ユリモト　ヒサヨシ

所属（マスター）

  • 理学研究院　地球惑星科学部門　地球惑星システム科学分野

所属（マスター）

  • 理学研究院　地球惑星科学部門　地球惑星システム科学分野

独自項目

syllabus

  • 2021, 地球惑星システム科学概論, Introduction to Earth and Planetary System Science, 修士課程, 理学院, 地球科学　地質学　物質科学　地球化学　進化古生物学
  • 2021, 大学院共通授業科目（一般科目）：自然科学・応用科学, Inter-Graduate School Classes(General Subject):Natural and Applied Sciences, 修士課程, 大学院共通科目, 地球科学　地質学　物質科学　地球化学　進化古生物学
  • 2021, 地球化学特論, Advanced Geochemistry, 修士課程, 理学院, 地球化学，宇宙化学
  • 2021, 教科教育法（理科II）, Teaching Method of School Subjects(Science Ⅱ), 学士課程, 教育学部, 教員養成、理科教育法、指導法
  • 2021, 地球化学, Geochemistry, 学士課程, 理学部, 宇宙，銀河，恒星，太陽系，惑星，地球，環境，生命，進化，分化，安定性，起源，元素，同位体
  • 2021, 地球惑星基礎化学, Introduction to Geochemistry, 学士課程, 理学部, 原子，分子，気体，固体，熱力学，液体，溶液
  • 2021, 地球惑星科学Ⅱ, Basic Earth and Planetary Science Ⅱ, 学士課程, 全学教育, 宇宙，惑星，大気と海洋の運動と構造，気候変動，地球環境

researchmap

プロフィール情報

学位

  • 理学博士（筑波大学）

プロフィール情報

  • 姓

    圦本, ユリモト

  • 名

    尚義, ヒサヨシ

  • ID各種

    200901099265633050

対象リソース

業績リスト

研究キーワード

  • 2次イオン質量分析法   隕石   同位体顕微鏡   同位体   惑星起源・進化   ジルコン   イオン検出器   地球化学   太陽系   同位体分析   質量分析   SIMS   宇宙科学   酸素   二次イオン質量分析   二次元分析   酸素同位体   ウラン-鉛年代   質量分析法   岩石・鉱物・鉱床学   微量元素   惑星系   宇宙化学   高感度イオン検出器   粒子線   固体撮像素子   白色包有物   原始星   星間物質   半導体素子   GeochemistryCosmochemistry   

研究分野

  • 自然科学一般 / 固体地球科学
  • ナノテク・材料 / 光工学、光量子科学
  • 自然科学一般 / 宇宙惑星科学

経歴

  • 2005年 - 現在 北海道大学 理学(系)研究科(研究院) 教授
  • 1994年 - 2005年 東京工業大学 大学院理工学研究科 助教授
  • 1992年 - 1994年 筑波大学 地球科学系 講師
  • 1986年 - 1992年 筑波大学 地球科学系 助手

受賞

  • 2021年02月 北海道大学教育研究総長表彰
     
    受賞者: 圦本尚義
  • 2020年 紫綬褒章
     
    受賞者: 圦本 尚義
  • 2020年 日本地球惑星科学連合 日本地球惑星科学連合フェロー
     
    受賞者: 圦本 尚義
  • 2019年07月 Meteoritical Society Leonard Medal
     
    受賞者: 圦本 尚義
  • 2015年 北海道大学研究総長賞
     
    受賞者: 圦本尚義
  • 2013年 三宅賞
     
    受賞者: 圦本 尚義
  • 2013年 Geochemistry Fellow
     
    受賞者: 圦本 尚義
  • 2012年 Meteoritical Society Fellow
     
    受賞者: 圦本 尚義
  • 2010年 北海道新聞文化賞
     
    受賞者: 圦本 尚義
  • 2008年 日本顕微鏡学会和文誌賞
     
    受賞者: 圦本 尚義
  • 2006年 日本地球化学会賞
     
    受賞者: 圦本 尚義
  • 2006年 日本鉱物学会賞
     
    受賞者: 圦本 尚義
  • 2004年 Geochemical Journal Award
     
    受賞者: 圦本 尚義
  • 1998年 榊賞
     
    受賞者: 圦本 尚義
  • 1990年 日本鉱物学会奨励賞
     
    受賞者: 圦本 尚義

論文

  • Shingo Sugawara, Wataru Fujiya, Noriyuki Kawasaki, Naoya Sakamoto, Akira Yamaguchi, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 382 40 - 50 2024年10月
  • Fridolin Spitzer, Thorsten Kleine, Christoph Burkhardt, Timo Hopp, Tetsuya Yokoyama, Yoshinari Abe, Jérôme Aléon, Conel M. O’D Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Mayu Morita, Fréderic Moynier, Kazuko Motomura, Izumi Nakai, Kazuhide Nagashima, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
    Science Advances 10 39 2024年09月27日 
    The isotopic compositions of samples returned from Cb-type asteroid Ryugu and Ivuna-type (CI) chondrites are distinct from other carbonaceous chondrites, which has led to the suggestion that Ryugu/CI chondrites formed in a different region of the accretion disk, possibly around the orbits of Uranus and Neptune. We show that, like for Fe, Ryugu and CI chondrites also have indistinguishable Ni isotope anomalies, which differ from those of other carbonaceous chondrites. We propose that this unique Fe and Ni isotopic composition reflects different accretion efficiencies of small FeNi metal grains among the carbonaceous chondrite parent bodies. The CI chondrites incorporated these grains more efficiently, possibly because they formed at the end of the disk’s lifetime, when planetesimal formation was also triggered by photoevaporation of the disk. Isotopic variations among carbonaceous chondrites may thus reflect fractionation of distinct dust components from a common reservoir, implying CI chondrites/Ryugu may have formed in the same region of the accretion disk as other carbonaceous chondrites.
  • Keisuke Ozawa, Naoya Sakamoto, Yutaro Tsutsumi, Kei Hirose, Tsuyoshi Iizuka, Hisayoshi Yurimoto
    Science Advances 10 33 2024年08月16日 
    Crystallization in Earth’s deep magma ocean could have caused trace element fractionation in the lower mantle that might be inherited to the isotopic compositions of the present-day mantle. However, the trace element partitioning has been experimentally investigated only up to the uppermost lower-mantle pressures. Here, we determined the bridgmanite/melt partition coefficients D of La, Nd, Sm, Lu, and Hf from 24 to 115 gigapascals, covering the wide pressure range of the lower mantle. Results demonstrate substantial reductions in D Lu and D Hf from >1 to ≪1 with increasing pressure to 91 gigapascals. We also found D Lu / D Hf > 1 and D Sm / D Nd < 1 under deep lower-mantle conditions, evolving melts toward low Lu/Hf and high Sm/Nd ratios by crystallizing bridgmanite. If residual melts form a dense hidden reservoir in the lowermost mantle, the complementary accessible mantle has the Hf and Nd isotopic compositions matching the observed terrestrial mantle array that deviates from the bulk silicate Earth reference.
  • Hiroharu Yui, Shu-hei Urashima, Morihiko Onose, Mayu Morita, Shintaro Komatani, Izumi Nakai, Yoshinari Abe, Yasuko Terada, Hisashi Homma, Kazuko Motomura, Kiyohiro Ichida, Tetsuya Yokoyama, Kazuhide Nagashima, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Peter Hoppe, Gary R. Huss, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Sasha Krot, Ming-Chang Liu, Yuki Masuda, Frédéric Moynier, Ann Nguyen, Larry Nittler, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Tommaso Di Rocco, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 379 172 - 183 2024年08月
  • Mutsumi Komatsu, Hikaru Yabuta, Yoko Kebukawa, Lydie Bonal, Eric Quirico, Timothy J. Fagan, George D. Cody, Jens Barosch, Laure Bejach, Emmanuel Dartois, Alexandre Dazzi, Bradley De Gregorio, Ariane Deniset‐Besseau, Jean Duprat, Cecile Engrand, Minako Hashiguchi, Zita Martins, Jérémie Mathurin, Gilles Montagnac, Smail Mostefaoui, Larry R. Nittler, Takuji Ohigashi, Taiga Okumura, Laurent Rémusat, Scott Sandford, Rhonda Stroud, Hiroki Suga, Yoshio Takahashi, Yasuo Takeichi, Yusuke Tamenori, Maximilien Verdier‐Paoletti, Shohei Yamashita, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hiroshi Naraoka, Kanako Sakamoto, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Tomohiro Usui, Masanao Abe, Tatsuaki Okada, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Shogo Tachibana, Sei‐ichiro Watanabe, Yuichi Tsuda
    Meteoritics & Planetary Science 2024年07月04日
  • Yutaro Tsutsumi, Naoya Sakamoto, Kei Hirose, Shoh Tagawa, Koichiro Umemoto, Yasuo Ohishi, Hisayoshi Yurimoto
    Nature Geoscience 2024年06月21日
  • Daiki Yamamoto, Noriyuki Kawasaki, Shogo Tachibana, Lily Ishizaki, Ryosuke Sakurai, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 2024年06月 [査読有り]
  • Ko Hashizume, Akizumi Ishida, Ayano Chiba, Ryuji Okazaki, Kasumi Yogata, Toru Yada, Fumio Kitajima, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Hikaru Yabuta, Hiroshi Naraoka, Yoshinori Takano, Kanako Sakamoto, Shogo Tachibana, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Fuyuto Terui, Satoshi Tanaka, Satoru Nakazawa, Sei‐ichiro Watanabe, Yuichi Tsuda, Michael W. Broadley, Henner Busemann
    Meteoritics & Planetary Science 2024年04月30日 
    Abstract The nitrogen isotope compositions of two samples returned from the asteroid Ryugu were determined using a stepwise combustion method, along with Ivuna (CI) and Y‐980115, a CI‐like Antarctic meteorite, as references. The two Ryugu samples A0105‐07 and C0106‐07 showed bulk δ15N values of +1.7 ± 0.5‰ and +0.2 ± 0.6‰, respectively, significantly lower than Ivuna with +36.4 ± 0.4‰, but close to Y‐980115 with +4.0 ± 0.3‰. The Ryugu samples are further characterized by C/N and 36Ar/N ratios up to 3.4× and 4.9× the value of Ivuna, respectively. Among all Ryugu samples and CI chondrites, a positive correlation was observed between nitrogen concentrations and δ15N values, with samples with lower nitrogen concentrations exhibiting lower δ15N. This trend is explained by a two‐component mixing model. One component is present at a constant abundance among all CI‐related samples, with a δ15N value around 0‰ or lower. The other varies in abundance between different samples, and exhibits a δ15N value of +56 ± 4‰. The first 15N‐poor endmember is seemingly tightly incorporated into a carbonaceous host phase, whereas the 15N‐rich endmember can be mobilized and decoupled from carbon, potentially because it is in the form of ammonia. Asteroid materials with volatile compositions that are similar to those reported here for the Ryugu samples are attractive candidates for the volatile sources among Earth's building blocks.
  • Jérémie Mathurin, Laure Bejach, Emmanuel Dartois, Cécile Engrand, Alexandre Dazzi, Ariane Deniset-Besseau, Jean Duprat, Yoko Kebukawa, Hikaru Yabuta, Lydie Bonal, Eric Quirico, Christophe Sandt, Ferenc Borondics, Jens Barosch, Pierre Beck, George D. Cody, Brad T. De Gregorio, Minako Hashiguchi, David A. L. Kilcoyne, Mutsumi Komatsu, Zita Martins, Megumi Matsumoto, Gilles Montagnac, Smail Mostefaoui, Larry R. Nittler, Takuji Ohigashi, Taiga Okumura, Van T. H. Phan, Laurent Remusat, Scott Sandford, Miho Shigenaka, Rhonda Stroud, Hiroki Suga, Yoshio Takahashi, Yasuo Takeichi, Yusuke Tamenori, Maximilien Verdier-Paoletti, Shohei Yamashita, Tomoki Nakamura, Tomoyo Morita, Mizuha Kikuiri, Kana Amano, Eiichi Kagawa, Takaaki Noguchi, Hiroshi Naraoka, Ryuji Okazaki, Kanako Sakamoto, Hisayoshi Yurimoto, Masanao Abe, Kanami Kamide, Akiko Miyazaki, Aiko Nakato, Satoru Nakazawa, Masahiro Nishimura, Tatsuaki Okada, Takanao Saiki, Shogo Tachibana, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Tomohiro Usui, Sei-ichiro Watanabe, Toru Yada, Kasumi Yogata, Makoto Yoshikawa
    Astronomy & Astrophysics 684 A198 - A198 2024年04月24日 
    Context. The JAXA Hayabusa2 mission returned well-preserved samples collected from the carbonaceous asteroid Ryugu, providing unique non-terrestrially weathered samples from a known parent body. Aims. This work aims to provide a better understanding of the formation and evolution of primitive asteroidal matter by studying the fine scale association of organic matter and minerals in Ryugu samples. We characterized the samples by IR nanospectroscopy using infrared photothermal nanospectroscopy (AFM-IR) technique. This technique overcomes the diffraction limit (of several microns) of conventional infrared microspectroscopy (µ-FTIR). The samples were mapped in the mid-IR range at a lateral spatial resolution about a hundred times better than with µ-FTIR. This provided us with unique in situ access to the distribution of the different infrared signatures of organic components at the sub-micron scale present in the Ryugu whole-rock samples as well as to the characterization of the compositional variability of Ryugu in the insoluble organic matter (IOM) chemically extracted from the Ryugu samples. Methods. The AFM-IR maps of whole-rock particles and IOM residues from Ryugu samples were recorded with a lateral resolution of tens of nanometers. Spectra were recorded in the 1900–900 cm−1 spectral range by AFM-IR (Icon-IR) for all samples, and additional spectra were recorded from 2700 to 4000 cm−1 for one IOM sample by an optical photothermal IR (O-PTIR) technique using a mIRage® IR microscope. Results. Organic matter is present in two forms in the whole-rock samples: as a diffuse phase intermixed with the phyllosilicate matrix and as individual organic nanoparticles. We identify the Ryugu organic nanoparticles as nanoglobule-like inclusions texturally resembling nanoglobules present in primitive meteorites. Using AFM-IR, we record for the first time the infrared spectra of Ryugu organic nanoparticles that clearly show enhanced carbonyl (C=O) and CH contributions with respect to the diffuse organic matter in Ryugu whole-rock and IOM residue.
  • Ken-ichi Bajo, Hisayoshi Yurimoto
    Journal of Analytical Science and Technology 15 1 2024年04月02日 
    Abstract Noble gases are useful tracers for geochemistry, used to elucidate the origin and evolution of the solar system and planets. Noble gas analyses have been limited to bulk and spot analyses of solids and have yet to be developed for two- and three-dimensional imaging analysis. Recent developments in He isotope imaging using secondary neutral mass spectrometry are reviewed. The images have been fully quantified, and the spatial resolution has reached the nanoscale. The detection limit has been reduced to the level of ~ 10–3 cm3 STP g−1 (~ 1017 cm−3, ~ 1 ppma) for helium at lateral micrometer resolution. With this development, the concentration distribution of He in solids has been visualized as a map for the first time.
  • Alice Aléon-Toppani, Rosario Brunetto, Zélia Dionnet, Stefano Rubino, Donia Baklouti, François Brisset, Maxime Vallet, Eva Heripre, Tomoki Nakamura, Cateline Lantz, Zahia Djouadi, Ferenc Borondics, Christophe Sandt, David Troadec, Obadias Mivumbi, Megumi Matsumoto, Kana Amano, Tomoyo Morita, Hisayoshi Yurimoto, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohira Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei-ichiro Watanabe, Yuichi Tsuda
    Geochimica et Cosmochimica Acta 371 1 - 30 2024年04月
  • Noriko T. Kita, Kouki Kitajima, Kazuhide Nagashima, Noriyuki Kawasaki, Naoya Sakamoto, Wataru Fujiya, Yoshinari Abe, Jérôme Aléon, Conel M. O'D. Alexander, Sachiko Amari, Yuri Amelin, Ken‐ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon‐Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming‐Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing‐Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai‐Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei‐ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
    Meteoritics & Planetary Science 2024年04月 
    Abstract Oxygen 3‐isotope ratios of magnetite and carbonates in aqueously altered carbonaceous chondrites provide important clues to understanding the evolution of the fluid in the asteroidal parent bodies. We conducted oxygen 3‐isotope analyses of magnetite, dolomite, and breunnerite in two sections of asteroid Ryugu returned samples, A0058 and C0002, using a secondary ion mass spectrometer (SIMS). Magnetite was analyzed by using a lower primary ion energy that reduced instrumental biases due to the crystal orientation effect. We found two groups of magnetite data identified from the SIMS pit morphologies: (1) higher δ18O (from 3‰ to 7‰) and ∆17O (~2‰) with porous SIMS pits mostly from spherulitic magnetite, and (2) lower δ18O (~ −3‰) and variable ∆17O (0‰–2‰) mostly from euhedral magnetite. Dolomite and breunnerite analyses were conducted using multi‐collection Faraday cup detectors with precisions ≤0.3‰. The instrumental bias correction was applied based on carbonate compositions in two ways, using Fe and (Fe + Mn) contents, respectively, because Ryugu dolomite contains higher amounts of Mn than the terrestrial standard. Results of dolomite and breunnerite analyses show a narrow range of ∆17O; 0.0‰–0.3‰ for dolomite in A0058 and 0.2‰–0.8‰ for dolomite and breunnerite in C0002. The majority of breunnerite, including large ≥100 μm grains, show systematically lower δ18O (~21‰) than dolomite (25‰–30‰ and 23‰–27‰ depending on the instrumental bias corrections). The equilibrium temperatures between magnetite and dolomite from the coarse‐grained lithology in A0058 are calculated to be 51 ± 11°C and 78 ± 14°C, depending on the instrumental bias correction scheme for dolomite; a reliable temperature estimate would require a Mn‐bearing dolomite standard to evaluate the instrumental bias corrections, which is not currently available. These results indicate that the oxygen isotope ratios of aqueous fluids in the Ryugu parent asteroid were isotopically heterogeneous, either spatially, or temporary. Initial water ice accreted to the Ryugu parent body might have ∆17O > 2‰ that was melted and interacted with anhydrous solids with the initial ∆17O < 0‰. In the early stage of aqueous alteration, spherulitic magnetite and calcite formed from aqueous fluid with ∆17O ~ 2‰ that was produced by isotope exchange between water (∆17O > 2‰) and anhydrous solids (∆17O < 0‰). Dolomite and breunnerite, along with some magnetite, formed at the later stage of aqueous alteration under higher water‐to‐rock ratios where the oxygen isotope ratios were nearly at equilibrium between fluid and solid phases. Including literature data, δ18O of carbonates decreased in the order calcite, dolomite, and breunnerite, suggesting that the temperature of alteration might have increased with the degree of aqueous alteration.
  • Ken-ichi Bajo, Noriyuki Kawasaki, Isao Sakaguchi, Taku T. Suzuki, Satoru Itose, Miyuki Matsuya, Morio Ishihara, Kiichiro Uchino, Hisayoshi Yurimoto
    Analytical Chemistry 96 13 5143 - 5149 2024年03月21日
  • Raimundo Brahm, Daniel Coulthard Jr, Georg Zellmer, Takeshi Kuritani, Naoya Sakamoto, Hajime Taniuchi, Hisayoshi Yurimoto, Mitsuhiro Nakagawa, Eiichi Sato
    Journal of Petrology 2024年02月29日 
    Abstract The stability and breakdown of mineral phases in subducting slabs control the cycling of trace elements through subduction zones. Stability of key minerals and the partitioning of trace elements between these minerals and liquid phases of interests have been charted by natural sample analysis and experimental constraints. However, systematic study from arc front to far back-arc has rarely shown that the expected geochemical variations of the slab liquid are actually recorded by natural samples. Complexities arise by uncertainties on the nature of the slab component (melts, fluids and supercritical liquids), source heterogeneities and transport processes. Using data from olivine-hosted melt inclusions sampled along and across the NE Japan and southern Kurile arcs, we demonstrate that experimentally and thermodynamically constrained phase stabilities in subducted materials indeed control the trace element signatures as predicted by these models and experiments. The main reactions that can be traced across arc are progressive breakdown of light rare earth element-rich accessory phases (e.g., allanite), enhanced dehydration of the lithospheric mantle (serpentine breakdown) and changes in the nature of the slab component. This work elucidates subduction zone elemental cycling in a well-characterized petrogenetic setting and provides important constraints on the interpretation of trace element ratios in arc magmas in terms of the prograde metamorphic reactions within the subducting slab.
  • Yan Hu, Frédéric Moynier, Wei Dai, Marine Paquet, Tetsuya Yokoyama, Yoshinari Abe, Jérôme Aléon, Conel M. O'D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Koki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Mayu Morita, Kazuko Motomura, Izumi Nakai, Kazuhide Nagashima, David Nesvorný, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
    Icarus 409 115884 - 115884 2024年02月
  • Kazuhiko Ninomiya, Takahito Osawa, Kentaro Terada, Taiga Wada, Shunsaku Nagasawa, I‐Haun Chiu, Tomoki Nakamura, Tadayuki Takahashi, Yasuhiro Miyake, M. Kenya Kubo, Soshi Takeshita, Akihiro Taniguchi, Izumi Umegaki, Shin Watanabe, Toshiyuki Azuma, Miho Katsuragawa, Takahiro Minami, Kazumi Mizumoto, Koichiro Shimomura, Shin'ichiro Takeda, Tomoyo Morita, Mizuha Kikuiri, Kana Amano, Eiichi Kagawa, Yoshihiro Furukawa, Hisayoshi Yurimoto, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei‐ichiro Watanabe, Yuichi Tsuda
    Meteoritics & Planetary Science 2024年01月31日 
    Abstract Samples from asteroid Ryugu, brought back by asteroid explorer Hayabusa2, are important for investigating the origin and evolution of the solar system. Here, we report the elemental compositions of a 123‐mg Ryugu sample determined with a nondestructive muon elemental analysis method. This method is a powerful tool for determining bulk chemical composition, including light elements such as C, N, and O. From the muonic x‐ray spectra with three carbonaceous chondrites, the relationship between the elemental composition and muonic x‐ray intensity was determined for each element. Calibration curves showed linearity, and the elemental composition of Ryugu was quantitatively determined. The results reflect the average bulk elemental composition of asteroid Ryugu owing to the large amount of samples. Ryugu has an elemental composition similar to that of Orgueil (CI1) and should be classified as CI1. However, the O/Si ratio of Ryugu is 25% lower than that of Orgueil, indicating that Orgueil may have been seriously contaminated by terrestrial materials after its fall to Earth. These results indicate that the Ryugu sample is more representative than the CI chondrites as a solid material of the solar system.
  • J. Aléon, S. Mostefaoui, H. Bureau, D. Vangu, H. Khodja, K. Nagashima, N. Kawasaki, Y. Abe, C. M. O'D. Alexander, S. Amari, Y. Amelin, K. Bajo, M. Bizzarro, A. Bouvier, R. W. Carlson, M. Chaussidon, B.‐G. Choi, N. Dauphas, A. M. Davis, T. Di Rocco, W. Fujiya, R. Fukai, I. Gautam, M. K. Haba, Y. Hibiya, H. Hidaka, H. Homma, P. Hoppe, G. R. Huss, K. Ichida, T. Iizuka, T. R. Ireland, A. Ishikawa, S. Itoh, N. T. Kita, K. Kitajima, T. Kleine, S. Komatani, A. N. Krot, M.‐C. Liu, Y. Masuda, M. Morita, K. Motomura, F. Moynier, I. Nakai, A. Nguyen, L. R. Nittler, M. Onose, A. Pack, C. Park, L. Piani, L. Qin, S. S. Russell, N. Sakamoto, M. Schönbächler, L. Tafla, H. Tang, K. Terada, Y. Terada, T. Usui, S. Wada, M. Wadhwa, R. J. Walker, K. Yamashita, Q.‐Z. Yin, T. Yokoyama, S. Yoneda, E. D. Young, H. Yui, A.‐C. Zhang, T. Nakamura, H. Naraoka, T. Noguchi, R. Okazaki, K. Sakamoto, H. Yabuta, M. Abe, A. Miyazaki, A. Nakato, M. Nishimura, T. Okada, T. Yada, K. Yogata, S. Nakazawa, T. Saiki, S. Tanaka, F. Terui, Y. Tsuda, S. Watanabe, M. Yoshikawa, S. Tachibana, H. Yurimoto
    Meteoritics & Planetary Science 2024年01月26日 
    Abstract In order to gain insights on the conditions of aqueous alteration on asteroid Ryugu and the origin of water in the outer solar system, we developed the measurement of water content in magnetite at the micrometer scale by secondary ion mass spectrometry (NanoSIMS) and determined the H and Si content of coarse‐grained euhedral magnetite grains (polyhedral magnetite) and coarse‐grained fibrous (spherulitic) magnetite from the Ryugu polished section A0058‐C1001. The hydrogen content in magnetite ranges between ~900 and ~3300 wt ppm equivalent water and is correlated with the Si content. Polyhedral magnetite has low and homogenous silicon and water content, whereas fibrous magnetite shows correlated Si and water excesses. These excesses can be explained by the presence of hydrous Si‐rich amorphous nanoinclusions trapped during the precipitation of fibrous magnetite away from equilibrium and testify that fibrous magnetite formed from a hydrous gel with possibly more than 20 wt% water. An attempt to determine the water content in sub‐μm framboids indicates that additional calibration and contamination issues must be addressed before a safe conclusion can be drawn, but hints at elevated water content as well. The high water content in fibrous magnetite, expected to be among the first minerals to crystallize at low water–rock ratio, points to the control of water content by local conditions of magnetite precipitation rather than large‐scale alteration conditions. Systematic lithological variations associated with water‐rich and water‐poor magnetite suggest that the global context of alteration may be better understood if local water concentrations are compared with millimeter‐scale distribution of the various morphologies of magnetite. Finally, the high water content in the magnetite precursor gel indicates that the initial O isotopic composition in alteration water must not have been very different from that of the earliest magnetite crystals.
  • Rhonda M. Stroud, Jens Barosch, Lydie Bonal, Katherine Burgess, George D. Cody, Bradley T. De Gregorio, Luke Daly, Emmanuel Dartois, Elena Dobrică, Jean Duprat, Cecile Engrand, Dennis Harries, Minako Hashiguchi, Hope Ishii, Yoko Kebukawa, A. David Kilcoyne, Falko Langenhorst, Martin R. Lee, Larry R. Nittler, Eric Quirico, Taiga Okumura, Laurent Remusat, Scott Sandford, Hikaru Yabuta, Masanao Abe, Neyda M. Abreu, Paul A. J. Bagot, Pierre Beck, Laure Bejach, Phil A. Bland, John C. Bridges, Brittany A. Cymes, Alexandre Dazzi, Francisco de la Peña, Ariane Deniset‐Besseau, Satomi Enju, Yuma Enokido, David R. Frank, Jennifer Gray, Mitsutaka Haruta, Satoshi Hata, Leon Hicks, Yohei Igami, Damien Jacob, Kanami Kamide, Mutsumi Komatsu, Sylvain Laforet, Hugues Leroux, Corentin Le Guillou, Zita Martins, Maya Marinova, James Martinez, Jérémie Mathurin, Megumi Matsumoto, Toru Matsumoto, Junya Matsuno, Samuel McFadzean, Tatsuhiro Michikami, Itaru Mitsukawa, Akira Miyake, Masaaki Miyahara, Akiko Miyazaki, Gilles Montagnac, Smail Mostefaoui, Tomoki Nakamura, Aiko Nakato, Hiroshi Naraoka, Yusuke Nakauchi, Satoru Nakazawa, Masahiro Nishimura, Takaaki Noguchi, Kenta Ohtaki, Takuji Ohigashi, Tatsuaki Okada, Shota Okumura, Ryuji Okazaki, Thi H. V. Phan, Rolando Rebois, Kanako Sakamoto, Takanao Saiki, Hikaru Saito, Yusuke Seto, Miho Shigenaka, William Smith, Hiroki Suga, Mingqi Sun, Shogo Tachibana, Yoshio Takahashi, Yasuo Takeichi, Akihisa Takeuchi, Aki Takigawa, Yusuke Tamenori, Satoshi Tanaka, Fuyuto Terui, Michelle S. Thompson, Naotaka Tomioka, Akira Tsuchiyama, Yuichi Tsuda, Kentaro Uesugi, Masayuki Uesugi, Tomohiro Usui, Maximilien Verdier‐Paoletti, Daisuke Wakabayashi, Sei‐ichiro Watanabe, Toru Yada, Shohei Yamashita, Masahiro Yasutake, Kasumi Yogata, Makoto Yoshikawa, Hisayoshi Yurimoto, Pierre‐M. Zanetta, Thomas Zega, Michael E. Zolensky
    Meteoritics & Planetary Science 2024年01月25日 
    Abstract Transmission electron microscopy analyses of Hayabusa2 samples show that Ryugu organic matter exhibits a range of morphologies, elemental compositions, and carbon functional chemistries consistent with those of carbonaceous chondrites that have experienced low‐temperature aqueous alteration. Both nanoglobules and diffuse organic matter are abundant. Non‐globular organic particles are also present, and including some that contain nanodiamond clusters. Diffuse organic matter is finely distributed in and around phyllosilicates, forms coatings on other minerals, and is also preserved in vesicles in secondary minerals such as carbonate and pyrrhotite. The average elemental compositions determined by energy‐dispersive spectroscopy of extracted, demineralized insoluble organic matter samples A0107 and C0106 are C100N3O9S1 and C100N3O7S1, respectively, with the difference in O/C slightly outside the difference in the standard error of the mean. The functional chemistry of the nanoglobules varies from mostly aromatic C=C to mixtures of aromatic C=C, ketone C=O, aliphatic (CHn), and carboxyl (COOH) groups. Diffuse organic matter associated with phyllosilicates has variable aromatic C, ketone and carboxyl groups, and some localized aliphatics, but is dominated by molecular carbonate (CO3) absorption, comparable to prior observations of clay‐bound organic matter in CI meteorites.
  • Megumi Matsumoto, Junya Matsuno, Akira Tsuchiyama, Tomoki Nakamura, Yuma Enokido, Mizuha Kikuiri, Aiko Nakato, Masahiro Yasutake, Kentaro Uesugi, Akihisa Takeuchi, Satomi Enju, Shota Okumura, Itaru Mitsukawa, Mingqi Sun, Akira Miyake, Mitsutaka Haruta, Yohei Igami, Hisayoshi Yurimoto, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Michael Zolensky, Toru Yada, Masahiro Nishimura, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei-ichiro Watanabe, Yuichi Tsuda
    Science Advances 10 3 2024年01月19日 
    The Hayabusa2 spacecraft delivered samples of the carbonaceous asteroid Ryugu to Earth. Some of the sample particles show evidence of micrometeoroid impacts, which occurred on the asteroid surface. Among those, particles A0067 and A0094 have flat surfaces on which a large number of microcraters and impact melt splashes are observed. Two impact melt splashes and one microcrater were analyzed to unveil the nature of the objects that impacted the asteroid surface. The melt splashes consist mainly of Mg-Fe–rich glassy silicates and Fe-Ni sulfides. The microcrater trapped an impact melt consisting mainly of Mg-Fe–rich glassy silicate, Fe-Ni sulfides, and minor silica-rich glass. These impact melts show a single compositional trend indicating mixing of Ryugu surface materials and impactors having chondritic chemical compositions. The relict impactor in one of the melt splashes shows mineralogical similarity with anhydrous chondritic interplanetary dust particles having a probable cometary origin. The chondritic micrometeoroids probably impacted the Ryugu surface during its residence in a near-Earth orbit.
  • Lydie Bonal, Eric Quirico, Gilles Montagnac, Mutsumi Komatsu, Yoko Kebukawa, Hikaru Yabuta, Kana Amano, Jens Barosch, Laure Bejach, George D. Cody, Emmanuel Dartois, Alexandre Dazzi, Bradley De Gregorio, Ariane Deniset-Besseau, Jean Duprat, Cécile Engrand, Minako Hashiguchi, Kanami Kamide, David Kilcoyne, Zita Martins, Jérémie Mathurin, Smail Mostefaoui, Larry Nittler, Takuji Ohigashi, Taiga Okumura, Laurent Remusat, Scott Sandford, Miho Shigenaka, Rhonda Stroud, Hiroki Suga, Yoshio Takahashi, Yasuo Takeichi, Yusuke Tamenori, Maximilien Verdier-Paoletti, Shohei Yamashita, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Hisayoshi Yurimoto, Shogo Tachibana, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Satoru Nakazawa, Masahiro Nishimura, Tatsuaki Okada, Takanao Saiki, Kanako Sakamoto, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Tomohiro Usui, Sei ichiro Watanabe, Toru Yada, Kasumi Yogata, Makota Yoshikawa
    Icarus 408 2024年01月15日 
    This paper is focused on the characterization of the thermal history of C-type asteroid Ryugu through the structure of the polyaromatic carbonaceous matter in the returned samples determined by Raman spectroscopy. Both intact particles and extracted Insoluble Organic Matter (IOM) from the two sampling sites on Ryugu have been characterized. The main conclusions are that (i) there is no structural difference of the polyaromatic component probed by Raman spectroscopy between the two sampling sites, (ii) in a manner similar to type 1 and 2 chondrites, the characterized Ryugu particles did not experience significant long-duration thermal metamorphism related to the radioactive decay of elements such as 26Al; (iii) some structural variability is nevertheless observed within our particle set. It can be interpreted as some particles having experienced some short-duration and weak heating (R3 in the scale defined by Quirico et al. 2018 and TII or lower according to the scale defined by Nakamura, 2005).
  • Nagi Ikuta, Naoya Sakamoto, Shoh Tagawa, Kei Hirose, Yutaro Tsutsumi, Shunpei Yokoo, Hisayoshi Yurimoto
    Scientific Reports 14 1 2024年01月12日 
    Abstract Previous experiments performed below 20 GPa suggested that the metal/silicate partition coefficient of phosphorus (P), DP, extrapolated to typical high-pressure and -temperature conditions of the Earth’s core formation gives too high P concentration in the core unless a large amount of silicon was included in metals. Here we examined DP between liquid metal and coexisting molten silicate at 27–61 GPa and 3820–4760 K, corresponding to conditions of core-forming metal segregation from silicate, by measuring recovered samples using a high-resolution imaging technique coupled with secondary ion mass spectrometry. The results demonstrate that the pressure dependence of DP changes from positive to negative above 15 GPa, likely because of an increase in the coordination number of P5+ in silicate melt. With the present new partitioning data, the observed mantle P abundance may indicate ~ 0.2 wt% P in the core, consistent with the cosmo-/geochemical estimates, based on both single-stage and multi-stage core formation models without involving high amounts of silicon in metals.
  • Akimasa Suzumura, Noriyuki Kawasaki, Hisayoshi Yurimoto, Shoichi Itoh
    Meteoritics and Planetary Science 2024年 
    A melilite-rich, compact type A Ca-Al-rich inclusion (CAI), KU-N-02, from the reduced CV3 chondrite Northwest Africa 7865, is mantled by an åkermanite-poor layer. We carried out a combined study of petrographic observations and in situ O and Al–Mg isotopic measurements for KU-N-02. The core shows a typical texture of igneous compact type A CAIs. The mantle consists of spinel, åkermanite-poor melilite, and perovskite. Individual mantle melilite crystals show reverse zoning toward the crystal grain boundary, in contrast to core melilite crystals showing normal zoning. The O isotopic compositions of the minerals in KU-N-02 plot along the carbonaceous chondrite anhydrous mineral line on a three O-isotope diagram. The mantle and core spinel crystals are uniformly 16O-rich (Δ17O ~ −23‰). The mantle melilite crystals exhibit variable O isotopic compositions ranging between Δ17O ~ −2‰ and −9‰, in contrast to the uniformly 16O-poor (Δ17O ~ −2‰) core melilite. The mantle melilite crystals also exhibit variable δ25Mg values (δ25MgDSM-3 ~ −2‰ to +3‰) compared with the nearly constant δ25Mg values of the core melilite (δ25MgDSM-3 ~ +2‰). The mantle minerals are likely to have formed by condensation from the solar nebular gas after core formation. The Al–Mg mineral isochrons of the core and mantle give initial 26Al/27Al ratios of (4.66 ± 0.15) × 10−5 and (4.74 ± 0.14) × 10−5, respectively. The age difference between the core and mantle formation is estimated to be within ~0.05 Myr, implying that both melting and condensation processes in the variable O isotopically solar nebular environments occurred within a short time during single CAI formation.
  • Mayu Morita, Hiroharu Yui, Shu-hei Urashima, Morihiko Onose, Shintaro Komatani, Izumi Nakai, Yoshinari Abe, Yasuko Terada, Hisashi Homma, Kazuko Motomura, Kiyohiro Ichida, Tetsuya Yokoyama, Kazuhide Nagashima, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Peter Hoppe, Gary R. Huss, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Sasha Krot, Ming-Chang Liu, Yuki Masuda, Frédéric Moynier, Ann Nguyen, Larry Nittler, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Tommaso Di Rocco, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
    Analytical Chemistry 2023年12月28日
  • Sarah S. Zeichner, José C. Aponte, Surjyendu Bhattacharjee, Guannan Dong, Amy E. Hofmann, Jason P. Dworkin, Daniel P. Glavin, Jamie E. Elsila, Heather V. Graham, Hiroshi Naraoka, Yoshinori Takano, Shogo Tachibana, Allison T. Karp, Kliti Grice, Alex I. Holman, Katherine H. Freeman, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Kanako Sakamoto, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei-ichiro Watanabe, Yuichi Tsuda, Kenji Hamase, Kazuhiko Fukushima, Dan Aoki, Minako Hashiguchi, Hajime Mita, Yoshito Chikaraishi, Naohiko Ohkouchi, Nanako O. Ogawa, Saburo Sakai, Eric T. Parker, Hannah L. McLain, Francois-Regis Orthous-Daunay, Véronique Vuitton, Cédric Wolters, Philippe Schmitt-Kopplin, Norbert Hertkorn, Roland Thissen, Alexander Ruf, Junko Isa, Yasuhiro Oba, Toshiki Koga, Toshihiro Yoshimura, Daisuke Araoka, Haruna Sugahara, Aogu Furusho, Yoshihiro Furukawa, Junken Aoki, Kuniyuki Kano, Shin-ichiro M. Nomura, Kazunori Sasaki, Hajime Sato, Takaaki Yoshikawa, Satoru Tanaka, Mayu Morita, Morihiko Onose, Fumie Kabashima, Kosuke Fujishima, Tomoya Yamazaki, Yuki Kimura, John M. Eiler
    Science 382 6677 1411 - 1416 2023年12月22日 
    Polycyclic aromatic hydrocarbons (PAHs) contain ≲20% of the carbon in the interstellar medium. They are potentially produced in circumstellar environments (at temperatures ≳1000 kelvin), by (~10 kelvin) interstellar clouds, or by processing of carbon-rich dust grains. We report isotopic properties of PAHs extracted from samples of the asteroid Ryugu and the meteorite Murchison. The doubly- 13 C substituted compositions (Δ2× 13 C values) of the PAHs naphthalene, fluoranthene, and pyrene are 9 to 51‰ higher than values expected for a stochastic distribution of isotopes. The Δ2× 13 C values are higher than expected if the PAHs formed in a circumstellar environment, but consistent with formation in the interstellar medium. By contrast, the PAHs phenanthrene and anthracene in Ryugu samples have Δ2× 13 C values consistent with formation by higher-temperature reactions.
  • Daniel A Coulthard Jr, Raimundo Brahm, Charline Lormand, Georg F Zellmer, Naoya Sakamoto, Yoshiyuki Iizuka, Hisayoshi Yurimoto
    Journal of Petrology 65 1 2023年12月13日 
    Abstract The residence timescales of antecrystic minerals contribute a key piece of information regarding the petrologic evolution of transcrustal magmatic systems and may be inferred using a combination of observations derived from microanalytical chemistry and diffusion modelling. Here, we present state-of-the-art stacked CMOS-type active pixel sensor (SCAPS) isotopographic images of tephra-hosted plagioclase microantecrysts from Tongariro Volcanic Centre in the southern Taupo Volcanic Zone, New Zealand. These crystals exhibit high-frequency Sr and anorthite zonation at sub-micron spatial resolution. We also find that all crystals display high-frequency intracrystalline Sr chemical potential variations, indicating that they have not resided at magmatic temperature for diffusive relaxation to advance significantly. To quantify crystal residence times at the well-constrained magmatic temperatures of these tephras, we first forward-modeled intracrystalline Sr diffusion over time using numerical methods. Results were then analyzed using novel spatial Fourier-transform techniques developed to understand the systematics the diffusive decay of Sr disequilibria in the spatial frequency domain. This ultimately permitted the estimation of Sr concentration profiles at crystal formation, prior to uptake into the carrier melt at the onset of eruption. Our data imply residence times of hours to days for the studied microantecrysts. This is inconsistent with long antecryst residence times in magmatic mushes at elevated temperatures, pointing instead to a cool plutonic nature of the magmatic plumbing system beneath the southern Taupo Volcanic Zone.
  • Kana Amano, Moe Matsuoka, Tomoki Nakamura, Eiichi Kagawa, Yuri Fujioka, Sandra M. Potin, Takahiro Hiroi, Eri Tatsumi, Ralph E. Milliken, Eric Quirico, Pierre Beck, Rosario Brunetto, Masayuki Uesugi, Yoshio Takahashi, Takahiro Kawai, Shohei Yamashita, Yuma Enokido, Taiga Wada, Yoshihiro Furukawa, Michael E. Zolensky, Driss Takir, Deborah L. Domingue, Camilo Jaramillo-Correa, Faith Vilas, Amanda R. Hendrix, Mizuha Kikuiri, Tomoyo Morita, Hisayoshi Yurimoto, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei-ichiro Watanabe, Yuichi Tsuda
    Science Advances 9 49 2023年12月08日 
    The carbonaceous asteroid Ryugu has been explored by the Hayabusa2 spacecraft to elucidate the actual nature of hydrous asteroids. Laboratory analyses revealed that the samples from Ryugu are comparable to unheated CI carbonaceous chondrites; however, reflectance spectra of Ryugu samples and CIs do not coincide. Here, we demonstrate that Ryugu sample spectra are reproduced by heating Orgueil CI chondrite at 300°C under reducing conditions, which caused dehydration of terrestrial weathering products and reduction of iron in phyllosilicates. Terrestrial weathering of CIs accounts for the spectral differences between Ryugu sample and CIs, which is more severe than space weathering that likely explains those between asteroid Ryugu and the collected samples. Previous assignments of CI chondrite parent bodies, i.e., chemically most primitive objects in the solar system, are based on the spectra of CI chondrites. This study indicates that actual spectra of CI parent bodies are much darker and flatter at ultraviolet to visible wavelengths than the spectra of CI chondrites.
  • Zachary A. Torrano, Michelle K. Jordan, Timothy D. Mock, Richard W. Carlson, Ikshu Gautam, Makiko K. Haba, Tetsuya Yokoyama, Yoshinari Abe, Jérôme Aléon, Conel Alexander, Sachiko Amari, Yuri Amelin, Ken‐ichi Bajo, Martin Bizzarro, Audrey Bouvier, Marc Chaussidon, Byeon‐Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Koki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming‐Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Kazuhide Nagashima, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing‐Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai‐Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei‐ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
    Meteoritics & Planetary Science 2023年12月07日 
    Abstract We report Nd and Sm isotopic compositions of four samples of Ryugu returned by the Hayabusa2 mission, including “A” (first touchdown) and “C” (second touchdown) samples, and several carbonaceous chondrites to evaluate potential genetic relationships between Ryugu and known chondrite groups and track the cosmic ray exposure history of Ryugu. We resolved Nd and Sm isotopic anomalies in small (<20 ng Nd and Sm) sample sizes via thermal ionization mass spectrometer using 1013 Ω amplifiers. Ryugu samples exhibit resolvable negative μ142Nd values consistent with carbonaceous chondrite values, suggesting that Ryugu is related to the parent bodies of carbonaceous chondrites. Ryugu's negative μ149Sm values are the result of exposure to galactic cosmic rays, as demonstrated by the correlation between 150Sm/152Sm and 149Sm/152Sm ratios that fall along the expected neutron capture correlation line. The neutron fluence calculated in the “A” samples (2.75 ± 1.94 × 1015 n cm−2) is slightly higher compared to the “C” samples (0.95 ± 2.04 × 1015 n cm−2), though overlapping within measurement uncertainty. The Sm results for Ryugu, at this level of precision, thus are consistent with a well‐mixed surface layer at least to the depths from which the “A” and “C” samples derive.
  • Akimasa Suzumura, Noriyuki Kawasaki, Yusuke Seto, Hisayoshi Yurimoto, Shoichi Itoh
    Geochimica et Cosmochimica Acta 362 128  2023年12月01日 
    The authors regret that on page 59, lines 380–384 of Section 3.2, the authors have been made aware of an error in the indexed zone axis of the SAED pattern for spinel. A mistake in the indexed zone axis of the SAED pattern is [0 1 1]spinel and the accurate indexed zone axis is [0 1 0]spinel. Error “Analysis of the SAED pattern of the interface between the perovskite and spinel grains yields the same crystallographic orientation relationship between them: [0 0 1]perovskite//[0 1 1]spinel and (0 1 –1)perovskite//(1 1 –1)spinel.” Corrected “Analysis of the SAED pattern of the interface between the perovskite and spinel grains yields the same crystallographic orientation relationship between them: [0 0 1]perovskite//[0 1 0]spinel and (0 1 –1)perovskite//(1 1 –1)spinel.” The correction does not change any fundamental conclusions of the paper. It only corrects the indexed zone axis of the SAED pattern of the spinel, but we believe this is important because of the first report to identify the crystallographic relationship between spinel and perovskite in coarse-grained Type A CAI. Acknowledgments I thank Prof. A. Miyake (Kyoto University) for his questions which led to the discovery of the missing sentence. The authors would like to apologise for any inconvenience caused.
  • N. Nakanishi, T. Yokoyama, A. Ishikawa, R.J. Walker, Y. Abe, J. Aléon, C.M.O'D. Alexander, S. Amari, Y. Amelin, K.-I. Bajo, M. Bizzarro, A. Bouvier, R.W. Carlson, M. Chaussidon, B.-G. Choi, N. Dauphas, A.M. Davis, T. Di Rocco, W. Fujiya, R. Fukai, I. Gautam, M.K. Haba, Y. Hibiya, H. Hidaka, H. Homma, P. Hoppe, G.R. Huss, K. Ichida, T. Iizuka, T.R. Ireland, S. Itoh, N. Kawasaki, N.T. Kita, K. Kitajima, T. Kleine, S. Komatani, A.N. Krot, M.-C. Liu, Y. Masuda, M. Morita, K. Motomura, F. Moynier, I. Nakai, K. Nagashima, A. Nguyen, L. Nittler, M. Onose, A. Pack, C. Park, L. Piani, L. Qin, S.S. Russell, N. Sakamoto, M. Schönbächler, L. Tafla, H. Tang, K. Terada, Y. Terada, T. Usui, S. Wada, M. Wadhwa, K. Yamashita, Q.-Z. Yin, S. Yoneda, E.D. Young, H. Yui, A.-C. Zhang, T. Nakamura, H. Naraoka, T. Noguchi, R. Okazaki, K. Sakamoto, H. Yabuta, M. Abe, A. Miyazaki, A. Nakato, M. Nishimura, T. Okada, T. Yada, K. Yogata, S. Nakazawa, T. Saiki, S. Tanaka, F. Terui, Y. Tsuda, S.-I. Watanabe, M. Yoshikawa, S. Tachibana, H. Yurimoto
    Geochemical Perspectives Letters 28 31 - 36 2023年12月
  • T. Hiroi, R.E. Milliken, K.M. Robertson, C.D. Schultz, K. Amano, T. Nakamura, H. Yurimoto, T. Noguchi, R. Okazaki, H. Naraoka, H. Yabuta, K. Sakamoto, T. Yada, M. Nishimura, A. Nakato, A. Miyazaki, K. Yogata, M. Abe, T. Okada, T. Usui, M. Yoshikawa, T. Saiki, S. Tanaka, S. Nakazawa, Y. Yokota, E. Tatsumi, Y. Tsuda, S. Tachibana, T. Fuyuto, S. Watanabe, S. Sasaki, H. Kaiden, K. Kitazato, M. Matsuoka
    Icarus 406 115755 - 115755 2023年12月
  • José C. Aponte, Jason P. Dworkin, Daniel P. Glavin, Jamie E. Elsila, Eric T. Parker, Hannah L. McLain, Hiroshi Naraoka, Ryuji Okazaki, Yoshinori Takano, Shogo Tachibana, Guannan Dong, Sarah S. Zeichner, John M. Eiler, Hisayoshi Yurimoto, Tomoki Nakamura, Hikaru Yabuta, Fuyuto Terui, Takaaki Noguchi, Kanako Sakamoto, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Satoru Nakazawa, Yuichi Tsuda, Sei ichiro Watanabe
    Earth, Planets and Space 75 1 2023年12月 [査読有り]
     
    Evaluating the molecular distribution of organic compounds in pristine extraterrestrial materials is cornerstone to understanding the abiotic synthesis of organics and allows us to better understand the molecular diversity available during the formation of our solar system and before the origins of life on Earth. In this work, we identify multiple organic compounds in solvent extracts of asteroid Ryugu samples A0106 and C0107 and the Orgueil meteorite using two-dimensional gas chromatography and time-of-flight high resolution mass spectrometry (GC×GC–HRMS). Our analyses found similarities between the molecular distribution of organic compounds in Ryugu and the CI carbonaceous chondrite Orgueil. Specifically, several PAHs and organosulfides were found in Ryugu and Orgueil suggesting an interstellar and parent body origin for these compounds. We also evaluated the common relationship between Ryugu, Orgueil, and comets, such as Wild-2; however, until comprehensive compound-specific isotopic analyses for these organic species are undertaken, and until the effects of parent body processes and Earth’s weathering processes on meteoritic organics are better understood, their parent–daughter relationships will remain unanswered. Finally, the study of organic compounds in Ryugu samples and the curation practices for the future preservation of these unvaluable materials are also of special interest for future sample return missions, including NASA’s OSIRIS-REx asteroid sample return mission. Graphical Abstract: [Figure not available: see fulltext.].
  • Toru Matsumoto, Takaaki Noguchi, Akira Miyake, Yohei Igami, Mitsutaka Haruta, Yusuke Seto, Masaaki Miyahara, Naotaka Tomioka, Hikaru Saito, Satoshi Hata, Dennis Harries, Aki Takigawa, Yusuke Nakauchi, Shogo Tachibana, Tomoki Nakamura, Megumi Matsumoto, Hope A. Ishii, John P. Bradley, Kenta Ohtaki, Elena Dobrică, Hugues Leroux, Corentin Le Guillou, Damien Jacob, Francisco de la Peña, Sylvain Laforet, Maya Marinova, Falko Langenhorst, Pierre Beck, Thi H. V. Phan, Rolando Rebois, Neyda M. Abreu, Jennifer Gray, Thomas Zega, Pierre-M. Zanetta, Michelle S. Thompson, Rhonda Stroud, Kate Burgess, Brittany A. Cymes, John C. Bridges, Leon Hicks, Martin R. Lee, Luke Daly, Phil A. Bland, Michael E. Zolensky, David R. Frank, James Martinez, Akira Tsuchiyama, Masahiro Yasutake, Junya Matsuno, Shota Okumura, Itaru Mitsukawa, Kentaro Uesugi, Masayuki Uesugi, Akihisa Takeuchi, Mingqi Sun, Satomi Enju, Tatsuhiro Michikami, Hisayoshi Yurimoto, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei-ichiro Watanabe, Yuichi Tsuda
    Nature Astronomy 2023年11月30日 
    Abstract Large amounts of nitrogen compounds, such as ammonium salts, may be stored in icy bodies and comets, but the transport of these nitrogen-bearing solids into the near-Earth region is not well understood. Here, we report the discovery of iron nitride on magnetite grains from the surface of the near-Earth C-type carbonaceous asteroid Ryugu, suggesting inorganic nitrogen fixation. Micrometeoroid impacts and solar wind irradiation may have caused the selective loss of volatile species from major iron-bearing minerals to form the metallic iron. Iron nitride is a product of nitridation of the iron metal by impacts of micrometeoroids that have higher nitrogen contents than the CI chondrites. The impactors are probably primitive materials with origins in the nitrogen-rich reservoirs in the outer Solar System. Our observation implies that the amount of nitrogen available for planetary formation and prebiotic reactions in the inner Solar System is greater than previously recognized.
  • Martin Bizzarro, Martin Schiller, Tetsuya Yokoyama, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Mayu Morita, Fréderic Moynier, Kazuko Motomura, Izumi Nakai, Kazuhide Nagashima, David Nesvorný, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
    The Astrophysical Journal Letters 958 2 L25 - L25 2023年11月24日 
    Abstract The nucleosynthetic isotope composition of planetary materials provides a record of the heterogeneous distribution of stardust within the early solar system. In 2020 December, the Japan Aerospace Exploration Agency Hayabusa2 spacecraft returned to Earth the first samples of a primitive asteroid, namely, the Cb-type asteroid Ryugu. This provides a unique opportunity to explore the kinship between primitive asteroids and carbonaceous chondrites. We report high-precision μ26Mg* and μ25Mg values of Ryugu samples together with those of CI, CM, CV, and ungrouped carbonaceous chondrites. The stable Mg isotope composition of Ryugu aliquots defines μ25Mg values ranging from –160 ± 20 ppm to –272 ± 30 ppm, which extends to lighter compositions relative to Ivuna-type (CI) and other carbonaceous chondrite groups. We interpret the μ25Mg variability as reflecting heterogeneous sampling of a carbonate phase hosting isotopically light Mg (μ25Mg ∼ –1400 ppm) formed by low temperature equilibrium processes. After correcting for this effect, Ryugu samples return homogeneous μ26Mg* values corresponding to a weighted mean of 7.1 ± 0.8 ppm. Thus, Ryugu defines a μ26Mg* excess relative to the CI and CR chondrite reservoirs corresponding to 3.8 ± 1.1 and 11.9 ± 0.8 ppm, respectively. These variations cannot be accounted for by in situ decay of 26Al given their respective 27Al/24Mg ratios. Instead, it requires that Ryugu and the CI and CR parent bodies formed from material with a different initial 26Al/27Al ratio or that they are sourced from material with distinct Mg isotope compositions. Thus, our new Mg isotope data challenge the notion that Ryugu and CI chondrites share a common nucleosynthetic heritage.
  • Mathieu Roskosz, Pierre Beck, Jean‐Christophe Viennet, Tomoki Nakamura, Barbara Lavina, Michael Y. Hu, Jiyong Zhao, Esen E. Alp, Yoshio Takahashi, Tomoyo Morita, Kana Amano, Hisayoshi Yurimoto, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei‐Ichiro Watanabe, Yuichi Tsuda
    Meteoritics & Planetary Science 2023年11月20日 
    Abstract The Hayabusa2 mission sampled Ryugu, an asteroid that did not suffer extensive thermal metamorphism, and returned rocks to the Earth with no significant air exposure. It therefore offers a unique opportunity to study the redox state of carbonaceous Cb‐type asteroids and evaluate the overall redox state of the most primitive rocks of the solar system. An analytical framework was developed to investigate the iron mineralogy and valence state in extraterrestrial material at the micron scale by combining x‐ray diffraction, conventional Mössbauer (MS), and nuclear forward scattering (NFS) spectroscopies. An array of standard minerals was analyzed and cross‐calibrated between MS and NFS. Then, MS and NFS spectra on three Ryugu grains were collected at the bulk and the micron scales. In Ryugu samples, iron is essentially accommodated in magnetite, clay minerals (serpentine–smectite), and sulfides. Only a single set of Mössbauer parameters was necessary to account for the entire variability observed in MS and NFS spectra, at all spatial scales investigated. These parameters therefore make up a fully consistent iron mineralogical model for the Ryugu samples. As far as MS and NFS spectroscopies are concerned, Ryugu grains are overall similar to each other and share most of their mineralogical features with CI‐type chondrites. In detail however, no ferrihydrite is found in Ryugu particles even at the very sensitive scale of Mössbauer spectroscopy. The typical Fe3+/Fetot of clay minerals is much lower than typical redox ratios measured in CI chondrites (Fe3+/Fetot = 85%–90%). Furthermore, magnetite from Ryugu is stoichiometric with no significant maghemite component, whereas up to 12% of maghemite was previously identified in the Orgueil's so‐called magnetite. These differences suggest that most CI meteorites suffered terrestrial alteration and that the preterrestrial composition of these carbon‐rich samples was less oxidized than previously measured. However, it is not clear yet whether or not the parent bodies of CI chondrites were as reduced as Ryugu. Finally, the high spatial resolution of NFS allows to disentangle the redox state and the crystal chemistry of iron accommodated in serpentine and smectite. The most likely polytype of serpentine is lizardite, containing <35% of Fe3+, a fraction of which being tetrahedrally coordinated. Smectite is more oxidized (Fe3+/Fetot > 65%) and mainly contains octahedral ferric iron. This finding implies that these clays formed from highly alkaline fluids and the spatial variability highlighted here may suggest a temporal evolution or a spatial variability of the nature of this fluid.
  • Toru Yada, Masanao Abe, Masahiro Nishimura, Hirotaka Sawada, Ryuji Okazaki, Yoshinori Takano, Kanako Sakamoto, Tatsuaki Okada, Aiko Nakato, Miwa Yoshitake, Yuki Nakano, Kasumi Yogata, Akiko Miyazaki, Shizuho Furuya, Ayako S. Iwamae, Shunichi Nakatsubo, Kentaro Hatakeda, Yuya Hitomi, Kazuya Kumagai, Shino Suzuki, Yayoi N. Miura, Motoo Ito, Naotaka Tomioka, Masayuki Uesugi, Yuzuru Karouji, Kentaro Uesugi, Naoki Shirai, Akira Yamaguchi, Naoya Imae, Hiroshi Naraoka, Yuhji Yamamoto, Shogo Tachibana, Hisayoshi Yurimoto, Tomohiro Usui
    Earth, Planets and Space 75 1 2023年11月15日 
    Abstract Developing a cleanroom and clean chambers (CCs) for Hayabusa2 returned samples has been discussed with the committee for Hayabusa2 sample curation facility since 2015. One major difference from the specifications of the CCs used for Itokawa samples is that a part of samples was decided to be handled and preserved in vacuum to avoid terrestrial nitrogen contamination with organics or unknown materials that might easily react with the samples. Thus, the CCs for Hayabusa2 samples were divided into two CCs for vacuum processes and three CCs for purified nitrogen conditions. The cleanroom was built in summer 2017, while the CCs were installed in the summer of 2018. After the installation of the CCs, instruments for initial descriptions, sample containers, handling tools for powder and particle samples, and jigs to assist handling samples were developed in parallel with functional checks and repeated rehearsals between the fall of 2018 and the fall of 2020. The curatorial works on Hayabusa2-retuned samples were conducted as previously planned. Simultaneously, contaminations and influences of inorganics, organics, microbial, and magnetic constructs have been assessed to evaluate their potential effects on the analysis of the returned samples. Additionally, the tools used to touch samples directly have been demagnetized to avoid sample magnetization during their handling and the tool magnetization was measured before and after their usages. The series of developments and experiences from the curatorial works of Hayabusa2-returned samples represent valuable implications for future sample return missions. Graphical Abstract
  • Eric Quirico, Lydie Bonal, Yoko Kebukawa, Kana Amano, Hikaru Yabuta, Van T. H. Phan, Pierre Beck, Laurent Rémusat, Emmanuel Dartois, Cecile Engrand, Zita Martins, Laure Bejach, Alexandre Dazzi, Ariane Deniset‐Besseau, Jean Duprat, Jérémie Mathurin, Gilles Montagnac, Jens Barosch, George D. Cody, Bradley De Gregorio, Yuma Enokido, Minako Hashiguchi, Kanami Kamide, David Kilcoyne, Mutsumi Komatsu, Megumi Matsumoto, Smail Mostefaoui, Larry Nittler, Takuji Ohigashi, Taiga Okumura, Scott Sandford, Miho Shigenaka, Rhonda Stroud, Hiroki Suga, Yoshio Takahashi, Yasuo Takeichi, Yusuke Tamenori, Maximilien Verdier‐Paoletti, Daisuke Wakabayashi, Shohei Yamashita, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Hisayoshi Yurimoto, Kanako Sakamoto, Shogo Tachibana, Sei‐Ichiro Watanabe, Yuichi Tsuda, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohitro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa
    Meteoritics & Planetary Science 2023年11月13日 
    Abstract We report a Fourier transform infrared analysis of functional groups in insoluble organic matter (IOM) extracted from a series of 100–500 μm Ryugu grains collected during the two touchdowns of February 22 and July 11, 2019. IOM extracted from most of the samples is very similar to IOM in primitive CI, CM, and CR chondrites, and shows that the extent of thermal metamorphism in Ryugu regolith was, at best, very limited. One sample displays chemical signatures consistent with a very mild heating, likely due to asteroidal collision impacts. We also report a lower carbonyl abundance in Ryugu IOM samples compared to primitive chondrites, which could reflect the accretion of a less oxygenated precursor by Ryugu. The possible effects of hydrothermal alteration and terrestrial weathering are also discussed. Last, no firm conclusions could be drawn on the origin of the soluble outlier phases, observed along with IOM in this study and in the preliminary analysis of Ryugu samples. However, it is clear that the HF/HCl residues presented in this publication are a mix between IOM and the nitrogen‐rich outlier phase.
  • Tetsuya Yokoyama, Meenakshi Wadhwa, Tsuyoshi Iizuka, Vinai Rai, Ikshu Gautam, Yuki Hibiya, Yuki Masuda, Makiko K. Haba, Ryota Fukai, Rebekah Hines, Nicole Phelan, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Trevor Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Koki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Kazuhide Nagashima, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
    Science Advances 9 45 2023年11月10日 
    Studies of material returned from Cb asteroid Ryugu have revealed considerable mineralogical and chemical heterogeneity, stemming primarily from brecciation and aqueous alteration. Isotopic anomalies could have also been affected by delivery of exogenous clasts and aqueous mobilization of soluble elements. Here, we show that isotopic anomalies for mildly soluble Cr are highly variable in Ryugu and CI chondrites, whereas those of Ti are relatively uniform. This variation in Cr isotope ratios is most likely due to physicochemical fractionation between 54 Cr-rich presolar nanoparticles and Cr-bearing secondary minerals at the millimeter-scale in the bulk samples, likely due to extensive aqueous alteration in their parent bodies that occurred after Solar System birth. In contrast, Ti isotopes were marginally affected by this process. Our results show that isotopic heterogeneities in asteroids are not all nebular or accretionary in nature but can also reflect element redistribution by water.
  • Philippe Schmitt-Kopplin, Norbert Hertkorn, Mourad Harir, Franco Moritz, Marianna Lucio, Lydie Bonal, Eric Quirico, Yoshinori Takano, Jason P. Dworkin, Hiroshi Naraoka, Shogo Tachibana, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hisayoshi Yurimoto, Kanako Sakamoto, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Tatsuaki Okada, Sei-ichiro Watanabe, Yuichi Tsuda, Kenji Hamase, Aogu Furusho, Minako Hashiguchi, Kazuhiko Fukushima, Dan Aoki, José C. Aponte, Eric T. Parker, Daniel P. Glavin, Hannah L. McLain, Jamie E. Elsila, Heather V. Graham, John M. Eiler, Alexander Ruf, Francois-Regis Orthous-Daunay, Junko Isa, Véronique Vuitton, Roland Thissen, Nanako O. Ogawa, Saburo Sakai, Toshihiro Yoshimura, Toshiki Koga, Haruna Sugahara, Naohiko Ohkouchi, Hajime Mita, Yoshihiro Furukawa, Yasuhiro Oba
    Nature Communications 14 1 2023年10月16日 
    Abstract The sample from the near-Earth carbonaceous asteroid (162173) Ryugu is analyzed in the context of carbonaceous meteorites soluble organic matter. The analysis of soluble molecules of samples collected by the Hayabusa2 spacecraft shines light on an extremely high molecular diversity on the C-type asteroid. Sequential solvent extracts of increasing polarity of Ryugu samples are analyzed using mass spectrometry with complementary ionization methods and structural information confirmed by nuclear magnetic resonance spectroscopy. Here we show a continuum in the molecular size and polarity, and no organomagnesium molecules are detected, reflecting a low temperature and water-rich environment on the parent body approving earlier mineralogical and chemical data. High abundance of sulfidic and nitrogen rich compounds as well as high abundance of ammonium ions confirm the water processing. Polycyclic aromatic hydrocarbons are also detected in a structural continuum of carbon saturations and oxidations, implying multiple origins of the observed organic complexity, thus involving generic processes such as earlier carbonization and serpentinization with successive low temperature aqueous alteration.
  • Zelia Dionnet, Stefano Rubino, Alice Aléon‐Toppani, Rosario Brunetto, Akira Tsuchiyama, Cateline Lantz, Zahia Djouadi, Donia Baklouti, Tomoki Nakamura, Ferenc Borondics, Christophe Sandt, Eva Heripre, David Troadec, Obadias Mivumbi, Jérome Aléon, Theo Ternier, Megumi Matsumoto, Kana Amano, Tomoyo Morita, Hisayoshi Yurimoto, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Seiichiro Watanabe, Yuichi Tsuda
    Meteoritics & Planetary Science 2023年09月02日 
    Abstract We report μm‐scale nondestructive infrared (IR) hyperspectral results (IR computed tomography, IR‐CT) in 3‐D and IR surface imaging, IR‐S) in 2‐D, at SOLEIL) combined with X‐ray nano‐computed tomography analyses (at SPring‐8) performed on eight small Ryugu fragments extracted from mm‐sized grains coming both from touchdown first and second sites. We describe the multiscale assembly of phyllosilicates, carbonates, sulfides, oxides, and organics. Two types of silicates, as well as diverse kinds of organic matter, were detected inside Ryugu material. Their spatial correlations are described to discuss the role of the mineralogical microenvironments in the formation/evolution of organic matter. In particular, we have shown that there is a redistribution of the organic matter diffuse component during aqueous alteration on the parent body, with a preferential circulation among fine‐grained phyllosilicates.
  • Moe Matsuoka, Ei-ichi Kagawa, Kana Amano, Tomoki Nakamura, Eri Tatsumi, Takahito Osawa, Takahiro Hiroi, Ralph Milliken, Deborah Domingue, Driss Takir, Rosario Brunetto, Antonella Barucci, Kohei Kitazato, Seiji Sugita, Yuri Fujioka, Osamu Sasaki, Shiho Kobayashi, Takahiro Iwata, Tomokatsu Morota, Yasuhiro Yokota, Toru Kouyama, Rie Honda, Shingo Kameda, Yuichiro Cho, Kazuo Yoshioka, Hirotaka Sawada, Masahiko Hayakawa, Naoya Sakatani, Manabu Yamada, Hidehiko Suzuki, Chikatoshi Honda, Kazunori Ogawa, Kei Shirai, Cateline Lantz, Stefano Rubino, Hisayoshi Yurimoto, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei-ichiro Watanabe, Yuichi Tsuda
    COMMUNICATIONS EARTH & ENVIRONMENT 4 1 2023年09月 
    Returned samples from Cb-type asteroid (162173) Ryugu exhibit very dark spectra in visible and near-infrared ranges, generally consistent with the Hayabusa2 observations. A critical difference is that a structural water absorption of hydrous silicates is around twice as deep in the returned samples compared with those of Ryugu's surface, suggesting Ryugu surface is more dehydrated. Here we use laboratory experiments data to indicate the spectral differences between returned samples and asteroid surface are best explained if Ryugu surface has (1) higher porosity, (2) larger particle size, and (3) more space-weathered condition, with the last being the most effective. On Ryugu, space weathering by micrometeoroid bombardments promoting dehydration seem to be more effective than that by solar-wind implantation. Extremely homogeneous spectra of the Ryugu's global surface is in contrast with the heterogeneous S-type asteroid (25143) Itokawa's spectra, which suggests space weathering has proceeded more rapidly on Cb-type asteroids than S-type asteroids.Samples returned from Ryugu contain fresher material than the space weathered outer asteroid surface observed by remote sensing, according to a comparison of spectral data from returned samples, orbital observations and Murchison meteorite samples.
  • Toshihiro Yoshimura, Yoshinori Takano, Hiroshi Naraoka, Toshiki Koga, Daisuke Araoka, Nanako O. Ogawa, Philippe Schmitt-Kopplin, Norbert Hertkorn, Yasuhiro Oba, Jason P. Dworkin, Jose C. Aponte, Takaaki Yoshikawa, Satoru Tanaka, Naohiko Ohkouchi, Minako Hashiguchi, Hannah Mclain, Eric T. Parker, Saburo Sakai, Mihoko Yamaguchi, Takahiro Suzuki, Tetsuya Yokoyama, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Kanako Sakamoto, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei-ichiro Watanabe, Yuichi Tsuda, Shogo Tachibana, Kenji Hamase, Aogu Furusho, Kazuhiko Fukushima, Dan Aoki, Daniel P. Glavin, Hannah L. Mclain, Jamie E. Elsila, Heather V. Graham, John M. Eiler, Alexander Ruf, Francois-Regis Orthous-Daunay, Cedric Wolters, Junko Isa, Mayu Morita, Veronique Vuitton, Roland Thissen, Shin-ichiro M. Nomura, Haruna Sugahara, Hajime Mita, Yoshihiro Furukawa, Yoshito Chikaraishi, Morihiko Onose, Fumie Kabashima, Kosuke Fujishima, Hajime Sato, Kazunori Sasaki, Kuniyuki Kano, Junken Aoki, Tomoya Yamazaki, Yuki Kimura
    NATURE COMMUNICATIONS 14 1 2023年09月 
    Samples from the carbonaceous asteroid (162173) Ryugu provide information on the chemical evolution of organic molecules in the early solar system. Here we show the element partitioning of the major component ions by sequential extractions of salts, carbonates, and phyllosilicate-bearing fractions to reveal primordial brine composition of the primitive asteroid. Sodium is the dominant electrolyte of the salt fraction extract. Anions and NH4+ are more abundant in the salt fraction than in the carbonate and phyllosilicate fractions, with molar concentrations in the order SO42- > Cl- > S2O32- > NO3- > NH4+. The salt fraction extracts contain anionic soluble sulfur-bearing species such as Sn-polythionic acids (n < 6), C-n-alkylsulfonates, alkylthiosulfonates, hydroxyalkylsulfonates, and hydroxyalkylthiosulfonates (n < 7). The sulfur-bearing soluble compounds may have driven the molecular evolution of prebiotic organic material transforming simple organic molecules into hydrophilic, amphiphilic, and refractory S allotropes.
  • Yoko Kebukawa, Eric Quirico, Emmanuel Dartois, Hikaru Yabuta, Laure Bejach, Lydie Bonal, Alexandre Dazzi, Ariane Deniset‐Besseau, Jean Duprat, Cecile Engrand, Jérémie Mathurin, Jens Barosch, George D. Cody, Bradley De Gregorio, Minako Hashiguchi, Kanami Kamide, David Kilcoyne, Mutsumi Komatsu, Zita Martins, Gilles Montagnac, Smail Mostefaoui, Larry R. Nittler, Takuji Ohigashi, Taiga Okumura, Laurent Remusat, Scott Sandford, Miho Shigenaka, Rhonda Stroud, Hiroki Suga, Yoshio Takahashi, Yasuo Takeichi, Yusuke Tamenori, Maximilien Verdier‐Paoletti, Daisuke Wakabayashi, Shohei Yamashita, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei‐ichiro Watanabe, Yuichi Tsuda
    Meteoritics & Planetary Science 2023年08月19日 [査読有り]
     
    Abstract The infrared spectral characteristics of organic‐rich acid residues prepared from Ryugu samples returned by the JAXA Hayabusa2 mission generally match those from unheated carbonaceous chondrite meteorites, but the residues from Ryugu are richer in methyl and methylene functional groups and have higher CH2/CH3 ratios. Moreover, two distinct outlier carbonaceous phases are found; one with spectral characteristics of N‐H functional groups, likely amides, and a second phase containing less nitrogen. Such infrared characteristics of Ryugu organic matter might indicate the pristine nature of the freshly collected samples and reflect the near‐surface chemistry in the parent asteroid.
  • Yuki Kimura, Takeharu Kato, Toshiaki Tanigaki, Tetsuya Akashi, Hiroto Kasai, Satoshi Anada, Ryuji Yoshida, Kazuo Yamamoto, Tomoki Nakamura, Masahiko Sato, Kana Amano, Mizuha Kikuiri, Tomoyo Morita, Eiichi Kagawa, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Hisayoshi Yurimoto, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Sei-ichiro Watanabe, Yuichi Tsuda, Shogo Tachibana
    SCIENTIFIC REPORTS 13 1 2023年08月 
    In the samples collected from the asteroid Ryugu, magnetite displays natural remanent magnetization due to nebular magnetic field, whereas contemporaneously grown iron sulfide does not display stable remanent magnetization. To clarify this counterintuitive feature, we observed their nanoscale magnetic domain structures using electron holography and found that framboidal magnetites have an external magnetic field of 300 A m(-1), similar to the bulk value, and its magnetic stability was enhanced by interactions with neighboring magnetites, permitting a disk magnetic field to be recorded. Micrometer-sized pyrrhotite showed a multidomain magnetic structure that was unable to retain natural remanent magnetization over a long time due to short relaxation time of magnetic-domain-wall movement, whereas submicron-sized sulfides formed a nonmagnetic phase. These results show that both magnetite and sulfide could have formed simultaneously during the aqueous alteration in the parent body of the asteroid Ryugu.
  • Haolan Tang, Edward D. Young, Lauren Tafla, Andreas Pack, Tommaso Di Rocco, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Kazuhide Nagashima, Izumi Nakai, Ann Nguyen, Larry Nittler, Morihiko Onose, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
    The Planetary Science Journal 4 8 144 - 144 2023年08月01日 
    Abstract We present oxygen isotopic analyses of fragments of the near-Earth Cb-type asteroid Ryugu returned by the Hayabusa2 spacecraft that reinforce the close correspondence between Ryugu and CI chondrites. Small differences between Ryugu samples and CI chondrites in ${ { \rm{\Delta } } }^{ { \prime} 17},{\rm{O } }$ can be explained at least in part by contamination of the latter by terrestrial water. The discovery that a randomly sampled C-complex asteroid is composed of CI-chondrite-like rock, combined with thermal models for formation prior to significant decay of the short-lived radioisotope 26Al, suggests that if lithified at the time of alteration, the parent body was small (≪50 km radius). If the parent planetesimal was large (>50 km in radius), it was likely composed of high-permeability, poorly lithified sediment rather than consolidated rock.
  • Ann. N. Nguyen, Prajkta Mane, Lindsay P. Keller, Laurette Piani, Yoshinari Abe, Jérôme Aléon, Conel M. O'D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Kazuhide Nagashima, David Nesvorný, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
    Science Advances 9 28 2023年07月14日 
    Preliminary analyses of asteroid Ryugu samples show kinship to aqueously altered CI (Ivuna-type) chondrites, suggesting similar origins. We report identification of C-rich, particularly primitive clasts in Ryugu samples that contain preserved presolar silicate grains and exceptional abundances of presolar SiC and isotopically anomalous organic matter. The high presolar silicate abundance (104 ppm) indicates that the clast escaped extensive alteration. The 5 to 10 times higher abundances of presolar SiC (~235 ppm), N-rich organic matter, organics with N isotopic anomalies (1.2%), and organics with C isotopic anomalies (0.2%) in the primitive clasts compared to bulk Ryugu suggest that the clasts formed in a unique part of the protoplanetary disk enriched in presolar materials. These clasts likely represent previously unsampled outer solar system material that accreted onto Ryugu after aqueous alteration ceased, consistent with Ryugu’s rubble pile origin.
  • Wataru Fujiya, Noriyuki Kawasaki, Kazuhide Nagashima, Naoya Sakamoto, Conel M. O’D. Alexander, Noriko T. Kita, Kouki Kitajima, Yoshinari Abe, Jérôme Aléon, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
    Nature Geoscience 16 8 675 - + 2023年07月10日 
    The Hayabusa2 spacecraft explored asteroid Ryugu and brought its surface materials to Earth. Ryugu samples resemble Ivuna-type (CI) chondrites-the most chemically primitive meteorites-and contain secondary phyllosilicates and carbonates, which are indicative of aqueous alteration. Understanding the conditions (such as temperature, redox state and fluid composition) during aqueous alteration is crucial to elucidating how Ryugu evolved to its present state, but little is known about the temporal changes in these conditions. Here we show that calcium carbonate (calcite) grains in Ryugu and Ivuna samples have variable O-18/O-16 and C-13/C-12 ratios that are, respectively, 24-46 & PTSTHOUSND; and 65-108 & PTSTHOUSND; greater than terrestrial standard values, whereas those of calcium-magnesium carbonate (dolomite) grains are much more homogeneous, ranging within 31-36 & PTSTHOUSND; for oxygen and 67-75 & PTSTHOUSND; for carbon. We infer that the calcite precipitated first over a wide range of temperatures and oxygen partial pressures, and that the proportion of gaseous CO2/CO/CH4 molecules changed temporally. By contrast, the dolomite formed later in a more oxygen-rich and thus CO2-dominated environment when the system was approaching equilibrium. The characteristic isotopic compositions of secondary carbonates in Ryugu and Ivuna are not observed for other hydrous meteorites, suggesting a unique evolutionary pathway for their parent asteroid(s).The asteroid Ryugu experienced aqueous alteration under changing temperature and redox conditions, according to an isotopic analysis of secondary calcite and dolomite grains in samples from Ryugu obtained by the Hayabusa2 spacecraft.
  • R. Brunetto, C. Lantz, Y. Fukuda, A. Aléon-Toppani, T. Nakamura, Z. Dionnet, D. Baklouti, F. Borondics, Z. Djouadi, S. Rubino, K. Amano, M. Matsumoto, Y. Fujioka, T. Morita, M. Kukuiri, E. Kagawa, M. Matsuoka, R. Milliken, H. Yurimoto, T. Noguchi, R. Okazaki, H. Yabuta, H. Naraoka, K. Sakamoto, S. Tachibana, T. Yada, M. Nishimura, A. Nakato, A. Miyazaki, K. Yogata, M. Abe, T. Okada, T. Usui, M. Yoshikawa, T. Saiki, S. Tanaka, F. Terui, S. Nakazawa, S. Watanabe, Y. Tsuda
    Astrophysical Journal Letters 951 2 2023年07月01日 
    Ryugu is a second-generation C-type asteroid formed by the reassembly of fragments of a previous larger body in the main asteroid belt. While the majority of Ryugu samples returned by Hayabusa2 are composed of a lithology dominated by aqueously altered minerals, clasts of pristine olivine and pyroxene remain in the least-altered lithologies. These clasts are objects of great interest for revealing the composition of the dust from which the original building blocks of Ryugu's parent asteroid formed. Here we show that some grains rich in olivine, pyroxene, and amorphous silicates discovered in one millimeter-sized stone of Ryugu have infrared spectra similar to the D-type asteroid Hektor (a Jupiter Trojan), to comet Hale-Bopp, and to some anhydrous interplanetary dust particles of probable cometary origin. This result indicates that Ryugu's primary parent body incorporated anhydrous ingredients similar to the building blocks of asteroids (and possibly some comets) formed in the outer solar system, and that Ryugu retained valuable information on the formation and evolution of planetesimals at different epochs of our solar system's history.
  • Keisuke Onodera, Yuta Ino, Satoshi Tanaka, Taichi Kawamura, Rei Kanemaru, Takuya Ishizaki, Ryota Fukai, Takeshi Tsuji, Tomoki Nakamura, Daisuke Nakashima, Masayuki Uesugi, Shogo Tachibana, Seiji Sugita, Hisayoshi Yurimoto, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoru Nakazawa, Fuyuto Terui, Sei-ichiro Watanabe, Yuichi Tsuda
    2023年05月25日 

    The elastic property of asteroids is one of the paramount parameters forunderstanding their physical nature. For example, the rigidity enablesus to discuss the asteroid’s shape and surface features such as cratersand boulders, leading to a better understanding of geomorphological andgeological features on small celestial bodies. The sound velocity allowsus to construct an equation of state that is the most fundamental stepto simulate the formation of small bodies numerically. Moreover, seismicwave velocities and attenuation factors are useful to account forresurfacing caused by impact-induced seismic shaking. The elasticproperty of asteroids thus plays an important role in elucidating theasteroid’s evolution and current geological processes. The Hayabusa2spacecraft brought back the rock samples from C-type asteroid (162173)Ryugu in December 2020. As a part of the initial analysis of returnedsamples, we measured the seismic wave velocity of the Ryugu samplesusing the pulse transmission method. We found that P- and S-wavevelocities of the Ryugu samples were about 2.1 km/s and 1.2 km/s,respectively. We also estimated Young’s modulus of 6.0 – 8.0 GPa. Acomparison of the derived parameters with those of carbonaceouschondrites showed that the Ryugu samples have a similar elastic propertyto the Tagish Lake meteorite, which may have come from a D-typeasteroid. Both Ryugu and Tagish Lake show a high degree of aqueousalteration and few high-temperature components such as chondrules,indicating that they formed in the outer region of the solar system.

  • Noriyuki Kawasaki, Daiki Yamamoto, Sohei Wada, Changkun Park, Hwayoung Kim, Naoya Sakamoto, Hisayoshi Yurimoto
    Meteoritics & Planetary Science 2023年05月15日 
    Al-Mg mineral isochron studies using secondary ion mass spectrometry (SIMS) have revealed the initial Al-26/Al-27 ratios, (Al-26/Al-27)(0), for individual Ca-Al-rich inclusions (CAIs) in meteorites. We find that the relative sensitivity factors of Al-27/Mg-24 ratio for SIMS analysis of hibonite, one of the major constituent minerals of CAIs, exhibit variations based on their chemical compositions. This underscores the critical need for using appropriate hibonite standards to obtain accurate Al-Mg data. We measured the Al-Mg mineral isochron for hibonite in a fine-grained CAI (FGI) from the Northwest Africa 8613 reduced CV chondrite by SIMS using synthesized hibonite standards with Al-27/Mg-24 of similar to 30, similar to 100, and similar to 400. The obtained mineral isochron of hibonite in the FGI yields (Al-26/Al-27)(0) of (4.73 +/- 0.09) x 10(-5), which is identical to that previously obtained from the mineral isochron of spinel and melilite in the same FGI (Kawasaki et al., 2020). The uncertainties of (Al-26/Al-27)(0) indicate that the constituent minerals in the FGI formed within similar to 0.02 Myr in the earliest solar system. The disequilibrium O-isotope distributions of the minerals in the FGI suggest that the O-isotope compositions of the nebular gas from which they condensed underwent a transitional change from O-16-rich to O-16-poor within similar to 0.02 Myr in the earliest solar system. Once formed, the FGI may have been removed from the forming region within similar to 0.02 Myr and transported to the accretion region of the parent body.
  • Elena Dobrica, Hope A. Ishii, John P. Bradley, Kenta Ohtaki, Adrian J. Brearley, Takaaki Noguchi, Toru Matsumoto, Akira Miyake, Yohei Igami, Mitsutaka Haruta, Hikaru Saito, Satoshi Hata, Yusuke Seto, Masaaki Miyahara, Naotaka Tomioka, Hugues Leroux, Corentin Le Guillou, Damien Jacob, Francisco de la Pena, Sylvain Laforet, Maya Marinova, Falko Langenhorst, Dennis Harries, Pierre Beck, Thi H. V. Phan, Rolando Rebois, Neyda M. Abreu, Jennifer Gray, Thomas Zega, Pierre-M. Zanetta, Michelle S. Thompson, Rhonda Stroud, Kate Burgess, Brittany A. Cymes, John C. Bridges, Leon Hicks, Martin R. Lee, Luke Daly, Phil A. Bland, Michael E. Zolensky, David R. Frank, James Martinez, Akira Tsuchiyama, Masahiro Yasutake, Junya Matsuno, Shota Okumura, Itaru Mitsukawa, Kentaro Uesugi, Masayuki Uesugi, Akihisa Takeuchi, Mingqi Sun, Satomi Enju, Aki Takigawa, Tatsuhiro Michikami, Tomoki Nakamura, Megumi Matsumoto, Yusuke Nakauchi, Hisayoshi Yurimoto, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei-ichiro Watanabe, Yuichi Tsuda
    GEOCHIMICA ET COSMOCHIMICA ACTA 346 65 - 75 2023年04月 
    We have investigated several particles collected during each of two touchdowns of the Hayabusa2 space-craft at the surface of the C-type asteroid 162173 Ryugu using various electron microscope techniques. Our detailed transmission electron microscopy study shows the presence of magnetite with various mor-phologies coexisting in close proximity. This is characteristic of CI chondrite-like materials and consistent with the mineral assemblages and compositions in the Ryugu parent body. We describe the microstruc-tural characteristics of magnetite with different morphologies, which could have resulted from the chem-ical conditions (growth vs. diffusion rate) during their formation. Furthermore, we describe the presence of magnetites with a spherulitic structure composed of individual radiating fibers that are characterized by pervasive, homogeneously distributed euhedral to subhedral pores that have not been described in previous chondrite studies. This particular spherulitic structure is consistent with crystallization under nonequilibrium conditions. Additionally, the presence of a high density of defects within the magnetite fibers, the high surface/volume ratio of this morphology, and the presence of amorphous materials in sev-eral pores and at the edges of the acicular fibers further support their formation under nonequilibrium conditions. We suggest that the growth processes that lead to this structure result from the solution reaching a supersaturated state, resulting in an adjustment to a lower free energy condition via nucle-ation and rapid growth.(c) 2023 Elsevier Ltd. All rights reserved.
  • Laurette Piani, Kazuhide Nagashima, Noriyuki Kawasaki, Naoya Sakamoto, Ken-ichi Bajo, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Liping Qin, Sara S. Russell, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
    The Astrophysical Journal Letters 946 2 L43 - L43 2023年04月01日 [査読有り]
     
    Abstract Rock fragments of the Cb-type asteroid Ryugu returned to Earth by the JAXA Hayabusa2 mission share mineralogical, chemical, and isotopic properties with the Ivuna-type (CI) carbonaceous chondrites. Similar to CI chondrites, these fragments underwent extensive aqueous alteration and consist predominantly of hydrous minerals likely formed in the presence of liquid water on the Ryugu parent asteroid. Here we present an in situ analytical survey performed by secondary ion mass spectrometry from which we have estimated the D/H ratio of Ryugu’s hydrous minerals, D/HRyugu, to be [165 ± 19] × 10−6, which corresponds to δDRyugu = +59 ± 121‰ (2σ). The hydrous mineral D/HRyugu’s values for the two sampling sites on Ryugu are similar; they are also similar to the estimated D/H ratio of hydrous minerals in the CI chondrites Orgueil and Alais. This result reinforces a link between Ryugu and CI chondrites and an inference that Ryugu’s samples, which avoided terrestrial contamination, are our best proxy to estimate the composition of water at the origin of hydrous minerals in CI-like material. Based on this data and recent literature studies, the contribution of CI chondrites to the hydrogen of Earth’s surficial reservoirs is evaluated to be ∼3%. We conclude that the water responsible for the alteration of Ryugu’s rocks was derived from water ice precursors inherited from the interstellar medium; the ice partially re-equilibrated its hydrogen with the nebular H2 before being accreted on the Ryugu’s parent asteroid.
  • Takuya Ishizaki, Hosei Nagano, Satoshi Tanaka, Naoya Sakatani, Tomoki Nakamura, Tatsuaki Okada, Ryohei Fujita, Abdulkareem Alasli, Tomoyo Morita, Mizuha Kikuiri, Kana Amano, Eiichi Kagawa, Hisayoshi Yurimoto, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Sei ichiro Watanabe, Yuichi Tsuda
    International Journal of Thermophysics 44 4 2023年04月 [査読有り]
     
    The thermophysical properties of small Solar System bodies are essential to be determined, on which the thermal evolution of small bodies largely depends. The carbonaceous asteroid Ryugu is one of the small undifferentiated bodies formed in the early Solar System. Hayabusa2 explored the asteroid Ryugu and returned the surface samples in 2020 for detailed on-ground investigation, including measurements of thermal properties. Because the available sample amount was limited, this study developed a novel method to measure the thermal diffusivity of small and irregularly shaped samples of about 1 mm in diameter by combining lock-in thermography and periodic heating methods on the microscale. This method enables us to measure the thermal diffusivity of both flat-plate and granular shape samples by selecting the suitable detecting direction of the temperature response. Especially, when the sample has a flat-plate shape, the anisotropic distribution of the in-plane thermal diffusivity can be evaluated. This method was applied to six Ryugu samples, and the detailed anisotropic distribution of the thermal diffusivity was obtained. The measurement results showed that the samples show local thermal anisotropy caused by cracks and voids. The average thermal diffusivity among all samples was (2.8 to 5.8) × 10−7 m2·s. Based on the density and specific heat of the samples obtained independently, the thermal effusivity was estimated to be 791 J·(s1/2·m2·K) to 1253 J·(s1/2·m2·K), which is defined as the resistance of surface temperature to the change of thermal input. The determined thermal effusivity, often called thermal inertia in planetary science, is larger than the observed value of 225 ± 45 J· (s1/2·m2·K) of the asteroid Ryugu's surface, obtained from the diurnal temperature change of the rotating asteroid by a thermal infrared camera onboard Hayabuas2. This difference is likely to be attributed to the difference in the analytical scale between the sample and the surface boulders compared with the thermal diffusion length. Consequently, it was found that the present result is more representative of the thermal diffusivity and thermal inertia of local part of individual Ryugu particles.
  • Eric T. Parker, Hannah L. McLain, Daniel P. Glavin, Jason P. Dworkin, Jamie E. Elsila, José C. Aponte, Hiroshi Naraoka, Yoshinori Takano, Shogo Tachibana, Hikaru Yabuta, Hisayoshi Yurimoto, Kanako Sakamoto, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Satoru Nakazawa, Yuichi Tsuda, Fuyuto Terui, Takaaki Noguchi, Ryuji Okazaki, Sei-ichiro Watanabe, Tomoki Nakamura
    Geochimica et Cosmochimica Acta 347 42 - 57 2023年04月 
    The hot water and acid extracts of two different Ryugu samples collected by the Hayabusa2 mission were analyzed for the presence of aliphatic amines and amino acids. The abundances and relative distributions of both classes of molecules were determined, as well as the enantiomeric compositions of the chiral amino acids. The Ryugu samples studied here were recovered from sample chambers A and C, which were composed of surface material, and a combination of surface and possible subsurface material, respectively. A total of thirteen amino acids were detected and quantitated in these samples, with an additional five amino acids that were tentatively identified but not quantitated. The abundances of four aliphatic amines identified in the Ryugu samples were also determined in the current work. Amino acids were observed in the acid hydrolyzed and unhydrolyzed hot water extracts of asteroid Ryugu regolith using liquid chromatography with UV fluorescence detection and high-resolution mass spectrometry. Conversely, aliphatic amines were only analyzed in the unhydrolyzed hot water Ryugu extracts. Two-to six-carbon (C-2-C-6) amino acids with individual abundances ranging from 0.02 to 15.8 nmol g(-1), and one- to three-carbon (C-1-C-3) aliphatic amines with individual abundances from 0.05 to 34.14 nmol g(-1), were found in the hot water extracts. Several non-protein amino acids that are rare in biology, including beta-amino-n-butyric acid (beta-ABA) and beta-aminoisobuytric acid (beta-AIB), were racemic or very nearly racemic, thus indicating their likely abiotic origins. Trace amounts of select protein amino acids that were enriched in the L-enantiomer may indicate low levels of terrestrial amino acid contamination in the samples. However, the presence of elevated abundances of free and racemic alanine, a common protein amino acid in terrestrial biology, and elevated abundances of the predominately free and racemic nonprotein amino acids, b-ABA and b-AIB, indicate that many of the amino acids detected in the Ryugu water extracts were indigenous to the samples. Although the Ryugu samples have been found to be chemically similar to CI type carbonaceous chondrites, the measured concentrations and relative distributions of amino acids and aliphatic amines in Ryugu samples were notably different from those previously observed for the CI1.1 carbonaceous chondrite, Orgueil. This discrepancy could be the result of differences in the original chemical compositions of the parent bodies and/or alteration conditions, such as space weathering. In addition to alpha-amino acids that could have been formed by Strecker cyanohydrin synthesis during a low temperature aqueous alteration phase, beta-, gamma-, and delta-amino acids, including C-3 - C-5 straight-chain n-x-amino acids that are not formed by Strecker synthesis, were also observed in the Ryugu extracts. The suite of amino acids measured in the Ryugu samples indicates that multiple amino acid formation mechanisms were active on the Ryugu parent body. The analytical techniques used here are well-suited to search for similar analytes in asteroid Bennu material collected by the NASA OSIRIS-REx mission scheduled for Earth return in September 2023. (C) 2023 Published by Elsevier Ltd.
  • Yasuhiro Oba, Toshiki Koga, Yoshinori Takano, Nanako O. Ogawa, Naohiko Ohkouchi, Kazunori Sasaki, Hajime Sato, Daniel P. Glavin, Jason P. Dworkin, Hiroshi Naraoka, Shogo Tachibana, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Kanako Sakamoto, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei-ichiro Watanabe, Yuichi Tsuda
    Nature Communications 14 1 2023年03月21日 
    Abstract The pristine sample from the near-Earth carbonaceous asteroid (162173) Ryugu collected by the Hayabusa2 spacecraft enabled us to analyze the pristine extraterrestrial material without uncontrolled exposure to the Earth’s atmosphere and biosphere. The initial analysis team for the soluble organic matter reported the detection of wide variety of organic molecules including racemic amino acids in the Ryugu samples. Here we report the detection of uracil, one of the four nucleobases in ribonucleic acid, in aqueous extracts from Ryugu samples. In addition, nicotinic acid (niacin, a B3 vitamer), its derivatives, and imidazoles were detected in search for nitrogen heterocyclic molecules. The observed difference in the concentration of uracil between A0106 and C0107 may be related to the possible differences in the degree of alteration induced by energetic particles such as ultraviolet photons and cosmic rays. The present study strongly suggests that such molecules of prebiotic interest commonly formed in carbonaceous asteroids including Ryugu and were delivered to the early Earth.
  • M. W. Broadley, D. J. Byrne, E. Füri, L. Zimmermann, B. Marty, R. Okazaki, T. Yada, F. Kitajima, S. Tachibana, K. Yogata, K. Sakamoto, H. Yurimoto, T. Nakamura, T. Noguchi, H. Naraoka, H. Yabuta, S. Watanabe, Y. Tsuda, M. Nishimura, A. Nakato, A. Miyazaki, M. Abe, T. Okada, T. Usui, M. Yoshikawa, T. Saiki, S. Tanaka, F. Terui, S. Nakazawa, H. Busemann, K. Hashizume, J. D. Gilmour, A. Meshik, M. E.I. Riebe, D. Krietsch, C. Maden, A. Ishida, P. Clay, S. A. Crowther, L. Fawcett, T. Lawton, O. Pravdivtseva, Y. N. Miura, J. Park, K. Bajo, Y. Takano, K. Yamada, S. Kawagucci, Y. Matsui, M. Yamamoto, K. Righter, S. Sakai, N. Iwata, N. Shirai, S. Sekimoto, M. Inagaki, M. Ebihara, R. Yokochi, K. Nishiizumi, K. Nagao, J. I. Lee, A. Kano, M. W. Caffee, R. Uemura
    Geochimica et Cosmochimica Acta 345 62 - 74 2023年03月15日 
    Carbonaceous chondrites are considered to have originated from C-type asteroids and represent some of the most primitive material in our solar system. Furthermore, since carbonaceous chondrites can contain significant quantities of volatile elements, they may have played a crucial role in supplying volatiles and organic material to Earth and other inner solar system bodies. However, a major challenge of unravelling the volatile composition of chondritic meteorites is distinguishing between which features were inherited from the parent body, and what may be a secondary feature attributable to terrestrial weathering. In December 2020, the Hayabusa2 mission of the Japan Aerospace Exploration Agency (JAXA) successfully returned surface material from the C-type asteroid (162173) Ryugu to Earth. This material has now been classified as closely resembling CI-type chondrites, which are the most chemically pristine meteorites. The analysis of material from the surface of Ryugu therefore provides a unique opportunity to analyse the volatile composition of material that originated from a CI-type asteroid without the complications arising from terrestrial contamination. Given their highly volatile nature, the noble gas and nitrogen inventories of chondrites are highly sensitive to different alteration processes on the asteroid parent body, and to terrestrial contamination. Here, we investigate the nitrogen and noble gas signature of two pelletized grains collected from the first and second touchdown sites (Okazaki et al., 2022a), to provide an insight into the formation and alteration history of Ryugu. The concentration of trapped noble gas in the Ryugu samples is greater than the average composition of previously measured CI chondrites and are primarily derived from phase Q, although a significant contribution of presolar nanodiamond Xe-HL is noted. The large noble gas concentrations coupled with a significant contribution of presolar nanodiamonds suggests that the Ryugu samples may represent some of the most primitive unprocessed material from the early solar system. In contrast to the noble gases, the abundance of nitrogen and δ15N composition of the two Ryugu pellets are lower than the average CI chondrite value. We attribute the lower nitrogen abundances and δ15N measured in this study to the preferential loss of a 15N-rich phase from our samples during aqueous alteration on the parent planetesimal. The analyses of other grains returned from Ryugu have shown large variations in nitrogen concentrations and δ15N indicating that alteration fluids heterogeneously interacted with material now present on the surface of Ryugu. Finally, the ratio of trapped noble gases to nitrogen is higher than CI chondrites, and is closer to refractory phase Q and nanodiamonds. This indicates that Ryugu experienced aqueous alteration that led to the significant and variable loss of nitrogen, likely from soluble organic matter, without modification of the noble gas budget, which is primarily hosted in insoluble organic matter and presolar diamonds and is therefore more resistant to aqueous alteration.
  • Emmanuel Dartois, Yoko Kebukawa, Hikaru Yabuta, Jérémie Mathurin, Cécile Engrand, Jean Duprat, Laure Bejach, Alexandre Dazzi, Ariane Deniset-Besseau, Lydie BONAL, Eric Quirico, Christophe Sandt, Ferenc Borondics, Jens Barosch, George D. Cody, Bradley De Gregorio, MINAKO HASHIGUCHI, David A. L. Kilcoyne, Mutsumi Komatsu, Zita Martins, Megumi Matsumoto, Gilles Montagnac, Smail Mostefaoui, Larry R. Nittler, Takuji Ohigashi, Taiga Okumura, Laurent Remusat, Scott Sandford, Miho Shigenaka, Rhonda Stroud, Hiroki Suga, Yoshio Takahashi, Yasuo Takeichi, Yusuke Tamenori, Maximilien Verdier-Paoletti, Shohei Yamashita, Tomoki Nakamura, Tomoyo Morita, Mizuha Kikuiri, Kana Amano, Eiichi Kagawa, Takaaki Noguchi, Hiroshi Naraoka, Ryuji Okazaki, Kanako Sakamoto, Hisayoshi Yurimoto, Masanao Abe, Kanami Kamide, Akiko Miyazaki, Aiko Nakato, Satoru Nakazawa
    Astronomy & Astrophysics 671 2023年03月 
    Context. The current period is conducive to exploring our Solar System's origins with recent and future space sample return missions, which provide invaluable information from known Solar System asteroids and comets The Hayabusa2 mission of the Japan Aerospace Exploration Agency (JAXA) recently brought back samples from the surface of the Ryugu carbonaceous asteroid. Aims. We aim to identify the different forms of chemical composition of organic matter and minerals that constitute these Solar System primitive objects, to shed light on the Solar System's origins. Methods. In this work, we recorded infrared (IR) hyper-spectral maps of whole-rock Ryugu asteroid samples at the highest achievable spatial resolution with a synchrotron in the mid-IR (MIR). Additional global far-IR (FIR) spectra of each sample were also acquired. Results. The hyper-spectral maps reveal the variability of the functional groups at small scales and the intimate association of phyl-losilicates with the aliphatic components of the organic matter present in Ryugu. The relative proportion of column densities of the identified IR functional groups (aliphatics, hydroxyl + interlayer and/or physisorbed water, carbonyl, carbonates, and silicates) giving access to the composition of the Ryugu samples is estimated from these IR hyper-spectral maps. Phyllosilicate spectra reveal the presence of mixtures of serpentine and saponite. We do not detect anhydrous silicates in the samples analysed, at the scales probed. The carbonates are dominated by dolomite. Aliphatics organics are distributed over the whole samples at the micron scale probed with the synchrotron, and intimately mixed with the phyllosilicates. The aromatic C=C contribution could not be safely deconvolved from OH in most spectra, due to the ubiquitous presence of hydrated minerals. The peak intensity ratios of the organics methylene to methyl (CH2/CH3) of the Ryugu samples vary between about 1.5 and 2.5, and are compared to the ratios in chondrites from types 1 to 3. Overall, the mineralogical and organic characteristics of the Ryugu samples show similarities with those of CI chondrites, although with a noticeably higher CH2/CH3 in Ryugu than generally measured in C1 chondrites collected on Earth, and possibly a higher carbonate content.
  • J.-C. Viennet, M. Roskosz, T. Nakamura, P. Beck, B. Baptiste, B. Lavina, E.E. Alp, M.Y. Hu, J. Zhao, M. Gounelle, R. Brunetto, H. Yurimoto, T. Noguchi, R. Okazaki, H. Yabuta, H. Naraoka, K. Sakamoto, S. Tachibana, T. Yada, M. Nishimura, A. Nakato, A. Miyazaki, K. Yogata, M. Abe, T. Okada, T. Usui, M. Yoshikawa, T. Saiki, S. Tanaka, F. Terui, S. Nakazawa, S.-I. Watanabe, Y. Tsuda
    Geochemical Perspectives Letters 25 8 - 12 2023年03月
  • Hiroshi Naraoka, Yoshinori Takano, Jason P. Dworkin, Yasuhiro Oba, Kenji Hamase, Aogu Furusho, Nanako O. Ogawa, Minako Hashiguchi, Kazuhiko Fukushima, Dan Aoki, Philippe Schmitt-Kopplin, José C. Aponte, Eric T. Parker, Daniel P. Glavin, Hannah L. McLain, Jamie E. Elsila, Heather V. Graham, John M. Eiler, Francois Regis Orthous-Daunay, Cédric Wolters, Junko Isa, Véronique Vuitton, Roland Thissen, Saburo Sakai, Toshihiro Yoshimura, Toshiki Koga, Naohiko Ohkouchi, Yoshito Chikaraishi, Haruna Sugahara, Hajime Mita, Yoshihiro Furukawa, Norbert Hertkorn, Alexander Ruf, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Kanako Sakamoto, Shogo Tachibana, Harold C. Connolly, Dante S. Lauretta, Masanao Abe, Toru Yada, Masahiro Nishimura, Kasumi Yogata, Aiko Nakato, Miwa Yoshitake, Ayako Suzuki, Akiko Miyazaki, Shizuho Furuya, Kentaro Hatakeda, Hiromichi Soejima, Yuya Hitomi, Kazuya Kumagai, Tomohiro Usui, Tasuku Hayashi, Daiki Yamamoto, Ryota Fukai, Kohei Kitazato, Seiji Sugita, Noriyuki Namiki, Masahiko Arakawa, Hitoshi Ikeda, Masateru Ishiguro, Naru Hirata, Koji Wada, Yoshiaki Ishihara, Rina Noguchi, Tomokatsu Morota, Naoya Sakatani, Koji Matsumoto, Hiroki Senshu, Rie Honda, Eri Tatsumi, Yasuhiro Yokota, Chikatoshi Honda, Tatsuhiro Michikami, Moe Matsuoka, Akira Miura, Hirotomo Noda, Tetsuya Yamada, Keisuke Yoshihara, Kosuke Kawahara, Masanobu Ozaki, Yu Ichi Iijima, Hajime Yano, Masahiko Hayakawa, Takahiro Iwata, Ryudo Tsukizaki, Hirotaka Sawada, Satoshi Hosoda, Kazunori Ogawa, Chisato Okamoto, Naoyuki Hirata, Kei Shirai, Yuri Shimaki, Manabu Yamada, Tatsuaki Okada, Yukio Yamamoto
    Science 379 6634 eabn9033 - + 2023年02月24日 [査読有り][通常論文]
     
    The Hayabusa2 spacecraft collected samples from the surface of the carbonaceous near-Earth asteroid (162173) Ryugu and brought them to Earth. The samples were expected to contain organic molecules, which record processes that occurred in the early Solar System. We analyzed organic molecules extracted from the Ryugu surface samples. We identified a variety of molecules containing the atoms CHNOS, formed by methylation, hydration, hydroxylation, and sulfurization reactions. Amino acids, aliphatic amines, carboxylic acids, polycyclic aromatic hydrocarbons, and nitrogen-heterocyclic compounds were detected, which had properties consistent with an abiotic origin. These compounds likely arose from an aqueous reaction on Ryugu’s parent body and are similar to the organics in Ivuna-type meteorites. These molecules can survive on the surfaces of asteroids and be transported throughout the Solar System.
  • Hikaru Yabuta, George D. Cody, Cécile Engrand, Yoko Kebukawa, Bradley De Gregorio, Lydie Bonal, Laurent Remusat, Rhonda Stroud, Eric Quirico, Larry Nittler, Minako Hashiguchi, Mutsumi Komatsu, Taiga Okumura, Jérémie Mathurin, Emmanuel Dartois, Jean Duprat, Yoshio Takahashi, Yasuo Takeichi, David Kilcoyne, Shohei Yamashita, Alexandre Dazzi, Ariane Deniset-Besseau, Scott Sandford, Zita Martins, Yusuke Tamenori, Takuji Ohigashi, Hiroki Suga, Daisuke Wakabayashi, Maximilien Verdier-Paoletti, Smail Mostefaoui, Gilles Montagnac, Jens Barosch, Kanami Kamide, Miho Shigenaka, Laure Bejach, Megumi Matsumoto, Yuma Enokido, Takaaki Noguchi, Hisayoshi Yurimoto, Tomoki Nakamura, Ryuji Okazaki, Hiroshi Naraoka, Kanako Sakamoto, Harold C. Connolly, Dante S. Lauretta, Masanao Abe, Tatsuaki Okada, Toru Yada, Masahiro Nishimura, Kasumi Yogata, Aiko Nakato, Miwa Yoshitake, Ayako Iwamae, Shizuho Furuya, Kentaro Hatakeda, Akiko Miyazaki, Hiromichi Soejima, Yuya Hitomi, Kazuya Kumagai, Tomohiro Usui, Tasuku Hayashi, Daiki Yamamoto, Ryota Fukai, Seiji Sugita, Kohei Kitazato, Naru Hirata, Rie Honda, Tomokatsu Morota, Eri Tatsumi, Naoya Sakatani, Noriyuki Namiki, Koji Matsumoto, Rina Noguchi, Koji Wada, Hiroki Senshu, Kazunori Ogawa, Yasuhiro Yokota, Yoshiaki Ishihara, Yuri Shimaki, Manabu Yamada, Chikatoshi Honda, Tatsuhiro Michikami, Moe Matsuoka, Naoyuki Hirata, Masahiko Arakawa, Chisato Okamoto, Masateru Ishiguro, Ralf Jaumann, Jean-Pierre Bibring, Matthias Grott, Stefan Schröder, Katharina Otto, Cedric Pilorget, Nicole Schmitz, Jens Biele, Tra-Mi Ho, Aurélie Moussi-Soffys, Akira Miura, Hirotomo Noda, Tetsuya Yamada, Keisuke Yoshihara, Kosuke Kawahara, Hitoshi Ikeda, Yukio Yamamoto, Kei Shirai, Shota Kikuchi, Naoko Ogawa, Hiroshi Takeuchi, Go Ono, Yuya Mimasu, Kent Yoshikawa, Yuto Takei, Atsushi Fujii, Yu-ichi Iijima, Satoru Nakazawa, Satoshi Hosoda, Takahiro Iwata, Masahiko Hayakawa, Hirotaka Sawada, Hajime Yano, Ryudo Tsukizaki, Masanobu Ozaki, Fuyuto Terui, Satoshi Tanaka, Masaki Fujimoto, Makoto Yoshikawa, Takanao Saiki, Shogo Tachibana, Sei-ichiro Watanabe, Yuichi Tsuda
    Science 379 6634 790 - U66 2023年02月24日 
    Samples of the carbonaceous asteroid (162173) Ryugu were collected and brought to Earth by the Hayabusa2 spacecraft. We investigated the macromolecular organic matter in Ryugu samples and found that it contains aromatic and aliphatic carbon, ketone, and carboxyl functional groups. The spectroscopic features of the organic matter are consistent with those in chemically primitive carbonaceous chondrite meteorites that experienced parent-body aqueous alteration (reactions with liquid water). The morphology of the organic carbon includes nanoglobules and diffuse carbon associated with phyllosilicate and carbonate minerals. Deuterium and/or nitrogen-15 enrichments indicate that the organic matter formed in a cold molecular cloud or the presolar nebula. The diversity of the organic matter indicates variable levels of aqueous alteration on Ryugu’s parent body.
  • Daisuke Nakashima, Tomoki Nakamura, Mingming Zhang, Noriko T. Kita, Takashi Mikouchi, Hideto Yoshida, Yuma Enokido, Tomoyo Morita, Mizuha Kikuiri, Kana Amano, Eiichi Kagawa, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Satoru Nakazawa, Fuyuto Terui, Hisayoshi Yurimoto, Takaaki Noguchi, Hikaru Yabuta, Hiroshi Naraoka, Ryuji Okazaki, Kanako Sakamoto, Sei-ichiro Watanabe, Shogo Tachibana, Yuichi Tsuda
    Nature Communications 14 1 532 - 532 2023年02月16日 [査読有り]
     
    Abstract Chondrule-like objects and Ca-Al-rich inclusions (CAIs) are discovered in the retuned samples from asteroid Ryugu. Here we report results of oxygen isotope, mineralogical, and compositional analysis of the chondrule-like objects and CAIs. Three chondrule-like objects dominated by Mg-rich olivine are 16O-rich and -poor with Δ17O (=δ17O – 0.52 × δ18O) values of ~ –23‰ and ~ –3‰, resembling what has been proposed as early generations of chondrules. The 16O-rich objects are likely to be melted amoeboid olivine aggregates that escaped from incorporation into 16O-poor chondrule precursor dust. Two CAIs composed of refractory minerals are 16O-rich with Δ17O of ~ –23‰ and possibly as old as the oldest CAIs. The discovered objects (<30 µm) are as small as those from comets, suggesting radial transport favoring smaller objects from the inner solar nebula to the formation location of the Ryugu original parent body, which is farther from the Sun and scarce in chondrules. The transported objects may have been mostly destroyed during aqueous alteration in the Ryugu parent body.
  • Ryuji Okazaki, Bernard Marty, Henner Busemann, Ko Hashizume, Jamie D. Gilmour, Alex Meshik, Toru Yada, Fumio Kitajima, Michael W. Broadley, David Byrne, Evelyn Fueri, My E. I. Riebe, Daniela Krietsch, Colin Maden, Akizumi Ishida, Patricia Clay, Sarah A. Crowther, Lydia Fawcett, Thomas Lawton, Olga Pravdivtseva, Yayoi N. Miura, Jisun Park, Ken-ichi Bajo, Yoshinori Takano, Keita Yamada, Shinsuke Kawagucci, Yohei Matsui, Mizuki Yamamoto, Kevin Righter, Saburo Sakai, Naoyoshi Iwata, Naoki Shirai, Shun Sekimoto, Makoto Inagaki, Mitsuru Ebihara, Reika Yokochi, Kunihiko Nishiizumi, Keisuke Nagao, Jong Ik Lee, Akihiro Kano, Marc W. Caffee, Ryu Uemura, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Hikaru Yabuta, Hisayoshi Yurimoto, Shogo Tachibana, Hirotaka Sawada, Kanako Sakamoto, Masanao Abe, Masahiko Arakawa, Atsushi Fujii, Masahiko Hayakawa, Naoyuki Hirata, Naru Hirata, Rie Honda, Chikatoshi Honda, Satoshi Hosoda, Yu-ichi Iijima, Hitoshi Ikeda, Masateru Ishiguro, Yoshiaki Ishihara, Takahiro Iwata, Kosuke Kawahara, Shota Kikuchi, Kohei Kitazato, Koji Matsumoto, Moe Matsuoka, Tatsuhiro Michikami, Yuya Mimasu, Akira Miura, Tomokatsu Morota, Satoru Nakazawa, Noriyuki Namiki, Hirotomo Noda, Rina Noguchi, Naoko Ogawa, Kazunori Ogawa, Tatsuaki Okada, Chisato Okamoto, Go Ono, Masanobu Ozaki, Takanao Saiki, Naoya Sakatani, Hiroki Senshu, Yuri Shimaki, Kei Shirai, Seiji Sugita, Yuto Takei, Hiroshi Takeuchi, Satoshi Tanaka, Eri Tatsumi, Fuyuto Terui, Ryudo Tsukizaki, Koji Wada, Manabu Yamada, Tetsuya Yamada, Yukio Yamamoto, Hajime Yano, Yasuhiro Yokota, Keisuke Yoshihara, Makoto Yoshikawa, Kent Yoshikawa, Shizuho Furuya, Kentaro Hatakeda, Tasuku Hayashi, Yuya Hitomi, Kazuya Kumagai, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Hiromichi Soejima, Ayako Iwamae, Daiki Yamamoto, Kasumi Yogata, Miwa Yoshitake, Ryota Fukai, Tomohiro Usui, Harold C. Connolly Jr, Dante Lauretta, Sei-ichiro Watanabe, Yuichi Tsuda
    SCIENCE 379 6634 788 - U52 2023年02月 
    The near-Earth carbonaceous asteroid (162173) Ryugu is expected to contain volatile chemical species that could provide information on the origin of Earth's volatiles. Samples of Ryugu were retrieved by the Hayabusa2 spacecraft. We measured noble gas and nitrogen isotopes in Ryugu samples and found that they are dominated by presolar and primordial components, incorporated during Solar System formation. Noble gas concentrations are higher than those in Ivuna-type carbonaceous (CI) chondrite meteorites. Several host phases of isotopically distinct nitrogen have different abundances among the samples. Our measurements support a close relationship between Ryugu and CI chondrites. Noble gases produced by galactic cosmic rays, indicating a similar to 5 million year exposure, and from implanted solar wind record the recent irradiation history of Ryugu after it migrated to its current orbit.
  • Stefano Rubino, Zélia Dionnet, Alice Aléon-Toppani, Rosario Brunetto, Tomoki Nakamura, Donia Baklouti, Zahia Djouadi, Cateline Lantz, Obadias Mivumbi, Ferenc Borondics, Stephane Lefrançois, Christophe Sandt, Francesco Capitani, Eva Héripré, David Troadec, Megumi Matsumoto, Kana Amano, Tomoyo Morita, Hisayoshi Yurimoto, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Seiichiro Watanabe, Yuichi Tsuda
    Earth, Planets and Space 75 1 2023年01月09日 
    Abstract Sample-return missions allow the study of materials collected directly from celestial bodies, unbiased by atmospheric entry effects and/or terrestrial alteration and contamination phenomena, using state-of-the-art techniques which are available only in a laboratory environment—but only if the collected material stays pristine. The scarcity of outer-space unaltered material recovered until now makes this material extremely precious for the potential scientific insight it can bring. To maximize the scientific output of current and future sample-return missions, the scientific community needs to plan for ways of storing, handling, and measuring this precious material while preserving their pristine state for as long as the ‘invasiveness’ of measurements allows. In July 2021, as part of the Hayabusa2 (JAXA) “Stone” preliminary examination team, we received several microscopic particles from the asteroid Ryugu, with the goal of performing IR hyper-spectral imaging and IR micro-tomography studies. Here, we describe the sample transfer, handling methods and analytical pipeline we implemented to study this very precious material while minimizing and surveilling their alteration history on Earth. Graphical Abstract
  • Alexander Meshik, Olga Pravdivtseva, Ryuji Okazaki, Kasumi Yogata, Toru Yada, Fumio Kitajima, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Sakai, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Seiichiro Watanabe, Yuichi Tsuda, Hayabusa2 Initial Analysis Volatile Team
    Journal of Analytical Atomic Spectrometry 2023年 
    Mass spectrometry of noble gas isotopes from the asteroid materials delivered by robotic space missions requires high sensitivity, high ion transmission, low detection limit, and other characteristics not readily available in commercial instruments.
  • Noriyuki Kawasaki, Kazuhide Nagashima, Naoya Sakamoto, Toru Matsumoto, Ken-ichi Bajo, Sohei Wada, Yohei Igami, Akira Miyake, Takaaki Noguchi, Daiki Yamamoto, Sara S. Russell, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
    Science Advances 8 50 2022年12月16日 
    The extraterrestrial materials returned from asteroid (162173) Ryugu consist predominantly of low-temperature aqueously formed secondary minerals and are chemically and mineralogically similar to CI (Ivuna-type) carbonaceous chondrites. Here, we show that high-temperature anhydrous primary minerals in Ryugu and CI chondrites exhibit a bimodal distribution of oxygen isotopic compositions: 16 O-rich (associated with refractory inclusions) and 16 O-poor (associated with chondrules). Both the 16 O-rich and 16 O-poor minerals probably formed in the inner solar protoplanetary disk and were subsequently transported outward. The abundance ratios of the 16 O-rich to 16 O-poor minerals in Ryugu and CI chondrites are higher than in other carbonaceous chondrite groups but are similar to that of comet 81P/Wild2, suggesting that Ryugu and CI chondrites accreted in the outer Solar System closer to the accretion region of comets.
  • Marine Paquet, Frederic Moynier, Tetsuya Yokoyama, Wei Dai, Yan Hu, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Izumi Nakai, Kazuhide Nagashima, David Nesvorný, Ann N. Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
    Nature Astronomy 7 2 182 - 189 2022年12月12日 
    Initial analyses showed that asteroid Ryugu's composition is close to CI (Ivuna-like) carbonaceous chondrites (CCs) - the chemically most primitive meteorites, characterized by near-solar abundances for most elements. However, some isotopic signatures (for example, Ti, Cr) overlap with other CC groups, so the details of the link between Ryugu and the CI chondrites are not yet fully clear. Here we show that Ryugu and CI chondrites have the same zinc and copper isotopic composition. As the various chondrite groups have very distinct Zn and Cu isotopic signatures, our results point at a common genetic heritage between Ryugu and CI chondrites, ruling out any affinity with other CC groups. Since Ryugu's pristine samples match the solar elemental composition for many elements, their Zn and Cu isotopic compositions likely represent the best estimates of the solar composition. Earth's mass-independent Zn isotopic composition is intermediate between Ryugu/CC and non-carbonaceous chondrites (NCs), suggesting a contribution of Ryugu-like material to Earth's budgets of Zn and other moderately volatile elements.
  • Takaaki Noguchi, Toru Matsumoto, Akira Miyake, Yohei Igami, Mitsutaka Haruta, Hikaru Saito, Satoshi Hata, Yusuke Seto, Masaaki Miyahara, Naotaka Tomioka, Hope A. Ishii, John P. Bradley, Kenta K. Ohtaki, Elena Dobrica, Hugues Leroux, Corentin Le Guillou, Damien Jacob, Francisco de la Pena, Sylvain Laforet, Maya Marinova, Falko Langenhorst, Dennis Harries, Pierre Beck, Thi H. Phan, Rolando Rebois, Neyda M. Abreu, Jennifer Gray, Thomas Zega, Pierre-M Zanetta, Michelle S. Thompson, Rhonda Stroud, Kate Burgess, Brittany A. Cymes, John C. Bridges, Leon Hicks, Martin R. Lee, Luke Daly, Phil A. Bland, Michael E. Zolensky, David R. Frank, James Martinez, Akira Tsuchiyama, Masahiro Yasutake, Junya Matsuno, Shota Okumura, Itaru Mitsukawa, Kentaro Uesugi, Masayuki Uesugi, Akihisa Takeuchi, Mingqi Sun, Satomi Enju, Aki Takigawa, Tatsuhiro Michikami, Tomoki Nakamura, Megumi Matsumoto, Yusuke Nakauchi, Masanao Abe, Masahiko Arakawa, Atsushi Fujii, Masahiko Hayakawa, Naru Hirata, Naoyuki Hirata, Rie Honda, Chikatoshi Honda, Satoshi Hosoda, Yu-ichi Iijima, Hitoshi Ikeda, Masateru Ishiguro, Yoshiaki Ishihara, Takahiro Iwata, Kousuke Kawahara, Shota Kikuchi, Kohei Kitazato, Koji Matsumoto, Moe Matsuoka, Yuya Mimasu, Akira Miura, Tomokatsu Morota, Satoru Nakazawa, Noriyuki Namiki, Hirotomo Noda, Rina Noguchi, Naoko Ogawa, Kazunori Ogawa, Tatsuaki Okada, Chisato Okamoto, Go Ono, Masanobu Ozaki, Takanao Saiki, Naoya Sakatani, Hirotaka Sawada, Hiroki Senshu, Yuri Shimaki, Kei Shirai, Seiji Sugita, Yuto Takei, Hiroshi Takeuchi, Satoshi Tanaka, Eri Tatsumi, Fuyuto Terui, Ryudo Tsukizaki, Koji Wada, Manabu Yamada, Tetsuya Yamada, Yukio Yamamoto, Hajime Yano, Yasuhiro Yokota, Keisuke Yoshihara, Makoto Yoshikawa, Kent Yoshikawa, Ryohta Fukai, Shizuho Furuya, Kentaro Hatakeda, Tasuku Hayashi, Yuya Hitomi, Kazuya Kumagai, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Hiromichi Soejima, Ayako Suzuki, Tomohiro Usui, Toru Yada, Daiki Yamamoto, Kasumi Yogata, Miwa Yoshitake, Harold C. Connolly, Dante S. Lauretta, Hisayoshi Yurimoto, Kazuhide Nagashima, Noriyuki Kawasaki, Naoya Sakamoto, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Sei-ichiro Watanabe, Yuichi Tsuda
    NATURE ASTRONOMY 2022年12月 
    Without a protective atmosphere, space-exposed surfaces of airless Solar System bodies gradually experience an alteration in composition, structure and optical properties through a collective process called space weathering. The return of samples from near-Earth asteroid (162173) Ryugu by Hayabusa2 provides the first opportunity for laboratory study of space-weathering signatures on the most abundant type of inner solar system body: a C-type asteroid, composed of materials largely unchanged since the formation of the Solar System. Weathered Ryugu grains show areas of surface amorphization and partial melting of phyllosilicates, in which reduction from Fe3+ to Fe2+ and dehydration developed. Space weathering probably contributed to dehydration by dehydroxylation of Ryugu surface phyllosilicates that had already lost interlayer water molecules and to weakening of the 2.7 mu m hydroxyl (-OH) band in reflectance spectra. For C-type asteroids in general, this indicates that a weak 2.7 mu m band can signify space-weathering-induced surface dehydration, rather than bulk volatile loss.
  • Pieter Tack, Ella De Pauw, Beverley Tkalcec, Miles Lindner, Benjamin Bazi, Bart Vekemans, Frank Brenker, Marco Di Michiel, Masayuki Uesugi, Hisayoshi Yurimoto, Tomoki Nakamura, Kana Amano, Megumi Matsumoto, Yuri Fujioka, Yuma Enokido, Daisuke Nakashima, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Shogo Tachibana, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei Ichiro Watanabe, Yuichi Tsuda, Laszlo Vincze
    Earth, Planets and Space 74 1 2022年12月 
    Millimetre-sized primordial rock fragments originating from asteroid Ryugu were investigated using high energy X-ray fluorescence spectroscopy, providing 2D and 3D elemental distribution and quantitative composition information on the microscopic level. Samples were collected in two phases from two sites on asteroid Ryugu and safely returned to Earth by JAXA’s asteroid explorer Hayabusa2, during which time the collected material was stored and maintained free from terrestrial influences, including exposure to Earth’s atmosphere. Several grains of interest were identified and further characterised to obtain quantitative information on the rare earth element (REE) content within said grains, following a reference-based and computed-tomography-assisted fundamental parameters quantification approach. Several orders of magnitude REE enrichments compared to the mean CI chondrite composition were found within grains that could be identified as apatite phase. Small enrichment of LREE was found for dolomite grains and slight enrichment or depletion for the general matrices within the Ryugu rock fragments A0055 and C0076, respectively. Graphical Abstract: [Figure not available: see fulltext.]
  • Timo Hopp, Nicolas Dauphas, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Kazuhide Nagashima, David Nesvorný, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto
    Science Advances 8 46 2022年11月18日 
    Little is known about the origin of the spectral diversity of asteroids and what it says about conditions in the protoplanetary disk. Here, we show that samples returned from Cb-type asteroid Ryugu have Fe isotopic anomalies indistinguishable from Ivuna-type (CI) chondrites, which are distinct from all other carbonaceous chondrites. Iron isotopes, therefore, demonstrate that Ryugu and CI chondrites formed in a reservoir that was different from the source regions of other carbonaceous asteroids. Growth and migration of the giant planets destabilized nearby planetesimals and ejected some inward to be implanted into the Main Belt. In this framework, most carbonaceous chondrites may have originated from regions around the birthplaces of Jupiter and Saturn, while the distinct isotopic composition of CI chondrites and Ryugu may reflect their formation further away in the disk, owing their presence in the inner Solar System to excitation by Uranus and Neptune.
  • Benjamin Bazi, Pieter Tack, Miles Lindner, Bart Vekemans, Ella De Pauw, Beverley Tkalcec, Frank E. Brenker, Jan Garrevoet, Gerald Falkenberg, Hikaru Yabuta, Hisayoshi Yurimoto, Tomoki Nakamura, Kana Amano, Megumi Matsumoto, Yuri Fujioka, Yuma Enokido, Daisuke Nakashima, Masayuki Uesugi, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Shogo Tachibana, Sei-ichiro Watanabe, Yuichi Tsuda, Laszlo Vincze
    Earth, Planets and Space 74 1 2022年11月04日 
    Abstract A fundamental parameter-based quantification scheme for confocal XRF was applied to sub-micron synchrotron radiation X-ray fluorescence (SR-XRF) data obtained at the beamline P06 of the Deutsches Elektronen-Synchrotron (DESY, Hamburg, Germany) from two sections C0033-01 and C0033-04 that were wet cut from rock fragment C0033 collected from Cb-type asteroid (162173) Ryugu by JAXA’s Hayabusa2 mission. Trace-element quantifications show that C0033 bulk matrix is CI-like, whereas individual mineral grains (i.e., magnetite, pyrrhotite, dolomite, apatite and breunnerite) show, depending on the respective phase, minor to strong deviations. The non-destructive nature of SR-XRF coupled with a new PyMca (a Python toolkit for XRF data analysis)-based quantification approach, performed in parallel with the synchrotron experiments, proves to be an attractive tool for the initial analysis of samples from return missions, such as Hayabusa2 and OSIRIS-REx, the latter returning material from a B-type asteroid (101955) Bennu in 2023. Graphical Abstract
  • Ryuji Okazaki, Yayoi N. Miura, Yoshinori Takano, Hirotaka Sawada, Kanako Sakamoto, Toru Yada, Keita Yamada, Shinsuke Kawagucci, Yohei Matsui, Ko Hashizume, Akizumi Ishida, Michael W. Broadley, Bernard Marty, David Byrne, Evelyn Furi, Alex Meshik, Olga Pravdivtseva, Henner Busemann, My E. Riebe, Jamie Gilmour, Jisun Park, Ken-ichi Bajo, Kevin Righter, Saburo Sakai, Shun Sekimoto, Fumio Kitajima, Sarah A. Crowther, Naoyoshi Iwata, Naoki Shirai, Mitsuru Ebihara, Reika Yokochi, Kunihiko Nishiizumi, Keisuke Nagao, Jong Ik Lee, Patricia Clay, Akihiro Kano, Marc W. Caffee, Ryu Uemura, Makoto Inagaki, Daniela Krietsch, Colin Maden, Mizuki Yamamoto, Lydia Fawcett, Thomas Lawton, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Hikaru Yabuta, Hisayoshi Yurimoto, Yuichi Tsuda, Sei-Ichiro Watanabe, Masanao Abe, Masahiko Arakawa, Atsushi Fujii, Masahiko Hayakawa, Naoyuki Hirata, Naru Hirata, Rie Honda, Chikatoshi Honda, Satoshi Hosoda, Yu-Ichi Iijima, Hitoshi Ikeda, Masateru Ishiguro, Yoshiaki Ishihara, Takahiro Iwata, Kosuke Kawahara, Shota Kikuchi, Kohei Kitazato, Koji Matsumoto, Moe Matsuoka, Tatsuhiro Michikami, Yuya Mimasu, Akira Miura, Tomokatsu Morota, Satoru Nakazawa, Noriyuki Namiki, Hirotomo Noda, Rina Noguchi, Naoko Ogawa, Kazunori Ogawa, Tatsuaki Okada, Chisato Okamoto, Go Ono, Masanobu Ozaki, Takanao Saiki, Naoya Sakatani, Hiroki Senshu, Yuri Shimaki, Kei Shirai, Seiji Sugita, Yuto Takei, Hiroshi Takeuchi, Satoshi Tanaka, Eri Tatsumi, Fuyuto Terui, Ryudo Tsukizaki, Koji Wada, Manabu Yamada, Tetsuya Yamada, Yukio Yamamoto, Hajime Yano, Yasuhiro Yokota, Keisuke Yoshihara, Makoto Yoshikawa, Kent Yoshikawa, Shizuho Furuya, Kentaro Hatakeda, Tasuku Hayashi, Yuya Hitomi, Kazuya Kumagai, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Hiromichi Soejima, Ayako Iwamae, Daiki Yamamoto, Kasumi Yogata, Miwa Yoshitake, Ryota Fukai, Tomohiro Usui, Trevor Ireland, Harold C. Connolly, Dante S. Lauretta, Shogo Tachibana
    SCIENCE ADVANCES 8 46 2022年11月 
    The Hayabusa2 spacecraft returned to Earth from the asteroid 162173 Ryugu on 6 December 2020. One day after the recovery, the gas species retained in the sample container were extracted and measured on-site and stored in gas collection bottles. The container gas consists of helium and neon with an extraterrestrial He-3/He-4 and Ne-20/Ne-22 ratios, along with some contaminant terrestrial atmospheric gases. A mixture of solar and Earth's atmospheric gas is the best explanation for the container gas composition. Fragmentation of Ryugu grains within the sample container is discussed on the basis of the estimated amount of indigenous He and the size distribution of the recovered Ryugu grains. This is the first successful return of gas species from a near-Earth asteroid.
  • Masahiko Sato, Yuki Kimura, Satoshi Tanaka, Tadahiro Hatakeyama, Seiji Sugita, Tomoki Nakamuna, Shogo Tachibana, Hisayoshi Yurimoto, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Hiroshi Naraoka, Kanako Sakamoto, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tatsuaki Okada, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Fuyuto Terui, Satoru Nakazawa, Sei‐ichiro Watanabe, Yuichi Tsuda
    Journal of Geophysical Research: Planets 127 11 2022年11月 
    In this study, systematic rock magnetic measurements and saturation isothermal remanent magnetization (SIRM) paleointensity calibration experiments were conducted for the returned samples from C-type asteroid (162173) Ryugu and two carbonaceous chondrites (Orgueil and Tagish Lake) to evaluate the remanence carriers of the Ryugu sample and its ability as a paleomagnetic recorder. Our magnetic measurements show that Ryugu samples exhibit signatures for framboidal magnetite, coarse-grained magnetite, and pyrrhotite, and that framboidal magnetite is the dominant remanence carrier of Ryugu samples in the middle-coercivity range. The SIRM paleointensity constant was obtained for two Ryugu samples, and the median value was 3,318 +/- 1,038 mu T, which is close to the literature's value based on the average among magnetite, titanomagnetite, pyrrhotite, and FeNi alloys and is widely used for SIRM paleointensity experiments. The paleointensity values estimated using the obtained SIRM paleointensity constant indicate a strong magnetic field of the protoplanetary disk, suggesting that Sun's protoplanetary disk existed at the disk location of Ryugu's parent planetesimal when framboidal magnetite precipitated from the aqueous fluid.
  • Daiki Yamamoto, Noriyuki Kawasaki, Shogo Tachibana, Michiru Kamibayashi, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 336 104 - 112 2022年11月 
    Coarse-grained igneous calcium-aluminum-rich inclusions (CAIs) are suggested to have experienced gas-melt isotope exchange of oxygen during the melting events of their precursors. Therefore, their oxygen isotope variation would preserve information about the high-temperature processes in the earliest Solar System. We experimentally determined oxygen isotope exchange kinetics between CAI analog melt and carbon monoxide (CO) gas at 1420 degrees C and 1460 degrees C under CO gas partial pressures of 0.1, 0.5, and 1 Pa to understand the role of CO gas on the oxygen isotope exchange. We observed oxygen isotope zoning profiles inside the reacted samples that formed through the oxygen isotope exchange reaction at the melt surface and oxygen diffusion in the melt. The zoning profiles were fitted using a three-dimensional spherical diffusion model with time-dependent surface concentration. The oxygen isotope exchange efficiency for colliding CO molecules is estimated to be similar to 3.3 x 10(-4), which is much smaller than that for H2O (0.28). The oxygen diffusion coefficient obtained in this study is similar to that obtained in the oxygen isotope exchange experiments between the CAI melt and H2O, suggesting that the diffusion species in the melt is O2-, despite the surrounding atmospheres.A comparison of the isotope exchange reaction kinetics between (1) CAI melt and CO gas, (2) CAI melt and H2O gas, and (3) CO and H2O gases shows that the reaction rate decreases in the order of (3), (2), and (1). The rapid isotope exchange of the reaction (1) indicates that the oxygen isotopic compositions of H2O and CO should have been equilibrated during the melting and crystallization processes of igneous CAIs. Both H2O and CO change the oxygen isotope compositions of molten CAI in the same direction, although reaction (2) controls the isotope exchange timescale between the CAI melt and surrounding gas. Our dataset demonstrates that type B CAIs having melilite with homogeneous oxygen isotope composition should have been heated for 2-3 days at P-H2 > 100 Pa above the melilite liquidus (similar to 1400 degrees C) in the solar protoplanetary disk. (C) 2022 Elsevier Ltd. All rights reserved.
  • Ken‐ichi Bajo, Jun Aoki, Morio Ishihara, Shizuho Furuya, Masahiro Nishimura, Miwa Yoshitake, Hisayoshi Yurimoto
    Journal of Mass Spectrometry 57 11 2022年10月26日 
    We developed an autocorrelation function to resolve the overtaking problem in a multiturn time-of-flight mass spectrometer (TOF-MS). The function analyzes the characteristic period for one lap of each ion packet and derives a mass spectrum from a signal pulse train composed of multiturn ion packets. To detect the ion pulse train, a new nondestructive ion detector was developed and installed in the multiturn orbit of MULTUM-S II. This detector is composed of an electrostatically induced charge detector, a preamplifier, and a digitizer. The electrostatic noises are smaller than the single-ion signals owing to the accumulation of the multiturn TOF spectrum. The conventional ion detector of TOF-MS is operated after collecting the signal pulse train. The multiturn TOF spectrum was convolved with an autocorrelation function to derive the mass spectrum. The convolved mass spectrum performed a mass resolving power (MRP) of 28,200 at m/z 69 and mass accuracy of 28 ppm for the perfluorotributylamine (PFTBA) gas sample.
  • F. Moynier, W. Dai, T. Yokoyama, Y. Hu, M. Paquet, Y. Abe, J. Aléon, C.M.O'D Alexander, S. Amari, Y. Amelin, K.-I. Bajo, M. Bizzarro, A. Bouvier, R.W. Carlson, M. Chaussidon, B.-G. Choi, N. Dauphas, A.M. Davis, T. Di Rocco, W. Fujiya, R. Fukai, I. Gautam, M.K. Haba, Y. Hibiya, H. Hidaka, H. Homma, P. Hoppe, G.R. Huss, K. Ichida, T. Iizuka, T.R. Ireland, A. Ishikawa, M. Ito, S. Itoh, N. Kawasaki, N.T. Kita, K. Kitajima, T. Kleine, S. Komatani, A.N. Krot, M.-C. Liu, Y. Masuda, K.D. McKeegan, M. Morita, K. Motomura, I. Nakai, K. Nagashima, D. Nesvorný, A. Nguyen, L. Nittler, M. Onose, A. Pack, C. Park, L. Piani, L. Qin, S.S. Russell, N. Sakamoto, M. Schönbächler, L. Tafla, H. Tang, K. Terada, Y. Terada, T. Usui, S. Wada, M. Wadhwa, R.J. Walker, K. Yamashita, Q.-Z. Yin, S. Yoneda, E.D. Young, H. Yui, A.-C. Zhang, T. Nakamura, H. Naraoka, T. Noguchi, R. Okazaki, K. Sakamoto, H. Yabuta, M. Abe, A. Miyazaki, A. Nakato, M. Nishimura, T. Okada, T. Yada, K. Yogata, S. Nakazawa, T. Saiki, S. Tanaka, F. Terui, Y. Tsuda, S.-I. Watanabe, M. Yoshikawa, S. Tachibana, H. Yurimoto
    Geochemical Perspectives Letters 24 1 - 6 2022年10月
  • Sohei Wada, Ken-ichi Bajo, Hisayoshi Yurimoto
    METEORITICS & PLANETARY SCIENCE 57 2022年08月
  • Jens Barosch, Larry R. Nittler, Jianhua Wang, Conel M. O’D. Alexander, Bradley T. De Gregorio, Cécile Engrand, Yoko Kebukawa, Kazuhide Nagashima, Rhonda M. Stroud, Hikaru Yabuta, Yoshinari Abe, Jérôme Aléon, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Laure Bejach, Martin Bizzarro, Lydie Bonal, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, George D. Cody, Emmanuel Dartois, Nicolas Dauphas, Andrew M. Davis, Alexandre Dazzi, Ariane Deniset-Besseau, Tommaso Di Rocco, Jean Duprat, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Minako Hashiguchi, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Kanami Kamide, Noriyuki Kawasaki, A. L. David Kilcoyne, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Mutsumi Komatsu, Alexander N. Krot, Ming-Chang Liu, Zita Martins, Yuki Masuda, Jérémie Mathurin, Kevin D. McKeegan, Gilles Montagnac, Mayu Morita, Smail Mostefaoui, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Ann N. Nguyen, Takuji Ohigashi, Taiga Okumura, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Eric Quirico, Laurent Remusat, Sara S. Russell, Naoya Sakamoto, Scott A. Sandford, Maria Schönbächler, Miho Shigenaka, Hiroki Suga, Lauren Tafla, Yoshio Takahashi, Yasuo Takeichi, Yusuke Tamenori, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Maximilien Verdier-Paoletti, Sohei Wada, Meenakshi Wadhwa, Daisuke Wakabayashi, Richard J. Walker, Katsuyuki Yamashita, Shohei Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Satoru Nakazawa, Masahiro Nishimura, Tatsuaki Okada, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Toru Yada, Kasumi Yogata, Makoto Yoshikawa, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Shogo Tachibana, Hisayoshi Yurimoto
    The Astrophysical Journal Letters 935 1 L3 - L3 2022年08月01日 
    Abstract We have conducted a NanoSIMS-based search for presolar material in samples recently returned from C-type asteroid Ryugu as part of JAXA's Hayabusa2 mission. We report the detection of all major presolar grain types with O- and C-anomalous isotopic compositions typically identified in carbonaceous chondrite meteorites: 1 silicate, 1 oxide, 1 O-anomalous supernova grain of ambiguous phase, 38 SiC, and 16 carbonaceous grains. At least two of the carbonaceous grains are presolar graphites, whereas several grains with moderate C isotopic anomalies are probably organics. The presolar silicate was located in a clast with a less altered lithology than the typical extensively aqueously altered Ryugu matrix. The matrix-normalized presolar grain abundances in Ryugu are ${4.8}_{-2.6}^{+4.7}$ ppm for O-anomalous grains, ${25}_{-5}^{+6}$ ppm for SiC grains, and ${11}_{-3}^{+5}$ ppm for carbonaceous grains. Ryugu is isotopically and petrologically similar to carbonaceous Ivuna-type (CI) chondrites. To compare the in situ presolar grain abundances of Ryugu with CI chondrites, we also mapped Ivuna and Orgueil samples and found a total of 15 SiC grains and 6 carbonaceous grains. No O-anomalous grains were detected. The matrix-normalized presolar grain abundances in the CI chondrites are similar to those in Ryugu: ${23}_{-6}^{+7}$ ppm SiC and ${9.0}_{-3.6}^{+5.4}$ ppm carbonaceous grains. Thus, our results provide further evidence in support of the Ryugu–CI connection. They also reveal intriguing hints of small-scale heterogeneities in the Ryugu samples, such as locally distinct degrees of alteration that allowed the preservation of delicate presolar material.
  • Minako Hashiguchi, Dan Aoki, Kazuhiko Fukushima, Hiroshi Naraoka, Yoshinori Takano, Dworkin P. Jason, Aponte C. Jose, Elsila E. Jamie, Eiler M. John, Yoshihiro Furukawa, Aogu Furusho, Glavin P. Daniel, Heather V. Graham, Kenji Hamase, Hertkorn Norbert, Junko Isa, Toshiki Koga, McLain L. Hannah, Hajime Mita, Yasuhiro Oba, Nanako O. Ogawa, Naohiko Ohkouchi, Francois-Regis Orthous-Daunay, Eric T. Parker, Ruf Alexander, Saburo Sakaki, Schmitt-Kopplin Philippe, Haruna Sugahara, Thissen Roland, Vuitton Véronique, Cédric Wolters, Toshihiro Yoshimura, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Ryuji Okazaki, Hikaru Yabuta, Kanako Sakamoto, Shogo Tachibana, Toru Yada, Masahiro Nishimura, Aiko Nakato, Akiko Miyazaki, Kasumi Yogata, Masanao Abe, Tomohiro Usui, Makoto Yoshikawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Satoru Nakazawa, Sei-ichiro Watanabe, Yuichi Tsuda
    EARTH PLANETS AND SPACE 75 1 2022年07月25日 
    Abstract We performed in-situ analysis on a ~1 mm-sized Ryugu grain A0080 returned by the Hayabusa2 spacecraft to investigate the relationship of soluble organic matter (SOM) to minerals. The DESI-HRMS (desorption electrospray ionization-high resolution mass spectrometry) imaging using methanol spray identified more than 200 soluble organic compounds, which were assigned as CHN, CHO, CHO-Na (sodium adducted), and CHNO in molecular composition. Heterogeneous spatial distribution was observed for different compound classes of SOM as well as among the same alkylated homologues on the sample surface. The A0080 sample showed similar mineralogy to that of CI chondrite and contained two different lithologies, which are rich in magnetite, pyrrhotite, and dolomite (lithology 1) and poor in those minerals (lithology 2). CHN compounds were relatively concentrated in lithology 1 than in lithology 2, on the other hand, CHO, CHO-Na, and CHNO compounds were distributed in both lithologies. Such different spatial distribution of SOM is the result of interaction of the SOM with minerals, during precipitation of the SOM via fluid activity, or could be due to difference in transportation efficiencies of SOMs in aqueous fluid. However, organic-related ions measured by ToF-SIMS did not coincide with the spatial distribution revealed by DESI-HRMS imaging, indicating that the ToF-SIMS data would be mainly derived from methanol-insoluble organic matter in A0080. Alkylated homologues of CHN compounds with large C number appeared more abundant in lithology 2 than lithology 1. In contrast, fragments of the Murchison meteorite showed different features to of A0080, implying different formation or growth mechanisms for the alkylated CHN compounds by interaction with fluid and minerals on Murchison parent body and asteroid Ryugu. This difference might be mainly attributed to the carbonate grains, which would have played as a catalyst for CH2 growth of CHN compounds. Future in-situ analysis of CI chondrite will provide more reliable constraints for the history of soluble organic compounds in asteroid Ryugu.
  • Ai-Cheng Zhang, Jie-Ya Li, Jia-Ni Chen, Yuan-Yun Wen, Yan-Jun Guo, Yang Li, Naoya Sakamoto, Hisayoshi Yurimoto
    GEOCHIMICA ET COSMOCHIMICA ACTA 329 38 - 50 2022年07月 [査読有り]
     
    Impact is a fundamental process shaping the formation and evolution of planets and asteroids. It is inevitable that some materials on the surface of planets and asteroids have been impacted for many times. However, unambiguous petrological records for multiple post-formation impact events are rarely described. Here, we report that the thin shock melt veins of the shocked eucrite Northwest Africa 8647 are dominated by a fine-grained intergranular or vermicular pigeonite and anorthite assemblage, rather than compact vacancy-rich clinopyroxene. Vacancy-rich clinopyroxene in the veins instead is ubiquitous as irregularly-shaped, relict grains surrounded by intergranular or vermicular pigeonite and anorthite assemblage. The silica fragments entrained in shock melt veins contain a coesite core and a quartz rim. The occurrences of vacancy-rich clinopyroxene and coesite can be best explained by two impact events. The first impact event produced the shock melt veins and lead to the formation of vacancy-rich clinopyroxene and coesite. The second impact event heated the fine-grained melt veins and lead to the widespread partial decomposition of vacancy-rich clinopyroxene and the partial back-transformation of coesite. This paper is the first report of the decomposition reaction of shock-induced vacancy-rich clinopyroxene in extraterrestrial materials. We propose that widespread decomposition and/or back-transformation of high-pressure minerals in shocked meteorites can be considered as important records of multiple impact events.(C) 2022 Elsevier Ltd. All rights reserved.
  • Tetsuya Yokoyama, Kazuhide Nagashima, Izumi Nakai, Edward D. Young, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Hiroharu Yui, Ai-Cheng Zhang, Harold C. Connolly, Dante S. Lauretta, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Masahiko Arakawa, Atsushi Fujii, Masahiko Hayakawa, Naoyuki Hirata, Naru Hirata, Rie Honda, Chikatoshi Honda, Satoshi Hosoda, Yu-ichi Iijima, Hitoshi Ikeda, Masateru Ishiguro, Yoshiaki Ishihara, Takahiro Iwata, Kosuke Kawahara, Shota Kikuchi, Kohei Kitazato, Koji Matsumoto, Moe Matsuoka, Tatsuhiro Michikami, Yuya Mimasu, Akira Miura, Tomokatsu Morota, Satoru Nakazawa, Noriyuki Namiki, Hirotomo Noda, Rina Noguchi, Naoko Ogawa, Kazunori Ogawa, Tatsuaki Okada, Chisato Okamoto, Go Ono, Masanobu Ozaki, Takanao Saiki, Naoya Sakatani, Hirotaka Sawada, Hiroki Senshu, Yuri Shimaki, Kei Shirai, Seiji Sugita, Yuto Takei, Hiroshi Takeuchi, Satoshi Tanaka, Eri Tatsumi, Fuyuto Terui, Yuichi Tsuda, Ryudo Tsukizaki, Koji Wada, Sei-ichiro Watanabe, Manabu Yamada, Tetsuya Yamada, Yukio Yamamoto, Hajime Yano, Yasuhiro Yokota, Keisuke Yoshihara, Makoto Yoshikawa, Kent Yoshikawa, Shizuho Furuya, Kentaro Hatakeda, Tasuku Hayashi, Yuya Hitomi, Kazuya Kumagai, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Hiromichi Soejima, Ayako Suzuki, Toru Yada, Daiki Yamamoto, Kasumi Yogata, Miwa Yoshitake, Shogo Tachibana, Hisayoshi Yurimoto
    Science 379 6634 786 - + 2022年06月09日 [査読有り]
     
    Carbonaceous meteorites are thought to be fragments of C-type (carbonaceous) asteroids. Samples of the C-type asteroid (162173) Ryugu were retrieved by the Hayabusa2 spacecraft. We measure the mineralogy, bulk chemical and isotopic compositions of Ryugu samples. They are mainly composed of materials similar to carbonaceous chondrite meteorites, particularly the CI (Ivuna-type) group. The samples consist predominantly of minerals formed in aqueous fluid on a parent planetesimal. The primary minerals were altered by fluids at a temperature of 37 ± 10°C, (Stat.) (Syst.) million years after formation of the first solids in the Solar System. After aqueous alteration, the Ryugu samples were likely never heated above ~100°C. The samples have a chemical composition that more closely resembles the Sun’s photosphere than other natural samples do.
  • Tachibana, S., Sawada, H., Okazaki, R., Takano, Y., Sakamoto, K., Miura, Y. N., Okamoto, C., Yano, H., Yamanouchi, S., Michel, P., Zhang, Y., Schwartz, S., Thuillet, F., Yurimoto, H., Nakamura, T., Noguchi, T., Yabuta, H., Naraoka, H., Tsuchiyama, A., Imae, N., Kurosawa, K., Nakamura, A. M., Ogawa, K., Sugita, S., Morota, T., Honda, R., Kameda, S., Tatsumi, E., Cho, Y., Yoshioka, K., Yokota, Y., Hayakawa, M., Matsuoka, M., Sakatani, N., Yamada, M., Kouyama, T., Suzuki, H., Honda, C., Yoshimitsu, T., Kubota, T., Demura, H., Yada, T., Nishimura, M., Yogata, K., Nakato, A., Yoshitake, M., Suzuki, A. I., Furuya, S., Hatakeda, K., Miyazaki, A., Kumagai, K., Okada, T., Abe, M., Usui, T., Ireland, T. R., Fujimoto, M., Yamada, T., Arakawa, M., Connolly, H. C., Fujii, A., Hasegawa, S., Hirata, N., Hirata, N., Hirose, C., Hosoda, S., Iijima, Y., Ikeda, H., Ishiguro, M., Ishihara, Y., Iwata, T., Kikuchi, S., Kitazato, K., Lauretta, D. S., Libourel, G., Marty, B., Matsumoto, K., Michikami, T., Mimasu, Y., Miura, A., Mori, O., Nakamura-Messenger, K., Namiki, N., Nguyen, A. N., Nittler, L. R., Noda, H., Noguchi, R., Ogawa, N., Ono, G., Ozaki, M., Senshu, H., Shimada, T., Shimaki, Y., Shirai, K., Soldini, S., Takahashi, T., Takei, Y., Takeuchi, H., Tsukizaki, R., Wada, K., Yamamoto, Y., Yoshikawa, K., Yumoto, K., Zolensky, M. E., Nakazawa, S., Terui, F., Tanaka, S., Saiki, T., Yoshikawa, M., Watanabe, S., Tsuda, Y.
    Science 375 6584 1011 - 1016 2022年03月 [査読有り]
     
    The Hayabusa2 spacecraft investigated the C-type (carbonaceous) asteroid (162173) Ryugu. The mission performed two landing operations to collect samples of surface and subsurface material, the latter exposed by an artificial impact. We present images of the second touchdown site, finding that ejecta from the impact crater was present at the sample location. Surface pebbles at both landing sites show morphological variations ranging from rugged to smooth, similar to Ryugu’s boulders, and shapes from quasi-spherical to flattened. The samples were returned to Earth on 6 December 2020. We describe the morphology of >5 grams of returned pebbles and sand. Their diverse color, shape, and structure are consistent with the observed materials of Ryugu; we conclude that they are a representative sample of the asteroid....
  • Toru Yada, Masanao Abe, Tatsuaki Okada, Aiko Nakato, Kasumi Yogata, Akiko Miyazaki, Kentaro Hatakeda, Kazuya Kumagai, Masahiro Nishimura, Yuya Hitomi, Hiromichi Soejima, Miwa Yoshitake, Ayako Iwamae, Shizuho Furuya, Masayuki Uesugi, Yuzuru Karouji, Tomohiro Usui, Tasuku Hayashi, Daiki Yamamoto, Ryota Fukai, Seiji Sugita, Yuichiro Cho, Koki Yumoto, Yuna Yabe, Jean-Pierre Bibring, Cedric Pilorget, Vincent Hamm, Rosario Brunetto, Lucie Riu, Lionel Lourit, Damien Loizeau, Guillaume Lequertier, Aurelie Moussi-Soffys, Shogo Tachibana, Hirotaka Sawada, Ryuji Okazaki, Yoshinori Takano, Kanako Sakamoto, Yayoi N. Miura, Hajime Yano, Trevor R. Ireland, Tetsuya Yamada, Masaki Fujimoto, Kohei Kitazato, Noriyuki Namiki, Masahiko Arakawa, Naru Hirata, Hisayoshi Yurimoto, Tomoki Nakamura, Takaaki Noguchi, Hikaru Yabuta, Hiroshi Naraoka, Motoo Ito, Eizo Nakamura, Kentaro Uesugi, Katsura Kobayashi, Tatsuhiro Michikami, Hiroshi Kikuchi, Naoyuki Hirata, Yoshiaki Ishihara, Koji Matsumoto, Hirotomo Noda, Rina Noguchi, Yuri Shimaki, Kei Shirai, Kazunori Ogawa, Koji Wada, Hiroki Senshu, Yukio Yamamoto, Tomokatsu Morota, Rie Honda, Chikatoshi Honda, Yasuhiro Yokota, Moe Matsuoka, Naoya Sakatani, Eri Tatsumi, Akira Miura, Manabu Yamada, Atsushi Fujii, Chikako Hirose, Satoshi Hosoda, Hitoshi Ikeda, Takahiro Iwata, Shota Kikuchi, Yuya Mimasu, Osamu Mori, Naoko Ogawa, Go Ono, Takanobu Shimada, Stefania Soldini, Tadateru Takahashi, Yuto Takei, Hiroshi Takeuchi, Ryudo Tsukizaki, Kent Yoshikawa, Fuyuto Terui, Satoru Nakazawa, Satoshi Tanaka, Takanao Saiki, Makoto Yoshikawa, Sei-ichiro Watanabe, Yuichi Tsuda
    NATURE ASTRONOMY 6 2 214 - + 2022年02月 
    C-type asteroids(1) are considered to be primitive small Solar System bodies enriched in water and organics, providing clues to the origin and evolution of the Solar System and the building blocks of life. C-type asteroid 162173 Ryugu has been characterized by remote sensing(2-7) and on-asteroid measurements(8,9) with Hayabusa2 (ref. (10)). However, the ground truth provided by laboratory analysis of returned samples is invaluable to determine the fine properties of asteroids and other planetary bodies. We report preliminary results of analyses on returned samples from Ryugu of the particle size distribution, density and porosity, spectral properties and textural properties, and the results of a search for Ca-Al-rich inclusions (CAIs) and chondrules. The bulk sample mainly consists of rugged and smooth particles of millimetre to submillimetre size, confirming that the physical and chemical properties were not altered during the return from the asteroid. The power index of its size distribution is shallower than that of the surface boulder observed on Ryugu(11), indicating differences in the returned Ryugu samples. The average of the estimated bulk densities of Ryugu sample particles is 1,282 +/- 231 kg m(-3), which is lower than that of meteorites(12), suggesting a high microporosity down to the millimetre scale, extending centimetre-scale estimates from thermal measurements(5,9). The extremely dark optical to near-infrared reflectance and spectral profile with weak absorptions at 2.7 and 3.4 mu m imply a carbonaceous composition with indigenous aqueous alteration, matching the global average of Ryugu(3,4) and confirming that the sample is representative of the asteroid. Together with the absence of submillimetre CAIs and chondrules, these features indicate that Ryugu is most similar to CI chondrites but has lower albedo, higher porosity and more fragile characteristics.
  • Yukari Kuga, Ting-Di Wu, Naoya Sakamoto, Chie Katsuyama, Hisayoshi Yurimoto
    MICROORGANISMS 9 12 2021年12月 
    Arbuscular mycorrhizal fungi are obligate symbionts of land plants; furthermore, some of the species harbor endobacteria. Although the molecular approach increased our knowledge of the diversity and origin of the endosymbiosis and its metabolic possibilities, experiments to address the functions of the fungal host have been limited. In this study, a C flow of the fungus to the bacteria was investigated. Onion seedlings colonized with Gigaspora margarita, possessing Candidatus Glomeribacter gigasporarum (CaGg, Gram-negative, resides in vacuole) and Candidatus Moeniiplasma glomeromycotorum (CaMg, Gram-positive, resides in the cytoplasm,) were labelled with (CO2)-C-13. The C-13 localization within the mycorrhiza was analyzed using high-resolution secondary ion mass spectrometry (SIMS). Correlative TEM-SIMS analysis of the fungal cells revealed that the C-13/C-12 ratio of CaGg was the lowest among CaMg and mitochondria and was the highest in the cytoplasm. By contrast, the plant cells, mitochondria, plastids, and fungal cytoplasm, which are contributors to the host, showed significantly higher C-13 enrichment than the host cytoplasm. The C allocation patterns implied that CaMg has a greater impact than CaGg on G. margarita, but both seemed to be less burdensome to the host fungus in terms of C cost.
  • Michiru Kamibayashi, Shogo Tachibana, Daiki Yamamoto, Noriyuki Kawasaki, Hisayoshi Yurimoto
    The Astrophysical Journal Letters 923 1 L12 - L12 2021年12月01日 
    Abstract Calcium–aluminum-rich inclusions (CAIs) are the oldest materials that formed in the protosolar disk. Igneous CAIs experienced melting and subsequent crystallization in the disk during which the evaporation of relatively volatile elements such as Mg and Si occurred. Evaporation from the melt would have played a significant role in the variation of chemical, mineralogical, and petrologic characteristics of the igneous CAIs. In this study, we investigated crystallization of CAI analog melt under disk-like low-pressure hydrogen (PH2) conditions of 0.1, 1, and 10 Pa to constrain the pressure condition of the early solar system in which type B CAIs were formed. At PH2 = 10 Pa, the samples were mantled by melilite crystals, as observed for type B1 CAIs. However, the samples heated at PH2 = 0.1 Pa exhibited random distribution of melilite, as in type B2 CAIs. At the intermediate PH2 of 1 Pa, type-B1-like structure formed when the cooling rate was 5°C hr−1, whereas the formation of type-B2-like structure required a cooling rate faster than 20°C hr−1. The compositional characteristics of melilite in type B1 and B2 CAIs could also be reproduced by experiments. The results of the present study suggest that PH2 required for type-B1-like textural and chemical characteristics is greater than 1 Pa. The hydrogen pressure estimated in this study would impose an important constraint on the physical condition of the protosolar disk where type B CAIs were formed.
  • Daiki Yamamoto, Noriyuki Kawasaki, Shogo Tachibana, Michiru Kamibayashi, Hisayoshi Yurimoto
    GEOCHIMICA ET COSMOCHIMICA ACTA 314 108 - 120 2021年12月 [査読有り]
     
    Calcium-aluminum-rich inclusions (CAIs) are known as the oldest high-temperature mineral assemblages of the Solar Sys-tem. The CAIs record thermal events that occurred during the earliest epochs of the Solar System formation in the form of heterogeneous oxygen isotopic distributions between and within their constituent minerals. Here, we explored the kinetics of oxygen isotope exchange during partial melting events of CAIs by conducting oxygen isotope exchange experiments between type B CAI-like silicate melt and 18O-enriched water vapor (PH2O = 5 x 10-2 Pa) at 1420 degrees C. We found that the oxygen iso-tope exchange between CAI melt and water vapor proceeds at competing rates with surface isotope exchange and self -diffusion of oxygen in the melt under the experimental conditions. The 18O concentration profiles were well fitted with the three-dimensional spherical diffusion model with a time-dependent surface concentration. We determined the self-diffusion coefficient of oxygen to be-1.62 x 10-11 m2 s-1, and the oxygen isotope exchange efficiency on the melt surface was found to be-0.28 in colliding water molecules. These kinetic parameters suggest that oxygen isotope exchange rate between cm -sized CAI melt droplets and water vapor is dominantly controlled by the supply of water molecules to the melt surface at PH2O < 10-2 Pa and by self-diffusion of oxygen in the melt at PH2O >-1 Pa at temperatures above the melilite liquidus (1420-1540 degrees C). To form type B CAIs containing 16O-poor melilite by oxygen isotope exchange between CAI melt and disk water vapor, the CAIs should have been heated for at least a few days at PH2O > 10-2 Pa above temperatures of the melilite liquidus in the protosolar disk. The larger timescale of oxygen isotopic equilibrium between CAI melt and H2O compared to that between H2O and CO in the gas phase suggests that the bulk oxygen isotopic compositions of ambient gas at-1400 degrees C in the type B CAI-forming region is preserved in the oxygen isotopic compositions of type B CAI melilite. Based on the observed oxygen isotopic composition, we suggest that a typical type B1 CAI (TS34) from Allende was cooled at a rate of-0.1-0.5 K h-1 during fassaite crystallization. (c) 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).
  • Shoh Tagawa, Naoya Sakamoto, Kei Hirose, Shunpei Yokoo, John Hernlund, Yasuo Ohishi, Hisayoshi Yurimoto
    Nature Communications 12 1 2588 - 2588 2021年12月 [査読有り]
     
    Hydrogen is one of the possible alloying elements in the Earth’s core, but its siderophile (iron-loving) nature is debated. Here we experimentally examined the partitioning of hydrogen between molten iron and silicate melt at 30–60 gigapascals and 3100–4600 kelvin. We find that hydrogen has a metal/silicate partition coefficient DH ≥ 29 and is therefore strongly siderophile at conditions of core formation. Unless water was delivered only in the final stage of accretion, core formation scenarios suggest that 0.3–0.6 wt% H was incorporated into the core, leaving a relatively small residual H2O concentration in silicates. This amount of H explains 30–60% of the density deficit and sound velocity excess of the outer core relative to pure iron. Our results also suggest that hydrogen may be an important constituent in the metallic cores of any terrestrial planet or moon having a mass in excess of ~10% of the Earth.
  • May Sas, Phil Shane, Noriyuki Kawasaki, Naoya Sakamoto, Georg F. Zellmer, Hisayoshi Yurimoto
    Journal of Volcanology and Geothermal Research 421 107430 - 107430 2021年11月 [査読有り][通常論文]
     
    The sources and processes involved in the genesis of the voluminous rhyolitic magmas of cataclysmic calderaforming eruptions, and the intervening lower-volume intra-caldera extrusions, have been subject to much debate. To better understand generation of high-volume and low-volume silicic eruptions within a single volcanic centre, and how they may differ, we examined ten volumetrically varied high-SiO2 rhyolite eruptions from the Okataina Volcanic Centre (OVC) in Aotearoa New Zealand. The OVC is one of the world'smost recurrently active silicic volcanoes. In the last similar to 600 ky, the OVCwas the focus of three knowncaldera-forming events and numerous intermittent dome-building and fissure eruption episodes, with rhyolitic eruption activity as recent as 1314 CE. To elucidate how mass contributions from the mantle and crust may have fluctuated over the lifespan of the OVC magmatic system, oxygen isotopic ratios (delta O-18) of quartz in rhyolites were investigated for the first time at inter-crystal and intra-crystal scales. Quartz crystals from four eruption episodes (two caldera-forming events, Utu, similar to 557 ka, Rotoiti, similar to 45 ka, and two intra-caldera dome-building events, Rotoma, similar to 9.5 ka, and Kaharoa, similar to 0.7 ka) yielded intra-crystal delta O-18 isotopic homogeneity (+/- 0.23 parts per thousand, 2sd) based on secondary ion mass spectrometry (SIMS). These samples also display inter-crystal and inter-unit homogeneity within slightly lower precision (7.6 +/- 0.5%, 2sd). Whole-crystal quartz from the same four units, as well as six other units (two intra-caldera dome-building episodes, Okareka, similar to 21.8 ka, Whakatane, similar to 5.5 ka, three pre-Rotoiti extra-caldera domes, Round Hill, Haparangi, Kakapiko, and one immediately post-Rotoiti eruption, Earthquake Flat), were then examined using high-precision laser fluorination. Single crystals also yielded mostly homogenous ratios with average delta O-18= 7.6 +/- 0.5 parts per thousand (2sd), which is consistent with intra-crystal SIMS analyses, albeit for a larger set of samples. Stable and radiogenic isotope mixing models using the newly obtained delta O-18 ratios demonstrate that OVC rhyolites can be produced by >= 25% assimilation of a regional (Torlesse-like) metasedimentary endmember by a depletedmantle sourcewith slightly variable amounts of subduction flux, and that any incorporation of hydrothermally alteredmaterial to the systemis limited to<5% in caldera and intra-caldera eruptions. The delta O-18 records of the OVC are among the most homogenous currently known and indicate stable and consistent mantle and crustal contributions across the lifespan of the magmatic system, with assimilation largely occurring prior to segregation of rhyolitic melts within the silicic reservoir. This isotopic homogeneity may be due to a relatively high-volume and constant magma flux at the OVC, which contrasts to other rhyolitic caldera volcanoes with greater isotopic variability. (C) 2021 Elsevier B.V. All rights reserved.
  • Charline Lormand, Georg Florian Zellmer, Naoya Sakamoto, Teresa Ubide, Geoff Kilgour, Hisayoshi Yurimoto, Alan Palmer, Karoly Nemeth, Yoshiyuki Iizuka, Anja Moebis
    CONTRIBUTIONS TO MINERALOGY AND PETROLOGY 176 11 2021年11月 [査読有り]
     
    Arc magmas typically contain phenocrysts with complex zoning and diverse growth histories. Microlites highlight the same level of intracrystalline variations but require nanoscale resolution which is globally less available. The southern Taupo Volcanic Zone (TVZ), New Zealand, has produced a wide range of explosive eruptions yielding glassy microlite-bearing tephras. Major oxide analyses and textural information reveal that microlite rims are commonly out of equilibrium with the surrounding glass. We mapped microlites and microcrysts at submicron resolution for major and trace element distributions and observed three plagioclase textural patterns: (1) resorption and overgrowth, (2) oscillatory zoning, and (3) normal (sharp) zoning. Pyroxene textures are diverse: (1) resorption and overgrowth, (2) calcium-rich bands, (3) hollow textures, (4) oscillatory zoning, (5) sector zoning, (6) normal zoning and (7) reverse zoning. Microlite chemistry and textures inform processes operating during pre-eruptive magma ascent. They indicate a plumbing system periodically intruded by short-lived sub-aphyric dykes that entrain microantecrysts grown under diverse physico-chemical conditions and stored in rapidly cooled, previously intruded dykes. Changes in temperature gradients between the intrusion and the host rock throughout ascent and repeated magma injections lead to fluctuations in cooling rates and generate local heterogeneities illustrated by the microlite textures and rim compositions. Late-stage degassing occurs at water saturation, forming thin calcic microcryst rims through local partitioning effects. This detailed investigation of textures cryptic to conventional imaging shows that a significant proportion of the micrometre-sized crystal cargo of the TVZ is of antecrystic origin and may not be attributed to late-stage nucleation and growth at the onset of volcanic eruptions, as typically presumed.
  • Kosuke Nagata, Ken-Ichi Bajo, Hideyuki Mitomo, Ryosuke Fujita, Ryota Uehara, Kuniharu Ijiro, Hisayoshi Yurimoto
    Cell structure and function 46 2 95 - 101 2021年09月25日 [査読有り]
     
    Among the inheritance of cellular components during cell division, deoxyribonucleic acid (DNA) and its condensate (chromosome) are conventionally visualized using chemical tag-labeled nucleotide analogs. However, associated mutagenesis with nucleotide analogs in the visualization of chromosomes is cause for concern. This study investigated the efficiency of using stable isotope labels in visualizing the replicating cultured human cell-chromosomes, in the absence of analog labels, at a high spatial resolution of 100 nm. The distinct carbon isotope ratio between sister chromatids reflected the semi-conservative replication of individual DNA strands through cell cycles and suggested the renewal of histone molecules in daughter chromosomes. Thus, this study provides a new, powerful approach to trace and visualize cellular components with stable-isotope labeling.Key Words: stable isotope, chromosome replication, semi-conservative replication, imaging, mass spectrometry.
  • Laurette Piani, Yves Marrocchi, Lionel G. Vacher, Hisayoshi Yurimoto, Martin Bizzarro
    Earth and Planetary Science Letters 567 2021年08月01日 [査読有り]
     
    Chondrites are rocky fragments of asteroids that formed at different times and heliocentric distances in the early solar system. Most chondrite groups contain water-bearing minerals, attesting that both water-ice and dust were accreted on their parent asteroids. Nonetheless, the hydrogen isotopic composition (D/H) of water in the different chondrite groups remains poorly constrained, due to the intimate mixture of hydrated minerals and organic compounds, the other main H-bearing phase in chondrites. Building on our recent works using in situ secondary ion mass spectrometry analyses, we determined the H isotopic composition of water in a large set of chondritic samples (CI, CM, CO, CR, and C-ungrouped carbonaceous chondrites) and report that water in each group shows a distinct and unique D/H signature. Based on a comparison with literature data on bulk chondrites and their water and organics, our data do not support a preponderant role of parent-body processes in controlling the D/H variations among chondrites. Instead, we propose that the water and organic D/H signatures were mostly shaped by interactions between the protoplanetary disk and the molecular cloud that episodically fed the disk over several million years. Because the preservation of D-rich interstellar water and/or organics in chondritic materials is only possible below their respective sublimation temperatures (160 and 350–450 K), the H isotopic signatures of chondritic materials depend on both the timing and location at which their parent body formed.
  • Akimasa Suzumura, Noriyuki Kawasaki, Yusuke Seto, Hisayoshi Yurimoto, Shoichi Itoh
    Geochimica et Cosmochimica Acta 303 51 - 65 2021年06月15日 [査読有り]
     
    We report the in-situ oxygen isotopic distributions corresponding to the petrographic-mineralogical observation on a compact Type A (CTA) Ca-Al-rich inclusion (CAI), KU-N-02, from a reduced CV3 chondrite, Northwest Africa 7865. The CTA has an igneous texture and mainly consists of spinel, melilite, and Al-Ti-rich clinopyroxene (fassaite). Oxygen isotopic compositions of the constituent minerals plot along the carbonaceous chondrite anhydrous mineral line. The spinel grains are poikilitically enclosed in the melilite and fassaite and are uniformly 16O-rich (Δ17O = approximately − 23‰). The fassaite is texturally classified into two types: blocky fassaite and intergranular fassaite. The blocky fassaite crystals exhibit growth zoning as they change from Ti-rich to Ti-poor along the inferred directions of crystal growth from core to rim, while the oxygen isotopic compositions change from 16O-poor (Δ17O = approximately − 6‰) to 16O-rich (Δ17O = approximately − 23‰) with crystal growth. The intergranular fassaite crystals exist between the melilite crystals and exhibit variable Ti abundance and oxygen isotopic compositions. Additionally, their relationships between Ti contents and oxygen isotopic composition are similar to those of the blocky fassaite. The melilite grains are homogeneously 16O-poor (Δ17O = approximately − 2‰), irrespective of their åkermanite (Åk) content. Each melilite grain generally exhibits growth zoning with increasing Åk contents from core to rim, although the melilite contains Åk-rich patches within single crystal. Åk-rich patches often include two types of fassaite: small blebby crystals attached to spinel crystals and round crystals. The oxygen isotopic compositions of the Åk-rich patch and blebby fassaite are 16O-poor (Δ17O = approximately − 2‰), similar to that of the host melilite. On the other hand, the round fassaite exhibits significant variation in oxygen isotopic compositions ranging from Δ17O = −23‰ to − 4‰, which are different from those of the host melilite. These petrographic textures and oxygen isotopic variations indicate the presence of a solid precursor with variable oxygen isotopic compositions for the CTA. The spinel and round fassaite grains are relicts of the precursor that melted in the 16O-poor nebular gas, resulting in the crystallization of the host melilite from the 16O-poor melt. The Åk-rich patches and blebby fassaite crystallized from melts trapped by the growing host melilite crystals. The blocky and intergranular fassaite crystallized after the melilite did, and the oxygen isotopic composition of the melt changed to 16O-rich during the crystallization process, suggesting that the oxygen isotopic composition of the surrounding nebular gas could be varied. The inferred oxygen isotopic evolution for CTA is consistent with those inferred for Type B CAIs, suggesting that coarse-grained igneous CAIs formed in a similar nebular environment regardless of precursor chemistry.
  • Noriyuki Kawasaki, Shoichi Itoh, Naoya Sakamoto, Steven B. Simon, Daiki Yamamoto, Hisayoshi Yurimoto
    Meteoritics and Planetary Science 56 6 1224 - 1239 2021年06月 [査読有り]
     
    Coarse-grained, igneous Ca-Al-rich inclusions (CAIs) in CV chondrites formed through multiple melting events. We conducted in situ O-isotope analysis and Al-Mg systematics by secondary ion mass spectrometry of relict and overgrown minerals from a partial melting event in an Allende Type B CAI, Golfball. Golfball has a Type B CAI bulk composition and a unique structure: a fassaite-rich mantle enclosing a melilite-rich core. Many of the blocky melilite crystals in the core have irregularly shaped, Al-rich (Åk5–15) cores enclosed in strongly zoned (Åk30–70) overgrowths. Since the Al-rich melilite grains could not have formed from a melt of Golfball, they are interpreted as relict grains that survived later melting events. The O-isotopic compositions of the blocky melilite crystals plot along the carbonaceous chondrite anhydrous mineral line, ranging between Δ17O ~ −14‰ and −5‰. The Al-rich relict melilite grains and their overgrowths exhibit the same O-isotopic compositions, while the O-isotopic compositions are varied spatially among melilites. We found that the O-isotopic compositions steeply change across several melilite crystals within few tens of micrometers, indicating the O-isotopic compositions of the melt could not have been homogenized during the partial melting in that scale. According to the time scale of O self-diffusivity in the melt, the cooling rate of the partial melting event is calculated to be >6 × 104 K h−1. Al-Mg isotope data for core minerals plot on a straight line on an Al-Mg evolution diagram. A mineral isochron for Golfball gives initial 26Al/27Al of (4.42 ± 0.20) × 10–5 and initial δ26Mg* of −0.035 ± 0.050‰. The chemical and O-isotopic compositions of melilite and those initial values imply that its precursor consisted of fluffy Type A and/or fine-grained CAIs. The partial melting event for Golfball may have occurred in very short order after the precursor formation.
  • Wei Sun, Takashi Yoshino, Naoya Sakamoto, Hisayoshi Yurimoto
    Earth and Planetary Science Letters 561 2021年05月01日 [査読有り]
     
    Classical view has interpreted deuterons in nominally anhydrous minerals (NAMs) diffuse slightly slower than protons by the Knudsen limit of 2, whereas here we report deuteron diffusion is about 3∼7 times faster than proton one in Mg2SiO4 wadsleyite based on the H-D interdiffusion couple experiments using a pair of wadsleyite single crystal at 16 GPa and 900-1300 K. Our results indicate hydrogen diffusion in wadsleyite is affected by multiple diffusion mechanisms, of which, proton (deuteron) migrating along interstitial defects is particularly efficient to separate hydrogen isotopes in crystalline network probably owing to a quantum sieving effect. The resulting diffusion-driven H/D fractionation can explain common observations of deuterium depletion of NAMs in mantle xenoliths, suggesting that MORB inclusions hosted in xenoliths are more reliable for indicating the hydrogen isotope composition of the mantle rather than the xenolithic NAMs.
  • Ai Cheng Zhang, Qin Ting Jiang, Naotaka Tomioka, Yan Jun Guo, Jia Ni Chen, Yang Li, Naoya Sakamoto, Hisayoshi Yurimoto
    Geophysical Research Letters 48 5 2021年03月16日 [査読有り]
     
    Shock-lithification is a fundamental process of making rocks from fine-grained and porous regoliths on the surface of the Moon. Previous investigations have constrained potential shock pressures during shock-lithification based on experimental and numerical simulations. However, pressure and temperature conditions during shock-lithification have not been directly inferred from natural lunar breccias. Here, we report the discovery of widespread tissintite in strongly shock-lithified lunar meteorites, accompanied occasionally by Si-rich corundum and coesite. The coexistence of tissintite and coesite and the absence of stishovite in molten regions indicate a shock pressure of 4–8 GPa, which might be the pressure boundary between weak and strong shock-lithification. Meanwhile, the presence of Si-rich corundum imposes a temperature constraint of ∼2,300 K for the intergranular melts. This temperature constraint has profound significance for interpreting the behaviors of volatile and moderately volatile elements and remanent magnetization records during strongly shock-lithification of lunar breccias.
  • Takayuki Nonoyama, Lei Wang, Masumi Tsuda, Yuki Suzuki, Ryuji Kiyama, Kazunori Yasuda, Shinya Tanaka, Kousuke Nagata, Ryosuke Fujita, Naoya Sakamoto, Noriyuki Kawasaki, Hisayoshi Yurimoto, Jian Ping Gong
    Advanced Healthcare Materials 10 3 e2001731  2021年02月03日 [査読有り]
     
    Tough double network (DN) hydrogels are promising substitutes of soft supporting tissues such as cartilage and ligaments. For such applications, it is indispensable to robustly fix the hydrogels to bones with medically feasible methods. Recently, robustly bonding the DN hydrogels to defected bones of rabbits in vivo has been proved successful. The low crystalline hydroxyapatite (HAp) of calcium-phosphate-hydroxide salt coated on the surface layer of the DN hydrogels induced spontaneous osteogenesis penetrating into the semi-permeable hydrogels to form a gel/bone composite layer. In this work, the 44Ca isotope-doped HAp/DN hydrogel is implanted in a defect of rabbit femoral bone and the dynamic osteogenesis process at the gel/bone interface is analyzed by tracing the calcium isotope ratio using isotope microscopy. The synthetic HAp hybridized on the surface layer of DN gel dissolves rapidly in the first two weeks by inflammation, and then the immature bone with a gradient structure starts to form in the gel region, reutilizing the dissolved Ca ions. These results reveal, for the first time, that synthetic HAp is reutilized for osteogenesis. These facts help to understand the lifetime of bone absorbable materials and to elucidate the mechanism of spontaneous, non-toxic, but strong fixation of hydrogels to bones.
  • Raimundo Brahm, Georg F. Zellmer, Takeshi Kuritani, Daniel Coulthard, Mitsuhiro Nakagawa, Naoya Sakamoto, Hisayoshi Yurimoto, Eiichi Sato
    Frontiers in Earth Science 8 2021年01月29日 [査読有り]
     
    Olivine-hosted melt inclusions (MIs) are widely used as a tool to study the early stages of magmatic evolution. There are a series of processes that affect MI compositions after trapping, including post-entrapment crystallization (PEC) of the host mineral at the MI boundaries, exsolution of volatile phases into a “shrinkage bubble” and diffusive exchange between a MI and its host. Classical correction schemes applied to olivine-hosted MIs include PEC correction through addition of olivine back to the melt until it reaches equilibrium with the host composition and “Fe-loss” correction due to Fe-Mg diffusive exchange. These corrections rely on the assumption that the original host composition is preserved. However, for many volcanic samples the crystal cargo is thought to be antecrystic, and the olivine composition may thus have been completely re-equilibrated during long crystal storage times. Here, we develop a novel MI correction scheme that is applicable when the original host crystal composition has not been preserved and the initial MI composition variability can be represented by simple fractional crystallization (FC). The new scheme allows correction of MI compositions in antecrystic hosts with long and varied temperature histories. The correction fits a set of MI compositions to modelled liquid lines of descent generated by FC. A MATLAB® script (called MushPEC) iterates FC simulations using the rhyolite-MELTS algorithm. In addition to obtaining the corrected MI compositions, the application of this methodology provides estimations of magmatic conditions during MI entrapment. A set of MIs hosted in olivine crystals of homogeneous composition (Fo77–78) from a basaltic tephra of Akita-Komagatake volcano was used to test the methodology. The tephra sample shows evidence of re-equilibration of the MIs to a narrow Mg# range equivalent to the carrier melt composition. The correction shows that olivine hosts were stored in the upper crust (c. 125 – 150 MPa) at undersaturated H2O contents of c. 1 – 2 wt% H2O).
  • Motoo ITO, Tatsuaki OKADA, Yoko KEBUKAWA, Jun AOKI, Yosuke KAWAI, Jun MATSUMOTO, Toshihiro CHUJO, Ryosuke NAKAMURA, Hajime YANO, Sho-ichiro YOKOTA, Michisato TOYODA, Hisayoshi YURIMOTO, Motoki WATANABE, Ryota IKEDA, Yuki KUBO, Noel GRAND, Herve COTTIN, Arnaud BUCH, Cyril SZOPA, Osamu MORI
    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN 19 4 477 - 484 2021年 [査読有り]
  • Noriyuki Kawasaki, Changkun Park, Shigeyuki Wakaki, Hwayoung Kim, Sunyoung Park, Toshihiro Yoshimura, Kazuya Nagaishi, Hyun Na Kim, Naoya Sakamoto, Hisayoshi Yurimoto
    GEOCHEMICAL JOURNAL 55 4 283 - 287 2021年 [査読有り]
     
    Instrumental mass fractionation of Mg-isotopes and the relative sensitivity factor (RSF) for Al-27/Mg-24 ratios for in situ analysis by secondary ion mass spectrometry were investigated for minerals in Ca-Al-rich inclusions (CAIs) of meteorites, to verify systematic errors in Al-Mg chronological systematics of CAIs. We synthesized seventeen glasses with different chemical compositions that imitate those for CAI minerals and measured their Al-Mg isotopic compositions. In particular, the variation range of RSFs for six melilite glasses almost covering chemical compositions of CAI melilite is 2.0 +/- 0.3%, indicating that systematic error for Al-27/Mg-24 for melilite is less than 2.0 +/- 0.3% and likely corresponds to that of an Al-26-Mg-26 relative age of similar to 0.01 Myr for melilite-rich CAIs. Our data strongly support the robustness of variations in initial Al-26/Al-27 ratios among CAIs, corresponding to a formation age spread of similar to 0.4 Myr at the very beginning of the Solar System formation.
  • Yoko Kebukawa, Sachio Kobayashi, Noriyuki Kawasaki, Ying Wang, Hisayoshi Yurimoto, George D. Cody
    Meteoritics and Planetary Science 56 3 440 - 454 2021年 [査読有り]
     
    The large variations in hydrogen isotope ratios found in insoluble organic matter (IOM) in chondritic meteorites may be attributed to hydrogen isotopic exchange between IOM and water during aqueous alteration. We conducted D–H exchange experiments (1) during synthesis of IOM simulant (hereafter called chondritic organic analog, COA) from formaldehyde, glycolaldehyde, and ammonia with water, and (2) with the synthesized COA with a secondary reservoir of water. The changes in the D/H ratios obtained by infrared spectra of the COA suggest that most of the hydrogen in the COA is derived from water during synthesis. We further investigated the kinetics of D–H exchange between D-rich COA and D-poor water, as well as the opposite case, D-poor COA and D-rich water. To help assess understanding exchange kinetics, two-dimensional isotope imaging obtained using isotope microscope revealed that no gradient D–H exchange profiles were present in the COA grains, indicating that the rate-limiting step for D–H exchange is not diffusion. Thus, the changes in D/(D + H) ratios were fit by the first-order reaction rate law. Apparent kinetic parameters—the rate constants, the activation energies, and the frequency factors—were obtained with the Arrhenius equation. Using these kinetic expressions, hydrogen isotopic exchange profiles were estimated for time and temperature behavior. The D–H exchange between organic matter and water is apparently relatively fast and this implies that the aqueous alteration temperatures should have been very low, likely close to 0 °C to maintain hydrogen isotopic disequilibrium between organic matter and liquid water for millions of years.
  • Hisayoshi Yurimoto, Alan E. Rubin, Shoichi Itoh, John T. Wasson
    Meteoritics and Planetary Science 57 2 472 - 483 2021年 [査読有り]
     
    We studied a unique super-refractory inclusion with a core-mantle structure from CO3.0 Yamato 81020 by secondary ion mass spectrometry, electron microprobe, and scanning electron microscope techniques. The core consists largely of hibonite and nonstoichiometric Al-rich spinel indicating formation as a liquid at an exceptionally high temperature (>1900 °C). The mantle consists almost entirely of melilite with gehlenitic compositions (ranging from Åk2 to Åk25). The oxygen- and magnesium-isotopic compositions of the core and mantle are very different; typically, Δ17O (≡δ17O − 0.52 δ18O) ~–26‰ and ƒMg (mass fractionation of Mg isotopes) ~10‰/amu in the core and Δ17O ~–7‰ and ƒMg ~1‰/amu in most of the mantle. The chemical and O, Mg-isotopic data indicate that the core and mantle formed in separate events, and that the melilite now in the core was formed during the mantle-melting event, probably filling preexisting voids and surficial cavities. Analyses of core and mantle phases plot along a single 26Al-26Mg isochron with initial (26Al/27Al)0 corresponding to 4.8 ± 1.0 (±2σ) × 10–5, suggesting a similar formation age to normal CAIs in chondrites.
  • Ai Cheng Zhang, Noriyuki Kawasaki, Huiming Bao, Jia Liu, Liping Qin, Minami Kuroda, Jian Feng Gao, Li Hui Chen, Ye He, Naoya Sakamoto, Hisayoshi Yurimoto
    Nature Communications 11 1 1289 - 1289 2020年12月01日 [査読有り][通常論文]
     
    Diogenites are a group of meteorites that are derived from the interior of the largest protoplanet Vesta. They provide a unique opportunity to understanding together the internal structure and dynamic evolution of this protoplanet. Northwest Africa (NWA) 8321 was suggested to be an unbrecciated noritic diogenite meteorite, which is confirmed by our oxygen and chromium isotopic data. Here, we find that olivine in this sample has been partly replaced by orthopyroxene, troilite, and minor metal. The replacement texture of olivine is unambiguous evidence of sulfur-involved metasomatism in the interior of Vesta. The presence of such replacement texture suggests that in NWA 8321, the olivine should be of xenolith origin while the noritic diogenite was derived from partial melting of pre-existing rocks and had crystallized in the interior of Vesta. The post-Rheasilvia craters in the north-polar region on Vesta could be the potential source for NWA 8321.
  • Jie Ya Li, Ai Cheng Zhang, Naoya Sakamoto, Hisayoshi Yurimoto, Li Xin Gu
    American Mineralogist 105 11 1656 - 1661 2020年11月25日 [査読有り]
     
    The diversity of lithologies is an important proxy of internal evolution in differentiated planets and asteroids. The major lithologies in Vesta, based on the howardite-eucrite-diogenite clan meteorites, include basalt, gabbro, noritic orthopyroxenite, orthopyroxenite, dunite, harzburgite, and dacite. No other lithology has been reported up to date. In this study, we report a new occurrence of corundum in eucrite meteorite Northwest Africa (NWA) 8647. Three-dimensional petrographic observations reveal that the corundum grain occurs as a mineral inclusion in a highly deformed pyroxene fragment. The texture indicates that the corundum is not a contaminant. The corundum-associated pyroxenes have Fe-Mn compositions consistent with typical pyroxenes from howardite-eucrite-diogenite meteorites. We suggest that the corundum grain could be a xenocryst incorporated during the ascent of a basaltic magma. The results might indicate the presence of an Al-rich, Si-poor region, probably lithology in the interior of Vesta, implying that the evolution and internal structure should be much more complex than previously thought.
  • O. S. Barnouin, M. G. Daly, E. E. Palmer, R. W. Gaskell, J. R. Weirich, C. L. Johnson, M. M. Al Asad, J. H. Roberts, M. E. Perry, H. C.M. Susorney, R. T. Daly, E. B. Bierhaus, J. A. Seabrook, R. C. Espiritu, A. H. Nair, L. Nguyen, G. A. Neumann, C. M. Ernst, W. V. Boynton, M. C. Nolan, C. D. Adam, M. C. Moreau, B. Rizk, C. Y. Drouet D’Aubigny, E. R. Jawin, K. J. Walsh, P. Michel, S. R. Schwartz, R. L. Ballouz, E. M. Mazarico, D. J. Scheeres, J. W. McMahon, W. F. Bottke, S. Sugita, N. Hirata, N. Hirata, S. I. Watanabe, K. N. Burke, D. N. DellaGiustina, C. A. Bennett, D. S. Lauretta, D. E. Highsmith, J. Small, D. Vokrouhlický, N. E. Bowles, E. Brown, K. L. Donaldson Hanna, T. Warren, C. Brunet, R. A. Chicoine, S. Desjardins, D. Gaudreau, T. Haltigin, S. Millington-Veloza, A. Rubi, J. Aponte, N. Gorius, A. Lunsford, B. Allen, J. Grindlay, D. Guevel, D. Hoak, J. Hong, D. L. Schrader, J. Bayron, O. Golubov, P. Sánchez, J. Stromberg, M. Hirabayashi, C. M. Hartzell, S. Oliver, M. Rascon, A. Harch, J. Joseph, S. Squyres, D. Richardson, J. P. Emery, L. McGraw, R. Ghent, R. P. Binzel, M. M.Al Asad, C. L. Johnson, L. Philpott, H. C.M. Susorney, E. A. Cloutis, R. D. Hanna, H. C. Connolly, F. Ciceri, A. R. Hildebrand, E. M. Ibrahim, L. Breitenfeld, T. Glotch, A. D. Rogers, B. E. Clark, S. Ferrone, C. A. Thomas, H. Campins, Y. Fernandez, W. Chang, A. Cheuvront
    Nature Geoscience 13 11 764  2020年11月01日 [査読有り][通常論文]
     
    An amendment to this paper has been published and can be accessed via a link at the top of the paper.
  • Sohei Wada, Noriyuki Kawasaki, Changkun Park, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 288 161 - 175 2020年11月01日 [査読有り][通常論文]
     
    Fine-grained Ca-Al-rich inclusions (FGIs) in CV chondrites are suggested to be condensates from the solar nebular gas and thus captured O-isotopes from the gas. We conducted a combined study of petrographic observations and in situ O-isotope analysis using secondary ion mass spectrometry for an FGI, named HKD01, from the reduced CV chondrite Northwest Africa 8613. HKD01 has an irregular shape and petrographically three-layered structures: a hibonite-rich core, a spinel-rich core, and a mantle. Each petrographic domain contains melilite, hibonite, and spinel with variable proportions of those minerals. The O-isotopic compositions of the constituent minerals plotted along the slope-1 line on an O three-isotope diagram ranged between Δ17O ∼ −23‰ and 1‰. Hibonite and spinel are uniformly 16O-rich (Δ17O = −23‰) irrespective of their occurrences, while melilite crystals exhibit wide O-isotope variations ranging between Δ17O ∼ −23‰ and 1‰. The O-isotopic composition in a melilite crystal changes abruptly within ∼2 µm, indicating that disturbances of O-isotopes in melilite after condensation are less than ∼2 µm. Because the melilite in the FGI typically has grain sizes of 5–10 µm, the abrupt change of O-isotopic composition demonstrates that melilite crystals in the FGI preserve the O-isotopic composition of the nebular gas from which they condensed. In the mantle, aggregates of melilite crystals, having relatively large grain sizes (10–25 µm) and oscillatory chemical zoning, exhibit 16O-poor compositions with small variations ranging between Δ17O ∼ −4 and 1‰. Among them, a large melilite crystal (∼20 µm) with homogeneously 16O-poor composition (Δ17O ∼ 0‰) across the single crystal was found. The coexistence of 16O-poor and 16O-rich melilite crystals without O-isotope disturbances in the FGI reveals that 16O-poor (Δ17O ∼ 0‰) nebular gas existed in the formation region of the FGI HKD01 in addition to 16O-rich (Δ17O ∼ –23‰) nebular gas.
  • C. Lormand, G. F. Zellmer, G. N. Kilgour, K. Németh, A. S. Palmer, N. Sakamoto, H. Yurimoto, T. Kuritani, Y. Iizuka, A. Moebis
    Journal of Petrology 61 10 2020年10月01日 [査読有り]
     
    To assess whether magma ascent rates control the style of volcanic eruption, we have studied the petrography, geochemistry and size distribution of microlites of plagioclase and pyroxene from historical eruptions from Tongariro, Ruapehu and Ngauruhoe volcanoes located in the southern Taupo Volcanic Zone, New Zealand. The studied deposits represent glassy andesitic and dacitic tephra shards from the Mangamate, Mangatawai, Tufa Trig and Ngauruhoe tephra formations, ranging in age from 11 000 years bp to ad 1996. Covering a range in eruption styles and sizes from Strombolian to Plinian, these samples provide an excellent opportunity to explore fundamental volcanic processes such as pre-eruptive magma ascent processes. Our quantitative petrographic analysis shows that larger microlites (>30 μm) display complex growth zoning, and only the smallest crystals (<30 μm) have formed during magma ascent in the conduit. Using a combination of orthopyroxene geothermometry, plagioclase hygrometry, and MELTS modelling, we show that these microlites nucleated at maximum pressures of 550 MPa (c. 16·5 km) from hot andesitic magmas (1010-1130 °C) with low H2O content (0-1·5 wt%). Size distributions of a total of >60 000 microlites, involving 22 tephras and 99 glass shards, yield concave-up curves, and the slopes of the pyroxene microlite size distributions, in combination with well-constrained orthopyroxene crystal growth rates from one studied tephra, indicate microlite population growth times of ∼3 ± 1 days, irrespective of eruption style. These data imply that microlites form in response to cooling of melts ascending at velocities of <5 cm s-1 prior to H2O exsolution, which occurs only at <33 MPa. Maximum magma ascent rates in the upper conduit, calculated using the exsolution of water during final decompression, range between 3 and 12 m s-1; that is, at least an order of magnitude lower than the hypersonic vent velocities typical of Vulcanian or sub-Plinian eruptions (up to 400 m s-1). This implies that magma ascent from depths of an average of 4 km occurs in dykes, and that vent velocities at the surface are controlled by a reduction of conduit cross-section towards the surface (e.g. dyke changing to cylindrical conduit).
  • Yong Xiong, Ai Cheng Zhang, Noriyuki Kawasaki, Chi Ma, Naoya Sakamoto, Jia Ni Chen, Li Xin Gu, Hisayoshi Yurimoto
    Meteoritics and Planetary Science 55 10 2184 - 2205 2020年10月 [査読有り][通常論文]
     
    Calcium-aluminum-rich inclusions (CAIs) are the first solid materials formed in the solar nebula. Among them, ultrarefractory inclusions are very rare. In this study, we report on the mineralogical features and oxygen isotopic compositions of minerals in a new ultrarefractory inclusion CAI 007 from the CV3 chondrite Northwest Africa (NWA) 3118. The CAI 007 inclusion is porous and has a layered (core–mantle–rim) texture. The core is dominant in area and mainly consists of Y-rich perovskite and Zr-rich davisite, with minor refractory metal nuggets, Zr,Sc-rich oxide minerals (calzirtite and tazheranite), and Fe-rich spinel. The calzirtite and tazheranite are closely intergrown, probably derived from a precursor phase due to thermal metamorphism on the parent body. The refractory metal nuggets either exhibit thin exsolution lamellae of Fe,Ni-dominant alloy in Os,Ir-dominant alloy or are composed of Os,Ir,Ru,Fe-alloy and Fe,Ni,Ir-alloy with troilite, scheelite, gypsum, and molybdenite. The later four phases are apparently secondary minerals. The Zr,Sc,Y-rich core is surrounded by a discontinuous layer of closely intergrown hibonite and spinel. The CAIs are rimmed by Fe-rich spinel and Al-rich diopside. Perovskite has high concentrations of the most refractory rare earth elements (REEs) but is relatively depleted in the moderately refractory and volatile REEs, consistent with the ultrarefractory REE pattern. Based on this unusual Zr,Sc,Y-rich mineral assemblage, the layered distribution in CAI 007, and the REE concentrations in perovskite, we suggest that CAI 007 is an ultrarefractory inclusion of condensation origin. In CAI 007, hibonite, spinel, and probably Al-rich diopside are 16O-rich (Δ17O ~–22‰) whereas perovskite and davisite are 16O-poor (Δ17O ~–3‰). Such oxygen isotope heterogeneity suggests that the UR inclusion formed in the various degrees of 16O-rich nebular setting or was originally 16O-rich and then experienced oxygen isotope exchange with 16O-poor fluid on the CV3 chondrite parent body.
  • Hiromi Hongo, Tomoka Hasegawa, Masami Saito, Kanako Tsuboi, Tomomaya Yamamoto, Muneteru Sasaki, Miki Abe, Paulo Henrique Luiz de Freitas, Hisayoshi Yurimoto, Nobuyuki Udagawa, Minqi Li, Norio Amizuka
    Journal of Histochemistry and Cytochemistry 68 10 651 - 668 2020年10月01日 [査読有り][通常論文]
     
    To demonstrate the ultrastructure of osteocytic osteolysis and clarify whether osteocytic osteolysis occurs independently of osteoclastic activities, we examined osteocytes and their lacunae in the femora and tibiae of 11-week-old male wild-type and Rankl−/− mice after injection of human parathyroid hormone (PTH) [1-34] (80 µg/kg/dose). Serum calcium concentration rose temporarily 1 hr after PTH administration in wild-type and Rankl−/− mice, when renal arteries and veins were ligated. After 6 hr, enlargement of osteocytic lacunae was evident in the cortical bones of wild-type and Rankl−/− mice, but not so in their metaphyses. Von Kossa staining and transmission electron microscopy showed broadly demineralized bone matrix peripheral to enlarged osteocytic lacunae, which contained fragmented collagen fibrils and islets of mineralized matrices. Nano-indentation by atomic force microscopy revealed the reduced elastic modulus of the PTH-treated osteocytic perilacunar matrix, despite the microscopic verification of mineralized matrix in that region. In addition, 44Ca deposition was detected by isotope microscopy and calcein labeling in the eroded osteocytic lacunae of wild-type and Rankl−/− mice. Taken together, our findings suggest that osteocytes can erode the bone matrix around them and deposit minerals on their lacunar walls independently of osteoclastic activity, at least in the murine cortical bone. (J Histochem Cytochem 68: –XXX, 2020)
  • Ai Cheng Zhang, Run Lian Pang, Naoya Sakamoto, Hisayoshi Yurimoto
    American Mineralogist 105 7 1021 - 1029 2020年07月28日 [査読有り][通常論文]
     
    "Cr-Zr-Ca armalcolite"is a mineral originally found in Apollo samples five decades ago. However, no structural information has been obtained for this mineral. In this study, we report a new occurrence of "Cr-Zr-Ca armalcolite"and its associated mineral assemblage in an Mg-suite lithic clast (Clast-20) from the brecciated lunar meteorite Northwest Africa 8182. In this lithic clast, plagioclase (An = 88-91), pyroxene (Mg#[Mg/(Mg+Fe)] = 0.87-0.91) and olivine (Mg# = 0.86-0.87) are the major rock-forming minerals. Armalcolite and "Cr-Zr-Ca armalcolite"are observed with other minor phases including ilmenite, chromite, rutile, fluorapatite, merrillite, monazite, FeNi metal, and Fe-sulfide. Based on 38 oxygen atoms, the chemical formula of "Cr-Zr-Ca armalcolite"is (Ca0.99Na0.01)ς1.00(Ti14.22Fe2.06Cr2.01 Mg1.20Zr0.54Al0.49Ca0.21Y0.05Mn0.04Ce0.03Si0.03La0.01Nd0.01Dy0.01)ς20.91O38. Electron backscatter diffraction (EBSD) results reveal that the "Cr-Zr-Ca armalcolite"has a loveringite R3 structure, differing from the armalcolite Bbmm structure. The estimated hexagonal cell parameters a and c of "Cr-Zr-Ca armalcolite"are 10.55 and 20.85 Å, respectively. These structural and compositional features indicate that "Cr-Zr-Ca armalcolite"is loveringite, not belonging to the armalcolite family. Comparison with "Cr-Zr-Ca armalcolite"and loveringite of other occurrences implies that loveringite might be an important carrier of rare earth elements in lunar Mg-suite rocks. The compositional features of plagioclase and mafic silicate minerals in Clast-20 differ from those in other Mg-suite lithic clasts from Apollo samples and lunar meteorites, indicating that Clast-20 represents a new example of diverse lunar Mg-suite lithic clasts.
  • Noriyuki Kawasaki, Sohei Wada, Changkun Park, Naoya Sakamoto, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 279 1 - 15 2020年06月15日 [査読有り][通常論文]
     
    Fine-grained Ca-Al-rich inclusions (FGIs) in CV chondrites are suggested to be condensates formed directly from the solar nebular gas. Al–Mg mineral isochrons of seven FGIs from reduced CV chondrites Efremovka, Vigarano, Thiel Mountains 07007, and Northwest Africa 8613 were obtained via in situ Al–Mg isotope measurements using secondary ion mass spectrometry. The slopes of the mineral isochrons for seven FGIs exhibit statistically significant variations in initial 26Al/27Al ratios, (26Al/27Al)0, ranging from (5.19 ± 0.17) to (3.35 ± 0.21) × 10−5, which correspond to a relative age spread of 0.44 ± 0.07 Myr. Inferred upper limit of (26Al/27Al)0 for the FGIs is identical to the Solar System (26Al/27Al)0 of ∼5.2 × 10−5 as determined by whole-rock Al–Mg isochron studies for CAIs in CV chondrites. The intercepts of the mineral isochrons, the initial 26Mg/24Mg ratios the FGIs formed with, are consistent with Mg-isotope evolution path of a solar-composition nebular gas. The observed variations in (26Al/27Al)0 for FGIs are essentially similar to those (∼5.2 to ∼4.2 × 10−5) for coarse-grained, igneous CAIs of CV chondrites that are formed by melting and solidification. If 26Al was distributed homogeneously in the forming region, then our data indicate that thermal processes of condensation and melting for CAI formation occurred contemporaneously and continued for at least ∼0.4 Myr at the very beginning of the Solar System. Alternatively, the observed variations in (26Al/27Al)0 also indicate the possibility of heterogeneous distributions of 26Al in the forming region, corresponding to a range of over at least 3.4 × 10–5 < (26Al/27Al)0 < 5.2 × 10–5.
  • Daiki Yamamoto, Shogo Tachibana, Noriyuki Kawasaki, Hisayoshi Yurimoto
    Meteoritics and Planetary Science 55 6 1281 - 1292 2020年06月01日 [査読有り][通常論文]
     
    Oxygen isotope exchange experiments between tens of nanometer-sized amorphous enstatite grains and water vapor were carried out under a condition of protoplanetary disk-like low water vapor pressure in order to investigate the survivability of distinct oxygen isotope signatures of presolar silicate grains in the protosolar disk. Oxygen isotope exchange between amorphous enstatite and water vapor proceeded at 923–1003 K and 0.3 Pa of water vapor through diffusive isotope exchange in the amorphous structure. The rate of diffusive isotope exchange is given by D (m2 s–1) = (5.0 ± 0.2) × 10–21 exp[–161.3 ± 1.7 (kJ mol–1) R–1 (1/T–1/1200)]. The activation energy for the diffusive isotope exchange for amorphous enstatite is the same as that for amorphous forsterite within the analytical uncertainties, but the isotope exchange rate is ~30 times slower in amorphous enstatite because of the difference in frequency factor of the reaction. The reaction kinetics indicates that 0.1–1 μm-sized presolar amorphous silicate dust with enstatite and forsterite compositions would avoid oxygen isotope exchange with protosolar disk water vapor only if they were kept at temperatures below ~500–650 K within the lifetime of the disk gas.
  • Ai Cheng Zhang, Noriyuki Kawasaki, Minami Kuroda, Yang Li, Hua Pei Wang, Xue Ning Bai, Naoya Sakamoto, Qing Zhu Yin, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 275 48 - 63 2020年04月 [査読有り][通常論文]
     
    Most meteorites are believed to be chips from planetesimals and can provide clues to constrain the chemical evolution and dynamic history of the early Solar System. In this study, we report two unique fragments (ALF-1 and ALF-2) enclosed in the CH3 carbonaceous chondrite Sayh al Uhaymir 290. These two fragments are dominated by Ca,Fe-rich olivine with various amounts of Al,Ti-rich augite, anorthite, oxide minerals, Ca-phosphate mineral, FeNi metal, enstatite, and less Al,Ti-rich augite. The Ca-Mg-Fe systematics and Fe/Mn ratios of olivine grains in the two fragments are similar to that of the volcanic angrites. These similar features imply that the parent body of the two fragments might have bulk chemistry, oxygen fugacity, and differentiation resembling the angrite parent body. However, high-precision SIMS measurements reveal oxygen isotope compositions Δ17O = 0.91 ± 0.18‰ (2σ) of olivine in the two fragments are distinctly different from that of known angrite meteorites, possibly representing a new type of basaltic planetesimal. The two fragments also have a few mineralogical features distinct from angrite meteorites. They include: (1) the lack of a typical igneous texture; (2) the coexistence of two spatially associated Al,Ti-rich augites with different contents of CaO, Al2O3, MgO, and P2O5; (3) the presence of an enstatite-dominant rim in ALF-1; (4) the presence of a Cr,Mn-rich margin in ALF-1; and (5) complex microscale heterogeneity in oxide minerals. We argue that these features could be due to complex thermal histories in their parent body and/or after ejection from their parent body. Among these features, the Mn,Cr-rich margin and the enstatite-dominant rim in ALF-1 can be best explained with thermal events in nebular settings. This implies that the differentiation of the parent body of the two fragments might have taken place prior to the dissipation of the nebular gas.
  • Yuichi Nakazawa, Sachio Kobayashi, Hisayoshi Yurimoto, Fumito Akai, Hidehiko Nomura
    Quaternary International 535 3 - 12 2020年01月10日 [査読有り][通常論文]
     
    Archaeologists have long used obsidian hydration dating method to give chronometric dates for obsidian artifacts. Models using these equations independently employ different measurement systems, which are based on rim thicknesses determined by optical microscope and hydrogen depths measured by secondary ion mass spectrometry (SIMS), respectively, although the inconsistency of both measurements has been reported. Firstly, this paper describes a systematic comparison that was done on optical rim thicknesses and hydrogen depths by means of an isotope microscope, which provides micro-imaging with SIMS. Depth profiles of hydrogen were precisely obtained from the spots where optical measurements were taken on the archaeological obsidian flakes from two distinctive cultural horizons (older: Upper Paleolithic, younger: Initial Jomon) in the stratified open-air site of Jozuka in southern Kyushu (Japan). Secondarily, using the measurements of hydrogen depths that are the most consistent to the measurements of optical thicknesses, the estimated hydration rate of the Holocene (Initial Jomon) is slower than that of the Late Pleistocene (Upper Paleolithic), implying that the difference in hydration rates was due to the difference of intrinsic water content of obsidian and/or obsidian geochemistry. An application of micro-imaging with SIMS to measure hydrogen depths on obsidian shows promise as a tool for improving the practice of hydration dating and evaluating local climatic condition.
  • Nozomi Matsuda, Naoya Sakamoto, Shogo Tachibana, Hisayoshi Yurimoto
    Chemie der Erde 79 4 2019年12月 [査読有り][通常論文]
     
    Due to their common occurrence in various types of chondrites, igneous rims formed on pre-existing chondrules throughout chondrule-forming regions of the solar nebula. Although the peak temperatures are thought to reach similar values to those achieved during chondrule formation events, the heating duration in chondrule rim formation has not been well defined. We determined the two-dimensional chemical and oxygen isotopic distributions in an igneous rim of a chondrule within the Northwest Africa 3118 CV3oxA chondrite with sub-micrometer resolution using secondary ion mass spectrometry and scanning electron microscopy. The igneous rim experienced aqueous alteration on the CV parent body. The aqueous alteration resulted in precipitation of the secondary FeO-rich olivine (Fa40–49) and slightly disturbed the Fe-Mg distribution in the MgO-rich olivine phenocrysts (Fa11–22) at about a 1 μm scale. However, no oxygen isotopic disturbances were observed at a scale greater than 100 nm. The MgO-rich olivine, a primary phase of igneous rim formation, has δ17O = −6 ± 3‰ and δ18O = −1 ± 4‰, and some grains contain extreme 16O-rich areas (δ17O, δ18O = ∼−30‰) nearly 10 μm across. We detected oxygen isotopic migration of approximately 1 μm at the boundaries of the extreme 16O-rich areas. Using oxygen self-diffusivity in olivine, the heating time of the igneous rim formation could have continued from several hours to several days at near liquidus temperatures (∼2000 K) in the solar nebula suggesting that the rim formed by a similar flash heating event that formed the chondrules.
  • C. W. Hergenrother, C. K. Maleszewski, M. C. Nolan, J. Y. Li, C. Y. Drouet d’Aubigny, F. C. Shelly, E. S. Howell, T. R. Kareta, M. R.M. Izawa, M. A. Barucci, E. B. Bierhaus, H. Campins, S. R. Chesley, B. E. Clark, E. J. Christensen, D. N. DellaGiustina, S. Fornasier, D. R. Golish, C. M. Hartzell, B. Rizk, D. J. Scheeres, P. H. Smith, X. D. Zou, D. S. Lauretta, D. E. Highsmith, J. Small, D. Vokrouhlický, N. E. Bowles, E. Brown, K. L. Donaldson Hanna, T. Warren, C. Brunet, R. A. Chicoine, S. Desjardins, D. Gaudreau, T. Haltigin, S. Millington-Veloza, A. Rubi, J. Aponte, N. Gorius, A. Lunsford, B. Allen, J. Grindlay, D. Guevel, D. Hoak, J. Hong, D. L. Schrader, J. Bayron, O. Golubov, P. Sánchez, J. Stromberg, M. Hirabayashi, S. Oliver, M. Rascon, A. Harch, J. Joseph, S. Squyres, D. Richardson, J. P. Emery, L. McGraw, R. Ghent, R. P. Binzel, M. M. Al Asad, C. L. Johnson, L. Philpott, H. C.M. Susorney, E. A. Cloutis, R. D. Hanna, H. C. Connolly, F. Ciceri, A. R. Hildebrand, E. M. Ibrahim, L. Breitenfeld, T. Glotch, A. D. Rogers, S. Ferrone, C. A. Thomas, Y. Fernandez, W. Chang, A. Cheuvront, D. Trang, S. Tachibana, H. Yurimoto, J. R. Brucato, G. Poggiali, M. Pajola, E. Dotto, E. Mazzotta Epifani, M. K. Crombie, C. Lantz, J. de Leon, J. Licandro, J. L.Rizos Garcia, S. Clemett, K. Thomas-Keprta, S. Van wal, M. Yoshikawa, J. Bellerose, S. Bhaskaran, C. Boyles
    Nature Communications 10 1 2019年12月01日 [査読有り][通常論文]
     
    During its approach to asteroid (101955) Bennu, NASA’s Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft surveyed Bennu’s immediate environment, photometric properties, and rotation state. Discovery of a dusty environment, a natural satellite, or unexpected asteroid characteristics would have had consequences for the mission’s safety and observation strategy. Here we show that spacecraft observations during this period were highly sensitive to satellites (sub-meter scale) but reveal none, although later navigational images indicate that further investigation is needed. We constrain average dust production in September 2018 from Bennu’s surface to an upper limit of 150 g s–1 averaged over 34 min. Bennu’s disk-integrated photometric phase function validates measurements from the pre-encounter astronomical campaign. We demonstrate that Bennu’s rotation rate is accelerating continuously at 3.63 ± 0.52 × 10–6 degrees day–2, likely due to the Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect, with evolutionary implications.
  • D. A. Zedgenizov, A. L. Ragozin, H. Kagi, H. Yurimoto, V. S. Shatsky
    Geochemistry International 57 9 964 - 972 2019年09月01日 [査読有り][通常論文]
     
    Abstract: The paper describes mineralogical characteristics of SiO2 inclusions in sublithospheric diamonds, which typically have complicated growth histories showing alternating episodes of growth, dissolution, and postgrowth deformation and crushing processes. Nitrogen contents in all of the crystals do not exceed 71 ppm, and nitrogen is detected exclusively as B-defects. The carbon isotope composition of the diamonds varies from δ13С = –26.5 to –6.7‰. The SiO2 inclusions occur in association with omphacitic clinopyroxenes, majoritic garnets, CaSiO3, jeffbenite, and ferropericlase. All SiO2 inclusions are coesite, which is often associated with micro-blocks of kyanite in the same inclusions. It was suggested that these phases have been produced by the retrograde dissolution of primary Al-stishovite, which is also evidenced by the significant internal stresses in the inclusions and by deformations around them. The oxygen isotope composition of SiO2 inclusions in sublithospheric diamonds (δ18O up to 12.9‰) indicates a crustal origin of the protoliths. The negative correlation between the δ18O of the SiO2 inclusions and the δ13C of their host diamonds reflects interaction processes between slab-derived melts and reduced mantle rocks at depths greater than 270 km.
  • Jean Bollard, Noriyuki Kawasaki, N. Sakamoto, Mia Olsen, Shoichi Itoh, Kirsten Larsen, Daniel Wielandt, Martin Schiller, James N. Connelly, Hisayoshi Yurimoto, Martin Bizzarro
    Geochimica et Cosmochimica Acta 260 62 - 83 2019年09月01日 [査読有り][通常論文]
     
    Chondrites are fragments of asteroids that avoided melting and, thus, provide a record of the material that accreted to form protoplanets. The dominant constituent of chondrites are millimeter-sized chondrules formed by transient heating events in the protoplanetary disk. Some chondritic components, including chondrules, contain evidence of the extinct short-lived radionuclide 26Al (half-life of 0.73 Myr). The decay of 26Al is postulated to have been an important heat source promoting asteroidal melting and differentiation. Thus, understanding the 26Al inventory in the accretion regions of differentiated asteroids is critical to constrain the accretion timescales of protoplanets. The current paradigm asserts that the canonical 26Al/27Al ratio of ∼ 5 × 10−5 recorded by the oldest dated solids, calcium-aluminium refractory inclusions, represents that of the bulk Solar System. We report, for the first time, the 26Al-26Mg systematics of chondrules from the North West Africa (NWA) 5697 L 3.10 ordinary chondrite and Allende CV3OxA (Vigarano type) carbonaceous chondrite that have been previously dated by U-corrected Pb-Pb dating. Eight chondrules, which record absolute ages ranging from 4567.57 ± 0.56 to 4565.84 ± 0.72 Ma, define statistically-significant internal isochron relationships corresponding to initial (26Al/27Al) ([26Al/27Al]0) ratios in their precursors at the time of CAI formation at 4567.3 ± 0.16 Ma ranging from (3.92+4.53-2.95) × 10−6 to (2.74+1.30-1.09) × 10−5. These initial ratios are much lower than those predicted by the Pb-Pb ages, corresponding to age mismatches between the Pb-Pb and 26Al-26Mg systems ranging from 0.69+0.54-0.44 to 2.71+0.66-0.59 Myr. All chondrules record 54Cr/52Cr compositions indicating an origin from inner Solar System precursor material and, as such, we interpret the age mismatch to reflect a reduced initial abundance of 26Al in the chondrule precursors, similar to that proposed for the angrite parent body. In particular, the range of [26Al/27Al]0 ratios essentially defines two groups, which are apparently correlated with the absolute ages of the chondrules. A first group, charactertized by chondrules with absolute Pb-Pb ages identical to CAIs, defines a mean [26Al/27Al]0 value of (4.75+1.99-1.21) × 10−6, whereas a second group, with absolute ages ∼1 Myr younger than CAIs, record a mean mean [26Al/27Al]0 of (1.82+0.57-0.40) × 10−5. We interpret this systematic variability in [26Al/27Al]0 values as reflecting progressive inward transport and admixing of dust of solar composition and 26Al content from the outer disk during chondrule recycling and remelting. Finally, a reduced [26Al/27Al]0 ratio in chondrule precursors impacts our understanding of the accretion timescales of differentiated planetesimals if chondrules are indeed representative of inner disk material. Using the average [26Al/27Al]0 ratio of (1.36 ± 0.72) × 10−5 defined by the eight chondrules, thermal modelling constrains the accretion of differentiated planetesimals formed with this 26Al inventory from ∼0.1 to ∼0.9 Myr after Solar System formation to ensure melting by 26Al decay.
  • Zhang A. C, Kawasaki N, Kuroda M, Li Y, Wang H, Bai X. N, Sakamoto N, Yin Q. Z, Yurimoto H
    METEORITICS & PLANETARY SCIENCE 54 2019年08月 [査読有り][通常論文]
  • Isono Y, Sakamoto N, Ishibashi A, Song J, Yurimoto H
    METEORITICS & PLANETARY SCIENCE 54 2019年08月 [査読有り][通常論文]
  • Park C, Sakamoto N, Wakaki S, Kobayashi S, Kawasaki N, Yurimoto H
    METEORITICS & PLANETARY SCIENCE 54 2019年08月 [査読有り][通常論文]
  • Kawasaki N, Park C, Sakamoto N, Yurimoto H
    METEORITICS & PLANETARY SCIENCE 54 2019年08月 [査読有り][通常論文]
  • Matsuda N, Sakamoto N, Tachibana S, Yurimoto H
    METEORITICS & PLANETARY SCIENCE 54 2019年08月 [査読有り][通常論文]
  • Sohei Wada, Noriyuki Kawasaki, Hisayoshi Yurimoto
    METEORITICS & PLANETARY SCIENCE 54 2019年08月 [査読有り][通常論文]
  • Hisayoshi Yurimoto
    METEORITICS & PLANETARY SCIENCE 54 8 1892 - 1892 2019年08月 [査読有り][通常論文]
  • Kosuke Nagata, Ken Ichi Bajo, Satoru Itose, Miyuki Matsuya, Morio Ishihara, Kiichiro Uchino, Hisayoshi Yurimoto
    Applied Physics Express 12 8 2019年08月01日 [査読有り][通常論文]
     
    A chromatic and spherical aberration corrector with liquid Ga ion metal source was developed. The aberration corrector reduced the ion probe diameter to ∼1.5 times smaller for the 69Ga+ beam in aberration correction mode compared with the corrector in non-aberration correction mode. The probe current at a given probe size is approximately two times larger in aberration correction mode than in non-aberration correction mode. The aberration-corrected focused ion beam yields higher lateral resolutions and higher sensitivities with lower acceleration voltage for the same acquisition time down to 10 nm with a current of 1 pA.
  • Wei Sun, Takashi Yoshino, Minami Kuroda, Naoya Sakamoto, Hisayoshi Yurimoto
    Journal of Geophysical Research: Solid Earth 124 6 5696 - 5707 2019年06月 [査読有り][通常論文]
     
    Knowledge of water content and distribution in the Earth's mantle is critical to understanding the geochemical evolution and geodynamic processes of the Earth, since water can incorporate into nominally anhydrous minerals at high pressure and dramatically affect the chemical and physical properties of mantle minerals. Hydrogen diffusion controls the transport of water and electrical conductivity in the deep Earth but is not fully understood for olivine, the most abundant mineral in the upper mantle. Here we present new hydrogen self-diffusion coefficients determined from interdiffusion in H- and D-doped olivine single-crystal couples at the upper mantle conditions (3–13 GPa and 1,000–1,300 K). Present activation enthalpy for hydrogen migration is significant smaller than previous work determined within a limited measured temperature range. Parallel interdiffusion experiments with diversified water concentrations demonstrated that hydrogen diffusivity strongly accelerated by the water content in olivine. The geometric average diffusion coefficient on olivine is showed as a function of temperature and water content: (Formula presented.). Combined with the Nernst-Einstein relation, the present results can constrain the contribution of water to the electrical conductivity on olivine. It suggests that in situ conductivity measurements on hydrous olivine at low temperatures (<1,000 K) produced too low activation enthalpy to extrapolate to the higher temperatures. Comparison with previous results by conductivity measurements on single-crystal olivine suggests that the literature data except for Dai and Karato (2014) might overestimate water effect on conductivity because of heterogeneity of synthetic single crystals. Because of a change of dominant hydrogen diffusion mechanism at high temperature, this study suggests that the modeling of mantle conductivity with a high activation enthalpy from diffusion data is more trustworthy. Considering a reevaluated activation enthalpy on hydrogen diffusion and water solubility in olivine, comparisons between present conductivity model and geophysical observations suggest that hydration of olivine cannot account for extremely high conductive values (10−2–10−1 S/m) observed in the oceanic asthenosphere.
  • May Sas, Noriyuki Kawasaki, Naoya Sakamoto, Phil Shane, Georg F. Zellmer, Adam J.R. Kent, Hisayoshi Yurimoto
    Chemical Geology 513 153 - 166 2019年05月20日 [査読有り][通常論文]
     
    We investigated the potential of multi-collector secondary ion mass spectrometry (MC-SIMS) as a tool for obtaining Sr isotopic compositions in plagioclase, a ubiquitous mineral in igneous rocks that serves as a recorder of crystallization history. MC-SIMS allows for high spatial resolution analysis (~12 μm in this study) of isotopes, and therefore improves the temporal scale at which fluctuations in crystallization conditions can be recognized, ultimately improving our understanding of rates of magmatic processes. Plagioclase crystals from two young rhyolitic deposits from two major eruptive complexes, Tarawera and Haroharo, of the Okataina Volcanic Centre in New Zealand were analysed. Results were corrected for matrix effects using linear modelling of MC-SIMS data versus An contents, as well as 87 Sr/ 86 Sr ratios acquired via laser ablation inductively-coupled plasma mass spectrometry (LA-MC-ICP-MS). Corrected MC-SIMS Sr isotopic ratios had an average 2σ uncertainty of ±0.0008 per spot, and were homogeneous in Okataina plagioclase at high spatial resolutions. Average LA-MC-ICP-MS 87 Sr/ 86 Sr ratios of plagioclase from both intra-caldera volcanic complexes (Tarawera 87 Sr/ 86 Sr = 0.7056 and Haroharo 87 Sr/ 86 Sr = 0.7054) suggest similar magma sources and similar assimilation and fractional crystallization processes for the two complexes. Overall homogeneity of plagioclase (excluding relict cores) indicates no significant changes in contributions (i.e., crustal assimilation, mafic influx) to the system during the majority of plagioclase crystal growth. Furthermore, lack of 87 Sr/ 86 Sr ratio fluctuations in plagioclase rims suggest interaction between the resident silicic magma and the intruding mafic magma that triggered the eruptions was largely limited to volatile and heat transfer. Using appropriate standards and analysis, this MC-SIMS method can be used to detect short-lived, open-system events in magma reservoirs where differences in 87 Sr/ 86 Sr isotopic ratios are significant.
  • K. J. Walsh, E. R. Jawin, R. L. Ballouz, O. S. Barnouin, E. B. Bierhaus, H. C. Connolly, J. L. Molaro, T. J. McCoy, M. Delbo’, C. M. Hartzell, M. Pajola, S. R. Schwartz, D. Trang, E. Asphaug, K. J. Becker, C. B. Beddingfield, C. A. Bennett, W. F. Bottke, K. N. Burke, B. C. Clark, M. G. Daly, D. N. DellaGiustina, J. P. Dworkin, C. M. Elder, D. R. Golish, A. R. Hildebrand, R. Malhotra, J. Marshall, P. Michel, M. C. Nolan, M. E. Perry, B. Rizk, A. Ryan, S. A. Sandford, D. J. Scheeres, H. C.M. Susorney, F. Thuillet, D. S. Lauretta, D. E. Highsmith, J. Small, D. Vokrouhlický, N. E. Bowles, E. Brown, K. L.Donaldson Hanna, T. Warren, C. Brunet, R. A. Chicoine, S. Desjardins, D. Gaudreau, T. Haltigin, S. Millington-Veloza, A. Rubi, J. Aponte, N. Gorius, A. Lunsford, B. Allen, J. Grindlay, D. Guevel, D. Hoak, J. Hong, D. L. Schrader, J. Bayron, O. Golubov, P. Sánchez, J. Stromberg, M. Hirabayashi, S. Oliver, M. Rascon, A. Harch, J. Joseph, S. Squyres, D. Richardson, J. P. Emery, L. McGraw, R. Ghent, R. P. Binzel, M. M.Al Asad, C. L. Johnson, L. Philpott, E. A. Cloutis, R. D. Hanna, F. Ciceri, E. M. Ibrahim, L. Breitenfeld, T. Glotch, A. D. Rogers, B. E. Clark, S. Ferrone, C. A. Thomas, H. Campins, Y. Fernandez, W. Chang, A. Cheuvront, S. Tachibana, H. Yurimoto, J. R. Brucato, G. Poggiali, E. Dotto, E. Mazzotta Epifani, M. K. Crombie
    Nature Geoscience 12 5 399 - 399 2019年05月01日 [査読有り][通常論文]
     
    In the version of this Article originally published, in the sentence “There are three identified boulders with long axes exceeding 40 m and more than 200 boulders larger than 10 m2”, the term “10 m2” should have been “10 m (ref.2)”. This has now been corrected.
  • D. N. DellaGiustina, J. P. Emery, D. R. Golish, B. Rozitis, C. A. Bennett, K. N. Burke, R. L. Ballouz, K. J. Becker, P. R. Christensen, C. Y. Drouet d’Aubigny, V. E. Hamilton, D. C. Reuter, B. Rizk, A. A. Simon, E. Asphaug, J. L. Bandfield, O. S. Barnouin, M. A. Barucci, E. B. Bierhaus, R. P. Binzel, W. F. Bottke, N. E. Bowles, H. Campins, B. C. Clark, B. E. Clark, H. C. Connolly, M. G. Daly, J. de Leon, M. Delbo’, J. D.P. Deshapriya, C. M. Elder, S. Fornasier, C. W. Hergenrother, E. S. Howell, E. R. Jawin, H. H. Kaplan, T. R. Kareta, L. Le Corre, J. Y. Li, J. Licandro, L. F. Lim, P. Michel, J. Molaro, M. C. Nolan, M. Pajola, M. Popescu, J. L.Rizos Garcia, A. Ryan, S. R. Schwartz, N. Shultz, M. A. Siegler, P. H. Smith, E. Tatsumi, C. A. Thomas, K. J. Walsh, C. W.V. Wolner, X. D. Zou, D. S. Lauretta, D. E. Highsmith, J. Small, D. Vokrouhlický, E. Brown, K. L. Donaldson Hanna, T. Warren, C. Brunet, R. A. Chicoine, S. Desjardins, D. Gaudreau, T. Haltigin, S. Millington-Veloza, A. Rubi, J. Aponte, N. Gorius, A. Lunsford, B. Allen, J. Grindlay, D. Guevel, D. Hoak, J. Hong, D. L. Schrader, J. Bayron, O. Golubov, P. Sánchez, J. Stromberg, M. Hirabayashi, C. M. Hartzell, S. Oliver, M. Rascon, A. Harch, J. Joseph, S. Squyres, D. Richardson, L. McGraw, R. Ghent, M. M.Al Asad, C. L. Johnson, L. Philpott, H. C.M. Susorney, E. A. Cloutis, R. D. Hanna
    Nature Astronomy 3 4 341 - 351 2019年04月 [査読有り][通常論文]
     
    Establishing the abundance and physical properties of regolith and boulders on asteroids is crucial for understanding the formation and degradation mechanisms at work on their surfaces. Using images and thermal data from NASA’s Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft, we show that asteroid (101955) Bennu’s surface is globally rough, dense with boulders, and low in albedo. The number of boulders is surprising given Bennu’s moderate thermal inertia, suggesting that simple models linking thermal inertia to particle size do not adequately capture the complexity relating these properties. At the same time, we find evidence for a wide range of particle sizes with distinct albedo characteristics. Our findings imply that ages of Bennu’s surface particles span from the disruption of the asteroid’s parent body (boulders) to recent in situ production (micrometre-scale particles).
  • O. S. Barnouin, M. G. Daly, E. E. Palmer, R. W. Gaskell, J. R. Weirich, C. L. Johnson, M. M. Al Asad, J. H. Roberts, M. E. Perry, H. C.M. Susorney, R. T. Daly, E. B. Bierhaus, J. A. Seabrook, R. C. Espiritu, A. H. Nair, L. Nguyen, G. A. Neumann, C. M. Ernst, W. V. Boynton, M. C. Nolan, C. D. Adam, M. C. Moreau, B. Rizk, C. Y. Drouet D’Aubigny, E. R. Jawin, K. J. Walsh, P. Michel, S. R. Schwartz, R. L. Ballouz, E. M. Mazarico, D. J. Scheeres, J. W. McMahon, W. F. Bottke, S. Sugita, N. Hirata, S. I. Watanabe, K. N. Burke, D. N. DellaGiustina, C. A. Bennett, D. S. Lauretta, D. E. Highsmith, J. Small, D. Vokrouhlický, N. E. Bowles, E. Brown, K. L. Donaldson Hanna, T. Warren, C. Brunet, R. A. Chicoine, S. Desjardins, D. Gaudreau, T. Haltigin, S. Millington-Veloza, A. Rubi, J. Aponte, N. Gorius, A. Lunsford, B. Allen, J. Grindlay, D. Guevel, D. Hoak, J. Hong, D. L. Schrader, J. Bayron, O. Golubov, P. Sánchez, J. Stromberg, M. Hirabayashi, C. M. Hartzell, S. Oliver, M. Rascon, A. Harch, J. Joseph, S. Squyres, D. Richardson, J. P. Emery, L. McGraw, R. Ghent, R. P. Binzel, M. M.Al Asad, L. Philpott, E. A. Cloutis, R. D. Hanna, H. C. Connolly, F. Ciceri, A. R. Hildebrand, E. M. Ibrahim, L. Breitenfeld, T. Glotch, A. D. Rogers, B. E. Clark, S. Ferrone, C. A. Thomas, H. Campins, Y. Fernandez, W. Chang, A. Cheuvront, D. Trang, S. Tachibana, H. Yurimoto
    Nature Geoscience 12 4 247 - 252 2019年04月 [査読有り][通常論文]
     
    The shapes of asteroids reflect interplay between their interior properties and the processes responsible for their formation and evolution as they journey through the Solar System. Prior to the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) mission, Earth-based radar imaging gave an overview of (101955) Bennu’s shape. Here we construct a high-resolution shape model from OSIRIS-REx images. We find that Bennu’s top-like shape, considerable macroporosity and prominent surface boulders suggest that it is a rubble pile. High-standing, north–south ridges that extend from pole to pole, many long grooves and surface mass wasting indicate some low levels of internal friction and/or cohesion. Our shape model indicates that, similar to other top-shaped asteroids, Bennu formed by reaccumulation and underwent past periods of fast spin, which led to its current shape. Today, Bennu might follow a different evolutionary pathway, with an interior stiffness that permits surface cracking and mass wasting.
  • D. J. Scheeres, J. W. McMahon, A. S. French, D. N. Brack, S. R. Chesley, D. Farnocchia, Y. Takahashi, J. M. Leonard, J. Geeraert, B. Page, P. Antreasian, K. Getzandanner, D. Rowlands, E. M. Mazarico, J. Small, D. E. Highsmith, M. Moreau, J. P. Emery, B. Rozitis, M. Hirabayashi, P. Sánchez, S. Van wal, P. Tricarico, R. L. Ballouz, C. L. Johnson, M. M. Al Asad, H. C.M. Susorney, O. S. Barnouin, M. G. Daly, J. A. Seabrook, R. W. Gaskell, E. E. Palmer, J. R. Weirich, K. J. Walsh, E. R. Jawin, E. B. Bierhaus, P. Michel, W. F. Bottke, M. C. Nolan, H. C. Connolly, D. S. Lauretta, D. Vokrouhlický, N. E. Bowles, E. Brown, K. L. Donaldson Hanna, T. Warren, C. Brunet, R. A. Chicoine, S. Desjardins, D. Gaudreau, T. Haltigin, S. Millington-Veloza, A. Rubi, J. Aponte, N. Gorius, A. Lunsford, B. Allen, J. Grindlay, D. Guevel, D. Hoak, J. Hong, D. L. Schrader, J. Bayron, O. Golubov, J. Stromberg, C. M. Hartzell, S. Oliver, M. Rascon, A. Harch, J. Joseph, S. Squyres, D. Richardson, L. McGraw, R. Ghent, R. P. Binzel, L. Philpott, E. A. Cloutis, R. D. Hanna, F. Ciceri, A. R. Hildebrand, E. M. Ibrahim, L. Breitenfeld, T. Glotch, A. D. Rogers, B. E. Clark, S. Ferrone, C. A. Thomas, H. Campins, Y. Fernandez, W. Chang, A. Cheuvront, D. Trang, S. Tachibana, H. Yurimoto, J. R. Brucato, G. Poggiali, M. Pajola, E. Dotto, E. Mazzotta Epifani, M. K. Crombie
    Nature Astronomy 3 4 352 - 361 2019年04月 [査読有り][通常論文]
     
    The top-shaped morphology characteristic of asteroid (101955) Bennu, often found among fast-spinning asteroids and binary asteroid primaries, may have contributed substantially to binary asteroid formation. Yet a detailed geophysical analysis of this morphology for a fast-spinning asteroid has not been possible prior to the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission. Combining the measured Bennu mass and shape obtained during the Preliminary Survey phase of the OSIRIS-REx mission, we find a notable transition in Bennu’s surface slopes within its rotational Roche lobe, defined as the region where material is energetically trapped to the surface. As the intersection of the rotational Roche lobe with Bennu’s surface has been most recently migrating towards its equator (given Bennu’s increasing spin rate), we infer that Bennu’s surface slopes have been changing across its surface within the last million years. We also find evidence for substantial density heterogeneity within this body, suggesting that its interior is a mixture of voids and boulders. The presence of such heterogeneity and Bennu’s top shape are consistent with spin-induced failure at some point in its past, although the manner of its failure cannot yet be determined. Future measurements by the OSIRIS-REx spacecraft will provide insight into and may resolve questions regarding the formation and evolution of Bennu’s top-shape morphology and its link to the formation of binary asteroids.
  • V. E. Hamilton, A. A. Simon, P. R. Christensen, D. C. Reuter, B. E. Clark, M. A. Barucci, N. E. Bowles, W. V. Boynton, J. R. Brucato, E. A. Cloutis, H. C. Connolly, K. L. Donaldson Hanna, J. P. Emery, H. L. Enos, S. Fornasier, C. W. Haberle, R. D. Hanna, E. S. Howell, H. H. Kaplan, L. P. Keller, C. Lantz, J. Y. Li, L. F. Lim, T. J. McCoy, F. Merlin, M. C. Nolan, A. Praet, B. Rozitis, S. A. Sandford, D. L. Schrader, C. A. Thomas, X. D. Zou, D. S. Lauretta, D. E. Highsmith, J. Small, D. Vokrouhlický, N. E. Bowles, E. Brown, K. L. Donaldson Hanna, T. Warren, C. Brunet, R. A. Chicoine, S. Desjardins, D. Gaudreau, T. Haltigin, S. Millington-Veloza, A. Rubi, J. Aponte, N. Gorius, A. Lunsford, B. Allen, J. Grindlay, D. Guevel, D. Hoak, J. Hong, D. L. Schrader, J. Bayron, O. Golubov, P. Sánchez, J. Stromberg, M. Hirabayashi, C. M. Hartzell, S. Oliver, M. Rascon, A. Harch, J. Joseph, S. Squyres, D. Richardson, J. P. Emery, L. McGraw, R. Ghent, R. P. Binzel, M. M.Al Asad, C. L. Johnson, L. Philpott, H. C.M. Susorney, E. A. Cloutis, R. D. Hanna, H. C. Connolly, F. Ciceri, A. R. Hildebrand, E. M. Ibrahim, L. Breitenfeld, T. Glotch, A. D. Rogers, B. E. Clark, S. Ferrone, C. A. Thomas, H. Campins, Y. Fernandez, W. Chang, A. Cheuvront, D. Trang, S. Tachibana, H. Yurimoto, J. R. Brucato, G. Poggiali, M. Pajola, E. Dotto, E. Mazzotta Epifani
    Nature Astronomy 3 4 332 - 340 2019年04月 [査読有り][通常論文]
     
    Early spectral data from the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission reveal evidence for abundant hydrated minerals on the surface of near-Earth asteroid (101955) Bennu in the form of a near-infrared absorption near 2.7 µm and thermal infrared spectral features that are most similar to those of aqueously altered CM-type carbonaceous chondrites. We observe these spectral features across the surface of Bennu, and there is no evidence of substantial rotational variability at the spatial scales of tens to hundreds of metres observed to date. In the visible and near-infrared (0.4 to 2.4 µm) Bennu’s spectrum appears featureless and with a blue (negative) slope, confirming previous ground-based observations. Bennu may represent a class of objects that could have brought volatiles and organic chemistry to Earth.
  • D. S. Lauretta, D. N. DellaGiustina, C. A. Bennett, D. R. Golish, K. J. Becker, S. S. Balram-Knutson, O. S. Barnouin, T. L. Becker, W. F. Bottke, W. V. Boynton, H. Campins, B. E. Clark, H. C. Connolly, C. Y. Drouet d’Aubigny, J. P. Dworkin, J. P. Emery, H. L. Enos, V. E. Hamilton, C. W. Hergenrother, E. S. Howell, M. R.M. Izawa, H. H. Kaplan, M. C. Nolan, B. Rizk, H. L. Roper, D. J. Scheeres, P. H. Smith, K. J. Walsh, C. W.V. Wolner, D. E. Highsmith, J. Small, D. Vokrouhlický, N. E. Bowles, E. Brown, K. L. Donaldson Hanna, T. Warren, C. Brunet, R. A. Chicoine, S. Desjardins, D. Gaudreau, T. Haltigin, S. Millington-Veloza, A. Rubi, J. Aponte, N. Gorius, A. Lunsford, B. Allen, J. Grindlay, D. Guevel, D. Hoak, J. Hong, D. L. Schrader, J. Bayron, O. Golubov, P. Sánchez, J. Stromberg, M. Hirabayashi, C. M. Hartzell, S. Oliver, M. Rascon, A. Harch, J. Joseph, S. Squyres, D. Richardson, L. McGraw, R. Ghent, R. P. Binzel, M. M.Al Asad, C. L. Johnson, L. Philpott, H. C.M. Susorney, E. A. Cloutis, R. D. Hanna, F. Ciceri, A. R. Hildebrand, E. M. Ibrahim, L. Breitenfeld, T. Glotch, A. D. Rogers, S. Ferrone, C. A. Thomas, Y. Fernandez, W. Chang, A. Cheuvront, D. Trang, S. Tachibana, H. Yurimoto, J. R. Brucato, G. Poggiali, M. Pajola, E. Dotto, E. Mazzotta Epifani, M. K. Crombie, C. Lantz, J. de Leon, J. Licandro, J. L.Rizos Garcia, S. Clemett, K. Thomas-Keprta, S. Van wal
    Nature 568 7750 55 - 60 2019年04月 [査読有り][通常論文]
     
    NASA’S Origins, Spectral Interpretation, Resource Identification and Security-Regolith Explorer (OSIRIS-REx) spacecraft recently arrived at the near-Earth asteroid (101955) Bennu, a primitive body that represents the objects that may have brought prebiotic molecules and volatiles such as water to Earth1. Bennu is a low-albedo B-type asteroid2 that has been linked to organic-rich hydrated carbonaceous chondrites3. Such meteorites are altered by ejection from their parent body and contaminated by atmospheric entry and terrestrial microbes. Therefore, the primary mission objective is to return a sample of Bennu to Earth that is pristine—that is, not affected by these processes4. The OSIRIS-REx spacecraft carries a sophisticated suite of instruments to characterize Bennu’s global properties, support the selection of a sampling site and document that site at a sub-centimetre scale5–11. Here we consider early OSIRIS-REx observations of Bennu to understand how the asteroid’s properties compare to pre-encounter expectations and to assess the prospects for sample return. The bulk composition of Bennu appears to be hydrated and volatile-rich, as expected. However, in contrast to pre-encounter modelling of Bennu’s thermal inertia12 and radar polarization ratios13—which indicated a generally smooth surface covered by centimetre-scale particles—resolved imaging reveals an unexpected surficial diversity. The albedo, texture, particle size and roughness are beyond the spacecraft design specifications. On the basis of our pre-encounter knowledge, we developed a sampling strategy to target 50-metre-diameter patches of loose regolith with grain sizes smaller than two centimetres4. We observe only a small number of apparently hazard-free regions, of the order of 5 to 20 metres in extent, the sampling of which poses a substantial challenge to mission success.
  • Noriyuki Kawasaki, Changkun Park, Naoya Sakamoto, Sun Young Park, Hyun Na Kim, Minami Kuroda, Hisayoshi Yurimoto
    Earth and Planetary Science Letters 511 25 - 35 2019年04月 [査読有り][通常論文]
     
    Al–Mg mineral isochrons of three Ca–Al-rich inclusions (CAIs) that formed primarily by condensation, one fine-grained, spinel-rich inclusion and two fluffy Type A CAIs, from the reduced CV chondrites Efremovka and Vigarano were obtained by in situ Al–Mg isotope measurements using secondary ion mass spectrometry. The slope of the isochron obtained for the fine-grained, spinel-rich inclusion gives an initial 26 Al/ 27 Al value, ( 26 Al/ 27 Al) 0 , of (5.19 ± 0.17) × 10 −5 . This is essentially identical to the Solar System initial 26 Al/ 27 Al determined by whole-rock Al–Mg isochron studies for CAIs in CV chondrites. In contrast, the isochron slopes for the two fluffy Type A CAIs from their Al–Mg mineral isochrons, (4.703 ± 0.082) × 10 −5 and (4.393 ± 0.084) × 10 −5 , are significantly lower than the Solar System initial value. The range of ( 26 Al/ 27 Al) 0 values of the three CAIs, from (5.19 ± 0.17) to (4.393 ± 0.084) × 10 −5 , corresponds to a formation age spread of 0.17 ± 0.04 Myr. This formation age spread is similar to that of igneous CAIs from CV chondrites. The data suggest that condensation and melting of minerals occurred in the hot nebular gas contemporaneously for ∼0.2 Myr at the very beginning of our Solar System, if 26 Al was distributed homogeneously in the CAI forming region. Alternatively, the observed variations in ( 26 Al/ 27 Al) 0 among fluffy Type A CAIs would also raise a possibility of heterogeneous distributions of 26 Al in the forming region.
  • Minami Kuroda, Shogo Tachibana, Naoya Sakamoto, Hisayoshi Yurimoto
    American Mineralogist 104 3 385 - 390 2019年03月01日 [査読有り][通常論文]
     
    Diffusion experiments of 2H2O at 900-750 °C and water vapor pressure of 50 bar found diffusion of water in SiO2 glass more than one order of magnitude faster than that reported previously. The fast diffusion profile of water was observed as an extended tail of the normal water diffusion profile by a line scan analysis with SIMS, and it can be fitted with a diffusion model with a constant diffusivity. The obtained fast diffusion coefficient suggests that the diffusion species responsible for the fast diffusion is not molecular hydrogen but molecular water. The diffusivity and activation energy for the fast water diffusion can be explained by the correlation between diffusivities of noble gases in silica glass and their sizes. Because noble gases diffuse through free volume in the glass structure, we conclude that molecular water can also diffuse through the free volume. The abundance of free volume in the silica glass structure estimated previously is higher than that of 2H observed in the fast diffusion in this study, suggesting that the free volume was not fully occupied by 2H2O under the present experimental condition. This implies that the contribution of the fast water diffusion to the total water transport in volcanic glass becomes larger under higher water vapor pressure conditions.
  • Walsh, K.J., Jawin, E.R., Ballouz, R.-L., Barnouin, O.S., Bierhaus, E.B., Connolly, H.C., Molaro, J.L., McCoy, T.J., Delbo’, M., Hartzell, C.M., Pajola, M., Schwartz, S.R., Trang, D., Asphaug, E., Becker, K.J., Beddingfield, C.B., Bennett, C.A., Bottke, W.F., Burke, K.N., Clark, B.C., Daly, M.G., DellaGiustina, D.N., Dworkin, J.P., Elder, C.M., Golish, D.R., Hildebrand, A.R., Malhotra, R., Marshall, J., Michel, P., Nolan, M.C., Perry, M.E., Rizk, B., Ryan, A., Sandford, S.A., Scheeres, D.J., Susorney, H.C.M., Thuillet, F., Lauretta, D.S., Highsmith, D.E., Small, J., Vokrouhlický, D., Bowles, N.E., Brown, E., Donaldson Hanna, K.L., Warren, T., Brunet, C., Chicoine, R.A., Desjardins, S., Gaudreau, D., Haltigin, T., Millington-Veloza, S., Rubi, A., Aponte, J., Gorius, N., Lunsford, A., Allen, B., Grindlay, J., Guevel, D., Hoak, D., Hong, J., Schrader, D.L., Bayron, J., Golubov, O., Sánchez, P., Stromberg, J., Hirabayashi, M., Hartzell, C.M., Oliver, S., Rascon, M., Harch, A., Joseph, J., Squyres, S., Richardson, D., Emery, J.P., McGraw, L., Ghent, R., Binzel, R.P., Al Asad, M.M., Johnson, C.L., Philpott, L., Susorney, H.C.M., Cloutis, E.A., Hanna, R.D., Connolly, H.C., Ciceri, F., Hildebrand, A.R., Ibrahim, E.-M., Breitenfeld, L., Glotch, T., Rogers, A.D., Clark, B.E., Ferrone, S., Thomas, C.A., Campins, H., Fernandez, Y., Chang, W., Cheuvront, A., Trang, D., Tachibana, S., Yurimoto, H., Brucato, J.R., Poggiali, G., Pajola, M., Dotto, E., Epifani, E.M., Crombie, M.K., Lantz, C., Izawa, M.R.M., de Leon, J., Licandro, J., Garcia, J.L.R., Clemett, S., Thomas-Keprta, K., Van wal, S., Yoshikawa, M., Bellerose, J., Bhaskaran, S., Boyles, C., Chesley, S.R., Elder, C.M., Farnocchia, D., Harbison, A., Kennedy, B., Knight, A., Martinez-Vlasoff, N., Mastrodemos, N., McElrath, T., Owen, W., Park, R., Rush, B., Swanson, L., Takahashi, Y., Velez, D., Yetter, K., Thayer, C., Adam, C., Antreasian, P., Bauman, J., Bryan, C., Carcich, B., Corvin, M., Geeraert, J., Hoffman, J., Leonard, J.M., Lessac-Chenen, E., Levine, A., McAdams, J., McCarthy, L., Nelson, D., Page, B., Pelgrift, J., Sahr, E., Stakkestad, K., Stanbridge, D., Wibben, D., Williams, B., Williams, K., Wolff, P., Hayne, P., Kubitschek, D., Barucci, M.A., Deshapriya, J.D.P., Fornasier, S., Fulchignoni, M., Hasselmann, P., Merlin, F., Praet, A., Bierhaus, E.B., Billett, O., Boggs, A., Buck, B., Carlson-Kelly, S., Cerna, J., Chaffin, K., Church, E., Coltrin, M., Daly, J., Deguzman, A., Dubisher, R., Eckart, D., Ellis, D., Falkenstern, P., Fisher, A., Fisher, M.E., Fleming, P., Fortney, K., Francis, S., Freund, S., Gonzales, S., Haas, P., Hasten, A., Hauf, D., Hilbert, A., Howell, D., Jaen, F., Jayakody, N., Jenkins, M., Johnson, K., Lefevre, M., Ma, H., Mario, C., Martin, K., May, C., McGee, M., Miller, B., Miller, C., Miller, G., Mirfakhrai, A., Muhle, E., Norman, C., Olds, R., Parish, C., Ryle, M., Schmitzer, M., Sherman, P., Skeen, M., Susak, M., Sutter, B., Tran, Q., Welch, C., Witherspoon, R., Wood, J., Zareski, J., Arvizu-Jakubicki, M., Asphaug, E., Audi, E., Ballouz, R.-L., Bandrowski, R., Becker, K.J., Becker, T.L., Bendall, S., Bennett, C.A., Bloomenthal, H., Blum, D., Boynton, W.V., Brodbeck, J., Burke, K.N., Chojnacki, M., Colpo, A., Contreras, J., Cutts, J., Drouet d’Aubigny, C.Y., Dean, D., DellaGiustina, D.N., Diallo, B., Drinnon, D., Drozd, K., Enos, H.L., Enos, R., Fellows, C., Ferro, T., Fisher, M.R., Fitzgibbon, G., Fitzgibbon, M., Forelli, J., Forrester, T., Galinsky, I., Garcia, R., Gardner, A., Golish, D.R., Habib, N., Hamara, D., Hammond, D., Hanley, K., Harshman, K., Hergenrother, C.W., Herzog, K., Hill, D., Hoekenga, C., Hooven, S., Howell, E.S., Huettner, E., Janakus, A., Jones, J., Kareta, T.R., Kidd, J., Kingsbury, K., Balram-Knutson, S.S., Koelbel, L., Kreiner, J., Lambert, D., Lauretta, D.S., Lewin, C., Lovelace, B., Loveridge, M., Lujan, M., Maleszewski, C.K., Malhotra, R., Marchese, K., McDonough, E., Mogk, N., Morrison, V., Morton, E., Munoz, R., Nelson, J., Nolan, M.C., Padilla, J., Pennington, R., Polit, A., Ramos, N., Reddy, V., Riehl, M., Rizk, B., Roper, H.L., Salazar, S., Schwartz, S.R., Selznick, S., Shultz, N., Smith, P.H., Stewart, S., Sutton, S., Swindle, T., Tang, Y.H., Westermann, M., Wolner, C.W.V., Worden, D., Zega, T., Zeszut, Z., Bjurstrom, A., Bloomquist, L., Dickinson, C., Keates, E., Liang, J., Nifo, V., Taylor, A., Teti, F., Caplinger, M., Bowles, H., Carter, S., Dickenshied, S., Doerres, D., Fisher, T., Hagee, W., Hill, J., Miner, M., Noss, D., Piacentine, N., Smith, M., Toland, A., Wren, P., Bernacki, M., Munoz, D.P., Watanabe, S.-I., Sandford, S.A., Aqueche, A., Ashman, B., Barker, M., Bartels, A., Berry, K., Bos, B., Burns, R., Calloway, A., Carpenter, R., Castro, N., Cosentino, R., Donaldson, J., Dworkin, J.P., Cook, J.E., Emr, C., Everett, D., Fennell, D., Fleshman, K., Folta, D., Gallagher, D., Garvin, J., Getzandanner, K., Glavin, D., Hull, S., Hyde, K., Ido, H., Ingegneri, A., Jones, N., Kaotira, P., Lim, L.F., Liounis, A., Lorentson, C., Lorenz, D., Lyzhoft, J., Mazarico, E.M., Mink, R., Moore, W., Moreau, M., Mullen, S., Nagy, J., Neumann, G., Nuth, J., Poland, D., Reuter, D.C., Rhoads, L., Rieger, S., Rowlands, D., Sallitt, D., Scroggins, A., Shaw, G., Simon, A.A., Swenson, J., Vasudeva, P., Wasser, M., Zellar, R., Grossman, J., Johnston, G., Morris, M., Wendel, J., Burton, A., Keller, L.P., McNamara, L., Messenger, S., Nakamura-Messenger, K., Nguyen, A., Righter, K., Queen, E., Bellamy, K., Dill, K., Gardner, S., Giuntini, M., Key, B., Kissell, J., Patterson, D., Vaughan, D., Wright, B., Gaskell, R.W., Le Corre, L., Li, J.-Y., Molaro, J.L., Palmer, E.E., Siegler, M.A., Tricarico, P., Weirich, J.R., Zou, X.-D., Ireland, T., Tait, K., Bland, P., Anwar, S., Bojorquez-Murphy, N., Christensen, P.R., Haberle, C.W., Mehall, G., Rios, K., Franchi, I., Rozitis, B., Beddingfield, C.B., Marshall, J., Brack, D.N., French, A.S., McMahon, J.W., Scheeres, D.J., Jawin, E.R., McCoy, T.J., Russell, S., Killgore, M., Bottke, W.F., Hamilton, V.E., Kaplan, H.H., Walsh, K.J., Bandfield, J.L., Clark, B.C., Chodas, M., Lambert, M., Masterson, R.A., Daly, M.G., Freemantle, J., Seabrook, J.A., Barnouin, O.S., Craft, K., Daly, R.T., Ernst, C., Espiritu, R.C., Holdridge, M., Jones, M., Nair, A.H., Nguyen, L., Peachey, J., Perry, M.E., Plescia, J., Roberts, J.H., Steele, R., Turner, R., Backer, J., Edmundson, K., Mapel, J., Milazzo, M., Sides, S., Manzoni, C., May, B., Delbó, M., Libourel, G., Michel, P., Ryan, A., Thuillet, F., Marty, B.
    Nature Geoscience 2019年 [査読有り][通常論文]
     
    © 2019, The Author(s), under exclusive licence to Springer Nature Limited. Small, kilometre-sized near-Earth asteroids are expected to have young and frequently refreshed surfaces for two reasons: collisional disruptions are frequent in the main asteroid belt where they originate, and thermal or tidal processes act on them once they become near-Earth asteroids. Here we present early measurements of numerous large candidate impact craters on near-Earth asteroid (101955) Bennu by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) mission, which indicate a surface that is between 100 million and 1 billion years old, predating Bennu’s expected duration as a near-Earth asteroid. We also observe many fractured boulders, the morphology of which suggests an influence of impact or thermal processes over a considerable amount of time since the boulders were exposed at the surface. However, the surface also shows signs of more recent mass movement: clusters of boulders at topographic lows, a deficiency of small craters and infill of large craters. The oldest features likely record events from Bennu’s time in the main asteroid belt.
  • Haruna Sugahara, Yoshinori Takano, Shogo Tachibana, Iyo Sugawara, Yoshito Chikaraishi, Nanako O. Ogawa, Naohiko Ohkouchi, Akira Kouchi, Hisayoshi Yurimoto
    Geochemical Journal 53 1 5 - 20 2019年 [査読有り][通常論文]
     
    Interstellar ice is a reaction site for molecular evolution. Gaseous molecules are frozen at low temperature (~10 K) to form ice mantles and the energy supplied by UV photons and other energy sources can lead to the synthesis of complex organics. Nitrogen-containing organic molecules are of special interest because of their biomolecular importance and their anomalous stable nitrogen isotopic composition ( 15 N/ 14 N) in the interstellar dust environment. Thus, N-containing organic molecules are the keys to understanding the evolution of organic molecules and the solar system. We focused on amino acids and amines in refractory organic residues formed from ultraviolet (UV) irradiated interstellar ice analogues. We developed analytical techniques that enable the identification of the small quantities of molecules formed from the simulated interstellar ice analogues. Organic residue analysis of the UV-irradiated H 2 O-CH 3 OH-NH 3 ice showed the formation of three amines (methylamine, ethylamine and propylamine) and 11 amino acids (e.g., glycine, a-alanine, balanine, sarcosine, a-aminobutyric acid and b-aminoisobutyric acid). Furthermore, the compound-specific isotope analysis of nitrogen within the amino acids and the bulk organic film revealed that little isotopic fractionation occurred during formation in the simulated environment.
  • Ken ichi Bajo, Osamu Fujioka, Satoru Itose, Morio Ishihara, Kiichiro Uchino, Hisayoshi Yurimoto
    Surface and Interface Analysis 51 1 35 - 39 2019年01月 [査読有り][通常論文]
     
    A new electric data acquisition and operational control system was developed for time-of-flight sputtered neutral mass spectrometry (TOF-SNMS). The system is designed for high-speed data acquisition, data processing, and data streaming. The developed system is constructed on an NI-PXI platform and provides timing clocks for the TOF-SNMS operation. The system performs data processing of noise suppression and ion counting while acquiring TOF mass spectrum for 13-microsecond length at sampling rate of 3 GS/s for every 1 millisecond. In addition, the system acquires and records TOF mass spectrum of 60-microsecond length at sampling rate of 3 GS/s for every 1 millisecond without data processing. The system detects single ion signals from accumulated TOF mass spectrum of 107 times and counts up to 10 ions accurately from a single event of TOF mass spectrum.
  • Charline Lormand, Georg F. Zellmer, Károly Németh, Geoff Kilgour, Stuart Mead, Alan S. Palmer, Naoya Sakamoto, Hisayoshi Yurimoto, Anja Moebis
    Microscopy and Microanalysis 24 6 667 - 675 2018年12月01日 [査読有り][通常論文]
     
    Crystals within volcanic rocks record geochemical and textural signatures during magmatic evolution before eruption. Clues to this magmatic history can be examined using crystal size distribution (CSD) studies. The analysis of CSDs is a standard petrological tool, but laborious due to manual hand-drawing of crystal margins. The trainable Weka segmentation (TWS) plugin in ImageJ is a promising alternative. It uses machine learning and image segmentation to classify an image. We recorded back-scattered electron (BSE) images of three volcanic samples with different crystallinity (35, 50 and ≥85 vol. %), using scanning electron microscopes (SEM) of variable image resolutions, which we then tested using TWS. Crystal measurements obtained from the automatically segmented images are compared with those of the manual segmentation. Samples up to 50 vol. % crystallinity are successfully segmented using TWS. Segmentation at significantly higher crystallinities fails, as crystal boundaries cannot be distinguished. Accuracy performance tests for the TWS classifiers yield high F-scores (>0.930), hence, TWS is a successful and fast computing tool for outlining crystals from BSE images of glassy rocks. Finally, reliable CSD's can be derived using a low-cost desktop SEM, paving the way for a wide range of research to take advantage of this new petrological method.
  • Edward D. Young, Kyoshi Kuramoto, Rudolph A. Marcus, Hisayoshi Yurimoto, Stein B. Jacobsen
    Oxygen in the Solar System 68 187 - 218 2018年11月15日 [査読有り][通常論文]
     
    In this chapter we compare and contrast chemical and photochemical pathways for massindependent fractionation (MIF) of oxygen isotopes in the solar nebula. We begin by assessing the galactic evolution model for oxygen isotope variation in the Solar System in order to compare the predictions of a leading nucleosynthetic model with those of the chemical models. There are two fundamentally different classes of possible chemical mechanisms for massindependent oxygen isotope fractionation in the early Solar System. One is symmetry-induced intramolecular vibrational disequilibrium of vibrationally excited reactant oxygen-bearing molecules. The other is isotope selective photodissociation of CO coupled with self-shielding and formation of H2O. Symmetry-induced fractionation is an experimentally verified process with solid theoretical foundations. It is observed to occur in Earth's atmosphere. It could have resulted in preservation of oxygen MIF effects only if mediated by dust grain surfaces. CO self-shielding is an attractive hypothesis for the origin of mass-independent oxygen isotope fractionation in the early Solar System because it appeals to a process that apparently occurs in the interstellar medium, but it lacks experimental verification. Three astrophysical settings for CO self-shielding are proposed as sites for generating δ170 variability in the early Solar System. One is the inner annulus of the protostellar disk at relatively high temperature. Another is the surface of the disk high above the midplane where light from the central star grazes the gas and dust of the disk, resulting in a zone of active CO predissociation and self-shielding. Interstellar light illuminating the disk at high incident angles causes a similar horizon of CO photodestruction. Variations in 16O could also have been inherited from self-shielding by CO in the molecular cloud that gave rise to the protosun. The overall consequence of CO self-shielding is conversion of CO gas to 16O-poor H2O. A key difference between galactic evolution, chemically-induced MIF effects, and CO self-shielding is the predicted relative oxygen isotopic compositions of primeval dust and the Sun. Therefore, the oxygen isotopic composition of the Sun will be a crucial arbiter that may permit us to narrow the list of possible origins for oxygen MIF in the early Solar System.
  • Hisayoshi Yurimoto, Alexander N. Krot, Byeon Gak Choi, Jerome Aleon, Takuya Kunihiro, Adrian J. Brearley
    Oxygen in the Solar System 68 141 - 186 2018年11月15日 [査読有り][通常論文]
     
    We review the oxygen isotopic compositions of chondrite components (refractory inclusions, chondrules, and matrix) and their inter- and intra- crystalline oxygen isotopic distributions. Primary oxygen isotopic compositions, acquired before planetesimal accretion, are easily disturbed by parent-body processes such as aqueous alternation and thermal metamorphism. Primary or original oxygen isotopic compositions of refractory inclusions (Ca-, Al-rich inclusions and amoeboid olivine aggregates) distribute along a slope-1 line on the three-oxygen isotope diagram over the range of -60% < SnO δ17O ≈ δ18 < +10%. The variations suggest that oxygen isotopic compositions of the solar nebular gas temporally and spatially varied between l6O-rich and 17O-, 18O-rich during refractory inclusion formation. On the other hand, primary minerals of most chondrules have small isotopic variations and are enriched in 17170 and l8O relative to refractory inclusions, suggesting that chondrule formation occurred in 17O-, 18O-rich nebular gas. However, rare 16O-rich chondrules have been found, suggesting some overlap in the timing of formation of chondrules and refractory inclusions in the solar nebula. Oxygen isotopic compositions of matrix grains distribute along the slope-1 line over the same range as refractory inclusions and chondrules. The similarity in oxygen isotopic distributions suggests that matrix was originally a mechanical mixture of nebular dusts co-generated with chondrules and refractory inclusions. Presolar grains with oxygen isotopic compositions that are clearly distinct from those of solar nebular materials are a trace component of chondrite matrices. Based on these oxygen isotopic characteristics, more than 99.5% of the solid materials in the nebula formed locally in the solar nebula, and the remainder formed in interstellar space. The astrophysical setting of chondrite component formation in the early Solar System is also discussed. Refractory inclusions and 16O-rich matrix dusts formed around the inner edge of the solar nebula. On the other hand, most chondrules and 17O-, 18O-rich matrix dusts seem to have formed elsewhere in the solar nebula. Efficient, large-scale radial mixing of the solar nebular materials may have been an essential process in the formation of chondritic planetesimals.
  • Daiki Yamamoto, Minami Kuroda, Shogo Tachibana, Naoya Sakamoto, Hisayoshi Yurimoto
    Astrophysical Journal 865 2 2018年10月01日 [査読有り][通常論文]
     
    Meteoritic evidence suggests that oxygen isotopic exchange between 16O-rich amorphous silicate dust and 16O-poor water vapor occurred in the early solar system. In this study, we experimentally investigated the kinetics of oxygen isotopic exchange between submicron-sized amorphous forsterite grains and water vapor at protoplanetary disk-like low pressures of water vapor. The isotopic exchange reaction rate is controlled either by diffusive isotopic exchange in the amorphous structure or by the supply of water molecules from the vapor phase. The diffusive oxygen isotopic exchange occurred with a rate constant D (m2 s-1) = (1.5 ± 1.0) × 10-19 exp[-(161.5 ± 14.1 (kJ mol-1))R -1(1/T-1/1200)] at temperatures below ∼800-900 K, and the supply of water molecules from the vapor phase could determine the rate of oxygen isotopic exchange at higher temperatures in the protosolar disk. On the other hand, the oxygen isotopic exchange rate dramatically decreases if the crystallization of amorphous forsterite precedes the oxygen isotopic exchange reaction with amorphous forsterite. According to the kinetics for oxygen isotopic exchange in protoplanetary disks, original isotopic compositions of amorphous forsterite dust could be preserved only if the dust was kept at temperatures below 500-600 K in the early solar system. The 16O-poor signatures for the most pristine silicate dust observed in cometary materials implies that the cometary silicate dust experienced oxygen isotopic exchange with 16O-poor water vapor through thermal annealing at temperatures higher than 500-600 K prior to their accretion into comets in the solar system.
  • Hongzhan Fei, Sanae Koizumi, Naoya Sakamoto, Minako Hashiguchi, Hisayoshi Yurimoto, Katharina Marquardt, Nobuyoshi Miyajima, Tomoo Katsura
    American Mineralogist 103 9 1354 - 1361 2018年09月25日 [査読有り][通常論文]
     
    The Mg grain boundary diffusion coefficients were measured in forsterite aggregates as a function of pressure (1 atm and 13 GPa), temperature (1100-1300 K), water content (<1-350 wt. ppm bulk water), and oxygen fugacity (10-18-10-0.7 bar) using a multi-anvil apparatus and a gas-mixing furnace. The diffusion profiles were analyzed by secondary ion mass spectrometer, whereas the water contents in the samples were measured by Fourier transform infrared spectrometer. The activation volume, activation enthalpy, water content exponent, and oxygen fugacity exponent for the Mg grain-boundary diffusion coefficients are found to be 3.9 ± 0.7 cm3/mol, 355 ± 25 kJ/mol, 1.0 ± 0.1, and-0.02 ± 0.01, respectively. By comparison with the Mg lattice diffusion data (Fei et al. 2018), the bulk diffusivity of Mg in forsterite is dominated by lattice diffusion if the grain size is larger than ∼1 mm under upper mantle conditions, whereas effective grain-boundary and lattice diffusivities are comparable when the grain size is ∼1-100 μm.
  • Sho Kakizawa, Toru Inoue, Hideto Nakano, Minami Kuroda, Naoya Sakamoto, Hisayoshi Yurimoto
    American Mineralogist 103 8 1221 - 1227 2018年08月28日 [査読有り][通常論文]
     
    We determined the stability and chemical composition of Al-bearing superhydrous phase B at 20-24 GPa and 1400-2000 °C to discuss the mechanism of water transport in the mantle transition zone and uppermost lower mantle at temperatures close to the mantle geotherm. Superhydrous phase B contained significant amounts of Al2O3, from 14 to 32 wt%, and Al-bearing superhydrous phase B remained stable, even at 2000 °C and pressures of approximately 20-24 GPa. Moreover, two types of superhydrous phase B with different chemical compositions coexisted at 20-24 GPa and 1600 °C. The Al2O3 and H2O contents increased, and the MgO and SiO2 contents decreased as the pressure and temperature increased up to 1600 °C. Above 1600 °C, the MgO and Al2O3 contents increased, and the SiO2 and H2O contents decreased as the temperature increased. We found two substitution mechanisms: (1) 2Mg2+ + Si4+ a, 2Al3+ + 2H+ + □Mg (Mg site vacancy) (2Mg2+ = Al3+ + H+ + □Mg):(Si4+ = Al3+ + H+) = 1:1, (2) Si4+ + 16H+ a 4Mg2+ + 4Al3+. The maximum H2O content of Al-bearing superhydrous phase B is 11.1(3) wt%, which is ~ 1.9 times larger than that of the Mg-end-member. The crystal structures of the two coexisting superhydrous phase B values are expected to be slightly different from each other. The present results indicate that Al-bearing superhydrous phase B can be stable in a subducted slab with a high Al content compared to pyrolite (e.g, chlorite) at temperatures typical of the mantle transition zone and the lower mantle. Thus, water can be transported to the lower mantle by Al-bearing superhydrous phase B in the subducting slab, even at the typical mantle geotherm.
  • Matsuda N, Sakamoto N, Tachibana S, Yurimoto H
    METEORITICS & PLANETARY SCIENCE 53 6179  2018年08月 [査読有り][通常論文]
  • N. Hiraishi, S. Kobayashi, H. Yurimoto, J. Tagami
    Dental Materials 34 4 e57 - e62 2018年04月 [査読有り][通常論文]
     
    Objective: The dental caries is developed as a result of an alternative course of mineral gain and loss. In order to distinguish between intrinsic Ca (tooth-derived mineral) and extrinsic Ca (solution-derived mineral) uptakes, a 44Ca doped pH-cycling was performed using 44Ca (a stable calcium isotope) remineralization solution. Methods: The natural abundance of 40Ca and 44Ca is 96.9% and 2.1%, respectively. The remineralization solution was prepared using 44Ca to contain 1.5 mmol/L CaCl2 (44Ca), 0.9 mmol/L KH2PO4 130 mmol/L KCl, 20 mmol/L HEPES at pH 7.0. The pH-cycling was conducted on bovine root dentin daily by demineralization (pH 5.0) for 2 h, incubation in 0% (control) and 0.2% NaF (900 ppm fluoride) for 2 h and 44Ca doped remineralization for 20 h. After 14 days pH-cycling, the specimens were sectioned longitudinally. On the sectioned surface, isotope imaging of 40Ca and 44Ca labeled mineral distribution was observed by a high mass-resolution stigmatic secondary ion 77 (Camera IMS 1270, Gennevilliers Cedex, France). Results: Uptake of 44Ca was greater in intensity for the 0.2% fluoride group than the control, especially in the superficial lesions. The control group showed 40Ca (intrinsic) distribution in the subsurface lesions and in the superficial lesions, meanwhile the fluoride group showed 40Ca distribution limited in subsurface lesions. The total Ca (44Ca + 40Ca) image revealed more homogeneously for the control than the fluoride group. Significance: Since the fluoride-treated surface is more acid-resistant than intrinsic dentin, alternative minerals were dissolved from the intact intrinsic lesion in the demineralization cycle.
  • Laurette Piani, Hisayoshi Yurimoto, Laurent Remusat
    Nature Astronomy 2 4 317 - 323 2018年04月 [査読有り][通常論文]
     
    Carbonaceous asteroids represent the principal source of water in the inner Solar System and might correspond to the main contributors for the delivery of water to Earth. Hydrogen isotopes in water-bearing primitive meteorites, for example carbonaceous chondrites, constitute a unique tool for deciphering the sources of water reservoirs at the time of asteroid formation. However, fine-scale isotopic measurements are required to unravel the effects of parent-body processes on the pre-accretion isotopic distributions. Here, we report in situ micrometre-scale analyses of hydrogen isotopes in six CM-type carbonaceous chondrites, revealing a dominant deuterium-poor water component (δD = -350 ± 40‰) mixed with deuterium-rich organic matter. We suggest that this deuterium-poor water corresponds to a ubiquitous water reservoir in the inner protoplanetary disk. A deuterium-rich water signature has been preserved in the least altered part of the Paris chondrite (δDParis ≥ -69 ± 163‰) in hydrated phases possibly present in the CM rock before alteration. The presence of the deuterium-enriched water signature in Paris might indicate that transfers of ice from the outer to the inner Solar System were significant within the first million years of the history of the Solar System.
  • Minami Kuroda, Shogo Tachibana, Naoya Sakamoto, Satoshi Okumura, Michihiko Nakamura, Hisayoshi Yurimoto
    American Mineralogist 103 3 412 - 417 2018年03月26日 [査読有り][通常論文]
     
    Water diffusion in silicate melts is a fundamental process controlling physical and chemical consequences for magmatism, but mechanisms of diffusion in silicate glasses and melts are not fully understood. In this study, water diffusion experiments in silica glass were performed at temperatures of 650-850 °C and water vapor pressure of 50 bar, with the aim of improving our understanding of the mechanism of water diffusion in a simple SiO2-H2O system, and to construct a general water diffusion model for multi-component silicate glasses. Hydrogen diffusion profiles in silica glass were measured by secondary ion mass spectrometry (SIMS) down to a water concentration of ∼10 ppm. Water diffusion profiles indicate that water diffusion becomes slower with decreasing water concentration in silica glass, with the water concentration dependence being greater than in multi-component silicate glasses, particularly at low concentrations (e.g., Doremus 1969, 2000; Zhang and Behrens 2000). A new water diffusion model is proposed for silica glass, where the greater concentration dependence is attributed to the limited number of diffusion pathways in silica glass, formed by breaking Si-O-Si bonds through hydroxyl formation. The model was applied to multi-component silicate glasses, taking into account the effects of metal cations that act as network modifiers by providing additional diffusion pathways for water molecules. The lower water concentration dependence in multi-component silicate glasses and melts is explained by little dependence of the number of diffusion pathways on water concentration because it is controlled extrinsically by network modifier cations. It is concluded that the number of diffusion pathways is an essential controlling factor for water diffusion in silica and silicate glasses.
  • Toru Matsumoto, S. Hasegawa, S. Nakao, M. Sakai, H. Yurimoto
    Icarus 303 22 - 33 2018年03月15日 [査読有り][通常論文]
     
    We investigated impact crater structures on regolith particles from asteroid Itokawa using scanning electron microscopy. We observed the surfaces of 51 Itokawa particles, ranging from 15 µm to 240 µm in size. Craters with average diameters ranging from 10 nm to 2.8 µm were identified on 13 Itokawa particles larger than 80 µm. We examined the abundance, spatial distribution, and morphology of approximately 900 craters on six Itokawa particles. Craters with sizes in excess of 200 nm are widely dispersed, with spatial densities from 2.6 µm2 to 4.5 µm2; a fraction of the craters was locally concentrated with a density of 0.1 µm2. The fractal dimension of the cumulative crater diameters ranges from 1.3 to 2.3. Craters of several tens of nanometers in diameter exhibit pit and surrounding rim structures. Craters of more than 100 nm in diameter commonly have melted residue at their bottom. These morphologies are similar to those of submicrometer-sized craters on lunar regolith. We estimated the impactor flux on Itokawa regolith-forming craters, assuming that the craters were accumulated during direct exposure to the space environment for 102 to 104 yr. The range of impactor flux onto Itokawa particles is estimated to be at least one order of magnitude higher than the interplanetary dust flux and comparable to the secondary impact flux on the Moon. This indicates that secondary ejecta impacts are probably the dominant cratering process in the submicrometer range on Itokawa regolith particles, as well as on the lunar surface. We demonstrate that secondary submicrometer craters can be produced anywhere in centimeter- to meter-sized depressions on Itokawa's surface through primary interplanetary dust impacts. If the surface unevenness on centimeter to meter scales is a significant factor determining the abundance of submicrometer secondary cratering, the secondary impact flux could be independent of the overall shapes or sizes of celestial bodies, and the secondary impact flux could have similar values on Itokawa and the Moon.
  • Hongzhan Fei, Sanae Koizumi, Naoya Sakamoto, Minako Hashiguchi, Hisayoshi Yurimoto, Katharina Marquardt, Nobuyoshi Miyajima, Tomoo Katsura
    Earth and Planetary Science Letters 484 204 - 212 2018年02月15日 [査読有り][通常論文]
     
    Mg lattice diffusion coefficients in iron-free olivine aggregates were measured as a function of pressure from 1 to 13 GPa, temperature from 1100 to 1300 K, and bulk water content from less than 1 up to 350 wt. ppm using multi-anvil apparatus and secondary ion mass spectrometer in depth profiling mode. The water contents in the samples were analyzed by Fourier transmission infrared spectrometer. The results show that Mg lattice diffusion coefficient increase with increasing temperature and water content, and decrease with pressure. The activation energy, water content exponent, and activation volume are 250 ± 30 kJ/mol, 1.2 ± 0.2, and 4.3 ± 0.3 cm3/mol, respectively. Since Mg lattice diffusion controls the ionic conduction in olivine based on the Nernst–Einstein relation, the ionic conductivity in the upper mantle appears as a maximum at the top of oceanic asthenosphere due to the negative correction for pressure and positive correction for water content, which well explains the high conductivity anomaly observed at ∼70–120 km depth beneath young oceanic plates.
  • Wei Sun, Wei Sun, Takashi Yoshino, Naoya Sakamoto, Hisayoshi Yurimoto, Hisayoshi Yurimoto
    Earth and Planetary Science Letters 484 309 - 317 2018年02月15日 [査読有り][通常論文]
     
    © 2017 Elsevier B.V. Knowledge of the distribution of water in the Earth's mantle is key to understanding the mantle convection and geochemical evolution of the Earth. As wadsleyite and ringwoodite can incorporate large amounts of water in their crystal structures, proton conduction has been invoked to account for the widespread conductive anomalies observed in the mantle wedge, where descending slab stagnates at the transition zone. However, there is a lot of controversy on whether proton conduction by itself is able to explain such anomalies, because of large discrepancy in the extent of the water effect deduced from previous electrical conductivity measurements on hydrous polycrystalline wadsleyite and ringwoodite. Here we report the hydrogen self-diffusion coefficient obtained from H–D interdiffusion experiments in wadsleyite single-crystal couples. Our results demonstrate that the effect of water on the electrical conductivity of wadsleyite is limited and hydrous wadsleyite by itself is unable to explain conductive anomalies in the transition zone. In contrast, the expected hydrogen effective diffusion does not allow the wide propagation of water between the stagnant slab and surrounding mantle, probably leading to persistence of local water saturation and continuous release of supercritical fluids at the stagnant slab roof on geological time scales. This phenomenon provides an alternative explanation for both the high-conductivity and seismic-velocity anomalies observed in the mantle wedge at the transition-zone depth.
  • Laurette Piani, Hisayoshi Yurimoto, Laurent Remusat
    低温科学 78 2018年02月 [査読有り][通常論文]
     
    Carbonaceous asteroids represent the principal source of water in the inner
    Solar System and might correspond to the main contributors for the delivery of
    water to Earth. Hydrogen isotopes in water-bearing primitive meteorites, e.g.
    carbonaceous chondrites, constitute a unique tool for deciphering the sources
    of water reservoirs at the time of asteroid formation. However, fine-scale
    isotopic measurements are required to unravel the effects of parent body
    processes on the pre-accretion isotopic distributions. Here we report in situ
    micrometer-scale analyses of hydrogen isotopes in six CM-type carbonaceous
    chondrites revealing a dominant deuterium-poor water component ({\delta}D =
    -350 +/- 40 permil) mixed with deuterium-rich organic matter. We suggest that
    this D-poor water corresponds to a ubiquitous water reservoir in the inner
    protoplanetary disk. A deuterium-rich water signature has been preserved in the
    least altered part of the Paris chondrite ({\delta}DParis > -69 +/- 163 permil)
    in hydrated phases possibly present in the CM rock before alteration. The
    presence of the D-enriched water signature in Paris might indicate that
    transfers of ice from the outer to the inner Solar System have been significant
    within the first million years of the Solar System history.
  • Hongzhan Fei, Michael Wiedenbeck, Naoya Sakamoto, Hisayoshi Yurimoto, Takashi Yoshino, Daisuke Yamazaki, Tomoo Katsura
    Physics of the Earth and Planetary Interiors 275 1 - 8 2018年02月 [査読有り][通常論文]
     
    Oxygen self-diffusion coefficients (DOx) were measured in single crystals of dry synthetic iron-free olivine (forsterite, Mg2SiO4) at a temperature of 1600 K and under pressures in the range 10−4 to 13 GPa, using a Kawai-type multi-anvil apparatus and an ambient pressure furnace. Diffusion profiles were obtained by secondary ion mass spectrometry operating in depth profiling mode. DOx in forsterite increases with increasing pressure with an activation volume of −3.9 ± 1.2 cm3/mol. Although Mg is the fastest diffusing species in forsterite under low-pressure conditions, O is the fastest diffusing species at pressures greater than ∼10 GPa. Si is the slowest throughout the stable pressure range of forsterite. Based on the observed positive and negative pressure dependence of DOx and DMg (Mg self-diffusion coefficient), respectively, DOx + DMg in forsterite decreases with increasing pressure, and then increases slightly at pressures greater than 10 GPa. This behavior is in agreement with the pressure dependence of ionic conductivity in forsterite based on conductivity measurements (Yoshino et al., 2017), and can be used to explain the conductivity increase from ∼300 km depth to the bottom of the asthenosphere.
  • Noriyuki Kawasaki, Steven B. Simon, Lawrence Grossman, Naoya Sakamoto, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 221 318 - 341 2018年01月15日 [査読有り][通常論文]
     
    TS34 is a Type B1 Ca-Al-rich inclusion (CAI) from the Allende CV3 chondrite, consisting of spinel, melilite, Ti-Al-rich clinopyroxene (fassaite) and minor anorthite in an igneous texture. Oxygen and magnesium isotopic compositions were measured by secondary ion mass spectrometry in spots of known chemical composition in all major minerals in TS34. Using the sequence of formation from dynamic crystallization experiments and from chemical compositions of melilite and fassaite, the oxygen isotopic evolution of the CAI melt was established. Oxygen isotopic compositions of the constituent minerals plot along the carbonaceous chondrite anhydrous mineral line. The spinel grains are uniformly 16O-rich (Δ17O = −22.7 ± 1.7‰, 2SD), while the melilite grains are uniformly 16O-poor (Δ17O = −2.8 ± 1.8‰) irrespective of their åkermanite content and thus their relative time of crystallization. The fassaite crystals exhibit growth zoning overprinting poorly-developed sector zoning; they generally grow from Ti-rich to Ti-poor compositions. The fassaite crystals also show continuous variations in Δ17O along the inferred directions of crystal growth, from 16O-poor (Δ17O ∼ −3‰) to 16O-rich (Δ17O ∼ −23‰), covering the full range of oxygen isotopic compositions observed in TS34. The early-crystallized 16O-poor fassaite and the melilite are in oxygen isotope equilibrium and formed simultaneously. The correlation of oxygen isotopic compositions with Ti content in the fassaite imply that the oxygen isotopic composition of the CAI melt evolved from 16O-poor to 16O-rich during fassaite crystallization, presumably due to oxygen isotope exchange with a surrounding 16O-rich nebular gas. Formation of spinel, the liquidus phase in melts of this composition, predates crystallization of all other phases, so its 16O-rich composition is a relic of an earlier stage. Anorthite exhibits oxygen isotopic compositions between Δ17O ∼ −2‰ and −9‰, within the range of those of fassaite, indicating co-crystallization of these two minerals during the earliest to intermediate stage of fassaite growth. The melilite and fassaite yield an 26Al–26Mg mineral isochron with an initial value of (26Al/27Al)0 = (5.003 ± 0.075) × 10−5, corresponding to a relative age of 0.05 ± 0.02 Myr from the canonical Al–Mg age of CAIs. These data demonstrate that both 16O-rich and 16O-poor reservoirs existed in the solar nebula at least ∼0.05 Myr after the birth of the Solar System.
  • Georg F. Zellmer, Naoya Sakamoto, Nozomi Matsuda, Yoshiyuki Iizuka, Anja Moebis, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 220 552 - 553 2018年01月01日 [査読有り][通常論文]
     
    Summary of errors and implications In the original article, an olivine dissolution rate of 3–6 × 10–11 m s–1 was quoted for the tephra we have studied. However, it was not considered that the crystal dissolves on all sides, rather than just on the one edge studied, so the diameter of the crystal will reduce by twice this rate, 9 (±3) × 10–11 m s–1. In the original article, it was stated that the growth rate of orthopyroxene microlites is initially not linear, and the authors argued for an initially volumetric growth rate. Fig. 8 is a new figure that shows pyroxene microlite length and volume versus time since overgrowing olivine. In this figure, uncertainties are recognized in time, which result from uncertainties in temperature; and in size, which result from uncertainties in our ability to correctly measure the dimensions of the microlites in Fig. 5 of the original article. Given these uncertainties, it becomes difficult to argue for or against linear versus volumetric growth. We conclude from Fig. 8 that pyroxene microlite crystal growth may be described as linear, at 3.7 (±2.6) × 10−11 m s−1, or as volumetric at 2.6 (±1.6) × 10−21 m3 s−1. The growth rate of pyroxene microlites determined in this study is within the range of experimentally determined linear growth rates of plagioclase microlites in andesitic melts of 3 × 10−12 m s−1 to 1 × 10−9 m s−1 (Couch et al., 2003). This corrigendum enables future workers to refer to a linear pyroxene microlite growth rate, e.g. when undertaking microlite crystal size distribution studies. Finally, we note that this corrigendum in no way changes the fundamental findings of our original article on the progress of the peritectic reaction in natural andesitic arc magmas.
  • Hisayoshi Yurimoto
    Encyclopedia of Earth Sciences Series 1129 - 1135 2018年 [査読有り][通常論文]
  • Ai Cheng Zhang, Yi Fan Bu, Run Lian Pang, Naoya Sakamoto, Hisayoshi Yurimoto, Li Hui Chen, Jian Feng Gao, De Hong Du, Xiao Lei Wang, Ru Cheng Wang
    Geochimica et Cosmochimica Acta 220 125 - 145 2018年01月01日 [査読有り][通常論文]
     
    Troilite-orthopyroxene intergrowths are present as a common material in the brecciated diogenite Northwest Africa (NWA) 7183. In this study, we report on the petrographic, mineralogical, and rare earth element abundances of the troilite-orthopyroxene intergrowths to constrain their origin and assess their implications for the diverse petrogenesis of diogenites. Two groups of troilite-orthopyroxene intergrowths with various grain sizes and mineral chemistry have been observed in NWA 7183. One group of intergrowths contains fine-grained (<5 μm) olivine and chromite as inclusions in orthopyroxene (10–20 μm in size). The other group, in which orthopyroxene is more fine-grained (<10 μm in size), is closely associated with coarse irregular olivine grains. The orthopyroxene grains in both groups of troilite-orthopyroxene intergrowths are depleted in Cr, Al, Ti, and Ca compared with diogenitic orthopyroxene. Based on the texture and mineral chemistry, we suggest that the two groups of troilite-orthopyroxene intergrowths formed via reactions between diogenitic olivine and S-rich vapors, probably at different temperatures. The fact that some of the intergrowths are included in diogenitic lithic clasts indicates that the formation of the host diogenite should postdate the formation of the majority of troilite-orthopyroxene intergrowths. This relationship further implies that not all of the diogenites are cumulates that directly crystallized from the Vestan magma ocean. Instead, they probably originated from partial melting and recrystallization of magma ocean cumulates. The replacement of olivine by troilite and orthopyroxene intergrowths can partly explain why the expected olivine-rich lithologies were not detected at the two south pole impact basins on Vesta.
  • Michael E. Zolensky, Robert J. Bodnar, Hisayoshi Yurimoto, Shoichi Itoh, Marc Fries, Andrew Steele, Queenie H.S. Chan, Akira Tsuchiyama, Yoko Kebukawa, Motoo Ito
    Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 375 2094 2017年05月28日 [査読有り][通常論文]
     
    We describe the current state of the search for direct, surviving samples of early, inner Solar System fluids-fluid inclusions in meteorites. Meteoritic aqueous fluid inclusions are not rare, but they are very tiny and their characterization is at the state of the art for most analytical techniques. Meteoritic fluid inclusions offer us a unique opportunity to study early Solar System brines in the laboratory. Inclusion-byinclusion analyses of the trapped fluids in carefully selected samples will, in the immediate future, provide us detailed information on the evolution of fluids as they interacted with anhydrous solid materials. Thus, real data can replace calculated fluid compositions in thermochemical calculations of the evolution of water and aqueous reactions in comets, asteroids, moons and the terrestrial planets. This article is part of the themed issue 'The origin, history and role of water in the evolution of the inner Solar System'.
  • Noriyuki Kawasaki, Shoichi Itoh, Naoya Sakamoto, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 201 201 83 - 102 2017年03月15日 [査読有り][通常論文]
     
    Fluffy Type A Ca–Al-rich inclusions (CAIs) containing reversely zoned melilite crystals are suggested to be aggregates of direct condensates from solar nebular gas. We conducted an investigation of 26Al−26Mg systematics of a fluffy Type A CAI from Vigarano, named V2-01, with known oxygen isotopic distributions of reversely zoned melilite crystals; we also conducted oxygen isotope measurements of coexisting minerals. Two of six reversely zoned melilite crystals show continuous variations in magnesium isotopic composition, with δ25Mg decreasing along the inferred direction of crystal growth, which supports the idea that they originated through condensation. Petrography suggests that the constituent minerals of V2-01 formed in the following order: first spinel and fassaite enclosed by melilite, then reversely zoned melilite crystals, and spinel and diopside in the Wark–Lovering rim. The spinel enclosed by melilite has 16O-rich compositions (Δ17O ∼ −24‰) and on an Al−Mg evolutionary diagram plots along model isochron with an initial value of (26Al/27Al)0 = (5.6 ± 0.2) × 10−5. The fassaite enclosed by melilite crystals shows variable oxygen isotopic compositions (Δ17O ∼ −12‰ and −17‰) and plots on an isochron with (26Al/27Al)0 = (5.6 ± 0.2) × 10−5. The oxygen isotopic compositions of reversely zoned melilite showed continuous variations in Δ17O along the inferred direction of crystal growth, suggesting that surrounding nebular gas, during the formation of the reversely zoned melilite, changed from 16O-poor (Δ17O values larger than −10‰) to 16O-rich (Δ17O ∼ −25‰). The six reversely zoned melilite crystals show indistinguishable initial 26Al/27Al values with an average (26Al/27Al)0 of (4.7 ± 0.3) × 10−5, which is clearly distinguishable from the value of enclosed spinel and fassaite, indicating a younger formation age than the enclosed spinel and fassaite. The spinel and diopside from the Wark–Lovering rim show 16O-rich compositions (Δ17O ∼ −23‰) with (26Al/27Al)0 = (4.5 ± 0.4) × 10−5. The values of (26Al/27Al)0 are consistent with the formation sequence inferred from petrography. The formation period for the V2-01 CAI is estimated to be 0.18 ± 0.07 Myr from the difference in initial 26Al/27Al values. These data suggest that the oxygen isotopic composition of solar nebular gas surrounding the CAI changed from 16O-rich to 16O-poor and back to 16O-rich during the first ∼0.2 Myr of Solar System formation.
  • L. Piani, S. Tachibana, T. Hama, H. Tanaka, Y. Endo, I. Sugawara, L. Dessimoulie, Y. Kimura, A. Miyake, J. Matsuno, A. Tsuchiyama, K. Fujita, S. Nakatsubo, H. Fukushi, S. Mori, T. Chigai, H. Yurimoto, A. Kouchi
    Astrophysical Journal 837 1 2017年03月01日 [査読有り][通常論文]
     
    Refractory organic compounds formed in molecular clouds are among the building blocks of the solar system objects and could be the precursors of organic matter found in primitive meteorites and cometary materials. However, little is known about the evolutionary pathways of molecular cloud organics from dense molecular clouds to planetary systems. In this study, we focus on the evolution of the morphological and viscoelastic properties of molecular cloud refractory organic matter. We found that the organic residue, experimentally synthesized at ∼10 K from UV-irradiated H2O-CH3OH-NH3 ice, changed significantly in terms of its nanometer- to micrometer-scale morphology and viscoelastic properties after UV irradiation at room temperature. The dose of this irradiation was equivalent to that experienced after short residence in diffuse clouds (≤104 years) or irradiation in outer protoplanetary disks. The irradiated organic residues became highly porous and more rigid and formed amorphous nanospherules. These nanospherules are morphologically similar to organic nanoglobules observed in the least-altered chondrites, chondritic porous interplanetary dust particles, and cometary samples, suggesting that irradiation of refractory organics could be a possible formation pathway for such nanoglobules. The storage modulus (elasticity) of photo-irradiated organic residues is ∼100 MPa irrespective of vibrational frequency, a value that is lower than the storage moduli of minerals and ice. Dust grains coated with such irradiated organics would therefore stick together efficiently, but growth to larger grains might be suppressed due to an increase in aggregate brittleness caused by the strong connections between grains.
  • Fang Xu, Daisuke Yamazaki, Naoya Sakamoto, Wei Sun, Hongzhan Fei, Hisayoshi Yurimoto
    Earth and Planetary Science Letters 459 332 - 339 2017年02月01日 [査読有り][通常論文]
     
    Diffusion of Si and O in single crystal stishovite was examined at pressures of 14.0–21.5 GPa and temperatures of 1673–2073 K. Self-diffusion coefficients of Si (DSi) and O (DO) were determined as DSi [m2/s]=2.4×10−12exp⁡{−(237[kJ/mol]+6.0[cm3/mol]×P)/RT} and DO [m2/s]=7.2×10−11exp⁡{−(263[kJ/mol]+4.8[cm3/mol]×P)/RT}, respectively, where P is pressure (in GPa), T is absolute temperature (in K) and R is the ideal gas constant. It was revealed that diffusion of Si is approximately one order of magnitude slower than that of O and, thus, Si is the rate-controlling element for plastic deformation of stishovite. Si diffusion in stishovite is assessed to be at least three orders of magnitude slower than that in bridgmanite under mid-mantle conditions. Therefore, it is anticipated that highly viscous SiO2-rich components subducted into the lower mantle persist as the seismic reflectors for long term without mixing up with the bridgmanite-dominated surrounding mantle.
  • Shogo Tachibana, Akira Kouchi, Tetsuya Hama, Yasuhiro Oba, Laurette Piani, Iyo Sugawara, Yukiko Endo, Hiroshi Hidaka, Yuki Kimura, Ken ichiro Murata, Hisayoshi Yurimoto, Naoki Watanabe
    Science Advances 3 9 eaao2538  2017年 [査読有り][通常論文]
     
    Interstellar ice is believed to be a cradle of complex organic compounds, commonly found within icy comets and interstellar clouds, in association with ultraviolet (UV) irradiation and subsequent warming. We found that UV-irradiated amorphous ices composed of H2O, CH3OH, and NH3 and of pure H2O behave like liquids over the temperature ranges of 65 to 150 kelvin and 50 to 140 kelvin, respectively. This low-viscosity liquid-like ice may enhance the formation of organic compounds including prebiotic molecules and the accretion of icy dust to form icy planetesimals under certain interstellar conditions.
  • James P. Greenwood, Naoya Sakamoto, Shoichi Itoh, Paul H. Warren, Jack A. Singer, Kaori Yanai, Hisayoshi Yurimoto
    Geochemical Journal 51 1 105 - 114 2017年 [査読有り][通常論文]
     
    The last liquids of the lunar magma ocean, known as urKREEP, should be highly enriched in volatiles, such as water, fluorine, and chlorine. We find chlorine-rich glasses in two pristine KREEP basalts from the Moon and calculate the volatile contents of the urKREEP component, and use this to estimate the fluorine and chlorine content of the lunar magma ocean. The Cl/Nb and F/Nd of KREEP imply that the lunar magma ocean was depleted in fluorine and chlorine by an order of magnitude compared to the Earth's mantle. The extremely dry nature of most lunar samples is simply a result of partial melting of magma ocean cumulates that had already lost their volatiles to the urKREEP layer. The volatile-rich KREEP component may have helped lower the solidus of high-temperature magma ocean cumulates that were melted to form the Mg-suite rocks of the highlands, and also aided the dissemination of the KREEP signature into the upper crust. The chlorine-rich KREEP glasses also demonstrate that the large chlorine isotope anomaly found in lunar samples is likely an early lunar signature.
  • Kenichi Abe, Naoya Sakamoto, Alexander N. Krot, Hisayoshi Yurimoto
    Geochemical Journal 51 1 3 - 15 2017年 [査読有り][通常論文]
     
    We describe the petrographic occurrences, abundances, and compositional variations of symplectically intergrown Fe,Ni-sulfides and 17,18O-rich magnetite (Δ17O ∼ 90‰), named cosmic symplectites (COS; Sakamoto et al., 2007), from the Acfer 094 (C3.0) ungrouped carbonaceous chondrite. A total of 314 COS studied in two polished sections of this meteorite are uniformly distributed in its matrix with ∼600 ppm surface area abundance. No COS have been identified in the Acfer 094 dark inclusions (chondritic lithic clasts) which appear to have experienced extensive aqueous alteration prior to incorporation into the host meteorite. The structure of COS can be arranged in a hierarchy of four categories (from finer to coarser): (1) symplectite structure composed of nanocrystalline magnetite and Fe,Ni-sulfides, (2) submicronsized wormy structure composed of nanocrystalline symplectites, (3) micrometer-sized irregular rope-like structure composed of wormy structure, and (4) aggregates of the rope-like structure. COS typically associate with fractured Fe,Nisulfides and lack Fe,Ni-metal. Most COS studied have smooth surfaces; four grains contain abundant pores. In a single COS, the pore-rich regions are depleted in sulfur and nickel relative to the pore-free regions, indicating that the former are depleted in Fe,Ni-sulfides. Most COS studied contain similar abundances of Fe,Ni-sulfides and magnetite, whereas Ni/ (Fe+Ni) atomic ratio in Fe,Ni-sulfides ranges from 0 to 0.4. The lack of Fe,Ni-metal associated with COS supports the formation process proposed by Seto et al. (2008), i.e., oxidation of Fe,Ni-metal and sulfides by 17,18O-rich water vapor in the outer part of the protoplanetary disk. The similar abundance ratio for Fe,Ni-sulfide and magnetite cannot be simply explained by oxidation processes of Fe,Ni-sulfide precursors after sulfurization of Fe,Ni-metal precursors for COS formation as proposed by Seto et al. (2008).
  • YOSHIMURA SHUMPEI, NAKAMURA MICHIHIKO, YURIMOTO HISAYOSHI
    ＧＥＯＣＨＥＭＩＣＡＬ ＪＯＵＲＮＡＬ 51 3 251 - 262 一般社団法人日本地球化学会 2017年 [査読有り][通常論文]
     

    We carried out equilibrium experiments of the CO2-H2O-rhyolite system at 0.1–1.5 GPa and 850 and 1200°C to examine the solubility and speciation of CO2 in high-SiO2 rhyolite (SiO2 > 76 wt%). We observed that both CO2 molecules (CO2mol) and carbonate anions (CO32–) are dissolved in the quenched rhyolitic glasses based on infrared spectroscopy. This result contrasts with the general understanding that high-SiO2 rhyolitic melt dissolves CO2mol only. The concentrations of CO2mol and CO32– were 199–9200 ppm and 58–2100 ppm, respectively, as quantified based on the Beer-Lambert's law and newly determined extinction coefficients of 1192 ± 130 L·cm–1·mol–1 and 91 ± 28 L·cm–1·mol–1 for CO2mol and CO32–, respectively. The water content ranged from 2.6 to 6.1 wt%. Using the thermodynamic analysis, we calculated the partial molar volume of CO2mol to be = 24.9 ± 2.0 cm3/mol and enthalpy of dissolution to be ΔslnH = –22.2 ± 6.3 kJ/mol. Changes in volume and enthalpy upon the formation reaction of CO32– were calculated to be ΔrV = –8.6 ± 0.9 cm3/mol and ΔrH = +1.1 ± 4.4 kJ/mol, respectively.

  • Jack A. Singer, James P. Greenwood, Shoichi Itoh, Naoya Sakamoto, Hisayoshi Yurimoto
    Geochemical Journal 51 1 95 - 104 2017年 [査読有り][通常論文]
     
    While it is now recognized that the Moon has indigenous water and volatiles, their total abundances are unclear, with current literature estimates ranging from nearly absent to Earth-like levels. Similarly unconstrained is the source of the Moon's water, which could be cometary, chondritic, or the primordial nebula. Here we measure H2O and D/H in olivinehosted melt inclusions in lunar mare basalts 12018, 12035, and 12040, part of the consanguineous suite of Apollo 12 olivine basalts that differ primarily because of cooling rate (Walker et al., 1976). We find that the water contents are higher in the more rapidly cooled 12018 (62-740 ppm H2O) compared to the more slowly cooled basalts 12035 (28-156 ppm H2O) and 12040 (27-90 ppm H2O), suggesting that lunar basalts may have been dehydrating during slow cooling. D/ H is similar in the olivine-hosted melt inclusions in all three samples, and indistinguishable from terrestrial water (ΔD = -183 ± 212‰ to +138 ± 61‰). When we compare the D/H of olivine-hosted melt inclusions to D/H of apatite in the same samples, the evolution of ΔD and water content can be better constrained. We propose that lunar magmas first exchange hydrogen with a low D/H reservoir during cooling, and then ultimately lose their water during extended subsolidus cooling. Due to high diffusion rates of hydrogen in olivine, it is likely that all basaltic olivine-hosted melt inclusions from the Moon exchanged hydrogen with a low D/H reservoir in near-surface magma chambers or lava flows. The most likely source of the low D/H reservoir on the Moon is the lunar regolith, which is known to have a significant solar wind hydrogen component.
  • Azusa Tonotani, Ken ichi Bajo, Satoru Itose, Morio Ishihara, Kiichiro Uchino, Hisayoshi Yurimoto
    Surface and Interface Analysis 48 11 1122 - 1126 2016年11月01日 [査読有り][通常論文]
     
    We have evaluated the performance of a multi-turn time-of-flight mass spectrometer (MULTUM II) equipped with the ion injection optics of a laser ionization mass nanoscope (LIMAS). We surveyed the optimal parameters for the ion injection optics, which consist of ion extraction from a sample surface and ion introduction into MULTUM II. We developed mass calibration methods for correcting the modulation of load voltage for MULTUM II and injection timing for the ion injection optics. As a result, the mass-resolving power of LIMAS increased linearly with increasing the flight path length, and reached 6.2 × 105 (full width at half maximum) at 1000 multi-turn cycles of MULTUM II (flight path length: 1.3 km). The transmittance of LIMAS decreased to 60–70% after 20 multi-turn cycles of MULTUM II, compared with the linear mode transmittance. The transmittance per multi-turn cycle became constant (99.96%) after 20 multi-turn cycles. A useful yield of 3 × 10−3 for Si ions was obtained for LIMAS at 30 multi-turn cycles of MULTUM II. Copyright © 2016 John Wiley & Sons, Ltd.
  • Hisayoshi Yurimoto, Ken ichi Bajo, Isao Sakaguchi, Taku T. Suzuki, Amy J.G. Jurewicz, Satoru Itose, Kiichiro Uchino, Morio Ishihara
    Surface and Interface Analysis 48 11 1181 - 1184 2016年11月01日 [査読有り][通常論文]
     
    Helium has the largest ionization potential of all elements; thus, it is difficult to ionize for measurement by mass spectrometry. In order to analyze He, a tunnel-ionization time-of-flight sputtered neutral mass spectrometry system (called LIMAS) has recently been developed. LIMAS uses a femtosecond laser technique and can ionize He. We quantified the effectiveness of this method for He analysis from a 2.5 × 4 µm2 area of He-implanted silicon. The amount of He in an implant was quantified by measuring the ion current, giving a nominal implant fluence per unit area. Thus, the fraction of total He measured by LIMAS during depth profiling could be quantified by comparison with the He concentration of the reference implant. The He+ intensities normalized by host ions of Si linearly correlated with the known He concentrations with a reproducibility of 10% at concentrations less than 1021 cm−3. The detection limit was down to 1018 He cm−3 (20 ppm). For concentrations exceeding 1021 cm−3, the He intensities are smaller than those expected from the lower concentration range. This non-linearity may reflect the limit of retention of He in the Si lattice, because He is chemically inert. Copyright © 2016 John Wiley & Sons, Ltd.
  • Ken ichi Bajo, Satoru Itose, Miyuki Matsuya, Morio Ishihara, Kiichiro Uchino, Masato Kudo, Isao Sakaguchi, Hisayoshi Yurimoto
    Surface and Interface Analysis 48 11 1190 - 1193 2016年11月01日 [査読有り][通常論文]
     
    Laser ionization mass nanoscope is a time-of-flight sputtered neutral mass spectrometer associated with laser post-ionization by tunneling effect. A spherical and chromatic aberration corrector is installed in the primary ion column. The lateral spatial resolving power of He imaging of solid surface has been evaluated by scanning image using a probe diameter of 90 nm from crater edge slope of a He ion-implanted Si substrate. Helium distribution from the scanning image is quantitatively equivalent with depth profiling analysis from surface of the same substrate, indicating that spatial resolving power of 20 nm for depth resolution has been achieved on the He scanning image through use of oblique incident effect of the primary beam. Copyright © 2016 John Wiley & Sons, Ltd.
  • Hiromi Hongo, Muneteru Sasaki, Sachio Kobayashi, Tomoka Hasegawa, Tomomaya Yamamoto, Kanako Tsuboi, Erika Tsuchiya, Tomoya Nagai, Naznin Khadiza, Miki Abe, Ai Kudo, Kimimitsu Oda, Paulo Henrique Luiz de Freitas, Minqi Li, Hisayoshi Yurimoto, Norio Amizuka
    Journal of Histochemistry and Cytochemistry 64 10 601 - 622 2016年10月01日 [査読有り][通常論文]
     
    Minodronate is highlighted for its marked and sustained effects on osteoporotic bones. To determine the duration of minodronate’s effects, we have assessed the localization of the drug in mouse bones through isotope microscopy, after labeling it with a stable nitrogen isotope ([15N]-minodronate). In addition, minodronate-treated bones were assessed by histochemistry and transmission electron microscopy (TEM). Eight-week-old male ICR mice received [15N]-minodronate (1 mg/kg) intravenously and were sacrificed after 3 hr, 24 hr, 1 week, and 1 month. Isotope microscopy showed that [15N]-minodronate was present mainly beneath osteoblasts rather than nearby osteoclasts. At 3 hr after minodronate administration, histochemistry and TEM showed osteoclasts with well-developed ruffled borders. However, osteoclasts were roughly attached to the bone surfaces and did not feature ruffled borders at 24 hr after minodronate administration. The numbers of tartrate-resistant acid phosphatase–positive osteoclasts and alkaline phosphatase–reactive osteoblastic area were not reduced suddenly, and apoptotic osteoclasts appeared in 1 week and 1 month after the injections. Von Kossa staining demonstrated that osteoclasts treated with minodronate did not incorporate mineralized bone matrix. Taken together, minodronate accumulates in bone underneath osteoblasts rather than under bone-resorbing osteoclasts; therefore, it is likely that the minodronate-coated bone matrix is resistant to osteoclastic resorption, which results in a long-lasting and bone-preserving effect.
  • Ai Cheng Zhang, Qiu Li Li, Hisayoshi Yurimoto, Naoya Sakamoto, Xian Hua Li, Sen Hu, Yang Ting Lin, Ru Cheng Wang
    Nature Communications 7 12844 - 12844 2016年09月29日 [査読有り][通常論文]
     
    Chondritic meteorites, consisting of the materials that have formed in the early solar system (ESS), have been affected by late thermal events and fluid activity to various degrees. Determining the timing of fluid activity in ESS is of fundamental importance for understanding the nature, formation, evolution and significance of fluid activity in ESS. Previous investigations have determined the relative ages of fluid activity with short-lived isotope systematics. Here we report an absolute 207 Pb/ 206 Pb isochron age (4,450±50 Ma) of apatite from Dar al Gani (DaG) 978, a type ∼3.5, ungrouped carbonaceous chondrite. The petrographic, mineralogical and geochemical features suggest that the apatite in DaG 978 should have formed during metamorphism in the presence of a fluid. Therefore, the apatite age represents an absolute age for fluid activity in an asteroidal setting. An impact event could have provided the heat to activate this young fluid activity in ESS.
  • Georg F. Zellmer, Naoya Sakamoto, Shyh Lung Hwang, Nozomi Matsuda, Yoshiyuki Iizuka, Anja Moebis, Hisayoshi Yurimoto
    Frontiers in Earth Science 4 2016年09月28日 [査読有り][通常論文]
     
    Crystal nucleation and growth are first order processes captured in volcanic rocks and record important information about the rates of magmatic processes and chemical evolution of magmas during their ascent and eruption. We have studied glass-rich andesitic tephras from the Central Plateau of the Southern Taupo Volcanic Zone by electron- and ion-microbeamimaging techniques to investigate down to sub-micrometer scale the potential effects of compositional boundary layers (CBLs) of melt around crystals on the nucleation and growth of mineral phases and the chemistry of crystal growth zones. We find that CBLs may influence the types of mineral phases nucleating and growing, and growth textures such as the development of swallowtails. The chemistry of the CBLs also has the capacity to trigger intermittent overgrowths of nanometer-scale bands of different phases in rapidly growing crystals, resulting in what we refer to as cryptic phase zoning. The existence of cryptic phase zoning has implications for the interpretation of microprobe compositional data, and the resulting inferences made on the conditions of magmatic evolution. Identification of cryptic phase zoning may improve thermobarometric estimates andthus geospeedometric constraints. In future, a more quantitative characterization of CBL formation and its effects on crystal nucleation and growth may contribute to a better understanding of melt rheology and magma ascent processes at the onset of explosive volcanic eruptions, and will likely be of benefit to hazard mitigation efforts.
  • T. Yada, M. Abe, T. Okada, H. Yurimoto, Masayuki Uesugi, Yuzuru Karouji, Aiko Nakato, Minako Hashiguchi, Toru Matsumoto, Masahiro Nishimura, Kazuya Kumagai, Shigeo Matsui, Miwa Yoshitake, Kanako Sakamoto, Yuki Nakano, Noriyuki Kawasaki, Masaki Fujimoto
    METEORITICS & PLANETARY SCIENCE 51 A677 - A677 2016年08月 [査読有り][通常論文]
  • Steeve Gréaux, Yoshio Kono, Yanbin Wang, Akihiro Yamada, Chunyin Zhou, Zhicheng Jing, Toru Inoue, Yuji Higo, Tetsuo Irifune, Naoya Sakamoto, Hisayoshi Yurimoto
    Geophysical Research Letters 43 9 4239 - 4246 2016年05月16日 [査読有り][通常論文]
     
    The elasticity of Al-bearing stishovite with 1.0, 3.3, and 4.5 wt % Al2O3 was investigated in the multianvil apparatus at high pressures and temperatures up to 21 GPa and 1700 K, by ultrasonic interferometry in conjunction with in situ X-ray techniques. The moduli KS and G are found to decrease with increasing Al2O3 content, while their pressure and temperature derivatives do not change in a significant manner for 1.0 and 3.3 wt % Al2O3. The temperature derivatives for 4.5 wt % Al2O3, however, are larger, which may result from a change in the Al substitution mechanism at high Al2O3 content. It is shown that acoustic velocities of any mid-ocean ridge basalt are lower by -0.4% than those calculated from pure stishovite data. Velocity perturbations up to -3.4% (VP) and -4.2% (VS) in subducted slabs are explained by the combination of the thermal equilibration (ΔT ~ 600 K) of the slab and Al enrichment in stishovite.
  • Run Lian Pang, Ai Cheng Zhang, Shu Zhou Wang, Ru Cheng Wang, Hisayoshi Yurimoto
    Scientific Reports 6 26063 - 26063 2016年05月16日 [査読有り][通常論文]
     
    High-pressure minerals in meteorites are important records of shock events that have affected the surfaces of planets and asteroids. A widespread distribution of impact craters has been observed on the Vestan surface. However, very few high-pressure minerals have been discovered in Howardite-Eucrite-Diogenite (HED) meteorites. Here we present the first evidence of tissintite, vacancy-rich clinopyroxene, and super-silicic garnet in the eucrite Northwest Africa (NWA) 8003. Combined with coesite and stishovite, the presence of these high-pressure minerals and their chemical compositions reveal that solidification of melt veins in NWA 8003 began at a pressure of >∼10 GPa and ceased when the pressure dropped to <∼8.5 GPa. The shock temperature in the melt veins exceeded 1900 °C. Simulation results show that shock events that create impact craters of ∼3 km in diameter (subject to a factor of 2 uncertainty) are associated with sufficiently high pressures to account for the occurrence of the high-pressure minerals observed in NWA 8003. This indicates that HED meteorites containing similar high-pressure minerals should be observed more frequently than previously thought.
  • Hongzhan Fei, Sanae Koizumi, Naoya Sakamoto, Minako Hashiguchi, Hisayoshi Yurimoto, Katharina Marquardt, Nobuyoshi Miyajima, Daisuke Yamazaki, Tomoo Katsura
    Earth and Planetary Science Letters 433 350 - 359 2016年01月01日 [査読有り][通常論文]
     
    The creep in the Earth's interior is dominated either by diffusion creep which causes Newtonian mantle flow, or by dislocation creep which results in non-Newtonian mantle flow. Although previous deformation studies on olivine claimed a transition from dislocation creep to diffusion creep with depth in the upper mantle, they might misunderstand the creep rates due to experimental difficulties. Since creep in olivine is controlled by silicon diffusion, we measured the silicon grain-boundary diffusion coefficient in well-sintered iron-free olivine aggregates as a function of temperature, pressure, and water content, showing activation energy, activation volume, and water content exponent of 220±30 kJ/mol, 4.0±0.7 cm3/mol, and 0.26±0.07, respectively. Our results based on Si diffusion in forsterite predict that diffusion creep dominates at low pressures and low temperatures, whereas dislocation creep dominates under high pressure and high temperature conditions. Water has negligible effects on both diffusion and dislocation creep. There is a transition from diffusion creep in the shallow upper mantle to dislocation creep in deeper regions. This explains the seismic anisotropy increases at the Gutenberg discontinuity beneath oceans and at the mid-lithosphere discontinuity beneath continents.
  • Georg F. Zellmer, Naoya Sakamoto, Nozomi Matsuda, Yoshiyuki Iizuka, Anja Moebis, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 185 383 - 393 2016年 [査読有り][通常論文]
     
    © 2016 Elsevier Ltd.Using a high resolution ion microprobe with SCAPS imaging, the peritectic reaction of forsterite+silica to enstatite was studied down to submicron level in a natural andesitic tephra from the Central Plateau of North Island, New Zealand. The fayalitic component of natural olivines is stable in high-silica melts, and therefore the reaction is in fact a two-step progress: 1. Dissolution of Mg-rich olivine, rate-limited by Fe-Mg interdiffusion at the crystal rim, results in enrichment of Fe in the crystal rim and of Mg in the c. 1μm wide melt boundary layer around the crystal. 2. Magnesian pyroxenes preferentially but not exclusively nucleate in the melt boundary layer and grow; as soon as these microlites touch the rim of the dissolving olivine, they shield the crystals from the silica-rich melt, thereby preventing further olivine dissolution. At this point, Fe-Mg interdiffusion begins to destroy the Fe-enrichment of the olivine rim. The reaction is completed when the dissolving olivine crystal is completely mantled by magnesian pyroxene microlites. Thick pyroxene mantles are likely the result of pyroxene overgrowth rather than due to peritectic transformation. The morphology of the olivine rim preserves information about the reaction history of the grain. Modeling of Fe-Mg interdiffusion in the olivine rim following its shielding from the melt by pyroxene overgrowth may yield the rates of olivine dissolution and the rates of pyroxene growth if temperature is known. For the tephra we have studied, microlite thermometry yields a temperature of 1137 (±41)°C, indicating an olivine dissolution rate of 3-6×10-11 ms-1 and an initially volumetric pyroxene growth rate of 2.2-5.6×10-21 m3 s-1. This points to timescales between olivine crystal uptake into the SiO2-rich melt and explosive eruption at the surface of a few hours to at most a day.
  • Ai Cheng Zhang, Shoichi Itoh, Hisayoshi Yurimoto, Wei Biao Hsu, Ru Cheng Wang, Lawrence A. Taylor
    Meteoritics and Planetary Science 51 1 56 - 69 2016年01月01日 [査読有り][通常論文]
     
    CM chondrites are a group of primitive meteorites that have recorded the alteration history of the early solar system. We report the occurrence, chemistry, and oxygen isotopic compositions of P-O-rich sulfide phase in two CM chondrites (Grove Mountains [GRV] 021536 and Murchison). This P-O-rich sulfide is a polycrystalline aggregate of nanometer-size grains. It occurs as isolated particles or aggregates in both CM chondrites. These grains, in the matrix and in type-I chondrules from Murchison, were partially altered into tochilinite; however, grains enclosed by Ca-carbonate are much less altered. This P-O-rich sulfide in Murchison is closely associated with magnetite, FeNi phosphide, brezinaite (Cr3S4), and eskolaite (Cr2O3). In addition to sulfur as the major component, this sulfide contains ∼6.3 wt% O, ∼5.4 wt% P, and minor amounts of hydrogen. Analyses of oxygen isotopes by SIMS resulted in an average δ18O value of -22.5 ‰ and an average Δ17O value of 0.2 ± 9.2 ‰ (2σ). Limited variations in both chemical compositions and electron-diffraction patterns imply that the P-O-rich sulfide may be a single phase rather than a polyphase mixture. Several features indicate that this P-O-rich sulfide phase formed at low temperature on the parent body, most likely through the alteration of FeNi metal (a) close association with other low-temperature alteration products, (b) the presence of hydrogen, (c) high Δ17O values and the presence in altered mesostasis of type-I chondrules and absence in type-II chondrules. The textural relations of the P-O-rich sulfide and other low-temperature minerals reveal at least three episodic-alteration events on the parent body of CM chondrites (1) formation of P-O-rich sulfide during sulfur-rich aqueous alteration of P-rich FeNi metal, (2) formation of Ca-carbonate during local carbonation, and (3) alteration of P-O-rich sulfide and formation of tochilinite during a period of late-stage intensive aqueous alteration.
  • Yun Yuan Chang, Steven D. Jacobsen, Craig R. Bina, Sylvia Monique Thomas, Joseph R. Smyth, Daniel J. Frost, Tiziana Boffa Ballaran, Catherine A. McCammon, Erik H. Hauri, Toru Inoue, Hisayoshi Yurimoto, Yue Meng, Przemyslaw Dera
    Journal of Geophysical Research: Solid Earth 120 12 8259 - 8280 2015年12月01日 [査読有り][通常論文]
     
    Review of recent mineral physics literature shows consistent trends for the influence of Fe and H2O on the bulk modulus (K0) of wadsleyite and ringwoodite, the major phases of Earth's mantle transition zone (410-660 km). However, there is little consensus on the first pressure derivative, K0′ = (dK/dP)P=0, which ranges from about 4 to >5 across experimental studies and compositions. Here we demonstrate the importance of K0′ in evaluating the bulk sound velocity of the transition zone in terms of water content and provide new constraints on the effect of H2O on K0′ for wadsleyite and ringwoodite by conducting a comparative compressibility study. In the experiment, multiple crystals of hydrous Fo90 wadsleyite containing 2.0 and 0.25 wt % H2O were loaded into the same diamond anvil cell, along with hydrous ringwoodite containing 1.4 wt % H2O. By measuring their pressure-volume evolution simultaneously up to 32 GPa, we constrain the difference in K0′ independent of the pressure scale, finding that H2O has no effect on K0′, whereas the effect of H2O on K0 is significant. The fitted K0′ values of hydrous wadsleyite (0.25 and 2.0 wt % H2O) and hydrous ringwoodite (1.4 wt % H2O) examined in this study were found to be identical within uncertainty, with K0′ ~3.7(2). New secondary-ion mass spectrometry measurements of the H2O content of these and previously investigated wadsleyite samples shows the bulk modulus of wadsleyite is reduced by 7.0(5) GPa/wt % H2O, independent of Fe content for upper mantle compositions. Because K0′ is unaffected by H2O, the reduction of bulk sound velocity in very hydrous regions of transition zone is expected to be on the order of 1.6%, which is potentially detectible in high-resolution, regional seismology studies.
  • Noriyuki Kawasaki, Chizu Kato, Shoichi Itoh, Shigeyuki Wakaki, Motoo Ito, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 169 99 - 114 2015年11月05日 [査読有り][通常論文]
     
    Disequilibrium oxygen isotopic distributions of Ca-Al-rich inclusions (CAIs) correspond to multiple melting events in the solar nebula. 26Al-26Mg systematics may be applicable for age differences among such melting events. We have carried out a coordinated study of detailed petrographic observations and in-situ oxygen and magnesium isotope measurements for a Type C CAI, EK1-04-2, from the Allende CV3 meteorite to determine the melting events and their ages. The CAI consists mainly of spinel, anorthite, olivine, and pyroxene, and has a core and mantle structure. Petrography of the core suggests that the crystallization sequence of the core minerals is from spinel, anorthite, olivine, and to pyroxene. The mantle has the same mineral assemblage as the core, and shows incomplete melting and solidification textures. Oxygen isotopic compositions of the minerals are distributed along the carbonaceous chondrite anhydrous mineral (CCAM) line (δ18O=-44‰ to +9‰), which indicates to preserve a chemical disequilibrium status in the CAI. Spinel shows a 16O-rich signature (δ18O~-43‰), while anorthite is 16O-poor (δ18O ~+8‰). Olivine and pyroxene in the core have the same oxygen isotopic composition (δ18O~-15‰), which indicates their equilibrium. Olivine and pyroxene in the mantle have variable oxygen isotopic compositions and are slightly depleted in 16O (δ18O=-13‰ to -4‰) compared with the same minerals in the core. The 26Al-26Mg systematics is consistent with the disequilibrium status observed according to the petrography and oxygen isotopes. Spinel is plotted on a line of (26Al/27Al)0=(3.5±0.2)×10-5, anorthite is plotted on a line of (-1±5)×10-7, and olivine and pyroxene in the core are plotted on a line of (-1±7)×10-6. Plots of olivine and pyroxene in the mantle are scattered below the isochron of these minerals in the core. This study indicates that the EK1-04-2 Type C CAI underwent multiple heating events after the formation of its CAI precursor. The precursor CAI was formed ~0.4Myr after the formation of the Solar System defined by canonical CAI formation. At least 1.6Myr after the precursor CAI formation, the CAI was partially melted and the melt exchanged oxygen isotopes with surrounding 16O-poor nebular gas. 16O-poor olivine and pyroxene in the core crystallized from the melt. Subsequently, Al-rich chondrules accreted onto the CAI, and the CAI experienced partial melting again and recrystallized to form the mantle. The oxygen and magnesium isotopes in anorthite were redistributed during thermal metamorphism in the Allende parent body. Our study reveals that the CAI had been retained in the solar nebula for at least 1.6Myr and underwent multiple melting events in the nebula, and oxygen and 26Al-26Mg systematics has been partially disturbed depending on crystal sizes by metamorphism on the parent body.
  • Nao Cai, Toru Inoue, Kiyoshi Fujino, Hiroaki Ohfuji, Hisayoshi Yurimoto
    American Mineralogist 100 10 2330 - 2335 2015年10月01日 [査読有り][通常論文]
     
    A new Al-bearing hydrous Mg-silicate that we named as 23 Å phase was synthesized at 10 GPa and 1000 °C, while also coexisting with diaspore and pyrope in the following system: phase A [Mg7Si2O8(OH)6] + Al2O3 + H2O. The chemical composition of this new 23 Å phase is Mg11Al2Si4O16(OH)12, and it contains about 12.1 wt% water. Powder X-ray diffraction and electron diffraction patterns show that this new 23 Å phase has a hexagonal structure, with a = 5.1972(2), c = 22.991(4) Å, and V = 537.8(2) Å3, and the possible space group is P6c2, P63cm, or P63/mcm. The calculated density is 2.761 g/cm3 accordingly, which was determined by assuming that the formula unit per cell (Z) is 1. This crystal structure is quite unique among mantle minerals in having an extraordinarily long c axis. Several experiments revealed that its stability region is very similar to that of phase A. We further confirmed that this new 23 Å phase was stable in the chlorite composition at 10 GPa and 1000 °C. The present results indicate that this new 23 Å hydrous phase will form in an Al-bearing subducting slab, and transport water together with Al into the deep upper mantle or even into the upper part of the transition zone.
  • Kanako Tsuboi, Tomoka Hasegawa, Hiromi Hongo, Hisayoshi Yurimoto, Sachio Kobayashi
    Clinical calcium 25 10 1505 - 1511 2015年10月01日 [査読有り][通常論文]
     
    The osteocytic cytoplasmic processes show regularly-arranged three-dimensional structure, a cellular network called osteocytic lacunar-canalicular system (OLCS). We have demonstrated the ultrastructure of the cellular network of OLCS by means of a structured illumination microscope method (SIM) and a Focused Ion Beam-Scanning Electron Microscope (FIB-SEM). We also attempted to localize exogenously-administered minodronate, a new generation of bisphosphonate, as well as calcium deposition onto the bone forming surface, using an isotope microscope system. Recent devised microscopic technique may provide new insights in the research field of bone.
  • Wei Sun, Takashi Yoshino, Naoya Sakamoto, Hisayoshi Yurimoto
    Geophysical Research Letters 42 16 6582 - 6589 2015年08月28日 [査読有り][通常論文]
     
    Hydrogen lattice diffusion in Fe-bearing ringwoodite was investigated through hydrogen and deuterium interdiffusing in a pair of synthesized single crystals at various temperatures (1000-1300 K) at 21 GPa. Diffusion profiles were investigated by secondary ion mass spectrometer to determine the hydrogen self-diffusivity in ringwoodite. Temperature dependences of hydrogen diffusion in ringwoodite were determined to be DH = 10- 7.29(±0.46) exp[-101(±10)kJ mol- 1/RT] m2/s in ringwoodite at 21 GPa. The proton conductivities of ringwoodite estimated from the present diffusion coefficients are similar to those of Yoshino et al. [2008] at the transition zone condition at low water content (<1000 ppm by weight (ppmw)) but lower at higher water content range (>1000 ppmw). If the proton-vacancy mechanism is assumed to be a main controlling mechanism, contribution of water to the electrical conductivity of ringwoodite is insignificant due to large contribution of hopping conduction at the transition zone condition, and global average water concentration in the lower part of transition zone is less than 1000 ppmw.
  • Ai Cheng Zhang, Chi Ma, Naoya Sakamoto, Ru Cheng Wang, Wei Biao Hsu, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 163 27 - 39 2015年08月05日 [査読有り][通常論文]
     
    Titanium-rich minerals are common in Ca-Al-rich inclusions from primitive chondrites. They are important not only for testing the condensation models for a gas with a solar composition, but also for constraining the redox conditions of the early solar nebula. In this study, we report the detailed mineralogical features and its oxygen isotope compositions of a Ti-Sc-rich ultrarefractory inclusion A0031 from a CH3 chondrite Sayh al Uhaymir 290. The A0031 inclusion has a compact and layered texture with the interior consisting of panguite, Sc-rich anosovite, Ti-rich davisite, and anorthite. A few hexaferrum, perovskite, and spinel crystals are present as inclusions in these minerals. Outside of Ti-rich davisite are a layer of Al-Ti-rich diopside and two grains of enstatite. This texture strongly suggests that A0031 has a condensation origin. Panguite is its third occurrence in nature and similar in composition to the type panguite from the Allende meteorite. Sc-rich anosovite in A0031 has a chemical formula of (Ti4+,Ti3+,Mg,Sc,Al)3O5 with the pseudobrookite structure. This is the second report of Ti3O5 in nature, but is the first description of anosovite formed in the solar nebula as an ultrarefractory phase. The discovery of Sc-rich anosovite in A0031 reveals the stability of Ti3O5 in the early solar nebula and supports the prediction of previous equilibrium condensation calculations. The panguite, Sc-rich anosovite, and Ti-rich davisite in A0031 show a large variation in Ti3+/Titot. The primitive nature of A0031 implies that the variations in Ti3+/Titot among different Ti-rich minerals are primary features. We propose that the distribution of Ti3+ and Ti4+ could be controlled mainly by their various competition abilities of incorporating into these Ti-Sc-Al-rich minerals. Similarity of Ti3+/Titot value between Ti-rich davisite from A0031 and those in other carbonaceous chondrites indicates that most refractory inclusions might have formed in highly reducing nebular settings. The 16O-depleted isotope compositions of A0031 confirm the existence of diverse oxygen reservoirs for CH Ca-Al-rich inclusions in the solar nebula.
  • H. Yurimoto, K. Bajo, I. Sakaguchi, T. T. Suzuki, S. Itose, M. Matsuya, M. Ishihara, K. Uchino
    METEORITICS & PLANETARY SCIENCE 50 2015年08月 [査読有り][通常論文]
  • Takuo Okuchi, Narangoo Purevjav, Naotaka Tomioka, Jung Fu Lin, Takahiro Kuribayashi, Louise Schoneveld, Huijeong Hwang, Naoya Sakamoto, Noriyuki Kawasaki, Hisayoshi Yurimoto
    American Mineralogist 100 7 1483 - 1492 2015年07月01日 [査読有り][通常論文]
     
    The presence of water in the Earth's deep mantle is an issue of increasing interest in the field of highpressure mineralogy. An important task for further advancing research in the field is to create homogeneous single crystals of candidate deep-mantle water-bearing minerals of 1 mm or larger in size, which is required for applying them for the time-of-flight (TOF) single-crystal Laue diffraction method with a third-generation neutron instrument. In this study, we perform several experiments to demonstrate an improved methodology for growing hydrous crystals of such large sizes at relevant transition zone and lower-mantle conditions via very slow cooling over a maximum period of 1 day. Successfully synthesized crystals using this methodology include dense hydrous magnesium silicate (DHMS) phase E, hydrous wadsleyite, hydrous ringwoodite, and bridgmanite (silicate perovskite). It is also demonstrated that these hydrous crystals can be grown from deuterium enriched starting materials in addition to those having a natural hydrogen isotope ratio. Magnitudes of chemical and crystallographic heterogeneities of the product crystals were characterized by comprehensive analysis of X-ray precession photography, single-crystal X-ray diffraction (SCXRD), field-emission scanning electron microscope (FE-SEM), electron probe microanalyzer (EPMA), secondary ion mass spectroscopy (SIMS), powder X-ray diffraction (PXRD), and TOF neutron powder diffraction (TOF-NPD). The product crystals were confirmed to be inclusion free and crystallographically homogeneous. Compositional and isotopic differences of major elements and hydrogen isotope abundances were lower than 1 and 3%, respectively, among intracrystals and intercrystals within each recovered sample capsule. Phase E crystals up to 600 μm in the largest dimension were grown at a constant temperature of 1100 °C kept for 3 h. Using a lattice parameter-to-temperature relation of phase E, the thermal gradient in the sample capsules for the phase E synthesis has been evaluated to be 20 °C/mm. Hydrous wadsleyite crystals up to 1100 μm in the largest dimension were grown at 1390 °C with a temperature reduction of 70 °C during heating for 10 h. Hydrous ringwoodite crystals up to 1000 μm in the largest dimension were grown at around 1400 °C with a temperature reduction of 110 °C during heating for 12 h. Bridgmanite crystals up to 600 μm in the largest dimension were grown at 1700 °C with a temperature reduction of 30 °C during heating for 12 h. A TOF single-crystal diffraction instrument has been successfully used for analyzing one of the hydrous wadsleyite crystals, which demonstrated that single crystals appropriate for their expected usage are created using the method proposed in the present study.
  • Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 159 306 - 306 2015年06月15日 [査読有り][通常論文]
  • Tsuboi, K., Hasegawa, T., Hongo, H., Yurimoto, H., Kobayashi, S.
    Clinical calcium 25 10 1505 - 1511 2015年 [査読有り][通常論文]
     
    The osteocytic cytoplasmic processes show regularly-arranged three-dimensional structure, a cellular network called osteocytic lacunar-canalicular system (OLCS). We have demonstrated the ultrastructure of the cellular network of OLCS by means of a structured illumination microscope method (SIM) and a Focused Ion Beam-Scanning Electron Microscope (FIB-SEM). We also attempted to localize exogenously-administered minodronate, a new generation of bisphosphonate, as well as calcium deposition onto the bone forming surface, using an isotope microscope system. Recent devised microscopic technique may provide new insights in the research field of bone.
  • Georg F. Zellmer, Shyh Lung Hwang, Naoya Sakamoto, Yoshiyuki Iizuka, Sakiko Harada, Jun Ichi Kimura, Yoshihiko Tamura, Hisayoshi Yurimoto
    Geological Society Special Publication 410 1 219 - 236 2015年 [査読有り][通常論文]
     
    Pleistocene basalts from Daisen and Mengameyama in the SW Japan volcanic arc of western Honshu are characterized by an abundance of olivine crystals with Fe-rich rims. At Daisen, these have previously been interpreted to have formed from their host melt by equilibrium crystal fractionation and by disequilibrium fractionation during supercooling. Here we use combined electron probe microanalysis, isotopography, transmission electron microscopy and selected area electron diffraction to show that crystal rims are significantly enriched in aluminium (up to c. 1 wt%) and hydrogen (up to c. 10 000 ppm) hosted in oriented low-density amorphous domains. These domains are interpreted to have formed by melting of deuteric and/or post-deuteric metasomatic alteration minerals upon uptake of older olivine crystals into fresh, initially aphyric host melts up to a few hours prior to eruption. It is argued that uptake of variably altered crystals into initially aphyric or sparsely phyric melts may be a common process at subduction zones, and can account for typical disequilibrium textures displayed by arc magmas erupted in SW Japan and elsewhere. Analyses of the altered crystal cargo in arc volcanic rocks therefore provides an important tool for understanding subvolcanic hydrothermal systems and the interaction of ascending melts with such systems.
  • Hisayoshi Yurimoto, Yuji Sano, Tasuku Akagi
    GEOCHEMICAL JOURNAL 49 3 319 - 319 2015年 [査読有り][通常論文]
  • Minako Hashiguchi, Sachio Kobayashi, Hisayoshi Yurimoto
    Geochemical Journal 49 4 377 - 391 2015年 [査読有り][通常論文]
     
    Carbonaceous matter from the matrix of the Murchison (CM2) meteorite and Northwest Africa (NWA) 801 (CR2) meteorite that were extremely rich in deuterium (D) and 15N was studied using in situ isotope imaging. The association of carbon, hydrogen, and nitrogen suggests that the carbonaceous matter was organic in nature, and the maximum magnitudes of D- and 15N-enrichment in the organic matter were δD = 2,880‰ and δ15N = 2,590‰ in Murchison, and δD = 7,500‰ and δ15N = 2,200‰ in NWA 801. The organic matter did not display a simple correlation between the magnitudes of D- and 15N-enrichment, and the isotopically anomalous organic matter was classified into three types based on the H and N isotopic characteristics: extremely 15N-rich without large D-enrichment (15N-rich), extremely D-rich without large 15N-enrichment (D-rich), and highly D- and 15N-rich (D-15N-rich). The occurrence of isotopically anomalous organic matter was attributed to their origin in the molecular clouds and outer solar nebula, ion-molecule reactions at low temperatures, grain surface reactions at low temperatures, and self-shielding effects in gas phase molecules. However, the observed D- and 15N-enrichment of the organic matter is much smaller than predicted by ion-molecule and grain surface reactions. This suggests a secondary modification of the H and N isotopic compositions of the organic matter in the solar nebula and in the parent body. In Murchison, the proportion of D-rich organic matter among the isotopically anomalous organic matter is smaller than in NWA 801, which presumably indicates that the D-enrichments are easily modified by aqueous alteration processes on the parent body. Scanning electron microscopy revealed the morphology of the D- and 15N-rich organic matter as aggregates of globules/particles or non-aggregated globules, where the size of each globule was <1 μm. Although there is no obvious correlation between the morphology of the organic matter and the H and N isotopic compositions, the result that Murchison contains more abundant globule/particle aggregates might suggests formation of aggregated nature due to aqueous activity.
  • Ken Ichi Bajo, Chad T. Olinger, Amy J.G. Jurewicz, Donald S. Burnett, Isao Sakaguchi, Taku Suzuki, Satoru Itose, Morio Ishihara, Kiichiro Uchino, Rainer Wieler, Hisayoshi Yurimoto
    Geochemical Journal 49 5 559 - 566 2015年 [査読有り][通常論文]
     
    The distribution of solar-wind ions in Genesis mission collectors, as determined by depth profiling analysis, constrains the physics of ion-solid interactions involving the solar wind. Thus, they provide an experimental basis for revealing ancient solar activities represented by solar-wind implants in natural samples. We measured the first depth profile of 4He in a Genesis collector; the shallow implantation (peaking at <20 nm) required us to use sputtered neutral mass spectrometry with post-photoionization by a strong field. The solar wind He fluence calculated using depth profiling is ∼8.5 × 1014 cm-2. The shape of the solar wind 4He depth profile is consistent with TRIM simulations using the observed 4He velocity distribution during the Genesis mission. It is therefore likely that all solar-wind elements heavier than H are completely intact in this Genesis collector and, consequently, the solar particle energy distributions for each element can be calculated from their depth profiles. Ancient solar activities and space weathering of solar system objects could be quantitatively reproduced by solar particle implantation profiles.
  • Yahachi Saito, Hisayoshi Yurimoto
    Surface and Interface Analysis 46 12-13 1119 - 1120 2014年12月01日 [査読有り][通常論文]
  • 慢性腎臓病に伴う骨・ミネラル代謝異常(CKD-MBD)の骨質の解析
    木村–須田廣美, 金沢恭祐, 伊藤哲平, 日高公介, 植野秀俊, 居城邦治, 小林幸雄, 圦本尚義
    北海道骨粗鬆症研究会雑誌 3 2 12 - 14 2014年10月 [査読有り][通常論文]
  • Yoshihiko Matsui, Asuka Sakamoto, Soichi Nakao, Takuma Taniguchi, Taku Matsushita, Nobutaka Shirasaki, Naoya Sakamoto, Hisayoshi Yurimoto
    Environmental Science and Technology 48 18 10897 - 10903 2014年09月16日 [査読有り][通常論文]
     
    Decreasing the particle size of powdered activated carbon may enhance its equilibrium adsorption capacity for small molecules and micropollutants, such as 2-methylisoborneol (MIB) and geosmin, as well as for macromolecules and natural organic matter. Shell adsorption, in which adsorbates do not completely penetrate the adsorbent but instead preferentially adsorb near the outer surface of the adsorbent, may explain this enhancement in equilibrium adsorption capacity. Here, we used isotope microscopy and deuterium-doped MIB and geosmin to directly visualize the solid-phase adsorbate concentration profiles of MIB and geosmin in carbon particles. The deuterium/hydrogen ratio, which we used as an index of the solid-phase concentration of MIB and geosmin, was higher in the shell region than in the inner region of carbon particles. Solid-phase concentrations of MIB and geosmin obtained from the deuterium/hydrogen ratio roughly agreed with those predicted by shell adsorption model analyses of isotherm data. The direct visualization of the localization of micropollutant adsorbates in activated carbon particles provided direct evidence of shell adsorption.
  • Masayuki Uesugi, Ryo Noguchi, Tooru Matsumoto, Junya Matsuno, Takashi Nagano, Akira Tsuchiyama, Shigenori Harada, Kaori Yokoyama, Yoshiaki Yodo, Noboru Takeda, Toru Yada, Shogo Yakame, Yuzuru Karouji, Yukihiro Ishibashi, Masanao Abe, Tatsuaki Okada, Akio Fujimura, Mitsuru Ebihara, Fumio Kitajima, Keisuke Nagao, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Hisayoshi Yurimoto
    Meteoritics and Planetary Science 49 7 1186 - 1201 2014年07月 [査読有り][通常論文]
     
    We report the investigation of cutting methods for Hayabusa samples. The purpose of our study is to explore the possibility of applying multiple analyses to a single particle effectively. We investigated the cutting performance of a blade dicing saw, laser, focused ion beam (FIB), and physical breaking by microindenter. Cutting performance was examined by estimating the aspect ratio of the cut slit, i.e., depth over width of the slit. We also investigated the possible contamination and sample damage by cutting. The result of the investigation shows that we can cut the samples from <50 μm to 500 μm using those methods with aspect ratios from 10 to 20, although they would introduce some contamination or damage to the samples. Our investigations also provide an important basis for the analysis of samples obtained by future sample return missions. © The Meteoritical Society, 2014.
  • Ai Cheng Zhang, Shoichi Itoh, Naoya Sakamoto, Ru Cheng Wang, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 130 78 - 92 2014年04月 [査読有り][通常論文]
     
    Aluminum-rich chondrules are one of the most interesting components of primitive chondrites, because they have characteristics that are similar to both Ca, Al-rich inclusions (CAIs) and ferromagnesian chondrules. However, their precursor and formation history remain poorly constrained, especially with respect to their oxygen isotopic distributions. In this study, we report on the petrography, mineralogy, oxygen isotope ratios, and rare-earth-element compositions of a sapphirine-bearing Al-rich chondrule (SARC) in the ungrouped chondrite Dar al Gani (DaG) 978. The SARC has a complex core-mantle-rim texture; while both the core and the mantle are mainly composed of Al-rich enstatite and anorthite with minor amounts of mesostasis, these regions are distinguished by the presence of Fe-rich spinel and sapphirine in the core and their absence in the mantle. The rim of the SARC consists mainly of Fe-rich olivine, enstatite, and Fe-Ni metal. Spinel and some olivine grains in the SARC are 16O-rich, with δ17O values down to -20‰ and -23‰, respectively. Enstatite, sapphirine, and most olivine grains have similar δ17O values (~ -7‰), which are lower than those of anorthite and the mesostasis (including augite therein) (δ17O: ~ -3‰). Mesostasis from both the core and mantle have Group II rare-earth-element (REE) patterns; however, the core mesostasis has higher REE concentrations than the mantle mesostasis. These observations provide a strong indication that the SARC formed by the melting and crystallization of a mixture of materials from Group II CAIs and ferromagnesian chondrules. Both spinel and olivine with 16O-rich features could be of relict origin. The 16O-poor isotopic compositions of most components in Al-rich chondrules can be explained by oxygen isotopic exchange between the melt and 16O-poor nebular gas (δ17O: ~ -7‰) during melting in chondrule-forming regions; whereas the anorthite and mesostasis could have experienced further oxygen isotopic exchange with a relatively 16O-poor reservoir (δ17O: ~ -3‰) on the parent body, likely during fluid-assisted thermal metamorphism. During the same thermal metamorphism event, spinel, olivine, some enstatite, and the mesostasis experienced Mg-Fe exchange to various extents. © 2013 Elsevier Ltd.
  • Yukari Kuga, Naoya Sakamoto, Hisayoshi Yurimoto
    New Phytologist 202 2 594 - 605 2014年04月 [査読有り][通常論文]
     
    Summary: The objective of this study was to elucidate the transfer of nutrient elements in orchid symbiotic protocorms at the cellular level by imaging of stable isotope tracers. We address the long-standing question of whether nutrients move by transport across the symbiotic interface or solely by lysis of fungal pelotons. [U-13C]glucose and 15NH415NO3 were added to Ceratobasidium sp. hyphae extending from symbiotic protocorms of Spiranthes sinensis. Isotope images were taken from resin-embedded sections of protocorms using ultra-high spatial resolution secondary ion mass spectrometry (SIMS). Analyses of regions of interest were conducted on isotope ratio images for fungal and host structures. Amyloplasts adjacent to young pelotons showed elevated 13C/12C, which indicated that fungal carbon (C) was transferred from live hyphae. Senescent pelotons and their surrounding host cytoplasm showed significantly higher isotope ratios than young pelotons and surrounding host cytoplasm. These results indicate an inflow of C to senescent hyphae, which was then transferred to the host. The findings of this study provide some support for each of the two contradictory hypotheses concerning nutrient exchange in the symbiotic protocorm: the interface between the symbionts is involved before fungal senescence, and peloton degradation also releases a significant amount of C and nitrogen to host cells. © 2014 New Phytologist Trust.
  • Jen Chieh Shiao, Shoichi Itoh, Hisayoshi Yurimoto, Yoshiyuki Iizuka, Yun Chih Liao
    Deep-Sea Research Part I: Oceanographic Research Papers 84 50 - 58 2014年02月 [査読有り][通常論文]
     
    This study using tuna otoliths as working standards established a high lateral resolution and precision analysis to measure δ18Ootolith by secondary ion mass spectrometry. This analytical approach of the ion probe was applied to deep-sea fishes to reconstruct the likely depths inhabited by the fishes at different life history stages based on the measured δ18Ootolith values as a proxy of water temperature. Dramatic increases up to 5-6‰ in δ18Ootolith, representing a temperature decrease of approximately 20°C, were detected in a blind cusk eel (Barathronus maculatus) otolith and in the otoliths of Synaphobranchus kaupii during leptocephalus metamorphosis to glass eel, inferred from the drop of otolith Sr/Ca ratios and increase of otolith growth increment width. δ18Ootolith profiles clearly divided the fish's life history into a planktonic stage in the mixed layer of the ocean and a benthic stage on the deep-sea ocean bottom. The habitat shift signal was recorded within a 150μm width of otolith growth zone, which was too narrow to be clearly detected by mechanical drilling and conventional isotopic ratio mass spectrometry. However, variations down to -7‰ were found in δ18Ootolith profiles as the result of Cs2+ beam sputter in the core and larval portions of the otoliths. Carbon mapping by electron probe microanalyzer and staining by toluidine blue suggested abundant proteins existed in the areas with anomaly negative δ18Ootolith values, which cannot be interpreted as a habitat change but due to the isotopic fractionation by O emission from the proteins. These results implied that careful design and understanding of the chemical composition of the analytical areas or tracks on the heterogeneous otolith was essential for highly accurate and precise analysis. © 2013 Elsevier Ltd.
  • S. Wakita, T. Nakamura, T. Ikeda, H. Yurimoto
    Meteoritics and Planetary Science 49 2 228 - 236 2014年02月 [査読有り][通常論文]
     
    We modeled the possible parent bodies of Itokawa, which was heated within by the decay energy of 26Al. Based on mineralogic studies of dust particles derived from Itokawa by the Hayabusa spacecraft, it appeared that they were thermally metamorphosed at a peak temperature of 800 °C, and kept at 700 °C or higher at 7.6 Myr after CAI formation. Our numerical results show that the parent bodies of Itokawa would have been larger than 20 km in radius and accreted at a period between 1.9 and 2.2 Myr after CAI formation, to satisfy mineralogic and isotopic evidence from dust particles. © The Meteoritical Society, 2013.
  • Hisayoshi Yurimoto, Shoichi Itoh, Michael Zolensky, Minoru Kusakabe, Akiya Karen, Robert Bodnar
    Geochemical Journal 48 6 549 - 560 2014年 [査読有り][通常論文]
     
    Determination of isotopic composition of extraterrestrial liquid water provides important information regarding the origin of water on Earth and the terrestrial planets. Fluid inclusions in halite of ordinary chondrites are the only direct samples of extraterrestrial liquid water available for laboratory measurements. We determined H and O isotopic compositions of this water by secondary ion mass spectrometry equipped with a cryogenic apparatus for sample cooling. Isotopic compositions of the fluid inclusion fluids (brines) were highly variable among individual inclusions, -400 < δD < +1300‰; -20 < Δ17O < +30‰, indicating that these aqueous fluids were in isotopic disequilibrium before trapping in halite on asteroids. The isotopic variation of fluids shows that various degrees of water-rock interaction had been underway on the asteroids before trapping between D-rich-16O-poor aqueous fluid, D-poor-16O-rich aqueous fluid, and asteroidal rock by delivery of cometary water onto hydrous asteroids. This may be a fundamental mechanism in the evolution of modern planetary water.
  • Georg F. Zellmer, Naoya Sakamoto, Yoshiyuki Iizuka, Masaya Miyoshi, Yoshihiko Tamura, Hui Ho Hsieh, Hisayoshi Yurimoto
    Geological Society Special Publication 385 1 161 - 184 2014年 [査読有り][通常論文]
     
    Minerals of mafic rocks from theSWJapan arc have been studied to deduce P-T-XH2O conditions and their variations in mafic arc magmas. Two-pyroxene thermobarometry of magmas from several volcanoes yields constant temperatures and variable pressures. MELTS fractional crystallization modelling is employed to show that such 'pseudo-decompression paths' (PDPs) are artefacts that derive from uptake of pyroxene antecrysts formed at a range of crustal levels by isobaric cooling of previously intruded mafic melts. It is shown that PDPs can be used to constrain oxygen fugacities and initial water contents of the intruded magmas. These constraints, and plagioclase hygrometry, indicate that initial melt H2O contents change systematically along the SW Japan arc. Direct determination of hydrogen in olivine by secondary ion mass spectrometry yields consistently low olivine H2O contents of 11+4 ppm (1s), with little, if any, along-arc variations. MELTS modelling indicates that crystallization of calcic plagioclase and olivine dominantly occurs during upper crustal differentiation of mafic melts. The combined data indicate that aphyric melts are released from the mantle wedge, taking up most if not all crystals from previously intruded plutonic rocks during rapid magma ascent to the surface. © The Geological Society of London 2014.
  • Toshihiro Watanabe, Ran Kouho, Tomo Katayose, Nobuyuki Kitajima, Naoya Sakamoto, Noriko Yamaguchi, Takuro Shinano, Hisayoshi Yurimoto, Mitsuru Osaki
    Plant, Cell and Environment 37 1 45 - 53 2014年01月 [査読有り][通常論文]
     
    Low-molecular-weight thiol (LMWT) synthesis has been reported to be directly induced by arsenic (As) in Pteris vittata, an As hyperaccumulator. Sulphur (S) is a critical component of LMWTs. Here, the effect of As treatment on the uptake and distribution of S in P. vittata was investigated. In P. vittata grown under low S conditions, the presence of As in the growth medium enhanced the uptake of SO42-, which was used for LMWT synthesis in fronds. In contrast, As application did not affect SO42- uptake in Nephrolepis exaltata, an As non-hyperaccumulator. Moreover, the isotope microscope system revealed that S absorbed with As accumulated locally in a vacuole-like organelle in epidermal cells, whereas S absorbed alone was distributed uniformly. These results suggest that S is involved in As transport and/or accumulation in P. vittata. X-ray absorption near-edge structure analysis revealed that the major As species in the fronds and roots of P. vittata were inorganic As(III) and As(V), respectively, and that As-LMWT complexes occurred as a minor species. Consequently, in case of As accumulation in P. vittata, S possibly acts as a temporary ligand for As in the form of LMWTs in intercellular and/or intracellular transport (e.g. vacuolar sequestration). In Pteris vittata, an arsenic (As) hyperaccumulator, As application enhanced the uptake of SO42-, which was used for low-molecular-weight thiol synthesis in fronds. Moreover, sulphur (S) absorbed with As accumulated locally in a vacuole-like organelle in epidermal cells of fronds, whereas S absorbed alone was distributed uniformly. Thus, this study demonstrates that As has a dramatic impact on the metabolisms and accumulation of S in P. vittata. © 2013 John Wiley & Sons Ltd.
  • Minako Hashiguchi, Isao Sakaguchi, Naoya Sakamoto, Hisayoshi Yurimoto, Shunichi Hishita, Naoki Ohashi
    Journal of the Ceramic Society of Japan 121 1420 1004 - 1007 2013年12月 [査読有り][通常論文]
     
    We studied the diffusion of Zn in dense SnO2 ceramics by using secondary ion mass spectrometry (SIMS). Dense SnO2 ceramics with additives of 6mol.% MgO and 0.2mol.% Sb2O5 were synthesized, and Zn was implanted in the SnO2 ceramics by ion implantation technique. The implanted samples were annealed at 850-1200°C, and the concentration profiles of Zn were evaluated by SIMS. The temperature dependence of Zn diffusion at 850-950°C could be expressed as DZn[cm2/s] = 3.3 × 106exp(-463.5[kJ/mol]/RT). These results in relation to the fabrication process of SnO2 with added ZnO was then discussed. © 2013 The Ceramic Society of Japan. All rights reserved.
  • Minako Hashiguchi, Sachio Kobayashi, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 122 306 - 323 2013年12月01日 [査読有り][通常論文]
     
    Eighty-five D-rich carbonaceous particles were identified in the matrix of the NWA 801 CR2 chondrite using isotope microscopy. The occurrence of 67 D-rich carbonaceous particles was characterized using secondary electron microscopy combined with X-ray elemental mapping. The close association of H and C, and D-enrichment suggests that the D-rich carbonaceous particles correspond to organic matter. The D-rich organic particles were scattered ubiquitously throughout the matrix at a concentration of approximately 660ppm. The morphology of the D-rich carbonaceous particles is globular up to about 1μm in diameter and is classified into four types: ring globules, round globules, irregular-shaped globules, and globule aggregates. The ring globules are ring-shaped organic matter containing silicate and/or oxide, with or without a void in the center. This is the first report of silicate and oxide grains surrounded by D-rich organic matter. The globule aggregates are composed of several D-rich organic globules mixed with silicates. Morphology of ring globules is very similar to core-mantle grain produced in the molecular cloud or in the outer solar nebula inferring by astronomy, suggesting that the organic globules have formed by UV photolysis in the ice mantle. Silicates or oxides attached to D-rich organic globules are the first observation among chondrites so far and may be unique nature of CR2 chondrites. The hydrogen isotopic compositions of the ring globules, round globules, irregular-shaped globules, and globule aggregates are δD=3000-4800, 2900-8100, 2700-11,000, and 2500-11,000‰, respectively. Variations of D/H ratio of these organic globules seemed to be attributed to variations of D/H ratio of the organic radicals or differences of content of the D-rich organic radicals. There are no significant differences in the hydrogen isotopic compositions among the four types of D-rich carbonaceous matter. The D-enrichments suggest that these organic globules have formed in a cold molecular cloud and/or the outer protoplanetary disk of the early solar system. The oxygen isotopic compositions of the silicates and oxides attached to the ring globules and globule aggregates range from δ17O=-49 to 50‰ and δ18O=-46 to 64‰. The oxygen isotopic compositions are not distinct from those of solar system materials, which suggests that the organic globules were formed in the outer solar system rather than in the presolar environment. Therefore, it is possible that the ring globules and globule aggregates in NWA 801 may have formed in the outer protoplanetary disk of the early solar system. Organic globules that exhibit clear presolar origin were not identified in this study. The lack of clear presolar signatures might suggest that modifications of isotopic compositions or morphologies of the presolar organic matter occurred in the early solar nebula. © 2013.
  • Hyodo H, Terao A, Furukawa J, Sakamoto N, Yurimoto H, Satoh S, Iwai H
    PloS one 8 11 e78949  2013年11月13日 [査読有り][通常論文]
     
    Fruit ripening is one of the developmental processes accompanying seed development. The tomato is a well-known model for studying fruit ripening and development, and the disassembly of primary cell walls and the middle lamella, such as through pectin de-methylesterified by pectin methylesterase (PE) and depolymerization by polygalacturonase (PG), is generally accepted to be one of the major changes that occur during ripening. Although many reports of the changes in pectin during tomato fruit ripening are focused on the relation to softening of the pericarp or the Blossom-end rot by calcium (Ca2+) deficiency disorder, the changes in pectin structure and localization in each tissues during tomato fruit ripening is not well known. In this study, to elucidate the tissue-specific role of pectin during fruit development and ripening, we examined gene expression, the enzymatic activities involved in pectin synthesis and depolymerisation in fruit using biochemical and immunohistochemical analyses, and uronic acids and calcium (Ca)-bound pectin were determined by secondary ion-microprobe mass spectrometry. These results show that changes in pectin properties during fruit development and ripening have tissue-specific patterns. In particular, differential control of pectin methyl-esterification occurs in each tissue. Variations in the cell walls of the pericarp are quite different from that of locular tissues. The Cabinding pectin and hairy pectin in skin cell layers are important for intercellular and tissue-tissue adhesion. Maintenance of the globular form and softening of tomato fruit may be regulated by the arrangement of pectin structures in each tissue. © 2013 Hyodo et al.
  • Isao Sakaguchi, Naoya Sakamoto, Minako Hashiguchi, Hisayoshi Yurimoto, Shunichi Hishita, Naoki Ohashi
    Journal of the Ceramic Society of Japan 121 1419 956 - 959 2013年11月 [査読有り][通常論文]
     
    We investigated the effect of zinc oxide addition for the defects in the dense SnO2 ceramics. Cathode and photoluminescence properties revealed the luminescence originated to oxygen vacancies in SnO2 grains and the presence of non-radiative defect at the grain boundaries. The oxygen diffusion profile showed that the oxygen diffusion was controlled by the limited process at the surface and uniform concentration of 18O at the grain boundaries inner side of sample. This sample exhibited a low Zn concentration in grains and a high Zn concentration at grain boundaries.We conclude that segregation of Zn at grain boundaries prevents SnO2 from decomposing at high temperatures, enabling dense SnO2 ceramics to be obtained. © 2013 The Ceramic Society of Japan. All rights reserved.
  • J. M. Paque, S. R. Sutton, S. B. Simon, J. R. Beckett, D. S. Burnett, L. Grossman, H. Yurimoto, S. Itoh, H. C. Connolly
    Meteoritics and Planetary Science 48 10 2015 - 2043 2013年10月 [査読有り][通常論文]
     
    Ti valence measurements in MgAl2O4 spinel from calcium-aluminum-rich inclusions (CAIs) by X-ray absorption near-edge structure (XANES) spectroscopy show that many spinels have predominantly tetravalent Ti, regardless of host phases. The average spinel in Allende type B1 inclusion TS34 has 87% Ti+4. Most spinels in fluffy type A (FTA) inclusions also have high Ti valence. In contrast, the rims of some spinels in TS34 and spinel grain cores in two Vigarano type B inclusions have larger amounts of trivalent titanium. Spinels from TS34 have approximately equal amounts of divalent and trivalent vanadium. Based on experiments conducted on CAI-like compositions over a range of redox conditions, both clinopyroxene and spinel should be Ti+3-rich if they equilibrated with CAI liquids under near-solar oxygen fugacities. In igneous inclusions, the seeming paradox of high-valence spinels coexisting with low-valence clinopyroxene can be explained either by transient oxidizing conditions accompanying low-pressure evaporation or by equilibration of spinel with relict Ti+4-rich phases (e.g., perovskite) prior to or during melting. Ion probe analyses of large spinel grains in TS34 show that they are enriched in heavy Mg, with an average Δ25Mg of 4.25 ± 0.028‰, consistent with formation of the spinel from an evaporating liquid. Δ25Mg shows small, but significant, variation, both within individual spinels and between spinel and adjacent melilite hosts. The Δ25Mg data are most simply explained by the low-pressure evaporation model, but this model has difficulty explaining the high Ti+4 concentrations in spinel. © The Meteoritical Society, 2013.
  • Ai Cheng Zhang, Hisayoshi Yurimoto
    Meteoritics and Planetary Science 48 9 1651 - 1677 2013年09月 [査読有り][通常論文]
     
    Dar al Gani (DaG) 978 is an ungrouped type 3 carbonaceous chondrite. In this study, we report the petrography and mineralogy of Ca,Al-rich inclusions (CAI), amoeboid olivine aggregates (AOAs), chondrules, mineral fragments, and the matrix in DaG 978. Twenty-seven CAIs were found: 13 spinel-diopside-rich inclusions, 2 anorthite-rich inclusions, 11 spinel-troilite-rich inclusions, and 1 spinel-melilite-rich inclusion. Most CAIs have a layered texture that indicates a condensation origin and are most similar to those in R chondrites. Compound chondrules represent a high proportion (approximately 8%) of chondrules in DaG 978, which indicates a local dusty chondrule-forming region and multiple heating events. Most spinel and olivine in DaG 978 are highly Fe-rich, which corresponds to a petrologic type of >3.5 and a maximum metamorphic temperature of approximately 850-950 K. This conclusion is also supported by other observations in DaG 978: the presence of coarse inclusions of silicate and phosphate in Fe-Ni metal, restricted Ni-Co distributions in kamacite and taenite, and low S concentrations in the matrix. Mineralogic records of iron-alkali-halogen metasomatism, such as platy and porous olivine, magnetite, hedenbergite, nepheline, Na-rich in CAIs, and chlorapatite, are present, but relatively limited, in DaG 978. The fine-grained, intergrowth texture of spinel-troilite-rich inclusions was probably formed by reaction between pre-existing Al-rich silicates and shock-induced, high-temperature S-rich gas on the surface of the parent body of DaG 978. A shock-induced vein is present in the matrix of DaG 978, which indicates that the parent body of DaG 978 at least experienced a shock event with a shock stage up to S3. © The Meteoritical Society, 2013.
  • Hamasaki T, Matsumoto T, Sakamoto N, Shimahara A, Kato S, Yoshitake A, Utsunomiya A, Yurimoto H, Gabazza EC, Ohgi T
    Nucleic acids research 41 12 e126  2013年07月 [査読有り][通常論文]
     
    Radioisotopes and fluorescent compounds are frequently used for RNA labeling but are unsuitable for clinical studies of RNA drugs because of the risk from radiation exposure or the nonequivalence arising from covalently attached fluorophores. Here, we report a practical phosphoramidite solid-phase synthesis of 18O-labeled RNA that avoids these disadvantages, and we demonstrate its application to quantification and imaging. The synthesis involves the introduction of a nonbridging 18O atom into the phosphate group during the oxidation step of the synthetic cycle by using 18O water as the oxygen donor. The 18O label in the RNA was stable at pH 3-8.5, while the physicochemical and biological properties of labeled and unlabeled short interfering RNA were indistinguishable by circular dichroism, melting temperature and RNA-interference activity. The 18O/16O ratio as measured by isotope ratio mass spectrometry increased linearly with the concentration of 18O-labeled RNA, and this technique was used to determine the blood concentration of 18O-labeled RNA after administration to mice. 18O-labeled RNA transfected into human A549 cells was visualized by isotope microscopy. The RNA was observed in foci in the cytoplasm around the nucleus, presumably corresponding to endosomes. These methodologies may be useful for kinetic and cellular-localization studies of RNA in basic and pharmaceutical studies. © 2013 The Author(s) 2013. Published by Oxford University Press.
  • Hiromi Kimura-Suda, Kajiwara Makoto, Sakamoto Naoya, Kobayashi Sachio, Ijiro Kuniharu, Yurimoto Hisayoshi, Yamato Hideyuki
    Journal of Oral Biosciences 55 2 61 - 65 2013年05月 [査読無し][通常論文]
     
    We describe the comprehensive analysis of bone quality by using the isotope microscopy, Fourier transform infrared (FTIR) imaging, and Raman spectroscopy, which are non-destructive techniques. Isotope microscopy is a novel tool for visualizing microdomains within materials through the imaging of the 3-dimensional distribution of isotopes. This technique enabled us to observe calcium metabolism in the tibiae of mice. Thus, a stable calcium isotope fed to mice was observed in the trabecular and cortical bones. FTIR and Raman spectroscopies are powerful tools for characterizing the chemical compositions of materials and provide both qualitative and quantitative information on molecular structure. An FTIR imaging system, which is an accessory for FTIR spectroscopy, provides a distribution map of functional components in the sample. The crystallinity, secondary structure of collagen, carbonate-to- phosphate ratio, and mineral-to-matrix ratio of bone can be obtained from the IR spectra extracted from the selected area of an FTIR image. Raman spectroscopy complements FTIR spectroscopy; however, the Raman spectrum provides information about functional groups in a sample as well as its FTIR spectrum. The major advantage of Raman spectroscopy for bone analysis is the ability to obtain spectra with higher spatial resolution compared with those acquired using FTIR spectroscopy. Moreover, a wide range of samples, including aqueous solutions, fibers, powders, or frozen materials can be readily analyzed, without any special preparation. Raman spectroscopy generates data on crystallinity, carbonate-to-phosphate ratio, and mineral-to-matrix ratio in bone. © 2013 Japanese Association for Oral Biology.
  • Hironori Negishi, Shoji Arai, Hisayoshi Yurimoto, Shoichi Ito, Satoko Ishimaru, Akihiro Tamura, Norikatsu Akizawa
    Lithos 164-167 22 - 35 2013年04月 [査読有り][通常論文]
     
    Peculiar dunites, in part wehrlitic, that contain up to 3vol.% sulfides from a thick (~1000m) Moho transition zone (MTZ) are found along Wadi Thuqbah in the northern Oman ophiolite. We discuss their relevance to the formation of Cyprus-type massive sulfide deposits near the surface. Field observations suggest that the sulfide-rich MTZ dunites are of late-intrusive origin. The sulfides form composite grains with magnetite and form angular clasts, which are enclosed or cut by magnetite. The sulfide part is composed of homogeneous pyrrhotite and vermicular intergrowth of pyrrhotite and pentlandite. Sulfide inclusions in clinopyroxene comprise pyrrhotite with pentlandite blebs, free of magnetite. Olivines in the sulfide-rich dunite characteristically show low NiO contents (0.1-0.3wt.%) relative to a high Fo value (~91), and as such they do not lie on a Fo-NiO trend of ordinary sulfide-free MTZ dunites-wehrlites. This low-Ni olivine was precipitated from a high-Mg magma that had segregated Ni-rich sulfide melts. The pentlandite-pyrrhotite intergrowth was formed by subsolidus exsolution at low temperatures (<200°C) from high-temperature mono-sulfide solid solution. Iron released from olivine during serpentinization produced magnetite, which was combined with the sulfides to form the composite grains. In-situ S isotope ratios of the sulfides (δ34S=0.7-2.8) are slightly higher than mantle values but lie within the range for magmas from oceanic island arcs, such as the Marianas. The δ34S are lower than those for sulfate from seawater and MORB-related sulfides, such as TAG (Trans-Atlantic Geotraverse) deposits. One of the Cyprus type massive sulfide deposits (Aarja) from the crustal section of the same area shows similar S isotope ratios to the sulfides in the Thuqbah sulfide-rich dunites/wehrlites, indicating their genetic linkage. The Aarja sulfide deposit was formed within the V2 lavas, which are relatively sulfur-rich and of an off-axis origin, as a result of high-temperature seawater circulation. The Thuqbah sulfide-rich dunite possibly represents an igneous root of the Cyprus-type massive sulfide deposit of Aarja formed in an off-ridge magmatic-hydrothermal system. © 2012 Elsevier B.V.
  • Kyoko Imamura, Yoshihide Ogasawara, Hisayoshi Yurimoto, Minoru Kusakabe
    International Geology Review 55 4 453 - 467 2013年03月01日 [査読有り][通常論文]
     
    We analysed isotopic compositions of metamorphic microdiamond secondary ion mass spectrometry. Typical microdiamonds in this dolomite marble show star-shaped morphologies (S-type) consisting of single-crystal cores and polycrystalline rims. Four S-type microdiamonds and two R-type microdiamonds (single crystals with rugged surfaces) were analysed using a 5 μm diameter ion beam. S-type microdiamonds have heterogeneous carbon isotopic compositions even in a single grain. Analysis of a typical S-type microdiamond (no. xx01-1-13) revealed clear difference in δ13C between core and rim. The rim shows lighter isotopic compositions ranging from -17.2% to -26.9%, whereas the core is much heavier, with δ13C ranging from -9.3% to -13.0%. The δ13C values of R-type microdiamonds fall into narrow ranges from -8.3% to -14.9% for no. xx01-1-10 and from -8.3% to -15.3% for no. xx01-1-16. These δ13C values are similar to those of the S-type microdiamond cores. The R-type probably formed at the same stage as the core of the S-type, whereas rim growth at a second stage did not occur or occurred very weakly in R-type microdiamonds. These carbon isotopic data support the two-stage growth of microdiamonds in the Kokchetav ultrahigh-pressure host rock. To explain the second stage growth of S-type microdiamonds, we postulate a simple fluid infiltration of light carbon from neighbouring gneisses into the dolomite marble. © 2013 Taylor & Francis.
  • Hiromi Kimura-Suda, Kyosuke Kanazawa, Sachio Kobayashi, Mieko Kuwahara, Teppei Ito, Naoya Sakamoto, Makoto Kajiwara, Hideyuki Yamato, Kuniharu Ijiro, Hisayoshi Yurimoto
    JOURNAL OF BONE AND MINERAL RESEARCH 28 2013年02月 [査読有り][通常論文]
  • S. Wakaki, S. Itoh, T. Tanaka, H. Yurimoto
    Geochimica et Cosmochimica Acta 102 261 - 279 2013年02月01日 [査読有り][通常論文]
     
    We report the petrology, trace element abundances and oxygen isotopic characteristics of a compound CAI-chondrule object, WI-025, found in the Allende CV3 chondrite. The WI-025 is an irregularly shaped inclusion consisting of three texturally and chemically distinct portions: the interior portion, the igneous rim and the intermediate zone located between these two portions. The interior portion consists of anorthite, spinel, olivine and Al-bearing low-Ca pyroxene. The major element chemistry of the interior portion corresponds to that of Al-rich chondrules and is of intermediate character between fine-grained spinel-rich CAIs and ferromagnesian chondrules. The interior portion has abundant 16O-rich spinel (Δ17O=-14.2 to -24.7) and displays a group II CAI-like REE composition. These observations indicate that the interior portion contains a CAI component formed by fractional condensation. The major and trace element chemistry of the interior portion indicate that the CAI had subsequently assimilated chondrule materials through partial melting. The maximum heating temperature of the partial melting is estimated at approximately 1400°C, similar to the maximum heating temperature of Type-B CAIs. The oxygen isotopic compositions of the olivine and low-Ca pyroxene (Δ17O=-6.3) in the interior portion indicate that the partial melting and chondrule assimilation took place under a moderately 16O-poor nebular gas. The igneous rim is texturally and chemically similar to ferromagnesian chondrules and entirely surrounds the interior portion. The oxygen isotopic compositions of the olivine and low-Ca pyroxene in the igneous rim are indistinguishable from those of the interior olivine and Al-bearing low-Ca pyroxenes. These observations indicate that a chondrule material, which was melted in the same nebular gas as the interior portion, was accreted to the interior portion. The intermediate zone represents a reaction zone accompanying the igneous rim formation. The formation history of WI-025 can be summarized by the following processes: (1) original CAI formation, (2) partial melting and chondrule assimilation, (3) igneous rim formation and (4) secondary alteration on the parent body. © 2012 Elsevier Ltd.
  • Shingo Ebata, Morio Ishihara, Kousuke Kumondai, Ryo Mibuka, Kiichiro Uchino, Hisayoshi Yurimoto
    Journal of the American Society for Mass Spectrometry 24 2 222 - 229 2013年02月 [査読有り][通常論文]
     
    A new system incorporating a multi-turn time-of-flight secondary ion/sputtered neutral mass spectrometer (TOF-SIMS/SNMS) with laser post-ionization was designed and constructed. This system consists of a gallium focused ion beam, femtosecond (fs) laser for post-ionization, and multi-turn TOF mass spectrometer. When laser post-ionization was used, the secondary ion signal strengths for several metals increased by up to 650 times, and were greater than the values obtained in conventional TOF-SIMS experiments. Use of the multi-turn mass spectrometer resulted in an increase in mass resolving power with increase in the total TOF. The mass resolving power reached to 23,000 after 800 multi-turn cycles, corresponding to a flight path length of 1040 m. These results indicated that this system is very effective for the analysis of valuable materials such as space samples with high sensitivity, high mass resolving power, and high lateral resolution. [Figure not available: see fulltext.] © 2013 American Society for Mass Spectrometry.
  • Sakaguchi, I., Sakamoto, N., Hashiguchi, M., Yurimoto, H., Hishita, S., Ohashi, N.
    Journal of the Ceramic Society of Japan 121 1419 956 - 959 2013年 [査読有り][通常論文]
     
    We investigated the effect of zinc oxide addition for the defects in the dense SnO2 ceramics. Cathode and photoluminescence properties revealed the luminescence originated to oxygen vacancies in SnO2 grains and the presence of non-radiative defect at the grain boundaries. The oxygen diffusion profile showed that the oxygen diffusion was controlled by the limited process at the surface and uniform concentration of 18O at the grain boundaries inner side of sample. This sample exhibited a low Zn concentration in grains and a high Zn concentration at grain boundaries.We conclude that segregation of Zn at grain boundaries prevents SnO2 from decomposing at high temperatures, enabling dense SnO2 ceramics to be obtained. © 2013 The Ceramic Society of Japan. All rights reserved.
  • Juri Katayama, Shoichi Itoh, Hisayoshi Yurimoto
    Meteoritics and Planetary Science 47 12 2094 - 2106 2012年12月 [査読有り][通常論文]
     
    The oxygen isotopic microdistributions within melilite measured using in situ secondary ion mass spectrometry correspond to the chemical zoning profiles in single melilite crystals of a fluffy type A Ca-Al-rich inclusions (CAIs) of reduced CV3 Vigarano meteorite. The melilite crystals show chemical reverse zoning within an individual single crystal from the åkermanite-rich core to the åkermanite-poor rim. The composition changes continuously with the crystal growth. The zoning structures suggest that the melilite grew in a hot nebular gas by condensation with decreasing pressure. The oxygen isotopic composition of melilite also changes continuously from 16O-poor to 16O-rich with the crystal growth. These observations suggest that the melilite condensation proceeded with change consistent with an astrophysical setting around the inner edge of a protoplanetary disk where both 16O-rich solar coronal gas and 16O-poor dense protoplanetary disk gas could coexist. Fluffy type A CAIs could have been formed around the inner edge of the protoplanetary disk surrounding the early sun. © 2012 The Meteoritical Society.
  • Changkun Park, Shigeyuki Wakaki, Naoya Sakamoto, Sachio Kobayashi, Hisayoshi Yurimoto
    Meteoritics and Planetary Science 47 12 2070 - 2083 2012年12月 [査読有り][通常論文]
     
    High-precision isotope imaging analyses of reversely zoned melilite crystals in the gehlenitic mantle of Type A CAI ON01 of the Allende carbonaceous chondrite reveal that there are four types of oxygen isotopic distributions within melilite single crystals: (1) uniform depletion of 16O (δ18O≈-10‰), (2) uniform enrichment of 16O (δ18O≈-40‰), (3) variations in isotopic composition from 16O-poor core to 16O-rich rim (δ18O≈-10‰ to -30‰, -20‰ to -45‰, and -10‰ to -35‰) with decreasing åkermanite content, and (4) 16O-poor composition (δ18O≥-10‰) along the crystal rim. Hibonite, spinel, and perovskite grains are 16O-rich (δ18O≈-45‰), and adjoin 16O-poor melilites. Gas-solid or gas-melt isotope exchange in the nebula is inconsistent with both the distinct oxygen isotopic compositions among the minerals and the reverse zoning of melilite. Fluid-rock interaction on the parent body resulted in 16O-poor compositions of limited areas near holes, cracks, or secondary phases, such as anorthite or grossular. We conclude that reversely zoned melilites mostly preserve the primary oxygen isotopic composition of either 16O-enriched or 16O-depleted gas from which they were condensed. The correlation between oxygen isotopic composition and åkermanite content may indicate that oxygen isotopes of the solar nebula gas changed from 16O-poor to 16O-rich during melilite crystal growth. We suggest that the radial excursions of the inner edge of the protoplanetary disk gas simultaneously resulted in both the reverse zoning and oxygen isotopic variation of melilite, due to mixing of 16O-poor disk gas and 16O-rich coronal gas. Gas condensates aggregated to form the gehlenite mantle of the Type A CAI ON01. © 2012 The Meteoritical Society.
  • Noriyuki Kawasaki, Naoya Sakamoto, Hisayoshi Yurimoto
    Meteoritics and Planetary Science 47 12 2084 - 2093 2012年12月 [査読有り][通常論文]
     
    Different oxygen isotopic reservoirs have been recognized in the early solar system. Fluffy type A Ca-Al-rich inclusions (CAIs) are believed to be direct condensates from a solar nebular gas, and therefore, have acquired oxygen from the solar nebula. Oxygen isotopic and chemical compositions of melilite crystals in a type A CAI from Efremovka CV3 chondrite were measured to reveal the temporal variation in oxygen isotopic composition of surrounding nebular gas during CAI formation. The CAI is constructed of two domains, each of which has a core-mantle structure. Reversely zoned melilite crystals were observed in both domains. Melilite crystals in one domain have a homogeneous 16O-poor composition on the carbonaceous chondrite anhydrous mineral (CCAM) line of δ18O=5-10‰, which suggests that the domain was formed in a 16O-poor oxygen isotope reservoir of the solar nebula. In contrast, melilite crystals in the other domain have continuous variations in oxygen isotopic composition from 16O-rich (δ18O=-40‰) to 16O-poor (δ18O=0‰) along the CCAM line. The oxygen isotopic composition tends to be more 16O-rich toward the domain rim, which suggests that the domain was formed in a variable oxygen isotope reservoir of the solar nebula. Each domain of the type A CAI has grown in distinct oxygen isotope reservoir of the solar nebula. After the domain formation, domains were accumulated together in the solar nebula to form a type A CAI. © 2012 The Meteoritical Society.
  • Satoko Motai, Takaya Nagai, Kohki Sowa, Tsuyoshi Watanabe, Naoya Sakamoto, Hisayoshi Yurimoto, Jun Kawano
    Journal of Structural Biology 180 3 389 - 393 2012年12月 [査読有り][通常論文]
     
    The skeletal texture and crystal morphology of the massive reef-building coral Porites lobata were observed from the nano- to micrometer scale using an analytical transmission electron microscope (ATEM). The skeletal texture consists of centers of calcification (COCs) and fiber area. Fiber areas contain bundles of needle-like aragonite crystals that are elongated along the crystallographic c-axis and are several hundred nanometers to one micrometer in width and several micrometers in length. The size distribution of aragonite crystals is relatively homogeneous in the fibers. Growth lines are observed sub-perpendicular to the direction of aragonite growth. These growth lines occur in 1-2μm intervals and reflect a periodic contrast in the thickness of an ion-spattered sample and pass through the interior of some aragonite crystals. These observations suggest that the medium filled in the calcification space maintains a CaCO3-supersaturated state during fiber growth and that a physical change occurs periodically during the aragonite crystals of the fiber area. © 2012 Elsevier Inc.
  • Hongzhan Fei, Chamathni Hegoda, Daisuke Yamazaki, Michael Wiedenbeck, Hisayoshi Yurimoto, Svyatoslav Shcheka, Tomoo Katsura
    Earth and Planetary Science Letters 345-348 95 - 103 2012年09月 [査読有り][通常論文]
     
    Silicon self-diffusion coefficients (D Si) in dry synthetic forsterite single crystals were measured at temperatures of 1600 and 1800K, from ambient pressure up to 13GPa using an ambient pressure furnace and Kawai-type multi-anvil apparatus. The water contents in the samples were carefully controlled at <1μg/g. Diffusion profiles were obtained by secondary ion mass spectrometry (SIMS) in depth profiling mode. Small negative pressure dependence of D Si is determined with an activation volume of 1.7±0.4cm 3/mol. The activation energy is found to be 410±30kJ/mol. LogD Si values (D Si in m 2/s) at 1600 and 1800K at ambient pressure are determined to be -19.7±0.4 and -18.1±0.3, respectively. These values are ~2.4 orders of magnitude higher than those reported by Jaoul et al. (1981). We speculate that their low D Si might reflect the effects of a horizontal migration of the isotopically enriched thin films applied on the sample surfaces, which may inhibit diffusion into the substrate during annealing. Our results for D Si resolve the inconsistency between D Si measured in diffusion experiments and those deduced from creep rates measured in deformation experiments. © 2012 Elsevier B.V.
  • Naoya Sakamoto, Satoshi Aoyama, Shoji Kawahito, Hisayoshi Yurimoto
    Japanese Journal of Applied Physics 51 7 PART 1 1 - 76701 2012年07月 [査読有り][通常論文]
     
    We designed a new type of stacked complementary metal-oxide-semiconductor active pixel sensor (SCAPS) for charged particles with real-time readout and single-ion detection capabilities. Here we present the characteristics of a new imager, SCAPS-II, which implements a newly devised pixel structure of 504 × 504 pixels for high sensitivity and a noise-reduction mechanism with analog accumulation capabilities inside the column readout circuits. The sensitivity for ions was estimated to be 150 μV/ion under 10 keV Si+ ion irradiation, which is 5 times greater than that of conventional SCAPS. The noise floor was at the 3 ion level without the noise-reduction mechanism at a frame rate of 0.16 s/frame. The noise reduction mechanism reduced the noise to the 1.7 ion level at 0.3 s/frame with 13 samplings. A combination of the noise-reduction mechanism and a multiple-frame-averaging technique achieved a noise level of 0.3 ions. Single-ion detectability was demonstrated using a combination of the noise-reduction mechanism and the multiple-frame-averaging technique that reduced the noise to the 0.3 ion level with 13 samplings, employing an integration circuit and 50-frame averaging at 14.4 s/frame. © 2012 The Japan Society of Applied Physics.
  • C. Park, S. Wakaki, H. Yurimoto
    Surface and Interface Analysis 44 6 678 - 681 2012年06月 [査読有り][通常論文]
     
    Ca-Al-rich inclusions (CAIs) are thought to be the oldest rocks in the solar system. CAIs have oxygen isotope heterogeneities on inter-mineral and intra-mineral scales that provide information about environments of the early solar system. We studied a type A CAI from the Allende meteorite, showing a core-mantle structure. Reversely zoned melilite found in the mantle was identified by a combination of energy dispersive X-ray spectrometer and electron back-scattered diffraction techniques. For investigation of oxygen isotopic variations of reversely zoned melilite, we developed a high-precision secondary ion mass spectrometry method that achieves to ∼1‰ (1σ) under the spatial resolution of ∼3 μm in diameter. Oxygen isotopic composition of core melilite is uniformly 16O-poor (δ 17, 18O ≈ -5 to 0‰), whereas mantle melilite varies widely from 16O-poor (δ 17, 18O ≈ -5‰) to rich (δ 17, 18O ≈ -45‰) at the micrometer scale. The variation possibly suggests that the oxygen isotopic composition of solar nebular gas was changed from 16O-poor to 16O-rich at the last stage of the CAI formation. Copyright © 2011 John Wiley & Sons, Ltd. Copyright © 2011 John Wiley & Sons, Ltd.
  • Shingo Ebata, Morio Ishihara, Kiichiro Uchino, Satoru Itose, Miyuki Matsuya, Masato Kudo, Ken Ichi Bajo, Hisayoshi Yurimoto
    Surface and Interface Analysis 44 6 635 - 640 2012年06月 [査読有り][通常論文]
     
    We have developed a new nano-beam time-of-flight secondary neutral mass spectrometry system: laser ionization mass nanoscope or LIMAS. The primary ion beam column was equipped with a Ga liquid metal ion source and aberration correction optics. The primary ion beam was down to 40 nm in diameter under a current of 100 pA with an energy of 20 keV. The sputtered particles were post-ionized under non-resonance mode by a femtosecond laser. The post-ionized ions were introduced into a multi-turn mass spectrometer. A mass resolution of up to 40 000 was achieved. The vacuum of the sample chamber was maintained under an ultrahigh vacuum of 2×10 -8 Pa. This instrument would be effective for ultrahigh sensitive analysis of nanosized particles such as return samples from asteroids, comets, and planets. Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd.
  • Hisayoshi Yurimoto
    AIP Conference Proceedings 1484 139 - 141 2012年 [査読有り][通常論文]
     
    Preliminary examinations of particles on asteroid Itokawa surface returned by Hayabusa mission have been completed by X-ray CT analysis, X-ray diffraction analysis, petrology, mineral chemistry, oxygen isotope analysis, trace element analysis and noble gas analysis. The laboratory characterization of Itokawa particles certified that Itokawa was composed of similar materials of ordinary chondrites. This is the first direct link showing that Stype asteroids is one of the sources of the ordinary chondrites, which are the most abundant meteorite species fallen into the Earth. © 2012 American Institute of Physics.
  • H. Naraoka, H. Mita, K. Hamase, M. Mita, H. Yabuta, K. Saito, K. Fukushima, F. Kitajima, S. A. Sandford, T. Nakamura, T. Noguchi, R. Okazaki, K. Nagao, M. Ebihara, H. Yurimoto, A. Tsuchiyama, M. Abe, K. Shirai, M. Ueno, T. Yada, Y. Ishibashi, T. Okada, A. Fujimura, T. Mukai, M. Yoshikawa, J. Kawaguchi
    Geochemical Journal 46 1 61 - 72 2012年 [査読有り][通常論文]
     
    Microparticles recovered from the Asteroid 25143 Itokawa surface by the Hayabusa mission have been examined for the occurrence of soluble organic compounds. After five individual particles (∼50 to 100 μm in diameter) were rinsed with organic solvents on a diamond plate, two extracts were hydrolyzed with hydrochloric acid for amino acid analysis (AAA), and three extracts were combined for time of flight-secondary ion mass spectrometry (ToF-SIMS) to look for other organic compounds, including polycyclic aromatic hydrocarbons. The organic compounds detected by both methods have the same concentrations as those in blank levels, indicating that indigenous organic compounds are not found in this study. Based on the sensitivities of AAA and ToF-SIMS with the reference sample analyses, the concentrations of indigenous organics in the samples are below part-per-million (ppm), if present. Copyright © 2012 by The Geochemical Society of Japan.
  • Junshan Xu, Daisuke Yamazaki, Tomoo Katsura, Xiaoping Wu, Patrick Remmert, Hisayoshi Yurimoto, Sumit Chakraborty
    Journal of Geophysical Research: Solid Earth 116 12 2011年12月01日 [査読有り][通常論文]
     
    Si and Mg self-diffusion coefficients were measured simultaneously in single crystals of MgSiO3 perovskite under lower mantle conditions. There is little difference in Si volume diffusivity measured directly using single crystals (this study) and those retrieved from experiments with polycrystals (earlier studies). This agreement between studies establishes the reliability of Si diffusion coefficients measured in perovskite. Within the uncertainties of our measurements, no anisotropy in the diffusion of either Si or Mg could be resolved. Diffusion of Si and Mg in perovskite are described by an Arrhenius equation, D=D0 exp (-H/RT) at 25GPa, with D 0=5.10×10-11m2/s for Si and 4.99×10-11m2/s for Mg, H=308kJ/mol for Si, and 305kJ/mol for Mg. Mg diffusivity in MgSiO3 perovskite is distinctly lower than those measured in olivine, wadsleyite, and ringwoodite. We find that Mg has very similar diffusivity to Si in perovskite. As a consequence, the rheological properties of the lower mantle may be controlled by the coupled motion of Si and Mg. A point defect-based model is discussed that may account for the diffusion behavior of Si and Mg in MgSiO3 perovskite. Our data indicate that, within realistic ranges of temperature, grain size, and state of stress, both diffusion creep as well as dislocation creep may be observed in the lower mantle. Copyright 2011 by the American Geophysical Union.
  • Junshan Xu, Daisuke Yamazaki, Tomoo Katsura, Xiaoping Wu, Patrick Remmert, Hisayoshi Yurimoto, Sumit Chakraborty
    JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 116 12 12205 - 12205 2011年12月 [査読有り][通常論文]
     
    Si and Mg self-diffusion coefficients were measured simultaneously in single crystals of MgSiO3 perovskite under lower mantle conditions. There is little difference in Si volume diffusivity measured directly using single crystals (this study) and those retrieved from experiments with polycrystals (earlier studies). This agreement between studies establishes the reliability of Si diffusion coefficients measured in perovskite. Within the uncertainties of our measurements, no anisotropy in the diffusion of either Si or Mg could be resolved. Diffusion of Si and Mg in perovskite are described by an Arrhenius equation, D = D-0 exp (-Delta H/RT) at 25 GPa, with D-0 = 5.10 x 10(-11) m(2)/s for Si and 4.99 x 10(-11) m(2)/s for Mg, Delta H = 308 kJ/mol for Si, and 305 kJ/mol for Mg. Mg diffusivity in MgSiO3 perovskite is distinctly lower than those measured in olivine, wadsleyite, and ringwoodite. We find that Mg has very similar diffusivity to Si in perovskite. As a consequence, the rheological properties of the lower mantle may be controlled by the coupled motion of Si and Mg. A point defect-based model is discussed that may account for the diffusion behavior of Si and Mg in MgSiO3 perovskite. Our data indicate that, within realistic ranges of temperature, grain size, and state of stress, both diffusion creep as well as dislocation creep may be observed in the lower mantle.
  • Madhusoodhan Satish-Kumar, Hisayoshi Yurimoto, Shoichi Itoh, Bernardo Cesare
    Contributions to Mineralogy and Petrology 162 4 821 - 834 2011年10月 [査読有り][通常論文]
     
    High-spatial resolution carbon isotope analyses of natural graphite using secondary ion mass spectrometry (SIMS), together with conventional mass spectrometry techniques, demonstrate isotopic heterogeneity within single graphite crystals precipitated from a partially melted metamorphic rock. SIMS 13C/12C measurements were calibrated using an internal graphite standard previously analyzed by conventional isotope ratio mass spectrometry, which gave a reproducibility of 0.3‰ (1σ) at a spatial resolution of 2-3 μm. This resolution helped to identify an unusual carbon isotope distribution in a single graphite crystal from a metapelitic leucosome, showing remarkable core to rim variations with sharp δ13C steps up to 10‰. The results suggest that the graphite crystal grew from one edge to other forming layers perpendicular to the c-axis. The sharp isotopic steps indicate the presence of disequilibrium carbon isotope zoning in graphite and points to the possible existence of carbon isotope sector zoning. Intra-crystalline carbon isotope disequilibrium in graphite is believed to have resulted from the difference in diffusivity between 12C and 13C in the growth medium to the interface of graphite precipitation in different growth sectors. © 2011 Springer-Verlag.
  • M. Ebihara, S. Sekimoto, N. Shirai, Y. Hamajima, M. Yamamoto, K. Kumagai, Y. Oura, T. R. Ireland, F. Kitajima, K. Nagao, T. Nakamura, H. Naraoka, T. Noguchi, R. Okazaki, A. Tsuchiyama, M. Uesugi, H. Yurimoto, M. E. Zolensky, M. Abe, A. Fujimura, T. Mukai, Y. Yada
    Science 333 6046 1119 - 1121 2011年08月26日 [査読有り][通常論文]
     
    A single grain (~3 micrograms) returned by the Hayabusa spacecraft was analyzed by neutron activation analysis. This grain is mainly composed of olivine with minor amounts of plagioclase, troilite, and metal. Our results establish that the Itokawa sample has similar chemical characteristics (iron/scandium and nickel/cobalt ratios) to chondrites, confirming that this grain is extraterrestrial in origin and has primitive chemical compositions. Estimated iridium/nickel and iridium/cobalt ratios for metal in the Itokawa samples are about five times lower than CI carbonaceous chondrite values. A similar depletion of iridium was observed in chondrule metals of ordinary chondrites. These metals must have condensed from the nebular where refractory siderophile elements already condensed and were segregated.
  • Hisayoshi Yurimoto, Ken Ichi Abe, Masanao Abe, Mitsuru Ebihara, Akio Fujimura, Minako Hashiguchi, Ko Hashizume, Trevor R. Ireland, Shoichi Itoh, Juri Katayama, Chizu Kato, Junichiro Kawaguchi, Noriyuki Kawasaki, Fumio Kitajima, Sachio Kobayashi, Tatsuji Meike, Toshifumi Mukai, Keisuke Nagao, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Changkun Park, Naoya Sakamoto, Yusuke Seto, Masashi Takei, Akira Tsuchiyama, Masayuki Uesugi, Shigeyuki Wakaki, Toru Yada, Kosuke Yamamoto, Makoto Yoshikawa, Michael E. Zolensky
    Science 333 6046 1116 - 1119 2011年08月26日 [査読有り][通常論文]
     
    Meteorite studies suggest that each solar system object has a unique oxygen isotopic composition. Chondrites, the most primitive of meteorites, have been believed to be derived from asteroids, but oxygen isotopic compositions of asteroids themselves have not been established. We measured, using secondary ion mass spectrometry, oxygen isotopic compositions of rock particles from asteroid 25143 Itokawa returned by the Hayabusa spacecraft. Compositions of the particles are depleted in 16O relative to terrestrial materials and indicate that Itokawa, an S-type asteroid, is one of the sources of the LL or L group of equilibrated ordinary chondrites. This is a direct oxygen-isotope link between chondrites and their parent asteroid.
  • Akira Tsuchiyama, Masayuki Uesugi, Takashi Matsushima, Tatsuhiro Michikami, Toshihiko Kadono, Tomoki Nakamura, Kentaro Uesugi, Tsukasa Nakano, Scott A. Sandford, Ryo Noguchi, Toru Matsumoto, Junya Matsuno, Takashi Nagano, Yuta Imai, Akihisa Takeuchi, Yoshio Suzuki, Toshihiro Ogami, Jun Katagiri, Mitsuru Ebihara, Trevor R. Ireland, Fumio Kitajima, Keisuke Nagao, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Hisayoshi Yurimoto, Michael E. Zolensky, Toshifumi Mukai, Masanao Abe, Toru Yada, Akio Fujimura, Makoto Yoshikawa, Junichiro Kawaguchi
    Science 333 6046 1125 - 1128 2011年08月26日 [査読有り][通常論文]
     
    Regolith particles on the asteroid Itokawa were recovered by the Hayabusa mission. Their three-dimensional (3D) structure and other properties, revealed by x-ray microtomography, provide information on regolith formation. Modal abundances of minerals, bulk density (3.4 grams per cubic centimeter), and the 3D textures indicate that the particles represent a mixture of equilibrated and less-equilibrated LL chondrite materials. Evidence for melting was not seen on any of the particles. Some particles have rounded edges. Overall, the particles' size and shape are different from those seen in particles from the lunar regolith. These features suggest that meteoroid impacts on the asteroid surface primarily formmuch of the regolith particle, and that seismic-induced grain motion in the smooth terrain abrades them over time.
  • Keisuke Nagao, Ryuji Okazaki, Tomoki Nakamura, Yayoi N. Miura, Takahito Osawa, Ken Ichi Bajo, Shintaro Matsuda, Mitsuru Ebihara, Trevor R. Ireland, Fumio Kitajima, Hiroshi Naraoka, Takaaki Noguchi, Akira Tsuchiyama, Hisayoshi Yurimoto, Michael E. Zolensky, Masayuki Uesugi, Kei Shirai, Masanao Abe, Toru Yada, Yukihiro Ishibashi, Akio Fujimura, Toshifumi Mukai, Munetaka Ueno, Tatsuaki Okada, Makoto Yoshikawa, Junichiro Kawaguchi
    Science 333 6046 1128 - 1131 2011年08月26日 [査読有り][通常論文]
     
    Noble gas isotopes were measured in three rocky grains from asteroid Itokawa to elucidate a history of irradiation from cosmic rays and solar wind on its surface. Large amounts of solar helium (He), neon (Ne), and argon (Ar) trapped in various depths in the grains were observed, which can be explained by multiple implantations of solar wind particles into the grains, combined with preferential He loss caused by frictional wear of space-weathered rims on the grains. Short residence time of less than 8 million years was implied for the grains by an estimate on cosmic-ray-produced 21Ne. Our results suggest that Itokawa is continuously losing its surface materials into space at a rate of tens of centimeters per million years. The lifetime of Itokawa should be much shorter than the age of our solar system.
  • F. Kitajima, M. Kotsugi, T. Ohkochi, H. Naraoka, Y. Ishibashi, M. Abe, A. Fujimura, R. Okazaki, T. Yada, T. Nakamura, T. Noguchi, K. Nagao, A. Tsuchiyama, H. Yurimoto, M. Ebihara, T. Mukai, S. A. Sandford, T. Okada, K. Shirai, M. Ueno, M. Yoshikawa, J. Kawaguchi
    METEORITICS & PLANETARY SCIENCE 46 A126 - A126 2011年07月 [査読有り][通常論文]
  • Ritsuro Miyawaki, Hidehiko Shimazaki, Masako Shigeoka, Kazumi Yokoyama, Satoshi Matsubara, Hisayoshi Yurimoto
    European Journal of Mineralogy 23 3 467 - 473 2011年06月 [査読有り][通常論文]
     
    Yangzhumingite, ideally KMg2.5Si4O10F2, occurs as subhedral to euhedral platy crystals up to ca. 0.5 mm across in metamorphosed carbonate rock from Bayan Obo, Inner Mongolia, China. It is associated with dolomite, calcite, tremolite, norbergite and huanghoite-(Ce) with minor phlogopite, barite, bastnäsite-(Ce), parisite-(Ce), and fluorite. Yangzhumingite is transparent and colorless with white streak and pearly luster. It is optically biaxial (-), n = 1.532-1.537 (589 nm), and 2V = 5-10°. The hardness is 3 on Mohs' scale (measured on a synthetic equivalent). It has a monoclinic unit cell with a = 5.249(4), b = 9.095(5), c = 10.142(5)Å , β = 99.96(6)°, V = 476.9(5)Å3, Z = 2, space group C2/m, and Dcalc. = 2.807 g/cm3. The five strongest lines in the powder XRD pattern are [d(Å ), I/I0, hkl]: (10.03, 95, 001); (3.37, 48, 022), (2.90, 49, 113), (2.59, 67, 131 200) and (2.41, 100, 132 201). The mean of 15 electron microprobe analyses and SIMS analysis for Li lead to the empirical formula (K0.70Li0.30Na0.01)(Mg2.48Fe 0.06) (Si3.96Al0.03)O10[F 1.92(OH)0.08] on the basis of 12 anions with (F + OH) = 2. Yangzhumingite is a member of the mica group (Nickel-Strunz grouping 9.EC.10), and it represents the Mg-dominant analogue of montdorite. © 2011 E. Schweizerbart'sche Verlagsbuchhandlung.
  • James P. Greenwood, Shoichi Itoh, Naoya Sakamoto, Paul Warren, Lawrence Taylor, Hisayoshi Yurimoto
    Nature Geoscience 4 2 79 - 82 2011年02月 [査読有り][通常論文]
     
    Water plays a critical role in the evolution of planetary bodies 1, and determination of the amount and sources of lunar water has profound implications for our understanding of the history of the Earth-Moon system. During the Apollo programme, the lunar samples were found to be devoid of indigenous water2,3. The severe depletion of volatiles, including water, in lunar rock samples4 has long been seen as strong support for the theory that the Moon formed during a giant impact event5. Water has now been identified in lunar volcanic glasses6 and apatite7-9, but the sources of water to the Moon have not been determined. Here we report ion microprobe measurements of water and hydrogen isotopes in the hydrous mineral apatite, derived from crystalline lunar mare basalts and highlands rocks collected during the Apollo missions. We find significant water in apatite from both mare and highlands rocks, indicating a role for water during all phases of the Moon's magmatic history. Variations of hydrogen isotope ratios in apatite suggest sources for water in lunar rocks could come from the lunar mantle, solar wind protons and comets. We conclude that a significant delivery of cometary water to the Earth-Moon system occurred shortly after the Moon-forming impact. © 2011 Macmillan Publishers Limited. All rights reserved.
  • 「月惑星探査の来たる10年」検討・第一段階報告
    大谷栄治, 倉本圭, 今村剛, 寺田直樹, 渡部重十, 荒川政彦, 伊藤孝士, 圦本尚義, 渡部潤一, 木村淳, 高橋幸弘, 中島健介, 中本泰史, 三好由純, 小林憲正, 山岸明彦, 並木則行, 小林直樹, 出村裕英, 大槻圭史
    日本惑星科学会誌 20 350 - 366 2011年 [査読有り][通常論文]
  • Toru Inoue, Tomoyuki Wada, Rumi Sasaki, Hisayoshi Yurimoto
    Physics of the Earth and Planetary Interiors 183 1-2 245 - 251 2010年11月 [査読有り][通常論文]
     
    We have conducted H2O partitioning experiments between wadsleyite and ringwoodite and between ringwoodite and perovskite at 1673K and 1873K, respectively. These experiments were performed in order to constrain the relative distribution of H2O in the upper mantle, the mantle transition zone, and the lower mantle. We successfully synthesized coexisting mineral assemblages of wadsleyite-ringwoodite and ringwoodite-perovskite that were large enough to measure the H2O contents by secondary ion mass spectrometry (SIMS). Combining our previous H2O partitioning data (Chen et al., 2002) with the present results, the determined water partitioning between olivine, wadsleyite, ringwoodite, and perovskite under H2O-rich fluid saturated conditions are 6:30:15:1, respectively. Because the maximum H2O storage capacity in wadsleyite is ∼3.3wt% (e.g. Inoue et al., 1995), the possible maximum H2O storage capacity in the olivine high-pressure polymorphs are as follows: ∼0.7wt% in olivine (upper mantle just above 410km depth), ∼3.3wt% in wadsleyite (410-520km depth), ∼1.7wt% in ringwoodite (520-660km depth), and ∼0.1wt% in perovskite (lower mantle). If we assume ∼0.2wt% of the H2O content in wadsleyite in the mantle transition zone estimated by recent electrical conductivity measurements (e.g. Dai and Karato, 2009), the estimated H2O contents throughout the mantle are as follows; ∼0.04wt% in olivine (upper mantle just above 410km depth), ∼0.2wt% in wadsleyite (410-520km depth), ∼0.1wt% in ringwoodite (520-660km depth) and ∼0.007wt% in perovskite (lower mantle). Thus, the mantle transition zone should contain a large water reservoir in the Earth's mantle compared to the upper mantle and the lower mantle. © 2010 Elsevier B.V.
  • Morio Ishihara, Shingo Ebata, Kousuke Kumondai, Ryo Mibuka, Kiichiro Uchino, Hisayoshi Yurimoto
    Surface and Interface Analysis 42 10-11 1598 - 1602 2010年10月 [査読有り][通常論文]
     
    The performance of a newly developed TOF-SIMS System with a femtosecond laser postionization and a multiturn mass spectrometer was investigated in linear mode. This system would be very effective for analyzing valuable material such as space samples. By using postionization the secondary ion signals of Ag were increased (up to 100 times), compared with the conventional TOF-SIMS experiments. The laser power dependence on the signal intensities was also investigated and it was confirmed that the signal intensities reached specific values above the specific laser power. Lateral resolution of the elemental map was calculated to be about 40 nm. © 2010 John Wiley & Sons, Ltd.
  • K. Yamamoto, N. Sakamoto, H. Yurimoto
    Surface and Interface Analysis 42 10-11 1603 - 1605 2010年10月 [査読有り][通常論文]
     
    By analyzing the noise characteristics of a stacked CMOS-type active pixel sensor (SCAPS), we developed a noise reduction method. We also developed a multiple frame-averaging method based on a correlated double sampling (CDS) between averaged frames, which use the multiple frames collected by nondestructive readout of signals before and after ion irradiation. This method suppresses SCAPS read noise to 11 μV, corresponding to 0.37 ions. Ion transfer and noise performance were evaluated by above method, leading to the confirmation of noise suppression below the level of single ion detection and the expansion of the dynamic range of SCAPS to 102 dB. © 2010 John Wiley & Sons, Ltd.
  • James P. Greenwood, Shoichi Itoh, Naoya Sakamoto, Paul H. Warren, Lawrence A. Taylor, Hisayoshi Yurimoto
    GEOCHIMICA ET COSMOCHIMICA ACTA 74 12 A354 - A354 2010年06月 [査読有り][通常論文]
  • Alexander N. Krot, Kazuhide Nagashima, Miwa Yoshitake, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 74 7 2190 - 2211 2010年04月 [査読有り][通常論文]
     
    It has been recently suggested that (1) CH chondrites and the CBb/CH-like chondrite Isheyevo contain two populations of chondrules formed by different processes: (i) magnesian non-porphyritic (cryptocrystalline and barred) chondrules, which are similar to those in the CB chondrites and formed in an impact-generated plume of melt and gas resulted from large-scale asteroidal collision, and (ii) porphyritic chondrules formed by melting of solid precursors in the solar nebula. (2) Porphyritic chondrules in Isheyevo and CH chondrites are different from porphyritic chondrules in other carbonaceous chondrites (Krot et al., 2005, 2008a,b). In order to test these hypotheses, we measured in situ oxygen isotopic compositions of porphyritic (magnesian, Type I and ferroan, Type II) and non-porphyritic (magnesian and ferroan cryptocrystalline) chondrules from Isheyevo and CBb chondrites MAC 02675 and QUE 94627, paired with QUE 94611, using a Cameca ims-1280 ion microprobe. On a three-isotope oxygen diagram (δ17O vs. δ18O), compositions of chondrules measured follow approximately slope-1 line. Data for 19 magnesian cryptocrystalline chondrules from Isheyevo, 24 magnesian cryptocrystalline chondrules and 6 magnesian cryptocrystalline silicate inclusions inside chemically-zoned Fe,Ni-metal condensates from CBb chondrites have nearly identical compositions: Δ17O = -2.2 ± 0.9‰, -2.3 ± 0.6‰ and -2.2 ± 1.0‰ (2σ), respectively. These observations and isotopically light magnesium compositions of cryptocrystalline magnesian chondrules in CBb chondrites (Gounelle et al., 2007) are consistent with their single-stage origin, possibly as gas-melt condensates in an impact-generated plume. In contrast, Δ17O values for 11 Type I and 9 Type II chondrules from Isheyevo range from -5‰ to +4‰ and from -17‰ to +3‰, respectively. In contrast to typical chondrules from carbonaceous chondrites, seven out of 11 Type I chondrules from Isheyevo plot above the terrestrial fractionation line. We conclude that (i) porphyritic chondrules in Isheyevo belong to a unique population of objects, suggesting formation either in a different nebular region or at a different time than chondrules from other carbonaceous chondrites; (ii) Isheyevo, CB and CH chondrites are genetically related meteorites: they contain non-porphyritic chondrules produced during the same highly-energetic event, probably large-scale asteroidal collision; (iii) the differences in mineralogy, petrography, chemical and whole-rock oxygen isotopic compositions between CH and CB chondrites are due to various proportions of the nebular and the impact-produced materials. © 2010 Elsevier Ltd. All rights reserved.
  • T. Tsuji, T. Tawara, R. Tanuma, Y. Yonezawa, N. Iwamuro, K. Kosaka, H. Yurimoto, S. Kobayashi, H. Matsuhata, K. Fukuda, O. Okumura, K. Arai
    Materials Science Forum 645-648 913 - 916 2010年 [査読有り][通常論文]
     
    The authors fabricated pn diodes with Al+ implantation in p-type epitaxial layers, and investigated the influence of the implantation dose on reverse leakage currents. Only in the highest dose with the Al concentration of 2×1020cm-3, more than 90% of the devices showed high leakage currents above 10-4A at the maximum electric field of 3MV/cm. In such devices, almost all of the emissive spots corresponded to threading screw dislocations (TSDs) by the analysis of emission microscopy and X-ray topography. These TSDs were defined as killer defects with the estimated density of 500cm-2 in the case of the highest dose. The emissions were supposed to be due to microplasmas, since the spectra of the emissions were different from those of heat radiation. Condensation of Al atoms, nitrogen atoms and DI defects were excluded as the origin of the emissions by secondary ion mass spectrometry and low temperature photoluminescence analyses. © (2010) Trans Tech Publications, Switzerland.
  • A. N. Krot, Y. Amelin, P. Bland, F. J. Ciesla, J. Connelly, A. M. Davis, G. R. Huss, I. D. Hutcheon, K. Makide, K. Nagashima, L. E. Nyquist, S. S. Russell, E. R.D. Scott, K. Thrane, H. Yurimoto, Q. Z. Yin
    Geochimica et Cosmochimica Acta 73 17 4963 - 4997 2009年09月01日 [査読有り][通常論文]
     
    Mineralogical observations, chemical and oxygen-isotope compositions, absolute 207Pb-206Pb ages and short-lived isotope systematics (7Be-7Li, 10Be-10B, 26Al-26Mg, 36Cl-36S, 41Ca-41K, 53Mn-53Cr, 60Fe-60Ni, 182Hf-182W) of refractory inclusions [Ca,Al-rich inclusions (CAIs) and amoeboid olivine aggregates (AOAs)], chondrules and matrices from primitive (unmetamorphosed) chondrites are reviewed in an attempt to test (i) the x-wind model vs. the shock-wave model of the origin of chondritic components and (ii) irradiation vs. stellar origin of short-lived radionuclides. The data reviewed are consistent with an external, stellar origin for most short-lived radionuclides (7Be, 10Be, and 36Cl are important exceptions) and a shock-wave model for chondrule formation, and provide a sound basis for early Solar System chronology. They are inconsistent with the x-wind model for the origin of chondritic components and a local, irradiation origin of 26Al, 41Ca, and 53Mn. 10Be is heterogeneously distributed among CAIs, indicating its formation by local irradiation and precluding its use for the early solar system chronology. 41Ca-41K, and 60Fe-60Ni systematics are important for understanding the astrophysical setting of Solar System formation and origin of short-lived radionuclides, but so far have limited implications for the chronology of chondritic components. The chronological significance of oxygen-isotope compositions of chondritic components is limited. The following general picture of formation of chondritic components is inferred. CAIs and AOAs were the first solids formed in the solar nebula ∼4567-4568 Myr ago, possibly within a period of <0.1 Myr, when the Sun was an infalling (class 0) and evolved (class I) protostar. They formed during multiple transient heating events in nebular region(s) with high ambient temperature (at or above condensation temperature of forsterite), either throughout the inner protoplanetary disk (1-4 AU) or in a localized region near the proto-Sun (<0.1 AU), and were subsequently dispersed throughout the disk. Most CAIs and AOAs formed in the presence of an 16O-rich (Δ17O ∼ -24 ± 2‰) nebular gas. The 26Al-poor [(26Al/27Al)0 < 1 × 10-5], 16O-rich (Δ17O ∼ -24 ± 2‰) CAIs - FUN (fractionation and unidentified nuclear effects) CAIs in CV chondrites, platy hibonite crystals (PLACs) in CM chondrites, pyroxene-hibonite spherules in CM and CO chondrites, and the majority of grossite- and hibonite-rich CAIs in CH chondrites-may have formed prior to injection and/or homogenization of 26Al in the early Solar System. A small number of igneous CAIs in ordinary, enstatite and carbonaceous chondrites, and virtually all CAIs in CB chondrites are 16O-depleted (Δ17O > -10‰) and have (26Al/27Al)0 similar to those in chondrules (<1 × 10-5). These CAIs probably experienced melting during chondrule formation. Chondrules and most of the fine-grained matrix materials in primitive chondrites formed 1-4 Myr after CAIs, when the Sun was a classical (class II) and weak-lined T Tauri star (class III). These chondritic components formed during multiple transient heating events in regions with low ambient temperature (<1000 K) throughout the inner protoplanetary disk in the presence of 16O-poor (Δ17O > -5‰) nebular gas. The majority of chondrules within a chondrite group may have formed over a much shorter period of time (<0.5-1 Myr). Mineralogical and isotopic observations indicate that CAIs were present in the regions where chondrules formed and accreted (1-4 AU), indicating that CAIs were present in the disk as free-floating objects for at least 4 Myr. Many CAIs, however, were largely unaffected by chondrule melting, suggesting that chondrule-forming events experienced by a nebular region could have been small in scale and limited in number. Chondrules and metal grains in CB chondrites formed during a single-stage, highly-energetic event ∼4563 Myr ago, possibly from a gas-melt plume produced by collision between planetary embryos. © 2009 Elsevier Ltd. All rights reserved.
  • Hisayoshi Yurimoto
    Japanese Journal of Clinical Chemistry 38 3 272 - 279 2009年 [査読有り][通常論文]
  • Yurimoto, H.
    Japanese Journal of Clinical Chemistry 38 3 272 - 279 2009年 [査読有り][通常論文]
  • Kumiko Fujimoto, Shoichi Itoh, Shingo Ebata, Hisayoshi Yurimoto
    Geochemical Journal 43 5 E11 - E15 2009年 [査読有り][通常論文]
     
    Oxygen isotopic compositions of metal grains in a noble-gas-rich chondrite, NWA 801 CR2, have been determined by secondary ion mass spectrometry. The results show bimodal distribution on δ17O histogram with peaks of δ17O = 2.3 and -35.0%c. The 16O-rich peak seems to be due to stellar wind from the protosun. The 16O enrichment is comparable with the most 16O-rich value from chondrite constituents. Difference of oxygen isotopic composition of stellar wind between protosun and the present sun implies how self-pollution by planetary embryos during the planet formation epoch have occurred and whether the present solar photosphere preserves the representative composition of the solar system. Copyright © 2009 by The Geochemical Society of Japan.
  • Masahiro Kudo, Retsu Oiwa, Hisayoshi Yurimoto
    Applied Surface Science 255 4 803 - 804 2008年12月15日 [査読有り][通常論文]
  • Shingo Ebata, Timothy J. Fagan, Hisayoshi Yurimoto
    Applied Surface Science 255 4 1468 - 1471 2008年12月15日 [査読有り][通常論文]
     
    An isotope ratio imaging technique using the HokuDai isotope microscope system has been applied to in situ survey for presolar grains in the type-3 enstatite chondrite ALHA81189. Rastered and static ion beam were used for primary beam. Lateral resolution of the isotope image was achieved to be 0.4 μm for static ion beam mode and to be 0.6 μm for rastered ion beam mode. As a result, the abundances of presolar grains are 150-200% larger under the static ion beam mode than under the rastered ion beam mode. Development of image processing introducing isotopography of 32 S - , 24 Mg 16 O - and 56 Fe - succeeded to increase efficiency of presolar grain characterization. Using the static ion beam and introducing appropriate isotopography were very useful methods of in situ characterization of presolar grains in meteorites. © 2008 Elsevier B.V. All rights reserved.
  • Naoya Sakamoto, Shoichi Itoh, Hisayoshi Yurimoto
    Applied Surface Science 255 4 1458 - 1460 2008年12月15日 [査読有り][通常論文]
     
    We report a discovery of a chemically and isotopically unique material distributed ubiquitously in fine-grained matrix of a primitive carbonaceous chondrite Acfer 094. The observations were made in situ using a novel high precision imaging technique adopted direct-imaging method. The material is extremely enriched in heavy oxygen isotopes of 17 O and 18 O of +18% relative to the Earth's ocean while previously reported variation of oxygen isotopes is as large as a range from -8% to 0%. Based on the unique chemical composition of the material, the abundance of the material in the meteorite matrix is calculated to be 94 ± 20 ppm (σ) by volume using elemental mapping with a 7 μm 2 spatial resolution by FE-SEM-EDS on the meteorite thin section. The average size of identified materials is 5 μm × 5 μm × 5 μm. Therefore, isotope imaging capability over 500 μm × 500 μm area with micron resolution and an isotopic ratio precision of 1% is required to investigate about the presence of such material. © 2008 Elsevier B.V. All rights reserved.
  • R. Mibuka, S. Hassaballa, K. Uchino, H. Yurimoto, R. Todokoro, K. Kumondai, M. Ishihara
    Applied Surface Science 255 4 1595 - 1598 2008年12月15日 [査読有り][通常論文]
     
    Characteristics of the post-ionization using femto-second laser (fs laser) combined with the secondary ion mass spectrometer were investigated. For many metals, ionization saturations were confirmed for the laser power density of >2 × 10 13 W/cm 2 . The characteristic curve of ionization of Ag against the laser power density suggests the occurrence of ionization through the multi-photon resonance excitation. Sensitivity increase after employing the fs laser post-ionization was manifested and a sputtered Cu signal from a minute circular area with a diameter of about 200 nm could be detected clearly. © 2008 Elsevier B.V. All rights reserved.
  • Shoichi Itoh, Kentaro Makide, Hisayoshi Yurimoto
    Applied Surface Science 255 4 1476 - 1478 2008年12月15日 [査読有り][通常論文]
     
    High precision Mg isotope measurements have been performed to determine radiogenic 26 Mg of CAI minerals by secondary ion mass spectrometry using Faraday cup multi-collection system. Terrestrial samples of spinel and augite, and synthetic glasses of melilite and fassaite, were prepared to correct instrumental mass fractionation. Reproducibility of Mg isotope measurements for each standard were limited to ∼0.4‰ (2σ). On the other hand, the standard errors for one spot are ∼0.05‰ (2σ). The poor reproducibility resulted from variations of instrumental mass fractionation among individual measurement spots. We propose novel calculation method of radiogenic 26 Mg considering instrumental and natural mass fractionation for each mineral. The overall measurement error of radiogenic 26 Mg of the minerals can be calculated less than 0.2‰ (2σ). This provides that the time resolution of early solar system chronometer was improved up to 100K year for ∼20 μm scale objects formed in the early solar system. © 2008 Elsevier B.V.
  • Yusuke Seto, Naoya Sakamoto, Kiyoshi Fujino, Takashi Kaito, Tetsuo Oikawa, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 72 11 2723 - 2734 2008年06月01日 [査読有り][通常論文]
     
    We report the mineral compositions and micro-texture of the isotopically anomalous (δ17,18OSMOW ∼ +180‰) Fe-S-Ni-O material recently discovered in matrix of the primitive carbonaceous chondrite Acfer 094 [Sakamoto N., Seto Y., Itoh S., Kuramoto K., Fujino K., Nagashima K., Krot A. N. and Yurimoto H. (2007) Oxygen isotope evidence for remnants of the early solar system primordial water. Science 317, 231-233]. Synchrotron radiation X-ray diffraction and transmission electron microscopy studies indicate that this material consists of the symplectitically intergrown magnetite (Fe3O4) and pentlandite (Fe5.7Ni3.3S8) with magnetite/pentlandite volume ratio of ∼2.3. Magnetite forms column-shaped grains (10-30 nm in diameter and 100-200 nm in length); pentlandite occurs as worm-shaped grains or aggregates of grains 100-300 nm in size between magnetite crystals. Although both the X-ray diffraction and electron energy loss spectra support identification of iron oxide as magnetite, the electron diffraction patterns show that magnetite has a weak 3-fold superstructure, possibly due to ordering of vacancies. We infer that the isotopically anomalous symplectite formed by sulfurization and oxidization of metal grains either in the solar nebula or on an icy planetesimal. The intersite cation distribution of pentlandite suggests that timescale of oxidation was no longer than 1000 years. © 2008 Elsevier Ltd. All rights reserved.
  • A. N. Krot, M. Chaussidon, H. Yurimoto, N. Sakamoto, K. Nagashima, I. D. Hutcheon, G. J. MacPherson
    Geochimica et Cosmochimica Acta 72 10 2534 - 2555 2008年05月15日 [査読有り][通常論文]
     
    In situ oxygen isotopic measurements of primary and secondary minerals in Type C CAIs from the Allende CV3 chondrite reveal that the pattern of relative enrichments and depletions of 16O in the primary minerals within each individual CAI are similar to the patterns observed in Types A and B CAIs from the same meteorite. Spinel is consistently the most 16O-rich (Δ17O = -25‰ to -15‰), followed by Al,Ti-dioside (Δ17O = -20‰ to -5‰) and anorthite (Δ17O = -15‰ to 0‰). Melilite is the most 16O-depleted primary mineral (Δ17O = -5‰ to -3‰). We conclude that the original melting event that formed Type C CAIs occurred in a 16O-rich (Δ17O ≤ -20‰) nebular gas and they subsequently experienced oxygen isotopic exchange in a 16O-poor reservoir. At least three of these (ABC, TS26F1 and 93) experienced remelting at the time and place where chondrules were forming, trapping and partially assimilating 16O-poor chondrule fragments. The observation that the pyroxene is 16O-rich relative to the feldspar, even though the feldspar preceded it in the igneous crystallization sequence, disproves the class of CAI isotopic exchange models in which partial melting of a 16O-rich solid in a 16O-poor gas is followed by slow crystallization in that gas. For the typical (not associated with chondrule materials) Type C CAIs as well for as the Types A and B CAIs, the exchange that produced internal isotopic heterogeneity within each CAI must have occurred largely in the solid state. The secondary phases grossular, monticellite and forsterite commonly have similar oxygen isotopic compositions to the melilite and anorthite they replace, but in one case (CAI 160) grossular is 16O-enriched (Δ17O = -10‰ to -6‰) relative to melilite (Δ17O = -5‰ to -3‰), meaning that the melilite and anorthite must have exchanged its oxygen subsequent to secondary alteration. This isotopic exchange in melilite and anorthite likely occurred on the CV parent asteroid, possibly during fluid-assisted thermal metamorphism. © 2008 Elsevier Ltd. All rights reserved.
  • James P. Greenwood, Shoichi Itoh, Naoya Sakamoto, Edward P. Vicenzi, Hisayoshi Yurimoto
    Geophysical Research Letters 35 5 5203  2008年03月16日 [査読有り][通常論文]
     
    The high D/H of the Martian atmosphere (∼5-6 × terrestrial) is considered strong evidence for the loss of a Martian water to space. The timing and magnitude of the losss of water from Mars can be constrained by measurements of D/H in Martian meteorites. Previous studies of Martian meteorites have shown a large range in D/H, from terrestrial values to as high as the current Martian atmosphere. Here we show that the ancient (∼4 Ga) Mars meteorite ALH84001 has a D/H 4 × terrestrial and that the young (∼0.17 Ga) Shergotty meteorite has a D/H 5.6 × terrestrial. We also find that the young Los Angeles shergottite has zoning in D/H that can be correlated to igneous growth zoning, strongly suggesting assimilation of D-enriched waterir during igneous crystallization near the Martian surface. In contrast to previous studies, we find higher and less variable D/H ratios in these three meteorites. Our results suggest a two-stage evolution for Martian water - a significant early loss of water to space (prior to 3.9 Ga) followed by only modest loss to space in the last 4 billion years. The current Martian atmospheric D/H has remained essentially unchanged for the last 165 Ma. Copyright 2008 by the American Geophysical Union.
  • S. Itoh, H. Yurimoto
    AIP Conference Proceedings 1016 394 - 399 2008年 [査読有り][通常論文]
     
    High precision Mg isotope measurements have been performed to determine radiogenic 26Mg of coarse-grained Ca-Al-rich inclusions (CAIs) in two carbonaceous chondrites by secondary ion mass spectrometry using faraday cup multi-collection system. Minerals in each CAI show individual internal isochrones of 26Al-26Mg with respect to each own oxygen isotopic composition of minerals. This indicates that 16O-rich and 16O-poor oxygen isotopic environments existed more than 0.45 Myrs in the solar nebula. The switching time scale between 16O-rich and 16O-poor gaseous environments surrounding CAIs was faster than 10 kyrs.
  • Edward D. Young, Kyoshi Kuramoto, Rudolph A. Marcus, Hisayoshi Yurimoto, Stein B. Jacobsen
    Reviews in Mineralogy and Geochemistry 68 1 187 - 218 2008年 [査読有り][通常論文]
     
    In this chapter we compare and contrast chemical and photochemical pathways for mass-independent fractionation (MIF) of oxygen isotopes in the solar nebula. We begin by assessing the galactic evolution model for oxygen isotope variation in the Solar System in order to compare the predictions of a leading nucleosynthetic model with those of the chemical models. There are two fundamentally different classes of possible chemical mechanisms for mass-independent oxygen isotope fractionation in the early Solar System. One is symmetry-induced intramolecular vibrational disequilibrium of vibrationally excited reactant oxygen-bearing molecules. The other is isotope selective photodissociation of CO coupled with self-shielding and formation of H2O. Symmetry-induced fractionation is an experimentally verified process with solid theoretical foundations. It is observed to occur in Earth's atmosphere. It could have resulted in preservation of oxygen MIF effects only if mediated by dust grain surfaces. CO self-shielding is an attractive hypothesis for the origin of mass-independent oxygen isotope fractionation in the early Solar System because it appeals to a process that apparently occurs in the interstellar medium, but it lacks experimental verification. Three astrophysical settings for CO self-shielding are proposed as sites for generating Δ17O variability in the early Solar System. One is the inner annulus of the protostellar disk at relatively high temperature. Another is the surface of the disk high above the midplane where light from the central star grazes the gas and dust of the disk, resulting in a zone of active CO predissociation and self-shielding. Interstellar light illuminating the disk at high incident angles causes a similar horizon of CO photodestruction. Variations in 16O could also have been inherited from self-shielding by CO in the molecular cloud that gave rise to the protosun. The overall consequence of CO self-shielding is conversion of CO gas to 16O-poor H2O. A key difference between galactic evolution, chemically-induced MIF effects, and CO self-shielding is the predicted relative oxygen isotopic compositions of primeval dust and the Sun. Therefore, the oxygen isotopic composition of the Sun will be a crucial arbiter that may permit us to narrow the list of possible origins for oxygen MIF in the early Solar System. Copyright © Mineralogical Society of America.
  • Shingo Ebata, Hisayoshi Yurimoto
    AIP Conference Proceedings 1016 412 - 414 2008年 [査読有り][通常論文]
     
    We surveyed presolar grains in primitive enstatite chondrites by isotopography using the HokuDai isotope microscope system. The mineral identification has been conducted by X-ray analysis with scanning electron microscopy. The chemical compositions are determined for eight silicate and ten carbonaceous presolar grains. Presolar grains of pyroxene compositions are dominant in the enstatite chondrites. This suggests that presolar silicates of enstatite composition were selectively survived in the enstatite chondrite parent body or the enstatite chondrite formation area in the solar nebula.
  • Alexander N. Krot, Hisayoshi Yurimoto, Ian D. Hutcheon, Guy Libourel, Marc Chaussidon, Laurent Tissandier, Michael I. Petaev, Glenn J. MacPherson, Julie Paque-Heather, David Wark
    Geochimica et Cosmochimica Acta 71 17 4342 - 4364 2007年09月01日 [査読有り][通常論文]
     
    The coarse-grained, igneous, anorthite-rich (Type C) CAIs from Allende studied (100, 160, 6-1-72, 3529-40, CG5, ABC, TS26, and 93) have diverse textures and mineralogies, suggesting complex nebular and asteroidal formation histories. CAIs 100, 160, 6-1-72, and 3529-40 consist of Al,Ti-diopside (fassaite; 13-23 wt% Al2O3, 2-14 wt% TiO2), Na-bearing åkermanitic melilite (0.1-0.4 wt% Na2O; Åk30-75), spinel, and fine-grained (∼5-10 μm) anorthite groundmass. Most of the fassaite and melilite grains have "lacy" textures characterized by the presence of abundant rounded and prismatic inclusions of anorthite ∼5-10 μm in size. Lacy melilite is pseudomorphed to varying degrees by grossular, monticellite, and pure forsterite or wollastonite. CAI 6-1-72 contains a relict Type B CAI-like portion composed of polycrystalline gehlenitic melilite (Åk10-40), fassaite, spinel, perovskite, and platinum-group element nuggets; the Type B-like material is overgrown by lacy melilite and fassaite. Some melilite and fassaite grains in CAIs 100 and 160 are texturally similar to those in the Type B portion of 6-1-72. CAIs ABC and TS26 contain relict chondrule fragments composed of forsteritic olivine and low-Ca pyroxene; CAI 93 is overgrown by a coarse-grained igneous rim of pigeonite, augite, and anorthitic plagioclase. These three CAIs contain very sodium-rich åkermanitic melilite (0.4-0.6 wt% Na2O; Åk63-74) and Cr-bearing Al,Ti-diopside (up to 1.6 wt% Cr2O3, 1-23 wt% Al2O, 0.5-7 wt% TiO2). Melilite and anorthite in the Allende Type C CAI peripheries are replaced by nepheline and sodalite, which are crosscut by andradite-bearing veins; spinel is enriched in FeO. The CAI fragment CG5 is texturally and mineralogically distinct from other Allende Type Cs. It is anorthite-poor and very rich in spinel poikilitically enclosed by Na-free gehlenitic melilite (Åk20-30), fassaite, and anorthite; neither melilite nor pyroxene have lacy textures; secondary minerals are absent. The Al-rich chondrules 3655b-2 and 3510-7 contain aluminum-rich and ferromagnesian portions. The Al-rich portions consist of anorthitic plagioclase, Al-rich low-Ca pyroxene, and Cr-bearing spinel; the ferromagnesium portions consist of fosteritic olivine, low-Ca pyroxene, and opaque nodules. We conclude that Type C CAIs 100, 160, 6-1-72, and 3529-40 formed by melting of coarse-grained Type B-like CAIs which experienced either extensive replacement of melilite and spinel mainly by anorthite and diopside (traces of secondary Na-bearing minerals, e.g., nepheline or sodalite, might have formed as well), or addition of silica and sodium during the melting event. CG5 could have formed by melting of fine-grained spinel-melilite CAI with melilite and spinel partially replaced anorthite and diopside. CAIs ABC, 93, and TS-26 experienced melting in the chondrule-forming regions with addition of chondrule-like material, such as forsteritic olivine, low-Ca pyroxene, and high-Ca pyroxene. Anorthite-rich chondrules formed by melting of the Al-rich (Type C CAI-like) precursors mixed with ferromagnesian, Type I chondrule-like precursors. The Allende Type C CAIs and Al-rich chondrules experienced fluid-assisted thermal metamorphism, which resulted in pseudomorphic replacement of melilite and anorthite by grossular, monticellite, and forsterite (100, 160, 6-1-72, 3592-40) or by grossular, monticellite, and wollastonite (ABC, 93, TS-26). The pseudomorphic replacement was followed or accompanied by iron-alkali metasomatic alteration resulting in replacement of melilite and anorthite by nepheline and sodalite, enrichment of spinel in FeO, and precipitation of salite-hedenbergite pyroxenes, wollastonite, and andradite in fractures and pores in and around CAIs. © 2007.
  • Naoya Sakamoto, Yusuke Seto, Shoichi Itoh, Kiyoshi Kuramoto, Kiyoshi Fujino, Kazuhide Nagashima, Alexander N. Krot, Hisayoshi Yurimoto
    Science 317 5835 231 - 233 2007年07月13日 [査読有り][通常論文]
     
    Oxygen isotopic composition of our solar system is believed to have resulted from mixing of two isotopically distinct nebular reservoirs, 16O-rich and 17,18O-rich relative to Earth. The nature and composition of the 17,18O-rich reservoir are poorly constrained. We report an in situ discovery of a chemically and isotopically unique material distributed ubiquitously in fine-grained matrix of a primitive carbonaceous chondrite Acfer 094. This material formed by oxidation of Fe,Ni-metal and sulfides by water either in the solar nebula or on a planetesimal. Oxygen isotopic composition of this material indicates that the water was highly enriched in 17O and 18O (δ17,18O SMOW = 180‰ per mil), providing the first evidence for an extremely 17,18O-rich reservoir in the early solar system.
  • Yurimoto Hisayoshi, Kuramoto Kiyoshi, Krot Alexander N, Scott Edward RD, Cuzzi Jeffrey N, Thiemens Mark H, Lyons James R
    Protostars and Planets V 849 - 862 Citeseer 2007年 [査読有り][通常論文]
  • Alexander N. Krot, Hisayoshi Yurimoto, Ian D. Hutcheon, Marc Chaussidon, Glenn J. MacPherson, Julie Paque
    Meteoritics and Planetary Science 42 7-8 1197 - 1219 2007年 [査読有り][通常論文]
     
    We describe the mineralogy, petrology, oxygen, and magnesium isotope compositions of three coarse-grained, igneous, anorthite-rich (type C) Ca-Al-rich inclusions (CAIs) (ABC, TS26, and 93) that are associated with ferromagnesian chondrule-like silicate materials from the CV carbonaceous chondrite Allende. The CAIs consist of lath-shaped anorthite (An99), Cr-bearing Al-Ti-diopside (Al and Ti contents are highly variable), spinel, and highly åkermanitic and Na-rich melilite (Åk63-74, 0.4-0.6 wt% Na2O). TS26 and 93 lack Wark-Lovering rim layers; ABC is a CAI fragment missing the outermost part. The peripheral portions of TS26 and ABC are enriched in SiO2 and depleted in TiO2 and Al2O3 compared to their cores and contain relict ferromagnesian chondrule fragments composed of forsteritic olivine (Fa6-8) and low-Ca pyroxene/pigeonite (Fs1Wo1-9). The relict grains are corroded by Al-Ti-diopside of the host CAIs and surrounded by haloes of augite Fs0.5 Wo30-42). The outer portion of CAI 93 enriched in spinel is overgrown by coarse-grained pigeonite (Fs0.5-2 Wo5-17). augite (Fs0.5 Wo38-42), and anorthitic plagioclase (An84). Relict olivine and low-Ca pyroxene/pigeonite in ABC and TS26, and the pigeonite-augite rim around 93 are 16O-poor (δ 17O ∼ -1‰ to -8‰). Spinel and Al-Ti-diopside in cores of CAIs ABC, TS26, and 93 are 16O-enriched (δ17O down to -20‰), whereas Al-Ti-diopside in the outer zones, as well as melilite and anorthite, are 16O-depleted to various degrees (δ 17O = -11‰ to 2‰). In contrast to typical Allende CAls that have the canonical initial 26Al/27Al ratio of ∼5 × 10-5, ABC, 93, and TS26 are 26Al-poor with (26 Al/27Al)0 ratios of (4.7 ± 1.4) × 10-6, (1.5 ± 1.8) × 10-6, and <1.2 × 10-6, respectively. We conclude that ABC, TS26, and 93 experienced remelting with addition of ferromagnesian chondrule silicates and incomplete oxygen isotopic exchange in an 16O-poor gaseous reservoir, probably in the chondrule-forming region. This melting episode could have reset the 26Al-26Mg systematics of the host CAIs, suggesting it occurred ∼2 Myr after formation of most CAIs. These observations and the common presence of relict CAIs inside chondrules suggest that CAIs predated formation of choudrules. © The Meteoritical Society, 2007.
  • Shoichi Itoh, Sara S. Russell, Hisayoshi Yurimoto
    Meteoritics and Planetary Science 42 7-8 1241 - 1247 2007年 [査読有り][通常論文]
     
    Amoeboid olivine aggregates (AOAs) in the LL3.0 Semarkona chondrite have been studied by secondary ion mass spectrometry. The AOAs mainly consist of aggregates of olivine grains with interstitial Al-Ti-rich diopside and anorthite. Oxygen-isotopic compositions of all phases are consistently enriched in 16O, with δ17,18O = ∼-50‰. The initial 26Al/27Al ratios are calculated to be 5.6 ± 0.9 (2σ) × 10-5. These values are equivalent to those of AOAs and fine-grained calcium- aluminum-rich inclusions (FGls) from pristine carbonaceous chondrites. This suggests that AOAs in ordinary chondrites formed in the same 16O-rich calcium-aluminum-rich inclusion (CAI)-forming region of the solar nebula as AOAs and FGIs in carbonaceous chondrites, and subsequently moved to the accretion region of the ordinary chondrite parent body in the solar nebula. © The Meteoritical Society, 2007.
  • Naoya Sakamoto, Hisayoshi Yurimoto
    Surface and Interface Analysis 38 12-13 1760 - 1762 2006年12月 [査読有り][通常論文]
     
    A direct ion imaging system with single ion detection and high-precision imaging modes has been developed. This system is composed of a movable microchannel plate unit and a stacked CMOS-type active pixel sensor (SCAPS). Capabilities of single ion detection were evaluated by ion irradiations using secondary ion mass spectrometry. The experiment shows that this system accurately detected single incident ions. Copyright © 2006 John Wiley & Sons, Ltd.
  • Motoo Ito, Hiroshi Nagasawa, Hisayoshi Yurimoto
    Meteoritics and Planetary Science 41 12 1871 - 1881 2006年12月 [査読有り][通常論文]
     
    The measurements of magnesium and potassium isotopic compositions of refractory minerals in Allende calcium-aluminum-rich inclusions (CAIs), 7R-19-1, HN3-1, and EGG3 were taken by secondary ion mass spectrometry (SIMS). The 7R-19-1 contains 16O-rich and 16O-poor melilite grains and define a single isochron corresponding to an initial 26Al/27Al ratio of (6.6 ± 1.3) × 10-5. The Al-Mg isochron, O isotope measurements and petrography of melilite in 7R-19-1 indicate that 16O-poor melilite crystallized within 0.4 Myr after crystallization of 16O-rich melilite, suggesting that oxygen isotopic composition of the CAI-forming region changed from 16O-rich to 16O-poor within this time interval. The 16O-poor melilite is highly depleted in K compared to the adjacent 16O-rich melilite, indicating evaporation during remelting of 7R-19-1. We determined the isochron for 41Ca-41K isotopic systematics in EGG3 pyroxene with (4.1 ± 2.0) × 10-9 (2σ) as an initial ratio of 41Ca/40Ca, which is at least two times smaller than the previous result (Sahijipal et al. 2000). The ratio of 41Ca/40Ca in the EGG3 pyroxene grain agrees within error with the value obtained by Hutcheon et al. (1984). No evidence for the presence of 41K excess (decay product of a short-lived radionuclide 41Ca) was found in 7R-19-1 and HN3-1. We infer that the CAI had at least an order of magnitude lower than canonical 41Ca/40Ca ratio at the time of the CAI formation. © The Meteoritical Society, 2006.
  • Alexander N. Krot, Hisayoshi Yurimoto, Kevin D. McKeegan, Laurie Leshin, Marc Chaussidon, Guy Libourel, Miwa Yoshitake, Gary R. Huss, Yunbin Guan, Brigitte Zanda
    Chemie der Erde 66 4 249 - 276 2006年11月 [査読有り][通常論文]
     
    We review the oxygen isotopic compositions of minerals in chondrules and compound objects composed of a chondrule and a refractory inclusion, and bulk oxygen isotopic compositions of chondrules in unequilibrated ordinary, carbonaceous, enstatite, and Kakangari-like chondrites, focusing on data acquired using secondary ion mass-spectrometry and laser fluorination coupled with mass-spectrometry over the last decade. Most ferromagnesian chondrules from primitive (unmetamorphosed) chondrites are isotopically uniform (within 3-4‰ in Δ17O) and depleted in 16O (Δ17O>-7‰) relative to amoeboid olivine aggregates (AOAs) and most calcium-aluminum-rich inclusions (CAIs) (Δ17O<-20‰), suggesting that these classes of objects formed in isotopically distinct gaseous reservoirs, 16O-poor and 16O-rich, respectively. Chondrules uniformly enriched in 16O (Δ17O<-15‰) are exceptionally rare and have been reported only in CH chondrites. Oxygen isotopic heterogeneity in chondrules is mainly due to the presence of relict grains. These appear to consist of chondrules of earlier generations and rare refractory inclusions; with rare exceptions, the relict grains are 16O-enriched relative to chondrule phenocrysts and mesostasis. Within a chondrite group, the magnesium-rich (Type I) chondrules tend to be 16O-enriched relative to the ferrous (Type II) chondrules. Aluminum-rich chondrules in ordinary, enstatite, CR, and CV chondrites are generally 16O-enriched relative to ferromagnesian chondrules. No systematic differences in oxygen isotopic compositions have been found among these chondrule types in CB chondrites. Aluminum-rich chondrules in carbonaceous chondrites often contain relict refractory inclusions. Aluminum-rich chondrules with relict CAIs have heterogeneous oxygen isotopic compositions (Δ17O ranges from -20‰ to 0‰). Aluminum-rich chondrules without relict CAIs are isotopically uniform and have oxygen isotopic compositions similar to, or approaching, those of ferromagnesian chondrules. Phenocrysts and mesostases of the CAI-bearing chondrules show no clear evidence for 16O-enrichment compared to the CAI-free chondrules. Spinel, hibonite, and forsterite of the relict refractory inclusions largely retained their original oxygen isotopic compositions. In contrast, plagioclase and melilite of the relict CAIs experienced melting and 16O-depletion to various degrees, probably due to isotopic exchange with an 16O-poor nebular gas. Several igneous CAIs experienced isotopic exchange with an 16O-poor nebular gas during late-stage remelting in the chondrule-forming region. On a three-isotope diagram, bulk oxygen isotopic compositions of most chondrules in ordinary, enstatite, and carbonaceous chondrites plot above, along, and below the terrestrial fractionation line, respectively. Bulk oxygen isotopic compositions of chondrules in altered and/or metamorphosed chondrites show evidence for mass-dependent fractionation, reflecting either interaction with a gaseous/fluid reservoir on parent asteroids or open-system thermal metamorphism. Bulk oxygen isotopic compositions of chondrules and oxygen isotopic compositions of individual minerals in chondrules and refractory inclusions from primitive chondrites plot along a common line of slope of ∼1, suggesting that only two major reservoirs (gas and solids) are needed to explain the observed variations. However, there is no requirement that each had a permanently fixed isotopic composition. The absolute (207Pb-206Pb) and relative (27Al-26Mg) chronologies of CAIs and chondrules and the differences in oxygen isotopic compositions of most chondrules (16O-poor) and most refractory inclusions (16O-rich) can be interpreted in terms of isotopic self-shielding during UV photolysis of CO in the initially 16O-rich (Δ17O∼-25‰) parent molecular cloud or protoplanetary disk. According to these models, the UV photolysis preferentially dissociates C17O and C18O in the parent molecular cloud and in the peripheral zones of the protoplanetary disk. If this process occurs in the stability field of water ice, the released atomic 17O and 18O are incorporated into water ice, while the residual CO gas becomes enriched in 16O. During the earliest stages of evolution of the protoplanetary disk, the inner solar nebula had a solar H2O/CO ratio and was 16O-rich. During this time, AOAs and the 16O-rich CAIs and chondrules formed. Subsequently, the inner solar nebula became H2O- and 16O-depleted, because ice-rich dust particles, which were depleted in 16O, agglomerated outside the snowline (∼5 AU), drifted rapidly towards the Sun and evaporated. During this time, which may have lasted for ∼3 Myr, most chondrules and the 16O-depleted igneous CAIs formed. We infer that most chondrules formed from isotopically heterogeneous, but 16O-depleted precursors, and experienced isotopic exchange with an 16O-poor nebular gas during melting. Although the relative roles of the chondrule precursor materials and gas-melt isotopic exchange in establishing oxygen isotopic compositions of chondrules have not been quantified yet, mineralogical, chemical, and isotopic evidence indicate that Type I chondrules may have formed in chemical and isotopic equilibrium with nebular gas of variable isotopic composition. Whether these variations were spatial or temporal are not known yet. © 2006 Elsevier GmbH. All rights reserved.
  • Alexander N. Krot, Hisayoshi Yurimoto, Fred J. Ciesla, James R. Lyons
    GEOCHIMICA ET COSMOCHIMICA ACTA 70 18 A337 - A337 2006年08月 [査読有り][通常論文]
  • Anders Meibom, Hisayoshi Yurimoto, Jean Pierre Cuif, Isabelle Domart-Coulon, Fanny Houlbreque, Brent Constantz, Yannicke Dauphin, E. Tambutté, Sylvie Tambutté, Denis Allemand, Joseph Wooden, Robert Dunbar
    Geophysical Research Letters 33 11 2006年06月16日 [査読有り][通常論文]
     
    Biological control over coral skeletal composition is poorly understood but critically important to paleoenvironmental reconstructions. We present microanalytical measurements of trace-element abundances as well as oxygen and carbon isotopic compositions of individual skeletal components in the zooxanthellate coral Colpophyllia sp. Our data show that centers of calcification (COC) have higher trace element concentrations and distinctly lighter isotopic compositions than the fibrous components of the skeleton. These observations necessitate that COC and the fibrous skeleton are precipitated by different mechanisms, which are controlled by specialized domains of the calicoblastic cell-layer. Biological processes control the composition of the skeleton even at the ultra-structure level. Copyright 2006 by the American Geophysical Union.
  • Ikuo Katayama, Satoru Nakashima, Hisayoshi Yurimoto
    Lithos 86 3-4 245 - 259 2006年02月 [査読有り][通常論文]
     
    Infrared spectroscopy and ion micro-probe measurements showed that the major constituent minerals of eclogites from the Kokchetav massif, which have been subducted to ∼180 km depths, contain significant amounts of water up to 870 ppm H2O (by weight) in omphacite, 130 ppm H2O in garnet and 740 ppm H2O in rutile. Omphacite shows three hydroxyl absorption bands at 3440-3460, 3500-3530 and 3600-3625 cm-1, garnet has a single band at 3580-3630 cm-1 and rutile has a single sharp band at 3280 cm-1. The hydroxyl absorbance at these wavenumbers changes with the crystal orientation in polarized infrared radiation, indicating that the water is structurally incorporated in these minerals. The water contents in omphacite and garnet increase systematically with the metamorphic pressure of the host eclogites. The partitioning coefficient of the water content between coexisting garnet and omphacite is similar in different eclogites, DGrt/Omp∼0.1-0.2, but decreases slightly at high pressure. Based on the mineral proportions of the eclogites, we estimate bulk-rock water content in the eclogites ranging from 3070 to 300 ppm H2O (by weight). Although hydrous minerals are absent in the diamond-grade eclogite (∼60 kbar and ∼1000 °C), trace amounts of water are incorporated in the nominally anhydrous minerals such as omphacite and garnet. The presence of significant water in these minerals implies that the subducting oceanic crust can transport considerable amounts of water into the deep upper mantle beyond the stability of hydrous minerals. Such water may be stored in the deep upper mantle and have an important influence on dynamics in the Earth's interior. © 2005 Elsevier B.V. All rights reserved.
  • K. D. Litasov, Yu D. Litasov, A. V. Ivanov, S. V. Rasskazov, H. Yurimoto, E. I. Demonterova, V. V. Sharygin, V. G. Mal'kovets
    Geologiya i Geofizika 47 1 132 - 152 2006年 [査読有り][通常論文]
     
    Study was given to Cr-diopside group mantle xenoliths from Late Cenozoic basaltoids of the Udokan volcanic field located at the boundary of the Aldan Shield and Baikal-Vitim terrane. Slightly depleted lherzolites are predominant xenoliths in the central part of the field (Pliocene basanites of Lake Kuas), whereas depleted harzburgites prevail in its northern part. The composition of the Udokan peridotites suggests that they are components of the Phanerozoic oceanic mantle subducted beneath the Siberian craton rather than the Archean mantle of the Aldan Shield. Xenoliths of Lake Kuas are divided into two series: harzburgite-lherzolite and lherzolite-websterite. The latter series probably represents ancient mantle, whereas the former might have been resulted from the later interaction of peridotites with hypothetic silicate melt, which was probably accompanied by Na-amphibole metasomatism. The Kuas spinel harzburgites and dunites are characterized by higher equilibrium temperatures (1000-1050°C) and higher oxidation state (average Δlogf O2(QFM) = -1.0) than the other rocks. Lherzolites have T = 950-1050°C and average ΔlogfO2(QFM) = -1.9, and websterites have T = 900-1000°C and average ΔlogfO2(QFM) = -3.1. Hence, having the same geothermal gradient, the harzburgite-lherzolite association formed at a greater depth than the lherzolite-websterite one. Most of the northern Udokan peridotites are highly oxidized; peridotites of the Ingamakit and Munduzhyak Volcanoes have ΔlogfO2(QFM) of -1 to +2. Two-pyroxene temperatures calculated for the Munduzhyak peridotites are higher (1050-1200°C) than those for the other mantle xenoliths, whereas the Ca-orthopyroxene temperatures are low for all xenoliths (800-900°C). Depleted harzburgite xenoliths of the Udokan field contain clinopyroxenes enriched in LREE and depleted in Nb, Zr, and Ti. These element patterns might be explained by the reaction of the peridotites with percolating silicate melt or fluid. The high contents of LREE and MREE reflect the final stage of the peridotite-melt interaction, when depleted peridotites reached an equilibrium with the melt (fluid).
  • Hisayoshi Yurimoto
    AIP Conference Proceedings 847 319 - 323 2006年 [査読有り][通常論文]
     
    Presolar circumstellar grains have been surveyed in 18 primitive meteorites. More than hundreds presolar grains have been identified. Presolar silicates are the most abundant species among presolar grains. The typical size is ∼300 nm and the abundance is ∼50 ppm in the most primitive chondrites. Main source of silicate presolar grains is from AGB and red giant stars. The average O-isotopic composition of presolar silicates is enriched in 17O relative to the solar composition. The counterpart to form solar isotope ratios having 17O-depleted compositions are missing in the chondrites. The missing matter would be supernovae ejecta but it is difficult to identify because the grain size is expected to be ∼10 nm. © 2006 American Institute of Physics.
  • Michihiko Nakamura, Hisayoshi Yurimoto, E. Bruce Watson
    Geology 33 10 829 - 832 2005年10月 [査読有り][通常論文]
     
    Isotope exchange between fluid and rocks has been traditionally considered to be rate limited by two elementary processes: lattice diffusion in the matrix minerals and dissolution into the fluid followed by precipitation from it. In this study we show the results of high-pressure experiments on 18O-water infiltration into quartzite that point to a third, highly efficient process: grain growth accompanied by migration of the grain boundaries (GBs) that are isotopically enriched by GB diffusion and surface exchange. We predict on the basis of a mass-transfer mechanism discrimination diagram that this GB sweeping is the primary control on isotopic equilibration under hydrothermal conditions in various fine-grained rocks with low fluid fraction. Grain growth should be considered when interpreting and simulating isotope and chemical composition of rocks and fluids. © 2005 Geological Society of America.
  • Miwa Yoshitake, Yoshiyuki Koide, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 69 10 2663 - 2674 2005年05月15日 [査読有り][通常論文]
     
    Oxygen-isotopic compositions in conjunction with petrologic investigation have been determined for a coarse-grained type B2 Ca, Al-rich inclusion (CAI) from the reduced CV3 Vigarano using secondary ion mass spectrometry. The oxygen-isotopic compositions of minerals are distributed along the carbonaceous chondrite anhydrous mineral line indicating mixing between 16O-rich and 16O-poor nebular components. The O-isotopic heterogeneities among and within minerals in the CAI interior indicate that CAI formation started in an 16O-rich nebula and subsequently continued in an 16O-poor nebula. 16O-rich signatures of melilite and fassaite in the Wark-Lovering rim and of olivine of the accretionary rim indicate that the nebular environment during formation of the CAI returned to an 16O-rich composition after processing in an 16O-poor nebula. These O-isotopic variations in the CAI support multiple heating events in the solar nebula and indicate that the nebular environments fluctuated from 16O-rich to 16O-poor and back to 16O-rich compositions during the formation of a single CAI. Copyright © 2005 Elsevier Ltd.
  • Alexander N. Krot, Timothy J. Fagan, Kazuhide Nagashima, Michael I. Petaev, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 69 7 1873 - 1881 2005年04月 [査読有り][通常論文]
     
    Amoeboid olivine aggregates (AOAs) in primitive carbonaceous chondrites consist of forsterite (Falt;2), Fe,Ni-metal, spinel, Al-diopside, anorthite, and rare gehlenitic melilite (Åk<15). ∼10% of AOAs contain low-Ca pyroxene (Fs1-3Wo1-5) that is in corrosion relationship with forsterite and is found in three major textural occurrences: (i) thin (<5 μm) discontinuous layers around forsterite grains or along forsterite grain boundaries in AOA peripheries; (ii) 5-10-μm-thick haloes and subhedral grains around Fe,Ni-metal nodules in AOA peripheries, and (iii) shells of variable thickness (up to 70 μm), commonly with abundant tiny (3-5 μm) inclusions of Fe,Ni-metal grains, around AOAs. AOAs with the low-Ca pyroxene shells are compact and contain euhedral grains of Al-diopside surrounded by anorthite, suggesting small (10%-20%) degree of melting. AOAs with other textural occurrences of low-Ca pyroxene are rather porous. Forsterite grains in AOAs with low-Ca pyroxene have generally 16O-rich isotopic compositions (Δ17O lt; -20‰). Low-Ca pyroxenes of the textural occurrences (i) and (ii) are 16O-enriched (Δ17O < -20‰), whereas those of (iii) are 16O-depleted (Δ17O = -6‰ to -4‰). One of the extensively melted (>50%) objects is texturally and mineralogically intermediate between AOAs and Al-rich chondrules. It consists of euhedral forsterite grains, pigeonite, augite, anorthitic mesostasis, abundant anhedral spinel grains, and minor Fe,Ni-metal; it is surrounded by a coarse-grained igneous rim largely composed of low-Ca pyroxene with abundant Fe,Ni-metal-sulfide nodules. The mineralogical observations suggest that only spinel grains in this igneous object were not melted. The spinel is 16O-rich (Δ17O ∼ -22‰), whereas the neighboring plagioclase mesostasis is 16O-depleted (Δ17O ∼ -11‰). We conclude that AOAs are aggregates of solar nebular condensates (forsterite, Fe,Ni-metal, and CAIs composed of Al-diopside, anorthite, spinel, and ±melilite) formed in an 16O-rich gaseous reservoir, probably CAI-forming region(s). Solid or incipiently melted forsterite in some AOAs reacted with gaseous SiO in the same nebular region to form low-Ca pyroxene. Some other AOAs appear to have accreted 16O-poor pyroxene-normative dust and experienced varying degrees of melting, most likely in chondrule-forming region(s). The most extensively melted AOAs experienced oxygen isotope exchange with 16O-poor nebular gas and may have been transformed into chondrules. The original 16O-rich signature of the precursor materials of such chondrules is preserved only in incompletely melted grains. Copyright © 2005 Elsevier Ltd.
  • Alexander N. Krot, Ian D. Hutcheon, Hisayoshi Yurimoto, Jeffrey N. Cuzzi, Kevin D. McKeeoan, Edward R.D. Scott, Guy Libourel, Marc Chaussidon, Jerome Aléon, Michael I. Petaev
    Astrophysical Journal 622 2 I 1333 - 1342 2005年04月 [査読有り][通常論文]
     
    Changes in the chemical and isotopic composition of the solar nebula with time are reflected in the properties of different constituents that are preserved in chondritic meteorites. CR-group carbonaceous chondrites are among the most primitive of all chondrite types and must have preserved solar nebula records largely unchanged. We have analyzed the oxygen and magnesium isotopes in a range of the CR constituents of different formation temperatures and ages, including refractory inclusions and chondrules of various types. The results provide new constraints on the time variation of the oxygen isotopic composition of the inner (<5 AU) solar nebula - the region where refractory inclusions and chondrules most likely formed. A chronology based on the decay of short-lived 26A1 (t1/2 ∼ 0.73 Myr) indicates that the inner solar nebula gas was 16O-rich when refractory inclusions formed, but less than 0.8 Myr later, gas in the inner solar nebula became 16O-poor, and this state persisted at least until CR chondrules formed ∼1-2 Myr later. We suggest that the inner solar nebula became 16O-poor because meter-sized icy bodies, which were enriched in 17O and 18O as a result of isotopic self-shielding during the ultraviolet photo-dissociation of CO in the protosolar molecular cloud or protoplanetary disk, agglomerated outside the snow line, drifted rapidly toward the Sun, and evaporated at the snow line. This led to significant enrichment in 16O-depleted water, which then spread through the inner solar system. Astronomical studies of the spatial and temporal variations of water abundance in protoplanetary disks may clarify these processes. © 2005. The American Astronomical Society. All rights reserved.
  • Alexander N. Krot, Hisayoshi Yurimoto, Ian B. Hutcheon, Glenn J. MacPherson
    Nature 434 7036 998 - 1001 2005年04月 [査読有り][通常論文]
     
    Chondrules and Ca-Al-rich inclusions (CAIs) are high-temperature components of meteorites that formed during transient heating events in the early Solar System. A major unresolved issue is the relative timing of CAI and chondrule formation1-4. From the presence of chondrule fragments in an igneous CAI, it was concluded that some chondrules formed before CAIs (ref. 5). This conclusion is contrary to the presence of relict CAIs inside chondrules 6-10, as well as to the higher abundance of 26Al in CAIs11; both observations indicate that CAIs predate chondrules by 1-3 million years (Myr). Here we report that relict chondrule material in the Allende meteorite, composed of olivine and low-calcium pyroxene, occurs in the outer portions of two CAIs and is 16O-poor (Δ17O ≈ 1‰ to -5‰). Spinel and diopside in the CAI cores are 16O-rich (Δ17O up to -20‰), whereas diopside in their outer zones, as well as melilite and anorthite, are 16O-depleted (Δ17O = -8‰ to 2‰). Both chondrule-bearing CAIs are 26Al-poor with initial 26Al/27Al ratios of (4.7 ± 1.4) × 10 -6 and <1.2 × 10-6. We conclude that these CAIs had chondrule material added to them during a re-melting episode ∼2Myr after formation of CAIs with the canonical 26Al/27 Al ratio of 5 × 10-5.
  • Toshiaki Tsunogae, Hisayoshi Yurimoto
    Science Reports of the University of Tsukuba, Institute of Geoscience, Section B: Geological Sciences 26 23 - 38 2005年03月31日 [査読有り][通常論文]
     
    Single zircon 207Pb/206Pb and U-Pb ages of granulite-facies quartzo-feldspathic gneisses from the Northern Marginal Zone (NMZ) of the Limpopo Belt, southern Africa, were examined by a secondary ion mass spectrometry (SIMS). The NMZ is composed mainly of charnockite and associated leucocratic rocks. Some of them contain a mineral assemblage of euhedral orthopyroxene and megaperthite, probably formed by a high-grade partial melting around the peak P-T condition of the NMZ (T∼800°C). Our new zircon ages for the rocks indicate emplacement of tonalitic to granodioritic plutons at >2.79 Ga and subsequent granulite-facies metamorphism at 2.62 to 2.71 Ga. The results suggest that the peak metamorphic age of the NMZ is almost consistent with that of the Southern Marginal Zone of the belt (2.70 to 2.65 Ga; Barton and van Reenen, 1992). We therefore confirmed that the two zones have been subjected to the peak metamorphism during late Archean probably by a collision of Zimbabwe and Kaapvaal Cratons.
  • A. Pack, H. Yurimoto, H. Palme
    Geochimica et Cosmochimica Acta 69 6 1649 - 1650 2005年03月15日 [査読有り][通常論文]
  • Takanori Koshikawa, Yoshikazu Homma, Hisayoshi Yurimoto
    Surface and Interface Analysis 37 2 95 - 95 2005年02月 [査読有り][通常論文]
  • Takuya Kunihiro, Kazuhide Nagashima, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 69 3 763 - 773 2005年02月01日 [査読有り][通常論文]
     
    Two-dimensional 18O/16O isotopic analysis of the Vigarano matrix was conducted by secondary ion-imaging using a novel two-dimensional ion-imager. Quantitative oxygen-isotope images (isotopographs) of the Vigarano matrix show that 16O-rich micrograins are scattered within 16O-poor matrix. This heterogeneous O-isotopic distribution indicates that matrix is composed of different O-isotopic components that formed in different locations and/or at different times. However, the O-isotopic composition of groundmass in the matrix is the same as the bulk isotopic composition of the matrix within ±5‰ uncertainty. The spatial resolution and isotopic precision of our technique should allow submicron-size objects (>0.2 μm) with extreme O-isotopic anomalous characteristics (δ18OSMOW ∼250‰) to be detectable in isotopographs. Because the mean grain size of the matrix is ∼0.2 μm, the inability to detect such O-isotopic anomalous objects indicates that isotopically anomalous micrograins (e.g., presolar grains) are extremely rare in the Vigarano matrix and that most objects in the matrix were formed in the solar nebula or in the parent body. Copyright © 2005 Elsevier Ltd.
  • The genetic relationship between refractory inclusions and Chondrules.
    Russell S. S, Krot A. N, Huss G. R, Keil K, Itoh S, Yurimoto H, MacPherson G. J
    In Chondrites and the Protoplanetary Disk, ASP Conference Series, The Astronomical Society of the Pacific 2005年 [査読有り][通常論文]
  • Kuramoto Kiyohi, Yurimoto Hisayoshi
    Chondrites and the Protoplanetary Disk 341 181 - 192 2005年 [査読有り][通常論文]
  • Krot A. N., Fagan T. J., Nagashima K., Petaev M. I., and Yurimoto H. (2005) Origin of low-Ca pyroxene in amoeboid olivine aggregates: Evidence from oxygen isotopic compositions. Geochimica et Cosmochimica Acta 69(7), 1873-1881.*
    2005年 [査読有り][通常論文]
  • Krot A. N., Yurimoto H., Hutcheon I. D., and MacPherson G. J. (2005) Chronology of the early Solar System from chondrule-bearing calcium-aluminium-rich inclusions. Nature 434(7036), 998-1001.*
    2005年 [査読有り][通常論文]
  • H. Yurimoto, K. Nagashima
    Microscopy and Microanalysis 11 SUPPL. 2 196 - 197 2005年 [査読有り][通常論文]
  • Alexander N. Krot, Michail I. Petaev, Sara S. Russell, Shoichi Itoh, Timothy J. Fagan, Hisayoshi Yurimoto, Lysa Chizmadia, Michael K. Weisberg, Matsumi Komatsu, Alexander A. Ulyanov, Klaus Keil
    Chemie der Erde 64 3 185 - 239 2004年09月22日 [査読有り][通常論文]
     
    Amoeboid olivine aggregates (AOAs) are the most common type of refractory inclusions in CM, CR, CH, CV, CO, and ungrouped carbonaceous chondrites Acfer 094 and Adelaide; only one AOA was found in the CBb chondrite Hammadah al Hamra 237 and none were observed in the CBa chondrites Bencubbin, Gujba, and Weatherford. In primitive (unaltered and unmetamorphosed) carbonaceous chondrites, AOAs consist of forsterite (Fa<2), Fe, Ni-metal (5-12 wt% Ni), and Ca, Al-rich inclusions (CAIs) composed of Al-diopside, spinel, anorthite, and very rare melilite. Melilite is typically replaced by a fine-grained mixture of spinel, Al-diopside, and ±anorthite; spinel is replaced by anorthite. About 10% of AOAs contain low-Ca pyroxene replacing forsterite. Forsterite and spinel are always 16O-rich (δ17,18O∼-40‰ to -50‰), whereas melilite, anorthite, and diopside could be either similarly 16O-rich or 16O-depleted to varying degrees; the latter is common in AOAs from altered and metamorphosed carbonaceous chondrites such as some CVs and COs. Low-Ca pyroxene is either 16O-rich (δ17,18O∼-40‰) or 16O-poor (δ17,18O∼0‰). Most AOAs in CV chondrites have unfractionated (∼2-10×CI) rare-earth element patterns. AOAs have similar textures, mineralogy and oxygen isotopic compositions to those of forsterite-rich accretionary rims surrounding different types of CAIs (compact and fluffy Type A, Type B, and fine-grained, spinel-rich) in CV and CR chondrites. AOAs in primitive carbonaceous chondrites show no evidence for alteration and thermal metamorphism. Secondary minerals in AOAs from CR, CM, and CO, and CV chondrites are similar to those in chondrules, CAIs, and matrices of their host meteorites and include phyllosilicates, magnetite, carbonates, nepheline, sodalite, grossular, wollastonite, hedenbergite, andradite, and ferrous olivine. Our observations and a thermodynamic analysis suggest that AOAs and forsterite-rich accretionary rims formed in 16O-rich gaseous reservoirs, probably in the CAI-forming region(s), as aggregates of solar nebular condensates originally composed of forsterite, Fe, Ni-metal, and CAIs. Some of the CAIs were melted prior to aggregation into AOAs and experienced formation of Wark-Lovering rims. Before and possibly after the aggregation, melilite and spinel in CAIs reacted with SiO and Mg of the solar nebula gas enriched in 16O to form Al-diopside and anorthite. Forsterite in some AOAs reacted with 16O-enriched SiO gas to form low-Ca pyroxene. Some other AOAs were either reheated in 16O-poor gaseous reservoirs or coated by 16O-depleted pyroxene-rich dust and melted to varying degrees, possibly during chondrule formation. The most extensively melted AOAs experienced oxygen isotope exchange with 16O-poor nebular gas and may have been transformed into magnesian (Type I) chondrules. Secondary mineralization and at least some of the oxygen isotope exchange in AOAs from altered and metamorphosed chondrites must have resulted from alteration in the presence of aqueous solutions after aggregation and lithification of the chondrite parent asteroids. © 2004 Elsevier GmbH. All rights reserved.
  • Hisayoshi Yurimoto, Kiyoshi Kuramoto
    Science 305 5691 1763 - 1766 2004年09月17日 [査読有り][通常論文]
     
    Meteorites and their components have anomalous oxygen isotopic compositions characterized by large variations in 18O/16O and 17O/16O ratios. On the basis of recent observations of star-forming regions and models of accreting protoplanetary disks, we suggest that these variations may originate in a parent molecular cloud by ultraviolet photodissociation processes. Materials with anomalous isotopic compositions were then transported into the solar nebula by icy dust grains during the collapse of the cloud. The icy dust grains drifted toward the Sun in the disk, and their subsequent evaporation resulted in the 17O- and 18O- enrichment of the inner disk gas.
  • John T. Wasson, Alan E. Rubin, Hisayoshi Yurimoto
    Meteoritics and Planetary Science 39 9 1591 - 1598 2004年09月 [査読有り][通常論文]
     
    Several recent studies have shown that materials such as magnetite that formed in asteroids tend to have higher Δ 17O (=δ 17O - 0.52 x δ 18O) values than those recorded in unaltered chondrules. Other recent studies have shown that, in sets of chondrules from carbonaceous chondrites, Δ 17O tends to increase as the FeO contents of the silicates increase. We report a comparison of the O isotopic composition of olivine phenocrysts in low-FeO (≤Fa1) type I and high-FeO (≥Fa15) type II porphyritic chondrules in the highly primitive CO3.0 chondrite Yamato-81020. In agreement with a similar study of chondrules in CO3.0 ALH A77307 by Jones et al. (2000), Δ 17O tends to increase with increasing FeO. We find that Δ 17O values are resolved (but only marginally) between the two sets of olivine phenocrysts. In two of the high-FeO chondrules, the difference between Δ 17O of the late-formed, high-FeO phenocryst olivine and those in the low-FeO cores of relict grains is well-resolved (although one of the relicts is interpreted to be a partly melted amoeboid olivine inclusion by Yurimoto and Wasson [2002]). It appears that, during much of the chondrule-forming period, there was a small upward drift in the Δ 17O of nebular solids and that relict cores preserve the record of a different (and earlier) nebular environment. © Meteoritical Society, 2004.
  • Hisayoshi Yurimoto, Tetsu Kogiso, Kanshi Abe, Hans G. Barsczus, Atsushi Utsunomiya, Shigenori Maruyama
    Physics of the Earth and Planetary Interiors 146 1-2 231 - 242 2004年08月16日 [査読有り][通常論文]
     
    Pb isotopic compositions of melt inclusions in olivine phenocrysts of lava samples from Mangaia and Rarotonga, Cook-Austral islands, have been determined by secondary ion mass spectrometry. The Pb isotopic compositions of melt inclusions from Rarotonga are consistent with those of bulk rock. On the other hand, Pb isotopic compositions of sulfide-free melt inclusions from Mangaia Island are widely distributed along the join between HIMU (i.e. highly radiogenic Pb) and less radiogenic components. The variation is much wider than that in bulk-rock samples that are invariably end-member HIMU values. In contrast, Pb isotopic compositions of sulfide and carbonate inclusions are restricted to HIMU end-member values. The variations in Pb isotopic ratios can be explained by mixing between the HIMU component and another component with less radiogenic Pb, and suggests that the HIMU component is enriched in sulfide and carbonate phases as well as Pb compared with the less radiogenic component. It seems paradoxical that a sulfide-rich component is associated with highly radiogenic Pb, because sulfides generally have extremely low U/Pb and Th/Pb ratios, which result in quite unradiogenic Pb. Subducted oceanic crust is not a likely source for such a sulfide-rich component because sulfides in subducted crust may not survive dehydration processes in subduction zones, although it can produce highly radiogenic Pb. The association of highly radiogenic Pb and sulfides implies that sulfides and radiogenic Pb in the HIMU source originate from distinct reservoirs. A possible origin of the sulfides is the Earth's core, because the core is the largest sulfur budget in the Earth. The highly radiogenic Pb may originate from subducted oceanic crust which resides at the core-mantle boundary. Alternative source for radiogenic Pb is Ca-perovskite in the lower mantle, which is the main host of incompatible elements in the lower mantle and has high U/Pb and Th/Pb ratios. The core-derived sulfides would exchange Pb isotopes with subducted oceanic crust or Ca-perovskite during upwelling in the lower mantle, resulting in production of a sulfur-rich reservoir with highly radiogenic Pb. © 2004 Elsevier B.V. All rights reserved.
  • A. N. Krot, H. Yurimoto, M. I. Petaev, I. D. Hutcheon, D. Wark
    Meteoritics and Planetary Science 39 SUPPL. A57 - A57 2004年08月 [査読有り][通常論文]
  • T. J. Fagan, A. N. Krot, K. Keil, H. Yurimoto
    Meteoritics and Planetary Science 39 8 1257 - 1272 2004年08月 [査読有り][通常論文]
     
    In situ SIMS oxygen isotope data were collected from a coarse-grained type B1 Ca-Al-rich inclusion (CAI) and an adjacent fine-grained CAI in the reduced CV3 Efremovka to evaluate the timing of isotopic alteration of these two objects. The coarse-grained CAI (CGI-10) is a sub-spherical object composed of elongate, euhedral, normally-zoned melilite crystals ranging up to several hundreds of μm in length, coarse-grained anorthite and Al, Ti-diopside (fassaite), all with fine-grained (∼10 μm across) inclusions of spinel. Similar to many previously examined coarse-grained CAIs from CV chondrites, spinel and fassaite are 16O-rich and melilite is 16O-poor, but in contrast to many previous results, anorthite is 16O-rich. Isotopic composition does not vary with textural setting in the CAI: analyses of melilite from the core and mantle and analyses from a variety of major element compositions yield consistent 16O-poor compositions. CGI-10 originated in an 16O-rich environment, and subsequent alteration resulted in complete isotopic exchange in melilite. The fine-grained CAI (FGI-12) also preserves evidence of a 1st-generation origin in an 16O-rich setting but underwent less severe isotopic alteration. FGI-12 is composed of spinel ± melilite nodules linked by a mass of Aldiopside and minor forsterite along the CAI rim. All minerals are very fine-grained (<5 μm) with no apparent igneous textures or zoning. Spinel, Al-diopside, and forsterite are 16O-rich, while melilite is variably depleted in 16O (δ17,18O from ∼-40% to -5%). The contrast in isojtopic distributions in CGI-10 and FGI-12 is opposite to the pattern that would result from simultaneous alteration: the object with finer-grained melilite and a greater surface area/volume has undergone less isotopic exchange than the coarser-grained object. Thus, the two CAIs were altered in different settings. As the CAIs are adjacent to each other in the meteorite, isotopic exchange in CGI-10 must have preceded incorporation of this CAI in the Efremovka parent body. This supports a nebular setting for isotopic alteration of the commonly observed 16O-poor melilite in coarse-grained CAIs from CV chondrites. © Meteoritical Society, 2004.
  • A. N. Krot, H. Yurimoto, I. D. Hutcheon, E. R.D. Scott
    Meteoritics and Planetary Science 39 SUPPL. A56 - A56 2004年08月 [査読有り][通常論文]
  • Akira Shimojuku, Tomoaki Kubo, Eiji Ohtani, Hisayoshi Yurimoto
    Geophysical Research Letters 31 13 2004年07月16日 [査読有り][通常論文]
     
    Si self-diffusion rates in Mg2SiO4 polycrystalline wadsleyite were measured at 18 GPa and 1430-1630°C using an isotopic tracer (29Si) and secondary ion mass spectrometry. The volume diffusion coefficient (Dv) and grain-boundary diffusion coefficient (Dgb) were determined to be Dv = 3.44 × 10-11 [m2/s] exp (-299 [kJ/mol]/RT) and δDgb = 1.14 × 10-17 [m3/s] exp (-248 [kJ/mol]/RT), respectively. Si diffusion rates in wadsleyite are about 5 orders of magnitude slower than Mg-Fe interdiffusion rates at 1400°C. Assuming that Si is the slowest diffusing species in wadsleyite, the geophysical model of the viscosity in the mantle transition zone can be explained by diffusion creep in wadsleyite for a grain size of about 0.5-5 mm. Some portions in cold subducting slabs, where the grain size reduces to less than 1 μm after the olivine-spinel transformation, become weaker than the surrounding mantle. Copyright 2004 by the American Geophysical Union.
  • Motoo Ito, Hiroshi Nagasawa, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 68 13 2905 - 2923 2004年07月01日 [査読有り][通常論文]
     
    The oxygen isotopic micro-distributions within and among minerals in a coarse-grained Ca, Al-rich inclusion (CAI), 7R-19-1 from the Allende meteorite, were measured by in situ using secondary ion mass spectrometry (SIMS). All values of O isotopic ratios in 7R-19-1 minerals fall along the carbonaceous chondrite anhydrous mineral mixing (CCAM) line on a δ17OSMOW vs. δ18OSMOW plot. Major refractory minerals (spinel, fassaite and melilite) in 7R-19-1 showed large negative anomalies of Δ17O in the order, spinel (-21‰) > 16O-rich melilite (∼-18‰) > fassaite (-15 to +1‰) > 16O-poor melilite (-8 to +2‰). However, the lower limit values of Δ17O are similar at about -21‰, a value commonly observed in CAIs. The similarity in the extreme values of the isotope anomaly anomalies suggests that crystallization of all CAIs started from an 16O enrichment of 21‰ (Δ17O) relative to terrestrial values. The order of the O isotopic anomalies observed for 7R-19-1, except for 16O-poor melilite, is parallel to the crystallization sequence determined by experiment from CAI liquid (Stolper, 1982), indicating that the O isotopic exchange in 7R-19-1 occurred between CAI melt and surrounding gas while 7R-19-1 was crystallizing from the 16O enriched CAI liquid (∼-21‰ in Δ17O) in the 16O-poor solar nebula. However, the a single crystallization sequence during the cooling stage cannot explain the existence of 16O-poor melilite. The presence of 16O-poor melilite suggests that multiple heating events occurred during CAI formation. The sharp contact between 16O-rich and 16O-poor melilite crystals and within 16O-rich melilite indicates that these multiple heatings occurred quickly. Based on the O isotopic and chemical compositions, fassaite crystals were aggregates of relic crystals formed from CAI melt whichthat have had various O isotopic compositions from the remelting processes. The results of intra-mineral distributions of O isotopes also support multiple heating events during CAI formation. © 2004 Elsevier Ltd.
  • T. J. Fagan, A. N. Krot, K. Keil, H. Yurimoto
    Geochimica et Cosmochimica Acta 68 11 2591 - 2611 2004年06月01日 [査読有り][通常論文]
     
    Amoeboid olivine aggregates (AOAs) from the reduced CV chondrites Efremovka, Vigarano, and Leoville consist of forsteritic olivine, FeNi-metal and a refractory component composed of spinel, Al-diopside, ±anorthite. Secondary ferrous olivine and alkali-rich minerals (nepheline and sodalite), commonly observed in the oxidized CVs, are rare. Mineralogy and chemical compositions of AOAs are similar to those predicted by equilibrium thermodynamic condensation models, suggesting that AOAs formed primarily by gas-solid condensation over a narrow temperature range, slightly below the temperatures over which most Ca-Al-rich inclusions (CAIs) formed. AOAs in the reduced CVs preserve a 1st- generation 16O-rich signal (δ17,18O ∼ -40‰) similar to that observed in many CAIs, suggesting that these refractory objects originated from a common source in the solar nebula. In fact AOAs and many fine-grained CAIs may have formed by the same processes, but at slightly different temperatures, and can be considered a single class of refractory objects. Alteration of the AOAs is manifested by differing extents of 16O- depletion in original AOA minerals, FeO-enrichment in olivine, and formation of interstitial very fine grained Na-bearing phases. From the six AOAs and one fine-grained, melilite-pyroxene-rich CAI examined in this study, five distinct patterns of alteration were identified. (1) One unaltered AOA from Vigarano is characterized by 16 O-rich forsterite without FeO-rich rims and interstitial Na-bearing phases. (2) Weak alteration in the melilite-pyroxene-rich CAI is characterized by incomplete 16O-depletion in some melilite and precipitation of Na-bearing phases near the CAI rim. (3) Oxygen isotopic composition and mineralogy are correlated in two AOAs from Leoville with 16O-rich olivine, 16O-poor anorthite and a range of intermediate compositions in Al-diopside. This pattern is consistent with model diffusion between original grains and a 16O-poor reservoir during a relatively short-term (<60 yr), high-temperature (900-1100°C) event. (4) Original forsterite has been enriched in FeO, but remained 16O-rich in one AOA from Vigarano. This result is consistent with the slower rate of diffusion of O than Fe and Mg in olivine. At least some interstitial phases are 16O-rich, and Na-bearing phases are abundant in this AOA. (5) In contrast, oxygen isotopic composition and Fo-content are correlated in two AOAs from Efremovka. The olivine in these AOAs tends to have forsteritic 16O-rich cores and FeO-rich 16O-depleted rims. The general correlation between oxygen isotopic composition and Fo-content is difficult to model by diffusion, and may have formed instead by aqueous dissolution and precipitation along the margins of preexisting olivine grains. Independent evidence for aqueous alteration of the Efremovka AOAs is provided by OH-rich signals detected during ion beam sputtering of some of the 16O-poor olivine. Elevated 16OH-count rates and order of magnitude increases in 16OH detected during single analyses reflect trapping of an aqueous phase in 16O-depleted olivine. An elevated 16OH signal was also detected in one analysis of relatively 16O-poor melilite in the melilite-pyroxene CAI from Vigarano, suggesting that this object also was altered by aqueous fluid. © 2004 Elsevier Ltd. All rights reserved.
  • Alexander N. Krot, Timothy J. Fagan, Klaus Keil, Kevin D. McKeegan, Sandeep Sahijpal, Ian D. Hutcheon, Mikhail I. Petaev, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 68 9 2167 - 2184 2004年05月01日 [査読有り][通常論文]
     
    Based on their mineralogy and petrography, ∼200 refractory inclusions studied in the unique carbonaceous chondrite, Acfer 094, can be divided into corundum-rich (0.5%), hibonite-rich (1.1%), grossite-rich (8.5%), compact and fluffy Type A (spinel-melilite-rich, 50.3%), pyroxene-anorthite-rich (7.4%), and Type C (pyroxene-anorthite-rich with igneous textures, 1.6%) Ca,Al-rich inclusions (CAIs), pyroxene-hibonite spherules (0.5%), and amoeboid olivine aggregates (AOAs, 30.2%). Melilite in some CAIs is replaced by spinel and Al-diopside and/or by anorthite, whereas spinel-pyroxene assemblages in CAIs and AOAs appear to be replaced by anorthite. Forsterite grains in several AOAs are replaced by low-Ca pyroxene. None of the CAIs or AOAs show evidence for Fe-alkali metasomatic or aqueous alteration. The mineralogy, textures, and bulk chemistry of most Acfer 094 refractory inclusions are consistent with their origin by gas-solid condensation and may reflect continuous interaction with SiO and Mg of the cooling nebula gas. It appears that only a few CAIs experienced subsequent melting. The Al-rich chondrules (ARCs; > 10 wt% bulk Al2O3) consist of forsteritic olivine and low-Ca pyroxene phenocrysts, pigeonite, augite, anorthitic plagioclase, ± spinel, FeNi-metal, and crystalline mesostasis composed of plagioclase, augite and a silica phase. Most ARCs are spherical and mineralogically uniform, but some are irregular in shape and heterogeneous in mineralogy, with distinct ferromagnesian and aluminous domains. The ferromagnesian domains tend to form chondrule mantles, and are dominated by low-Ca pyroxene and forsteritic olivine, anorthitic mesostasis, and Fe,Ni-metal nodules. The aluminous domains are dominated by anorthite, high-Ca pyroxene and spinel, occasionally with inclusions of perovskite; have no or little FeNi-metal; and tend to form cores of the heterogeneous chondrules. The cores are enriched in bulk Ca and Al, and apparently formed from melting of CAI-like precursor material that did not mix completely with adjacent ferromagnesian melt. The inferred presence of CAI-like material among precursors for Al-rich chondrules is in apparent conflict with lack of evidence for melting of CAIs that occur outside chondrules, suggesting that these CAIs were largely absent from chondrule-forming region(s) at the time of chondrule formation. This may imply that there are several populations of CAIs in Acfer 094 and that mixing of "normal" CAIs that occur outside chondrules and chondrules that accreted into the Acfer 094 parent asteroid took place after chondrule formation. Alternatively, there may have been an overlap in the CAI- and chondrule-forming regions, where the least refractory CAIs were mixed with Fe-Mg chondrule precursors. This hypothesis is difficult to reconcile with the lack of evidence of melting of AOAs which represent aggregates of the least refractory CAIs and forsterite grains. © 2004 Elsevier Ltd.
  • Alexander N. Krot, Michail I. Petaev, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 68 8 1923 - 1941 2004年04月 [査読有り][通常論文]
     
    Amoeboid olivine aggregates (AOAs) in primitive (unmetamorphosed and unaltered) carbonaceous chondrites are uniformly 16O-enriched (Δ17O ∼ -20‰) and consist of forsterite (Fa<2), FeNi-metal, and a refractory component (individual CAIs and fine-grained minerals interspersed with forsterite grains) composed of Al-diopside, anorthite, ±spinel, and exceptionally rare melilite (Åk<15); some CAIs in AOAs have compact, igneous textures. Melilite in AOAs is replaced by a fine-grained mixture of spinel, Al-diopside, and anorthite. Spinel is corroded by anorthite or by Al-diopside. In ∼10% of > 500 AOAs studied in the CR, CV, CM, CO, CH, CB, and ungrouped carbonaceous chondrites Acfer 094, Adelaide, and LEW85332, forsterite is replaced to a various degree by low-Ca pyroxene. There are three major textural occurrences of low-Ca pyroxene in AOAs: (i) thin (<10 μm) discontinuous layers around forsterite grains or along forsterite grain boundaries in AOA peripheries; (ii) haloes and subhedral grains around FeNi-metal nodules in AOA peripheries, and (iii) thick (up to 70 μm) continuous layers with abundant tiny inclusions of FeNi-metal grains around AOAs. AOAs with low-Ca pyroxene appear to have experienced melting of various degrees. In the most extensively melted AOA in the CV chondrite Leoville, only spinel grains are relict; forsterite, anorthite and Al-diopside were melted. This AOA has an igneous rim of low-Ca pyroxene with abundant FeNi-metal nodules and is texturally similar to Type I chondrules. Based on these observations and thermodynamic analysis, we conclude that AOAs are aggregates of relatively low temperature solar nebular condensates originated in 16O-rich gaseous reservoir(s), probably CAI-forming region(s). Some of the CAIs were melted before aggregation into AOAs. Many AOAs must have also experienced melting, but of a much smaller degree than chondrules. Before and possibly after aggregation, melilite and spinel reacted with the gaseous SiO and Mg to form Ca-Tschermakite (CaAl2SiO6)-diopside (CaMgSi2O6) solid solution and anorthite. Solid or incipiently melted olivine in some AOAs reacted with gaseous SiO in the CAI- or chondrule-forming regions to form low-Ca pyroxene: Mg2SiO4 + SiO(g) + H2O(g) = Mg2Si2O6 + H2(g). Some low-Ca pyroxenes in AOAs may have formed by oxidation of Si-bearing FeNi-metal: Mg2SiO4 + Si(inFeNi) + 2H2O(g) = Mg2 Si2O6 + 2H2(g) and by direct gas-solid condensation: Mg(g) + SiO(g) +H2 O(g) = Mg2Si2O6(s) + H2(g) from fractionated (Mg/Si ratio < solar) nebular gas. Although bulk compositions of AOAs are rather similar to those of Type I chondrules, on the projection from spinel onto the plane Ca2SiO4-Mg2SiO4- Al2O3, these objects plot on different sides of the anorthite-forsterite thermal divide, suggesting that Type I chondrules cannot be produced from AOAs by an igneous fractionation. Formation of low-Ca pyroxene by reaction of AOAs with gaseous SiO and by melting of silica-rich dust accreted around AOAs moves bulk compositions of the AOAs towards chondrules, and provide possible mechanisms of transformation of refractory materials into chondrules or chondrule precursors. The rare occurrences of low-Ca pyroxene in AOAs may indicate that either AOAs were isolated from the hot nebular gas before condensation of low-Ca pyroxene or that condensation of low-Ca pyroxene by reaction between forsterite and gaseous SiO was kinetically inhibited. If the latter is correct, then the common occurrences of pyroxene-rich Type I chondrules may require either direct condensation of low-Ca pyroxenes or SiO2 from fractionated nebular gas or condensation of gaseous SiO into chondrule melts. © 2004 Elsevier Ltd.
  • Kazuhide Nagashima, Alexander H. Krot, Hisayoshi Yurimoto
    Nature 428 6986 921 - 924 2004年04月 [査読有り][通常論文]
     
    Primitive chondritic meteorites contain material (presolar grains), at the level of a few parts per million, that predates the formation of our Solar System. Astronomical observations and the chemical composition of the Sun both suggest that silicates must have been the dominant solids in the protoplanetary disk from which the planets of the Solar System formed, but no presolar silicates have been identified in chondrites. Here we report the in situ discovery of presolar silicate grains 0.1-1 μm in size in the matrices of two primitive carbonaceous chondrites. These grains are highly enriched in O (δ17OSMOW > 100-400%o), but have solar silicon isotopic compositions within analytical uncertainties, suggesting an origin in an oxygen-rich red giant or an asymptotic giant branch star. The estimated abundance of these presolar silicates (3-30 parts per million) is higher than reported for other types of presolar grains in meteorites, consistent with their ubiquity in the early Solar System, but is about two orders of magnitude lower than their abundance in anhydrous interplanetary dust particles. This result is best explained by the destruction of silicates during high-temperature processing in the solar nebula.
  • Andreas Pack, Hisayoshi Yurimoto, Herbert Palme
    Geochimica et Cosmochimica Acta 68 5 1135 - 1157 2004年03月01日 [査読有り][通常論文]
     
    We have conducted petrographic, chemical and in-situ oxygen isotopic studies of refractory forsterites from unequilibrated ordinary and carbonaceous chondrites as well as an unequilibrated R-chondrite. Refractory forsterites occur in all types of unequilibrated chondrites and all have very similar chemical composition with low FeO and high refractory lithophile element (RLE) contents. Refractory forsterites are typically enriched in 16O relative to 'normal' olivine independent of the bulk O-isotope ratios of the parent meteorites. Analyses of refractory forsterites spread along a Δ17O mixing line with Δ17O ranging from +2 to -10‰. Due to similarities in oxygen isotopes and chemical compositions, we conclude that refractory forsterites of various types of chondrites come from a single common reservoir. Implications of this hypothesis for the chemical and O-isotope evolution of silicates in the early solar nebular are discussed. © 2004 Elsevier Ltd.
  • Tsuyoshi Komiya, Shigenori Maruyama, Takafumi Hirata, Hisayoshi Yurimoto, Susumu Nohda
    Island Arc 13 1 47 - 72 2004年03月 [査読有り][通常論文]
     
    Recent geological investigations of the Isua Supracrustal Belt (3.8 Ga), southern West Greenland, have suggested that it is the oldest accretionary complex on earth, defined by an oceanic plate-type stratigraphy and a duplex structure. Plate history from mid-oceanic ridge through plume magmatism to subduction zone has been postulated from analysis of the reconstructed oceanic plate stratigraphy in the accretionary complex. Comparison between field occurrence of greenstones in modern and ancient accretionary complexes reveals that two types of tholeiitic basalt from different tectonic settings, mid-oceanic ridge basalt (MORB) and oceanic island basalt (OIB), occur. This work presents major, trace and rare earth element (REE) compositions of greenstones derived from Isua MORB and OIB, and of extremely rare relict igneous clinopyroxene in Isua MORB. The Isua clinopyroxenes (Cpx) have compositional variations equivalent to those of Cpx in modern MORB; in particular, low TiO2 and Na2O contents. The Isua Cpx show slightly light (L)REE-depleted REE patterns, and the calculated REE pattern of the host magma is in agreement with that of Isua MORB. Analyses of 49 least-altered greenstones carefully selected from approximately 1200 samples indicate that Isua MORB are enriched in Al2O3, and depleted in TiO2, FeO*, Y and Zr at the given MgO content, compared with Isua OIB. In addition, Isua MORB show an LREE-depleted pattern, whereas Isua OIB forms a flat REE pattern. Such differences suggest that the Early Archean mantle had already become heterogeneous, depending on the tectonic environment. Isua MORB are enriched in FeO compared with modern MORB. Comparison of Isua MORB with recent melting experiments shows that the source mantle had 85-87 in Mg# and was enriched in FeO. Potential mantle temperature is estimated to be approximately 1480°C, indicating that the Early Archean mantle was hotter by at most approximately 150°C than the modern mantle. © 2004 Blackwelll Publishing Asia Pty Ltd.
  • Y Shimizu, S Arai, T Morishita, H Yurimoto, F Gervilla
    TRANSACTIONS OF THE ROYAL SOCIETY OF EDINBURGH-EARTH SCIENCES 95 265 - 276 2004年 [査読有り][通常論文]
     
    Felsic and related veins within mantle-derived peridotite xenoliths from Tallante, Spain, were examined in order to understand the mantle-wedge processes related to the behaviour of Si-rich melt. The thickest part of the vein has a quartz diorite lithology, and is composed mainly of quartz and plagioclase.. with pyroxenes, hydrous mineral, apatite, zircon and rutile present as minor phases. The thinner parts are free of quartz and predominantly composed of plagioclase. Orthopyroxene always intervenes between the internal part (plagioclase quartz) and host peridotite, indicating that it is a product of interaction between silica-oversaturated melt and olivine. This indicates that a sufficiently high melt/wall rock ratio enabled the melt to retain its silica-oversaturated character. The quartz diorite part has adakite-like geochemical signatures, except for negative Ba, Rb Eu and Sr anomalies, and positive Th and U anomalies. These negative anomalies indicate that fractionation of plagioclase and hydrous minerals was achieved between the upper most mantle and the slab melting zone. The shape of the rare-earth element (REE) pattern of clinopyroxene in quartz diorite is strikingly similar to that of clinopyroxene phenocrysts from Aleutian adakites. However, the former has one order higher REE contents than the latter, except for Eu which shows a prominent negative spike. This feature was caused by the precipitation of large amounts of plagioclase and small amounts of clinopyroxene from a fractionated adakitic melt before and during solidification. This adakitic melt was produced by partial melting of a detached and sinking slab beneath the Belie area in the Tertiary.
  • Yohei Shimizu, Shoji Arai, Tomoaki Morishita, Hisayoshi Yurimoto, Fernando Gervilla
    Transactions of the Royal Society of Edinburgh, Earth Sciences 95 1-2 265 - 276 2004年 [査読有り][通常論文]
     
    Felsic and related veins within mantle-derived peridotite xenoliths from Tallante, Spain, were examined in order to understand the mantle-wedge processes related to the behaviour of Si-rich melt. The thickest part of the vein has a quartz diorite lithology, and is composed mainly of quartz and plagioclase, with pyroxenes, hydrous mineral, apatite, zircon and rutile present as minor phases. The thinner parts are free of quartz and predominantly composed of plagioclase. Orthopyroxene always intervenes between the internal part (plagioclase ± quartz) and host peridotite, indicating that it is a product of interaction between silica-oversaturated melt and olivine. This indicates that a sufficiently high melt/wall rock ratio enabled the melt to retain its silica-oversaturated character. The quartz diorite part has adakite-lik e geochemical signatures, except for negative Ba, Rb Eu and Sr anomalies, and positive Th and U anomalies. These negative anomalies indicate that fractionation of plagioclase and hydrous minerals was achieved between the upper most mantle and the slab melting zone. The shape of the rare-earth element (REE) pattern of clinopyroxene in quartz diorite is strikingly similar to that of clinopyroxene phenocrysts from Aleutian adakites. However, the former has one order higher REE contents than the latter, except for Eu which shows a prominent negative spike. This feature was caused by the precipitation of large amounts of plagioclase and small amounts of clinopyroxene from a fractionated adakitic melt before and during solidification. This adakitic melt was produced by partial melting of a detached and sinking slab beneath the Betic area in the Tertiary.
  • Shoichi Itoh, Hideyasu Kojima, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 68 1 183 - 194 2004年01月01日 [査読有り][通常論文]
     
    Fine-grained Ca-Al-rich inclusions (FGIs) in Yamato-81020 (CO3.0) and Kainsaz (CO3.1-CO3.2) chondrites have been studied by secondary ion mass spectrometry. The FGIs from Yamato-81020 consist of aggregates of hibonite, spinel, melilite, anorthite, diopside and olivine grains with no petrographic evidence of alteration. In contrast, the FGIs from Kainsaz commonly contain alteration products such as nepheline. From replacement textures and chemical compositions of altered and unaltered FGIs, we conclude that the alteration products formed by decomposition of melilite and anorthite. All phases in the Yamato-81020 FGIs are enriched in 16O, with δ17,18O = ∼-40‰ except for one FGI that experienced melting. Oxygen isotopic compositions of melilite, anorthite, some spinel and diopside in Kainsaz FGIs changed from δ17,18O = ∼-40‰ toward 0‰ by aqueous alteration. Alteration products in FGIs are depleted in 16O relative to primary phases, with δ17,18O = ∼0‰. These results show that FGIs in CO chondrites commonly had 16O-rich compositions in the solar nebula. The original 16O-rich FGIs were modified to 16O-poor compositions during aqueous alteration in the parent body. © 2004 Elsevier Ltd.
  • Ikuo Katayama, Kei Hirose, Hisayoshi Yurimoto, Satoru Nakashima
    Geophysical Research Letters 30 22 2003年11月15日 [査読有り][通常論文]
     
    Water in majoritic garnet synthesized in the mid-oceanic ridge basalt (MORB) + H2O composition at 20 GPa and 1400-1500°C was measured by secondary ion mass spectrometry (SIMS) and infrared spectroscopy. We found that the majorite contains 1130 to 1250 ppm OH by weight. The infrared absorption band showed that incorporation of the hydroxyl in majorite is most likely due to the hydrogarnet substitution. Our results indicate that water can be transported into the mantle transition zone by nominally anhydrous minerals such as omphacite and majorite in the subducting basaltic crust. Such water may have great influences on the physical properties of slab in the transition zone.
  • Seiji Maruyama, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 67 20 3943 - 3957 2003年10月15日 [査読有り][通常論文]
     
    The petrological properties, and O and Al-Mg isotopic compositions of two spinel-bearing chondrules from the Allende CV chondrite were investigated using scanning electron microscopy and secondary ion mass spectrometry. A coarse spinel grain in a barred-olivine (BO) chondrule is less enriched in 16O (Δ17O ∼ -5‰; Δ17O = δ17O - 0.52 δ18O), whereas smaller spinel grains in a plagioclase-rich chondrule member of a compound chondrule are extremely 16O-rich (Δ17O ∼ -17‰) and the spinels have a strongly serrated character. The petrological features and 16O-enrichments of the spinels in the plagioclase-rich chondrule indicate that spinels originating in coarse-grained Ca-Al-rich Inclusions (CAIs) were incorporated into chondrule precursors and survived the chondrule-forming event. The degree of 16O-excesses among minerals within each chondrule is correlated to the crystallization sequences. This evidence suggests that the O isotopic variation among minerals may have resulted from incomplete exchange of O isotopes between 16O-rich chondrule melt and 16O-poor nebular gas. Aqueous alteration also has changed the O-isotope compositions in the mesostasis. The feldspathic mesostasis in the BO chondrule shows a disturbed Mg-Al isochron indicating that the BO chondrule experienced secondary alteration. While plagioclase in the plagioclase-rich chondrule member of the compound chondrule shows slight 26Mg-excesses corresponding to (26Al/27Al)0 = [4.6±4.0(2σ)] × 10-6, nepheline formed by secondary alteration shows no detectable excess. The Al-Mg isotopic system of these chondrules was disturbed by aqueous alteration and thermal metamorphism on the Allende parent body. Copyright © 2003 Elsevier Ltd.
  • Yasuhiko Ohara, Kantaro Fujioka, Teruaki Ishii, Hisayoshi Yurimoto
    Geochemistry, Geophysics, Geosystems 4 7 2003年07月 [査読有り][通常論文]
     
    Peridotite samples from a backarc basin setting will help better understand global mid-oceanic ridge processes. Here we report detailed petrological data of serpentinized peridotite and gabbro from the extinct Parece Vela Basin in the Philippine Sea. Despite its relatively fast spreading rate (8.8-7.0 cm/y full-rate), the Parece Vela Basin spreading ridge (the Parece Vela Rift) has the distinct morpho-tectonic characteristics that indicate a small degree of mantle melting, including the presence of a huge mullion structure (the Godzilla Mullion). Peridotites in the Parece Vela Rift are exposed on the Godzilla Mullion as well as at a segment midpoint. The most notable characteristic of Parece Vela Rift peridotites is small-scale juxtaposition (i.e., a single-dredge-haul scale) of fertile peridotite and depleted peridotite (dunite and plagioclase-bearing peridotite). We interpret that the fertile peridotite (F-type) is the residue of a small degree of mantle melting (̃4% near-fractional melting of a MORB-type mantle), whereas dunite (D-type) and plagioclase-bearing peridotite (P-type) are products of melt-mantle interaction. The associated evolved gabbros may represent the shallow level fractionated melt intruded into P-type. The distinct morphotectonic characteristics, peridotite exposure at a segment midpoint, and the presence of fertile peridotite may result from an extreme transform fault effect caused by the ridge-transform geometry of short firstorder segments sandwiched by closely spaced fracture zones ("transform sandwich effect"). © 2003 by the American Geophysical Union.
  • Konstantin Litasov, Eiji Ohtani, Falko Langenhorst, Hisayoshi Yurimoto, Tomoaki Kubo, Tadashi Kondo
    Earth and Planetary Science Letters 211 1-2 189 - 203 2003年06月15日 [査読有り][通常論文]
     
    The water storage capacity of the major constituent of the lower mantle, Mg-perovskite, is a matter of debate. Here we report water solubility of Mg-perovskites with different compositions observed in peridotite and MORB systems. IR spectra of pure MgSiO3-perovskite show bands at 3397, 3423, 3448, and 3482 cm-1 and suggest about 100 ppm H2O. The H2O content in Al-Mg-perovskite (4-7 wt% Al2O3; Mg#=100) is 1000-1500 ppm (major band at 3448 cm-1), whereas Al-Fe-Mg-perovskite in MORB (Al2O3=13-17 wt%; Mg#=58-61) contains 40-110 ppm H2O (major band at 3397 cm-1). The H2O content in Al-Fe-Mg-perovskite observed in peridotite (Al2O3=5-6 wt%; Mg#=88-90) is 1400-1800 ppm (major band at 3397 cm-1). Al-Fe-Mg-perovskite from the MORB system has a high Fe3+ content, Fe3+/∑Fe=0.6, determined by electron energy loss spectroscopy measurements. Water can enter into the perovskite structure with oxygen vacancies originating from the substitution of Si by Al and Fe3+. Oxygen vacancy incorporation is favored for aluminous perovskite synthesized from the MgO-rich peridotite system. The substitution of Si4++Mg2+=2(Al,Fe)3+ prevails however in the Al-Fe-Mg-perovskite from the MORB system (MgO-poor, Al- and Fe-rich), explaining its restricted water solubility. The maximum amount of water stored in the lower mantle is estimated to be 3.42×1021 kg, which is 2.5 times the present ocean mass. Comparison of the phase relations in hydrous pyrolite and hydrous MORB indicates that pyrolite is more important as water container and water carrier in the mantle. Pyrolite contains: (1) dense hydrous magnesium silicates, existing under conditions of subducting slabs, and (2) hydrous wadsleyite, hydrous ringwoodite and water-bearing perovskite under the normal mantle and hotter conditions. Distribution of water to the MORB is restricted at the conditions of the transition zone and lower mantle. © 2003 Elsevier Science B.V. All rights reserved.
  • Shoichi Itoh, Hisayoshi Yurimoto
    Nature 423 6941 728 - 731 2003年06月12日 [査読有り][通常論文]
     
    Chondrules and calcium-aluminium-rich inclusions (CAIs) are preserved materials from the early history of the Solar System, where they resulted from thermal processing of pre-existing solids during various flash heating episodes which lasted for several million years. CAIs are believed to have formed about two million years before the chondrules. Here we report the discovery of a chondrule fragment embedded in a CAI. The chondrule's composition is poor in 16O, while the CAI has a 16O-poor melilite (Ca, Mg, Al-Silicate) core surrounded by a 16O-rich igneous mantle. These observations, when combined with the previously reported CAI-bearing chondrules, strongly suggest that the formation of chondrules and CAIs overlapped in time and space, and that there were large fluctuations in the oxygen isotopic compositions in the solar nebula probably synchronizing astrophysical pulses.
  • Hajime Imai, Hisayoshi Yurimoto
    Geochimica et Cosmochimica Acta 67 4 765 - 772 2003年02月15日 [査読有り][通常論文]
     
    The oxygen isotopic distribution in an amoeboid olivine aggregate (AOA), TTA1-02, from the Allende CV3 chondrite has been determined by secondary ion mass spectrometry. The irregular shaped TTA1-3mm) consists mostly of olivine grains of ca.μ in diameter. Olivine grains of Mg-rich (Fo95) and Fe-rich (Fo60) composition are in direct contact with each other, with a sharp compositional boundary. Oxygen isotopic compositions of Fe-rich olivine grains are 16O-poor (Δ17O ≅ -5‰) whereas Mg-rich olivine is 16O-rich (Δ17O ≅ -25‰).Several Al-rich inclusions (
  • Hisayoshi Yurimoto, Kazuhide Nagashima, Takuya Kunihiro
    Applied Surface Science 203-204 793 - 797 2003年01月15日 [査読有り][通常論文]
     
    Secondary ion mass spectrometry (SIMS) is widely used to identify the isotope ratio of the micro-area of materials. We demonstrate that the precision and spatial resolution of an ion microscope using SIMS coupled with a newly developed solid-state ion imager can be extended to two-dimensional isotope ratio imaging with permil-precision. An isotopic map for oxygen clearly reveals the distribution of 4% enrichment of 16 O in spinel particles embedded in melilite from a Ca-Al-rich inclusion of a carbonaceous chondrite. This characterization technique called isotopography thus provides the eyes to see small heterogeneity of isotope abundance in micro-scale. It is likely to find broad application in earth, material, and life science research. © 2002 Elsevier Science B.V. All rights reserved.
  • Katayama, I, Hirose, K, Yurimoto, H, Nakashima, S
    Geophysical Research Letters30 30 2003年 [査読有り][通常論文]
  • Sachio Kobayashi, Hajime Imai, Hisayoshi Yurimoto
    Geochemical Journal 37 6 663 - 669 2003年 [査読有り][通常論文]
     
    An enrichment of oxygen-16 of about 8% relative to the Earth has been found in a chondrule from the Acfer 214 carbonaceous chondrite. In contrast, isotopic abundances of major cations, Mg and Si, are similar to those of the Earth. These suggest that oxygen isotopic heterogeneity in the early solar system was much larger ever thought and assist mass-independent-isotopic fractionation for the origin. Because the chondrule has solar abundance for refractory and normal lithophile elements, we propose that silicate dusts in the early solar system were initially enriched in 16O corresponding to the 16O-rich reservoir.
  • Isao Takayanagi, Junichi Nakamura, Eric R. Fossum, Kazuhide Nagashima, Takuya Kunihoro, Hisayoshi Yurimoto
    IEEE Transactions on Electron Devices 50 1 70 - 76 2003年01月 [査読有り][通常論文]
     
    A stacked CMOS-active pixel sensor (APS) with a newly devised pixel structure for charged particle detection has been developed. At low operation temperatures (<200K), the dark current of the CMOS-APS is determined by the hot carrier effect. A twin well CMOS pixel with a p-MOS readout and n-MOS reset circuit achieves low leakage current as low as 5 × 10-8 V/s at the pixel electrode under liquid nitrogen temperature of 77 K. The total read noise floor of 0.1 mVrms at the pixel electrode was obtained by nondestructive readout correlated double sampling (CDS) with the CDS interval of 21 s.
  • Hisayoshi Yurimoto, John T. Wasson
    Geochimica et Cosmochimica Acta 66 24 4355 - 4363 2002年12月15日 [査読有り][通常論文]
     
    We describe a phenocryst in a CO-chondrite type-II chondrule that we infer to have formed by melting an amoeboid olivine aggregate (AOA). This magnesian olivine phenocryst has an extremely 16O-rich composition Δ17O (=δ17O - 0.52 · δ18O) = -23‰. It is present in one of the most pristine carbonaceous chondrites, the CO3.0 chondrite Yamato 81020. The bulk of the chondrule has a very different Δ17O of -1‰, thus the Δ17O range within this single chondrule is 22‰, the largest range encountered in a chondrule. We interpret the O isotopic and Fe-Mg distributions to indicate that a fine-grained AOA assemblage was incompletely melted during the flash melting that formed the chondrule. Some Fe-Mg exchange but negligible O-isotopic exchange occurred between its core and the remainder of the chondrule. A diffusional model to account for the observed Fe-Mg and O-isotopic exchange yields a cooling rate of 105 to 106 K hr-1. This estimate is much higher than the cooling rates of 101 to 103 K hr-1 inferred from furnace simulations of type-II chondrule textures (e.g. Lofgren, 1996); however, our cooling-rate applies to higher temperatures (near 1900 K) than are modeled by the crystal-growth based cooling rates. We observed a low 26Al/27Al initial ratio ((4.6 ± 3.0) · 10-6) in the chondrule mesostasis, a value similar to those in ordinary chondrites (Kita et al., 2000). If the 26Al/27Al system is a good chronometer, then chondrule I formed about 2 Ma after the formation of refractory inclusions. Copyright © 2002 Elsevier Science Ltd.
  • Tsuyoshi Komiya, Mamoru Hayashi, Shigenori Maruyama, Hisayoshi Yurimoto
    American Journal of Science 302 9 806 - 826 2002年11月 [査読有り][通常論文]
     
    The Isua supracrustal belt (ISB) rocks are dated at about 3.8 Ga and constitute the oldest accretionary complex in the world. Petrochemical and geothermobarometric studies of over 1,500 rock samples in ISB enabled us to estimate the extent of regional metamorphism, petrotectonic environment and subduction- zone geothermal gradient in the Archean. The following lines of evidence indicate the first discovery of progressive, prograde metamorphism from greenschist (Zone A) through Ab-Ep-amphibolite (Zone B) to amphibolite facies (Zones C and D) in the northeast part of the Isua supracrustal belt: (1) systematic change of mineral paragenesis in metabasites and metapelites; (2) progressive change of composition of major metamorphic minerals, including plagioclase, amphibole, chlorite, epidote, and garnet; (3) normal zoning of amphibole and garnet; and (4) absence of any vestige of high-grade metamorphism even in the lowest metamorphic zone. Geology and chronological constraints of ISB indicate that the regional metamorphism was related to the subduction of Archean lithosphere. Metamorphic pressures and temperatures of the metamorphism are estimated to be 5 to 7 kbar from Grt-Hbl-Pl-Qz geobarometry and 380° to 550°C from the Grt-Bt geothermometry in Zones B to D. These P-T estimates indicate that ISB was affected by progressive metamorphism of an intermediate P/T ratio metamorphic facies series, and that it records a much higher geothermal gradient of a subduction zone in the Archean than is known from the Phanerozoic. The high geothermal gradient may have resulted from the subduction of young lithosphere and a high potential temperature of mantle. The Archean high geothermal gradient led to melting of thick oceanic crust in a thin oceanic plate, creating many huge granitic (tonalite, trondhjemite, and granodiorite) batholiths. The slab melting changed the oceanic crust (density = 3.07) into a denser Grt-bearing residue (density = 3.55), implying that TTG melt extraction provided a potential driving force for Archean plate tectonics. In addition to the preservation of the oldest accretionary complex, this suggests that Precambrian-type plate tectonics, whose driving force is slab-pull due to densification of the residue of oceanic crust as a consequence of slab melting, was already operating in the Early Archean. The transition from Precambrian-type to Phanerozoic-type plate tectonics may be caused by thinning of oceanic crust and thickening of oceanic lithosphere in the late Archean, due to decrease of mantle temperature.
  • Jiuhua Chen, Toru Inoue, H. Yurimoto, Donald J. Weidner
    Geophysical Research Letters 29 18 22 - 1 2002年09月15日 [査読有り][通常論文]
     
    The phase boundary between San Carlos olivine and its high pressure phase, wadsleyite, have been studied comparatively in dry and water saturated condition. By comparing saturated and dry samples from the same experimental run, we determine that both boundaries of the two-phase coexisting loop shift towards lower pressure or lower iron content, and the pressure width of the loop decreases to 0.3 GPa under saturated conditions at 1473 K. Thus, the presence of water in the Earth's mantle will sharpen the 410-kilometer seismic discontinuity, shallow the depth of the discontinuity, and reduce the velocity jump across the discontinuity.
  • Yasuhiko Ohara, Robert J. Stern, Teruaki Ishii, Hisayoshi Yurimoto, Toshitsugu Yamazaki
    Contributions to Mineralogy and Petrology 143 1 1 - 18 2002年04月 [査読有り][通常論文]
     
    Two dives of the DSV Shinkai 6500 in the Mariana Trough back-arc basin in the western Pacific sampled back-arc basin mantle exposures. Reports of peridotite exposures in back-arc basin setting are very limited and the lack of samples has hindered our understanding of this important aspect of lithospheric evolution. The Mariana Trough is a slow-spreading ridge, and ultramafic exposures with associated gabbro dykes or sills are located within a segment boundary. Petrological data suggest that the Mariana Trough peridotites are moderately depleted residues after partial melting of the upper mantle. Although some peridotite samples are affected by small-scale metasomatism, there is no evidence of pervasive post-melting metasomatism or melt-mantle interaction. Spinel compositions plot in the field for abyssal peridotites. Clinopyroxenes show depletions in Ti, Zr, and REE that are intermediate between those documented for peridotites from the Vulcan and Bouvet fracture zones “the American-Antarctic and Southwest Indian ridges, respectively”. The open-system melting model indicates that the Mariana Trough peridotite compositions roughly correspond to theoretical residual compositions after ∼ 7% near-fractional melting of a depleted MORB-type upper mantle with only little melt or fluid/mantle interactions. The low degree of melting is consistent with a low magma budget, resulting in ultramafic exposure. We infer that the mantle flow beneath the Mariana Trough Central Graben is episodic, resulting in varying magma supply rate at spreading segments.
  • Motohiko Murakami, Kei Hirose, Hisayoshi Yurimoto, Satoru Nakashima, Naoto Takafuji
    Science 295 5561 1885 - 1887 2002年03月08日 [査読有り][通常論文]
     
    Secondary ion mass spectrometry measurements show that Earth's representative lower mantle minerals synthesized in a natural peridotitic composition can dissolve considerable amounts of hydrogen. Both MgSiO3-rich perovskite and magnesiowüstite contain about 0.2 weight percent (wt%) H2O, and CaSiO3-rich perovskite contains about 0.4 wt% H2O. The OH absorption bands in Mg-perovskite and magnesiowüstite were also confirmed with the use of infrared microspectroscopic measurements. Earth's lower mantle may store about five times more H2O than the oceans.
  • Guk Lac Kim, Hisayoshi Yurimoto, Shigeho Sueno
    Journal of Mineralogical and Petrological Sciences 97 4 161 - 167 2002年 [査読有り][通常論文]
     
    A calcium-aluminum-rich inclusion (CAI) containing big palisade bodies was found within the Allende meteorite. The bulk composition and mineral assemblages show that the CAI belongs to coarse-grained Type B. Oxygen isotopic distributions in palisade bodies in the CAI are similar to those observed in typical Type B CAIs, whereas all minerals including melilite in the host parts are enriched in 16O. The oxygen isotopic distribution in the CAI indicates that exchange of oxygen isotopes in the palisade bodies occurred before the trapping of palisades into the host. The palisade bodies were formed separately as small CAIs in the solar nebula and then accumulated together to form a large CAI. This suggests the possibility that during the CAI formation, O isotopic environment of CAI-forming region in the solar nebula repeatedly changed from 16O-rich to 16O-poor.
  • Yuichiro Ueno, Hisayoshi Yurimoto, Hideyoshi Yoshioka, Tsuyoshi Komiya, Shigenori Maruyama
    Geochimica et Cosmochimica Acta 66 7 1257 - 1268 2002年 [査読有り][通常論文]
     
    In-situ ion microprobe measurements of carbon isotopic compositions of graphite were made in seven metasediments and two carbonate rocks from the ca. 3.8 Ga Isua supracrustal belt, West Greenland. The δ13C values of micron-scale graphite globules in the metasediments and the carbonate rocks vary from -18 to +2‰ and from -7 to -3‰, respectively. The maximum δ13C value of graphite globules in the metasediment rises from -14 to -5‰, as the metamorphic grade increases from epidote-amphibolite to upper amphibolite facies. In a single hand specimen, the δ13C values of graphite inclusions in garnet are ~7‰ lower on average than those outside garnet. Similarly, graphite armored by quartz apparently shows a few permil lower δ13C values than those on grain boundaries between noncarbonate minerals. The fact that early crystallized minerals include relatively 13C-depleted graphite indicates that the regional metamorphism increased the δ13C values of the Isua graphite. This is consistent with the regional trend of 13C-enrichment accompanied by the increase of metamorphic grade. The minimum fractionation between graphite and carbonate is consistent with the equilibrium fractionation at about 400 to 550 °C. These observations indicate that isotopic exchange with isotopically heavy carbonate caused 13C-enrichment of Isua graphite. The δ13C values of graphite reported here (δ13C > -18‰) were produced either as a metamorphic modification of organic carbon with initially much lower δ13C values, or as an abiological reaction such as decomposition of carbonate. If the isotopic exchange between carbonate and graphite during the regional metamorphism controlled the 13C-enrichment of Isua graphite, previously reported large 13C-depletion of graphite, especially armored by apatite (Mojzsis et al., 1996) was probably premetamorphic in origin. This supports the existence of life at Isua time (ca. 3.8 Ga). Copyright © 2002 Elsevier Science Ltd.
  • Tsuyoshi Komiya, Shigenori Maruyama, Takafumi Hirata, Hisayoshi Yurimoto
    International Geology Review 44 11 988 - 1016 2002年 [査読有り][通常論文]
     
    It is necessary and important to determine the tectonic setting of mafic volcanism, because compositions of magma are strongly related to tectonic setting. Our recent geological investigation of the North Pole (NP) region (3.5 Ga), Pilbara, showed that the greenstone belt was an accretionary complex, defined by oceanic-plate stratigraphy and duplex structure. Moreover, application of accretionary geology reveals that there are two types of tholeiitic basalts from different tectonic settings: midocean ridge (MORB) and oceanic island (OIB). This work presents geochemistry of major, trace, and rare-earth elements (REE) of greenstones originating as MORB and OIB in the mid-Archean. Relict igneous clinopyroxenes (Cpx) in NP MORB and OIB have compositional variations equivalent to chemical variations of Cpx in modern MORB and OIB. In addition, TiO2 content and Mg# = (MgO/(MgO+FeO*)) in the host magma calculated from those in Cpx are consistent with whole-rock compositions, indicating preservation of original compositions in terms of TiO2, FeO, and MgO contents. The Cpx in NP MORB and OIB show LREE-depleted and slightly LREE-depleted REE patterns, respectively. Calculated REE patterns of host magmas also are in agreement with the wholerock compositions. Analyses of 64 alteration-free greenstones selected from 2662 samples indicate that NP MORB is enriched in Al2O3 and depleted in TiO2, FeO*, Y, and Zr at any MgO content, compared with NP OIB. In addition, NP MORB show a slightly LREE-depleted, whereas NP OIB forms a slightly LREE-enriched REE patterns. Such differences suggest that the Archean mantle already was differentiated. However, the compositional difference between the source mantles is relatively small, and differentiation into MORB and OIB source mantles was in the process of development. NP MORB are enriched in FeO, compared with modern MORB. Comparison of NP MORB with recent melting experiments shows that the source mantle of the NP MORB had Mg# = 85-87 and was enriched in FeO relative to the modern upper mantle. A possible mechanism to decrease the FeO content in the mantle is precipitation of metallic iron at the point of slab penetration into the lower mantle through time. The potential temperature of the source mantle of NP MORB is estimated to be ~1500 °C, indicating that even the mid-Archean mantle was hotter by at most ~150-200°C than the modern mantle, in contrast to the estimate from peridotitic komatiites. © 2002 Taylor & Francis Group, LLC.
  • Yuji Higo, Toru Inoue, Tetsuo Irifune, Hisayoshi Yurimoto
    Geophysical Research Letters 28 18 3505 - 3508 2001年09月15日 [査読有り][通常論文]
     
    The phase boundary between ringwoodite and perovskite plus periclase in Mg2SiO4 was determined at 1600 °C under hydrous conditions with 1~3 wt% H2O. We found that the boundary moved to high-pressure side by ~0.2 GPa in these hydrous conditions compared with that in anhydrous condition. The SIMS measurements confirmed that the ringwoodite in hydrous condition contained a significant amount (~1 wt%) of water, whereas the perovskite accepted only very little (~0.05 wt%) water in its crystal structure. The discrepancy between the pressure of 660 km seismic discontinuity and that of the postspinel transformation reported in a recent in situ x-ray study is not explained by the effect of water on the transformation.
  • Takuya Kunihiro, Kazuhide Nagashima, Isao Takayanagi, Junichi Nakamura, Koji Kosaka, Hisayoshi Yurimoto
    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 470 3 512 - 519 2001年09月11日 [査読有り][通常論文]
     
    The noise characteristics of a stacked CMOS active pixel sensor (SCAPS) for incident charged particles have been analyzed under 4.5 keV Si+ ion irradiation. The source of SCAPS dark current was found to change from thermal to electron leakage with decreasing device temperature. Leakage current at charge integration part in a pixel has been reduced to 0.1electronss-1 at 77K. The incident ion signals are computed by subtracting reset frame values from each frame using a non-destructive readout operation. With increase of irradiated ions, the dominant noise source changed from read noise, and shot noise from the incident ions, to signal frame fixed-pattern noise from variations in sensitivity between pixels. Pixel read noise is equivalent to ten incident ions. The charge of an incident ion is converted to 1.5electrons in the pixel capacitor. Shot noise corresponds to the statistical fluctuation of incident ions. Signal frame fixed-pattern noise is 0.7% of the signal. By comparing full well conditions to noise floor, a dynamic range of 80dB is achieved. SCPAS is useful as a two-dimensional detector for microanalyses such as stigmatic secondary ion mass spectrometry. © 2001 Elsevier Science B.V. All rights reserved.
  • Kazuhide Nagashima, Takuya Kunihiro, Isao Takayanagi, Junichi Nakamura, Koji Kosaka, Hisayoshi Yurimoto
    Surface and Interface Analysis 31 2 131 - 137 2001年02月 [査読有り][通常論文]
     
    A stacked CMOS-type active pixel sensor (SCAPS) for charged particles has been developed. The SCAPS is an integral-type detector that has several advantages over conventional systems, including two-dimensional detection, wide dynamic range, no insensitive time, direct detection of charged particles and a high degree of robustness. The output characteristics of the SCAPS for incident charged particles has been analysed both theoretically and experimentally. The relationships between the output voltage of the SCAPS and the number of incident charged particles were formulated by including corrections for the non-ideal characteristics of transistors in a pixel. The fluctuation of output characteristics of the SCAPS was evaluated experimentally by irradiation of secondary 4.5 keV Si+ ions generated by SIMS. The function was used to determine the number of incident ions into each SCAPS pixel within twice the statistical error. The SCAPS is useful as a two-dimensional detector for microanalysis, such as stigmatic SIMS. Copyright © 2001 John Wiley & Sons, Ltd.
  • Shoji Arai, Megumi Kida, Natsue Abe, Hisayoshi Yurimoto
    Journal of Mineralogical and Petrological Sciences 96 3 89 - 99 2001年 [査読有り][通常論文]
     
    Peridotite xenoliths in alkali basalt of about 11.0 Ma in age from Boun, which erupted in the Ogcheon belt, a tectonic belt between the Sino-Korean and Yangtze cratons, are examined to understand the petrological nature of the upper mantle beneath the Korean Peninsula. The xenolithic suite is almost composed of lherzolite containing spinel of low Cr# [=Cr/(Cr+Al) atomic ratio] around 0.1, and clinopyroxene with relatively high Na2O content (about 1 to 2 wt%). Predominance of the fertile lherzolite within the mantle may indicate that appreciable amount of melts did not pass through it and not leave dunite and/or pyroxenites with aureole of restite with higher degree of melting. The lherzolite from Boun has mineralogical characteristics of continental rift-zone mantle peridotite and is distinctly different from sub-arc and abyssal mantle peridotites. It is noteworthy that the peridotite xenoliths with arc or abyssal mantle signatures apparently have not been found from the eastern margin of the Asian continent, including the Korean Peninsula, despite possible arc settings experienced through geologic time. It is highly speculative but is possible that the arc-type mantle material had not been accreted upon arc crust accretion. Alternatively the arc type mantle which had once been present beneath the continental margin was replaced later by the continental rift-zone type mantle.
  • John T. Wasson, Hisayoshi Yurimoto, Sara S. Russell
    Geochimica et Cosmochimica Acta 65 24 4539 - 4549 2001年 [査読有り][通常論文]
     
    A problem of long-standing is the origin of the high Δ17O (= δ17O - 0.52 - δ18O) values of melilite in the refractory inclusions of carbonaceous chondrites. The spinel and, usually, also the diopside in the inclusions have "primitive" Δ17O ≤ - 20‰, but in the widely studied CV3 chondrite Allende, the melilite commonly has a Δ17O of about -4±2‰. Recent studies of oxygen diffusion coefficients in melilite and spinel have shown that the traditional model for altering the melilite-diffusive exchange with the gas in the solar nebula-cannot occur under plausible nebular scenarios. Because of increasing evidence for aqueous alteration of Allende and other carbonaceous chondrites, we tested the hypothesis that melilite alteration might occur during aqueous alteration by studying melilite in CO chondrites showing variable degrees of alteration. Our results show that almost all melilite in CO3.2 Kainsaz and CO3.3 Ornans has Δ17O >-15‰, whereas in CO3.0 Colony (and inclusions in CO3.0 Yamato 81020 studied by Itoh et al. [2000]) Δ17O in the melilite is <-20‰ (with the exception of one unusual inclusion that has undergone two melting episodes). We suggest that the O-isotopic composition of the melilite is reset by dissolution of the primitive melilite and reprecipitation in the presence of H2O having a high Δ17O value similar to that inferred from studies of CV magnetite (Choi et al., 1997, 2000). Although alteration of melilite can produce phases such as nepheline, andradite, and hedenbergite, it appears that, depending on the composition of the microenvironment, melilite present in a high-energy state (because of fine grain size, dislocations, other defects) can dissolve and reprecipitate with an O-isotopic composition intermediate between the initial composition and that of the H2O. A possible implication of our study is that the slope ≈0.9 arrays observed in the minerals of refractory inclusions of many carbonaceous chondrites could be mainly the result of aqueous alteration. Copyright © 2001 Elsevier Science Ltd.
  • Isao Takayanagi, Junichi Nakamura, El Sayed Eid, Eric R. Fossum, Kazuhide Nagashima, Takuya Kunihiro, Hisayoshi Yurimoto
    Technical Digest-International Electron Devices Meeting 551 - 554 2001年 [査読有り][通常論文]
     
    A stacked CMOS-active pixel sensor (APS) with a newly devised pixel structure for charged particle detection has been developed. A twin well pixel with a p-MOS readout transistor achieves low leakage current caused by a hot carrier effect at low temperature as low as 5×10-8 V/s at the pixel electrode. The total read noise floor of 0.1mVrms was obtained by non-destructive readout CDS with the CDS interval of 21 seconds.
  • Hiroshi Taura, Hisayoshi Yurimoto, Takumi Kato, Shigeho Sueno
    Physics of the Earth and Planetary Interiors 124 1-2 25 - 32 2001年 [査読有り][通常論文]
     
    Determination of partition coefficients for Mg- and Ca-perovskite/melt has been performed for 27 trace elements by combination of high pressure-temperature experiments using a multi-anvil apparatus and in situ trace element analysis by secondary ion mass spectrometry (SIMS). Each of the crystallographic sites for the perovskites gives rise to a parabola-shaped peak on the partition coefficient versus ionic radius diagram. This suggests that the elemental partitioning is governed by the structural control even under the lower mantle condition. On the diagrams for Mg- and Ca-perovskites, sharpness and peak position of peaks are consistent with geometrical flexibility of the corresponding coordination polyhedra. The relative height between the partition curves for homovalent ions is controlled by electrostatic charge balancing among their crystallographic sites. Large partition coefficients of Th and U in Ca-perovskite suggest that these elements play an important role for the heat source in the Earth's lower mantle. © 2001 Elsevier Science B.V. All rights reserved.
  • Yuichiro Ueno, Yukio Isozaki, Hisayoshi Yurimoto, Shigenori Maruyama
    International Geology Review 43 3 196 - 212 2001年 [査読有り][通常論文]
     
    New types of carbonaceous filamentous microstructures have been identified in silica veins at two new localities in the ˜3.5 Ga North Pole area of Western Australia. Their carbon isotopic compositions were measured in situ by secondary-ion mass spectrometry. The carbonaceous filaments are ˜1 μm wide, 10 to 100 μm long, and are permineralized in a fine-grained (˜1 μm) silica matrix. They are morphologically divided into three types (i.e., spiral, thread-like, and branched filaments). Their sizes and morphologies resemble modern and previously reported fossil bacteria. These similarities and their complex three-dimenstional geometry suggest that they may represent morphologically preserved fossil bacteria. δ13C values of the carbonaceous filaments range from -42 to -32‰, which strongly suggest that they are composed of biologically fixed organic compounds, possibly via the reductive acetyl-CoA pathway or the Calvin cycle. This is consistent with the hypothesis that autotrophs already existed on the Archean Earth.
  • Daisuke Yamazaki, Takumi Kato, Hisayoshi Yurimoto, Eiji Ohtani, Mitsuhiro Toriumi
    Physics of the Earth and Planetary Interiors 119 3-4 299 - 309 2000年05月 [査読有り][通常論文]
     
    Silicon self-diffusion coefficients in MgSiO3 perovskite were measured under lower mantle conditions. The MgSiO3 perovskite was synthesized and diffusion annealing experiments were conducted at pressure of 25 GPa and temperature of 1673-2073 K using a MA8 type high-pressure apparatus. The diffusion profiles were obtained by secondary ion mass spectrometry. The lattice and grain boundary diffusion coefficients (D1 and D(gb)) were determined to be D1 [m2/s] = 2.74 X 10-10 exp(-336 [kJ/mol]/RT) and δD(gb) [m3/s] = 7.12 X 10-17 exp(-311 [kJ/mol]/RT), respectively, where δ is the width of grain boundary, R is the gas constant and T is the absolute temperature. These diffusion coefficient play a key role for understanding the rheology of the lower mantle. (C) 2000 Elsevier Science B.V. All rights reserved.
  • Wuyi Wang, Shigeho Sueno, Eiichi Takahashi, Hisayoshi Yurimoto, Tibor Gasparik
    Contributions to Mineralogy and Petrology 139 6 720 - 733 2000年 [査読有り][通常論文]
     
    Trace element concentrations of peridotitic garnet inclusions in diamonds from two Chinese kimberlite pipes were determined using the ion microprobe. Garnet xenocrysts from the same two kimberlite pipes were also analyzed for comparison. In contrast to their extremely refractory major element compositions, all harzburgitic garnets showed enrichment in light rate earth elements (REE) relative to chondrite, resulting in sinuous REE patterns. Both normal and sinuous REE patterns were observed from the lherzolitic garnets. Concentrations of REE in garnets changed significantly from diamond to diamond and no specific correlations were observed with their major element compositions. Analyses of randomly selected two to three points within every grain of a large number of garnet inclusions by the ion microprobe demonstrated that there was no evident compositional heterogeneity, and multiple grains of one phase from a single diamond host also exhibit very similar compositions. This implies that the trace element heterogeneity within one grain or among multiple inclusions from the same diamond host, as reported from Siberian diamonds, is not a common feature for these Chinese diamonds. Concentrations of Na, Ti, and Zr tend to decrease when garnets become more refractory, but variations of Sr and Li are more complex. Compositions rich in light REE and relatively poor in high field strength elements (HFSE) of the harzburgitic garnet inclusions in diamonds are generally consistent with metasomatism by carbonatite melts. The trace element features observed from the garnet inclusions in Chinese diamonds may be caused by carbonatite melt infiltration and partial melt extraction. Spatial and temporal gradients in melt/rock ratio and temperature are the main reasons for the large variations of REE patterns and other trace element concentrations.
  • E. Ohtani, H. Mizobata, H. Yurimoto
    Physics and Chemistry of Minerals 27 8 533 - 544 2000年 [査読有り][通常論文]
     
    We conducted high-pressure phase equilibrium experiments in the systems MgSiO3 with 15 wt% H2O and Mg2SiO4 with 5 wt% and 11 wt% H2O at 20 ~ 27 GPa. Based on the phase relations in these systems, together with the previous works on the related systems, we have clarified the stability relations of dense hydrous magnesium silicates in the system MgO-SiO2-H2O in the pressure range from 10 to 27 GPa. The results show that the stability field of phase G, which is identical to phase D and phase F, expands with increasing water contents. Water stored in serpentine in the descending cold slabs is transported into depths greater than 200 km, where serpentine decomposes to a mixture of phase A, enstatite, and fluid. Reaction sequences of the hydrous phases which appear at higher pressures vary with water content. In the slabs with a water content less than about 2 wt%, phase A carries water to a depth of 450 km. Hydrous wadsleyite, hydrous ringwoodite, and ilmenite are the main water reservoirs in the transition zone from 450 to 660 km. Superhydrous phase B is the water reservoir in the uppermost part of the lower mantle from 670 to 800 km, whereas phase G appears in the lower mantle only at depths greater than 800 km. In cold slabs with local water enrichment greater than 2 wt%, the following hydrous phases appear with increasing depths; phase A to 450 km, phase A and phase G from 450 km to 550 km, brucite, superhydrous phase B, and phase G from 550 km to 800 km, and phase G at depths greater than 800 km.
  • M. Ito, H. Yurimoto, M. Morioka, H. Nagasawa
    Physics and Chemistry of Minerals 26 6 425 - 431 1999年07月 [査読有り][通常論文]
     
    Diffusion coefficients of Co2+ and Ni2+ in synthetic single crystal forsterite along the c-axis were determined in the temperature ranges, 700-1200 °C and 800-1300 °C, respectively. The synthesized forsterite specimens were coated with thin evaporated films of CoO and NiO on the c-surface and annealed for diffusion experiments. The short penetration distance of diffusing ions in forsterite was measured by secondary ion mass spectrometry using the depth profile method. The observed diffusion coefficient values show good linear relationships in Arrhenius plots and the activation energy values obtained agree well with the previous values, although the diffusion coefficient values observed at the high temperature end of the experimental range deviate from the previous values. These results indicate that Co and Ni diffuse in olivine with a single mechanism within the temperature range observed, possibly with an extrinsic in nature as in the case of Mg tracer diffusion observed by Chakraborty et al. 1994 and of Fe-Mg interdiffusion by Chakraborty.
  • Seiji Maruyama, Hisayoshi Yurimoto, Shigeho Sueno
    Earth and Planetary Science Letters 169 1-2 165 - 171 1999年05月30日 [査読有り][通常論文]
     
    Oxygen isotope compositions of individual mineral grains in two spinel-bearing chondrules have been determined by secondary ion mass spectrometry. O isotope ratios of spinel grains in a plagioclase-rich chondrule were extremely 16O-rich (δ18O ~ δ17O ~ -35‰) indicating close relationship to spinels in Ca-Al-rich inclusions (CAIs), whereas O isotope ratios of a spinel grain in barred-olivine chondrule were less enriched in 16O (δ18O ~ δ17O ~ -10‰). The degree of 16O-excesses among minerals within each chondrule was parallel to the crystallization sequences. These measurements suggest that some CAI-spinel grains were incorporated into the chondrule precursors, and that the O isotopic variation among minerals may result in incomplete exchange of O isotopes between 16O-rich chondrule melt and 16O-poor ambient nebular gas. The mesostasis having an O-isotopic composition near the terrestrial fractionation line may have been somewhat affected by the aqueous alteration in the parent body.
  • H. Yurimoto
    Science 283 5410 2102 - 2102 1999年03月26日 [査読有り][通常論文]
  • H. Yurimoto
    Science 283 5398 35 - 35 1999年01月01日 [査読有り][通常論文]
  • Hisayoshi Yurimoto, Hiroshi Nagasawa Motoo Ito
    Science 282 5395 1874 - 1877 1998年12月04日 [査読有り][通常論文]
     
    A calcium-aluminum-rich inclusion (CAI) from the Allende meteorite was analyzed and found to contain melilite crystals with extreme oxygen-isotope compositions (~5 percent oxygen-16 enrichment relative to terrestrial oxygen-16). Some of the melilite is also anomalously enriched in oxygen-16 compared with oxygen isotopes measured in other CAIs. The oxygen isotopic variation measured among the minerals (melilite, spinel, and fassaite) indicates that crystallization of the CAI started from oxygen-16-rich materials that were probably liquid droplets in the solar nebula, and oxygen isotope exchange with the surrounding oxygen-16-poor nebular gas progressed through the crystallization of the CAI. Additional oxygen isotope exchange also occurred during subsequent reheating events in the solar nebula.
  • H. Taura, H. Yurimoto, K. Kurita, S. Sueno
    Physics and Chemistry of Minerals 25 7 469 - 484 1998年08月 [査読有り][通常論文]
     
    Partition coefficients between olivine and melt at upper mantle conditions, 3 to 14 GPa, have been determined for 27 trace elements (Li, Be, B, Na, Mg, Al, Si, P, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Rb, Sr, Y, Zr, Cs, Ba, La and Ce) using secondary-ion mass-spectrometry (SIMS) and electron-probe microanalysis (EPMA). The general pattern of olivine/melt partitioning on Onuma diagrams resembles those reported previously for natural systems. This agreement strongly supports the argument that partitioning is under structural control of olivine even at high pressure. The partition coefficients for mono- andtri-valent cations show significant pressure dependence, both becoming larger with pressure, and are strongly correlated with coupled substitution into cation sites in the olivine structure. The dominant type of trace element substitution for mono- and tri-valent cations into olivine changes gradually from (Si, Mg)↔(Al, Cr) at low pressure to (Si, Mg)↔(Al, Al) and Mg, Mg)↔(Na, Al) at high pressure. the change in substitution type results in an increase in partition coefficients of Al and Na with pressure. An inverse correlation between the partition coefficients for divalent cations and pressure has been observed, especially for Ni, Co and Fe. The order of decreasing rate of partition coefficients of Al and Na with pressure. An inverse correlation between the partition coefficients for divalent cations and pressure has been observed, especially for Ni, Co and Fe. The order of decreasing rate of partition coefficient with pressure correlates to strength of crystal field effect of the cation. The pressure dependence of olivine/melt partitioning can be attributed to the compression of cation polyhedra induced by pressure and the compensation of electrostatic valence by cation substitution.
  • LIU L‐G, IRIFUNE T, OHTANI E, MIZOBATA H, KUDOH Y, NAGASE T, ARASHI H, YURIMOTO H, MIYAGI I
    Geophys. Res. Lett. 25 7 979 - 982 1998年04月01日 [査読有り][通常論文]
     
    © Copyright 1998 by the American Geophysical Union. On the basis of the available powder X-ray diffraction data, chemical composition, Raman spectrum and synthesis P-T conditions, it is concluded that the so-called new phase claimed by Ohtani et al. [1997] is in reality the phase D reported earlier by Liu [1987], Irifune et al. [1996] and Kuroda and Irifune [1997]. Phase F first reported by Kanzaki [1991] is also probably in reality the phase D. The powder X-ray diffraction pattern of the so-called phase F studied by Kudoh et al. [1995] bears no resemblance to that reported by Kanzaki [1991], suggesting a totally different material was employed in the study of Kudoh et al. [1995].
  • Toru Inoue, Tetsuo Irifune, Hisayoshi Yurimoto, Isoji Miyagi
    Physics of the Earth and Planetary Interiors 107 1-3 221 - 231 1998年04月 [査読有り][通常論文]
     
    The stability of K-amphibole has been studied at pressures 12.6-16.5 GPa, and at temperatures 940-1450°C. K-amphibole decomposes into an assemblage of clinoenstatite + diopside + an unknown phase (X) + stishovite + fluid at pressures above 16 GPa and temperatures below 1200°C. The phase boundary has a negative Clapeyron slope, and the high temperature assemblage is clinoenstatite + diopside + X + wadeite-type K2Si4O9 + fluid at pressures 14-16 GPa. The X phase has a cation ratio of approximately K:Mg:Si = 1:2:2, and contains 1.7 ± 0.1 wt.% H2O as determined by SIMS measurements, leading to a formula of K4Mg8Si8O25(OH)2. The present results suggest that the decomposition of K-amphibole in the dragged hydrous peridotite layer at the base of the mantle wedge may produce certain amounts of H2O-rich fluid at 14-16 GPa (α450 km depth), while some of H2O is trapped in the new hydrous phase X and is further carried into deeper regions of the mantle. The aqueous fluid released by the decomposition of K-amphibole should react with β-phase to form hydrous β-phase in the mantle transition region. Thus, the dehydration of K-amphibole would not cause any volcanic activities in the back arc regions, in contrast to the dehydrations of amphibole, chlorite and phlogopite, which are presumably responsible for the first and the second volcanic chains. However, some of the volcanic activities such as in Muriah, Indonesia, may be related to the dehydration of K-amphibole in unusually hot regions about the subducting slab.
  • Natsue Abe, Shoji Arai, Hisayoshi Yurimoto
    Physics of the Earth and Planetary Interiors 107 1-3 233 - 248 1998年04月 [査読有り][通常論文]
     
    Geochemical characteristics of clinopyroxene in peridotite xenoliths from three volcanos, Megata, On-yama and Kurose, in the Japan arcs are important for understanding igneous and metasomatic processes within the mantle wedge. The clinopyroxenes in peridotite xenoliths from the Japan arcs are clearly different from those in abyssal peridotites and the peridotite xenoliths from other tectonic settings, such as continental rifts and oceanic hotspots. Geochemical characteristics of the sub-arc clinopyroxenes are not apparently related either to degree of hydration or to degree of refractoriness, but are consistent from one sample to another. The REE patterns vary from LREE-depleted pattern to flat or slightly LREE-enriched patterns. Then their (Ce/Yb)N (subscript N = chondite-normalized) vary widely from 0.04 to 4.0. On the other hand the Ti/Zr ratio is rather constant in each sample, around 100. Clinopyroxenes in the Japan arcs peridotite xenoliths are intermediate for Ce and Sr contents, and (Ce/Yb)N and Ti£Zr ratios. Furthermore, the most fertile peridotites from Japan arcs are similar for the clinopyroxene chemistry to the most fertile abyssal peridotites. The peridotite xenoliths from Japan arcs had possibly evolved through different process from common source peridotite to abyssal peridotite. The Japan arc mantle peridotites had been polluted by the metasomatic agent with consistent chemical characteristics due to regional mantle wedge metasomatism.
  • Eiji Ohtani, Hiroki Mizobata, Yasuhiro Kudoh, Toshiro Nagase, Haruo Arashi, Hisayoshi Yurimoto, Isoji Miyagi
    Geophysical Research Letters 25 7 981 - 982 1998年04月 [査読有り][通常論文]
     
    Phase G reported by Ohtani et al. [1997] and Kudoh et al. [1997a] is identical with the new phase D reported by Kuroda and Irifune [1998] and Yang et al. [1997]. However, there is ambiguity on existence of phase D defined by Liu [1987]. There are following possibilities on existence of Liu's phase D; (1) the product was a mixture of phase G and the other contaminant phases, (2) it realy exists stably in different pressure and temperature conditions from those studied by our works, or (3) the phase is a metastable phase formed due to a short run duration and/or no sealing of water in the diamond anvil cell. Therefore, it is not appropriate to use the name phase D for the dense hydrous magnesium silicate phase G reported by us [Ohtani et al., 1997].
  • KITA N. T., Togashi Shigeko, Morishita Yuichi, Terashima Shigeru, Yurimoto Hisayoshi
    Antarctic meteorite research 11 11 103 - 121 国立極地研究所 1998年03月 [査読無し][通常論文]
     
    We have developed a technique for in-situ Ni isotopic analysis using the ion microprobe, in order to detect ^<60>Ni excess from the decay of the short lived nuclide ^<60>Fe (half life=1.5Ma) in ureilite samples. The silicate minerals from MET-78008 ureilite with an old U-Pb age of 4.563±0.006 Ga were analyzed. The ^<56>Fe/^<58>Ni ratios of olivine and orthopyroxene are between 2700 and 5400. In spite of the high Fe/Ni ratios, we could not observe any detectable ^<60>Ni excess. From the mean value of olivine core data, we obtain an upper limit of the ^<60>Fe/^<56>Fe ratio at the time of ureilite formation of 1.8×10^<-7>. The time difference between CAI formation and ureilite formation was estimated to be more than 4 million years, which is consistent with the UPb data from the same meteorite. We concluded that the impact event for the disruption of the ureilite parent body happened more than 4 million years after CAI formation. However, a large uncertainty in the initial ^<60>Fe/^<56>Fe ratio is introduced by the possibility that the ^<60>Ni excess observed in CAIs is of nucleosynthetic origin. Our conclusion may change if the initial ^<60>Fe/^<56>Fe ratio of the solar system using CAI data is too high.
  • M. Kurosawa, H. Yurimoto, S. Sueno
    Physics and Chemistry of Minerals 24 6 385 - 395 1997年08月 [査読有り][通常論文]
     
    The concentrations of hydrogen and the other trace elements in olivines from mantle xenoliths have been determined by secondary ion mass spectrometry (SIMS) for clarifying the incorporation mechanism and the behavior of the hydrogen. The hydrogen contents in olivines from mantle xenoliths range from 10 to 60 ppm wt. H2O and the concentration range is consistent with the previous infrared (IR) spectroscopic data. IR spectra of the olivine crystals show no effects of the weathering or secondary alteration. The hydrogen is distributed homogeneously among olivine grains in each mantle xenolith. However, the hydrogen contents of the olivine crystals are less than those for the olivine phenocrysts crystallized from the host magma. Olivine inclusions in diamonds also show similar hydrogen contents to the xenolithic olivines. Thus the hydrogen content of xenolithic olivines does not attain equilibrium with water in the host magma during the transportation from the Earth's mantle to the surface, and is taken as a reflection of the hydrogen condition in the mantle. Correlations of hydrogen with trivalent cation contents in garnet peridotitic olivines indicate the incorporation of hydrogen into mantle olivines by a coupled substitution mechanism, with the hydrogen present in the form of hydroxyl in oxygen positions adjacent to the M site vacancies. The hydrogen content of xenolithic olivines increases with pressure but decreases with increasing temperature, suggesting importance of olivine as a water reservoir at low temperature regions such as in subducting slabs.
  • Silicon self-diffusion in perovskite at high prossure
    D. Yamazaki, T, Kato, H. Yurimoto, E. Ohtani, M. Toriumi
    Extended abstract of International Symposium on New Images of the Earth's Interior through long-term Ocean-floor obsevation, Ocean Hemisphere Project 116  1997年04月 [査読無し][招待有り]
  • Eiji Ohtani, Hisayoshi Yurimoto, Shuji Seto
    Physics of the Earth and Planetary Interiors 100 1-4 97 - 114 1997年03月 [査読有り][通常論文]
     
    We determined the partition coefficients of 19 elements between metallic liquid and silicate liquid at 20 GPa and 2500°C, and between metallic liquid and silicate perovskite at 27 GPa and 2200°C. Remarkable differences were observed in the partitioning behaviors of Si, P, W, Re, and Pb among the silicate liquid, perovskite, and magnesiowüstite coexisting with metallic liquid, reflecting incompatibility of the elements in the silicate or oxide phase. We could not observe any significant difference in the partitioning behaviors of V, Cr, Mn, Co, Ni, and Cu among the phases coexisting with metallic liquid. Comparison of the present partitioning data with those obtained previously at lower pressure and temperature suggests that the exchange partition coefficients, Kmet/sil, of Co, Ni, Mo, and W decrease, whereas those of V, Cr, and Mn increase and tend to approach unity with increasing pressure and temperature. We also made preliminary experiments to clarify the effect of sulfur on the partitioning behaviors. Sulfur lowers the exchange partition coefficients, Kmet/sil, of Mo and W between metallic liquid and silicate liquid significantly at 20 GPa and 2300°C. The mantle abundances of Co, Ni, Cu, Mo, and W calculated for the metal-silicate equilibrium model are lower than those of the real mantle, whereas P, K, and Mn are overabundant in the calculated mantle. The discrepancies in the abundances of Co and Ni could be explained by the chemical equilibrium at higher pressure and temperature. Large discrepancies in Mo and W between the calculated and real mantles could be accounted for by the effect of sulfur combined with the effects of pressure and temperature on the chemical equilibrium. The mantle abundances of P, K, and Cu could be accounted for by volatile loss in the nebula, perhaps before accretion of the Earth, combined with the chemical equilibrium at higher pressure and temperature. Thus the observed mantle abundances of P, K, Co, Ni, Cu, Mo, and W may be consistent with a model of sulfur-bearing metal-silicate equilibrium in lower-mantle conditions. © 1997 Elsevier Science B.V.
  • I. Miyagi, H. Yurimoto, E. Takahashi
    Geochemical Journal 31 1 57 - 61 1997年 [査読有り][通常論文]
     
    Water solubilities in albite (Ab)-orthoclase (Or) join and JR-1 rhyolite melts at 1000°C and up to 2000 bars were determined by the 'excess of water' method using an internally heated pressure vessel (IHPV) with rapid quenching and a secondary ion microprobe mass spectrometer (SIMS). We have found that secondary hydration of run product glass with coexisting aqueous fluid occurs during quenching. The hydration is significant in sodium-rich glass. The bulk analysis of such secondary hydrated run-products will cause overestimation of the water solubility, while the true water solubility can be obtained by micro-analysis on non-attacked portion of the glass. The apparent compositional dependence in the published water solubility data could be due to the secondary hydration of run product glass. Newly determined water solubility for the Ab-Or join and rhyolite melts is expressed as H2O (mol%) = 0.19√ PH2O (bar), at 1000°C.
  • Eiji Ohtani, Hiroki Mizobata, Yasuhiro Kudoh, Toshiro Nagase, Haruo Arashi, Hisayoshi Yurimoto, Isoji Miyagi
    Geophysical Research Letters 24 9 1047 - 1050 1997年 [査読有り][通常論文]
     
    We synthesized a new hydrous silicate in the pressure range from 20 GPa to 24 GPa at 800-1300°C. This phase, named tentatively as phase G, has a hexagonal unit cell, a=4.790(3)Å and c=4.344(3)Å, and V=86.3(2)Å3 and the atomic ratio Mg/Si=0.66±0.03. SIMS analysis revealed that it contains 14.5±2.0wt% water. Phase G has a chemical formula of Mg1.14Si1.73H2.81O6 and a density of 3.37g/cm3. Phase G coexists with periclase and Mg-perovskite under the lower mantle conditions, and thus it can be a reservoir of water in cold slabs penetrating into the lower mantle. Copyright 1997 by the American Geophysical Union.
  • Miyagi, I., Yurimoto, H., Takahashi, E.
    Geochemical Journal 31 1 57 - 61 1997年 [査読有り][通常論文]
     
    Water solubilities in albite (Ab)-orthoclase (Or) join and JR-1 rhyolite melts at 1000°C and up to 2000 bars were determined by the 'excess of water' method using an internally heated pressure vessel (IHPV) with rapid quenching and a secondary ion microprobe mass spectrometer (SIMS). We have found that secondary hydration of run product glass with coexisting aqueous fluid occurs during quenching. The hydration is significant in sodium-rich glass. The bulk analysis of such secondary hydrated run-products will cause overestimation of the water solubility, while the true water solubility can be obtained by micro-analysis on non-attacked portion of the glass. The apparent compositional dependence in the published water solubility data could be due to the secondary hydration of run product glass. Newly determined water solubility for the Ab-Or join and rhyolite melts is expressed as H2O (mol%) = 0.19√ PH2O (bar), at 1000°C.
  • Flotation of diamond in magmas at high pressure and its implications for diamond genesis and fractionation in the deep mantle
    Ohtani, E, Suzuki, A, Kato, T, Yurimoto, H
    Proceeding of the 3rd NIRIM International Symposium on Advanced Materials (ISAM '96) 345 - 350 1996年 [査読無し][通常論文]
  • Eiji Ohtani, Eiji Ohtani, Hisayoshi Yurimoto, Hisayoshi Yurimoto
    Geophysical Research Letters 23 15 1993 - 1996 1996年 [査読有り][通常論文]
     
    We determined the partition coefficients of 20 elements between metallic liquid, magnsesiowustite, and silicate liquid at 20 GPa and 2500°C. The partition coefficients of V, Cr, Mn, Co, Ni, and Cu between metallic liquid and magnesiowustite are similar to those between metallic liquid and silicate liquid. The partitioning behavior of Si, P, W and Pb between metallic liquid and magnesiowustite show remarkable differences to that between metallic liquid and silicate liquid, reflecting incompatibility of these elements in magnesiowustite. Comparison of the present data with the previous ones implies that the metallic liquid-siicate liquid partition coefficients of Co, Ni, W, and Mo decrease whereas those of Cr, and Mn increase due to the combined effect of pressure and temperature, although some other factors such as the liquid composition might play some roles on a large difference in D for Mo and W. The core and mantle concentrations for Co and Ni estimated by Allegre et al. [1995] are consistent with the metal-silicate equilibrium at lower mantle conditions, although other models such as inhomogeneous accretion are also able to explain the core-mantle concentrations. Copyright 1996 by the American Geophysical Union.
  • Shoji Arai, Hisayoshi Yurimoto
    Island Arc 4 2 104 - 111 1995年06月 [査読有り][通常論文]
     
    Abstract The sub‐arc mantle condition possibly favors the formation of podiform chromitites. The Cr/(Cr + Al) atomic ratio (= Cr#) of their chromian spinel frequently is higher than 0.7, which is comparable with the range for arc‐related primitive magmas. This almost excludes the possibility of their sub‐oceanic origin, because both oceanic peridotites and MORB have chromian spinel with the Cr# < 0.6. Precipitation of chromitite and associated dunite enhances a relative depletion of high‐field strength elements (HFSE) to large‐ion lithophile elements (LILE), one of chemical characteristics of arc magmas, for the involved magma. This cannot alter completely, however, the MORB to the arc‐type magma, especially for Ti and Zr. The presence of chromitite xenoliths, similar both in texture and in chemistry to podiform chromitites of some ophiolitic complexes, in some Cenozoic alkali basalts from the southwest Japan arc indicates directly that the upper mantle beneath the Japan arcs has chromitites. Copyright © 1995, Wiley Blackwell. All rights reserved
  • Toru Inoue, Hisayoshi Yurimoto, Yasuhiro Kudoh
    Geophysical Research Letters 22 2 117 - 120 1995年01月15日 [査読有り][通常論文]
     
    The water content in modified spinel, synthesized at 15.5 GPa under hydrous conditions, has been measured by means of secondary ion mass spectrometry (SIMSrpar;. We found that the modified spinel crystals contain up to 3.1±0.4 wt % H2O, which is consistent with the amounts estimated from the deficits in the oxide totals of the microprobe analysis. X‐ray diffraction analyses for a single crystal showed that the sample containing 2.5±0.3 wt % H2O is of the modified spinel structure with the lattice parameters a=5.663(1), b=11.546(2), c=8.247(4)Å and V=539.2(5)ų. The present results suggest that a considerable amount of H2O may exist as hydrous modified spinel in the mantle transition zone, which could have important implications for the constitution and dynamics of the mantle. Copyright 1995 by the American Geophysical Union.
  • Toshiaki Tsunogae, Hisayoshi Yurimoto
    Geochemical Journal 29 3 197 - 205 1995年 [査読有り][通常論文]
     
    Single zircon U-Pb chronology was applied to help understanding the evolution of the Limpopo Belt in southern Africa. High mass resolution = 6000) obtained by a CAMECA IMS-3F ion microprobe was sufficient to determine Pb/U ratios of zircon crystals without any significant mass interferences. U-Pb ages of euhedral zircons from the belt cluster at around 3.2 Ga for the Central Zone and 2.8 Ga for the Northern Marginal Zone. The difference in age between the two zones can be explained by difference in protolith age. Timing of metamorphism was identified for the Northern Marginal Zone as 2 to 1.7 Ga which is younger than previously reported metamorphic ages of the Limpopo Belt. © 1995, GEOCHEMICAL SOCIETY OF JAPAN. All rights reserved.
  • Hiroshi Nagasawa, Hisayoshi Yurimoto, Masana Morioka
    GEOCHEMICAL JOURNAL 29 2 155 - 161 1995年 [査読有り][通常論文]
     
    Hf-Zr interdiffusivity in zircon has been determined on hafnon-zircon double-layered crystals using back-scattered electron image contrast in a scanning electron microscope. The observed Hf-Zr interdiffusion coefficient at 1600°C and 1500°C in the direction perpendicular to the c-axis is 2 x 10–15 and 3 x 10–16 cm2/sec, respectively. The value observed at 1600°C perpendicular to the c-axis is about an order of magnitude higher compared with the value of ~2 x 10-16 cm2/sec along the c-axis. These observed low diffusivity values suggest that diffusivities of Th and U in zircon are expected to be similarly low. © 1995, GEOCHEMICAL SOCIETY OF JAPAN. All rights reserved.
  • Hisayoshi Yurimoto, Hiroshi Nagasawa, Yoshiharu Mori, Osamu Matsubaya
    Earth and Planetary Science Letters 128 1-2 47 - 53 1994年11月 [査読有り][通常論文]
     
    Isotope ratios of oxygen have been measured on a fassaite crystal and the surrounding area of a coarse-grained CAI from the Allende meteorite using secondary ion mass spectrometry. Values of δ18OSMOW for fassaite, spinel, anorthite grains and alteration products are -27 ± 5, -38 ± 2, +5 ± 6, and +4‰, respectively, which are consistent with the results obtained on mineral separates. The O isotopic distributions are homogeneous either within individual single crystals of fassaite and anorthite or among the spinel grains within the analytical error. No gradual variation in O isotopic composition was detected even at the boundary between different phases or at cracks inside a phase with a spatial resolution of 10 μm. These observations strongly suggest that the partial exchange of O isotopes in the minerals in the CAI with the surrounding gas through diffusion is an unlikely origin for the observed inter-mineral heterogeneity of O isotopes in the Allende CAIs. © 1994.
  • Inoue, T, H. Yurimoto, Y. Kudoh
    Geophys. Res. Lett. 22 117 - 120 Elsevier 1994年 [査読有り][通常論文]
  • S. Arai, H. Yurimoto
    Economic Geology 89 6 1279 - 1288 1994年 [査読有り][通常論文]
     
    Petrological and geochemical data for chromian spinel from the Tari-Misaka ultramafic complex, southwest Japan, are discussed. In this complex, the spinels form a chromitite pod coated by a dunite envelope and are collectively enclosed by clinopyroxene-bearing harzburgite. The chemistry of the chromian spinel and the mode of occurrence of the dunite-chromitite association are consistent with an origin by interaction of an exotic melt with wall-rock harzburgite. The dunite may be of replacive origin. Podiform chromitite is most commonly formed in the mantle beneath island arcs. The spread in Cr ratios of spinel in podiform chromitites is almost comparable with that of spinel in primitive arc-related magmas. -from Authors
  • KOIKE O., Yurimoto Hisayoshi, Nagasawa Hiroshi, Sueno Shigeho
    Proceedings of the NIPR Symposium on Antarctic Meteorites 6 6 357 - 363 国立極地研究所 1993年05月 [査読無し][通常論文]
     
    Magnesium isotopes in individual mineral grains of a Ca-Al rich inclusion from the Allende meteorite have been measured by secondary ion mass spectrometry. An electrostatic peak switching system was used to make a precise isotopic measurement in high mass resolution mode (M/⊿M=∿4000). The inclusion shows excess of ^<26>Mg correlated with the ^<27>Al/^<24>Mg ratio. The results suggest that live ^<26>Al decayed in the inclusion which formed simultaneously in the solar nebula. The relative abundance of ^<26>Al(^<26>Al/^<27>Al=3.12×10^<-5>) is close to the "canonical" value (^<26>Al/^<27>Al=∿5×10^<-5>) for coarse-grained CAIs.
  • Wang Wuyi, Y. Hisayoshi
    Annual Report - University of Tsukuba, Institute of Geoscience 19 87 - 91 1993年 [査読有り][通常論文]
     
    In this study a comparatively simple method is described for analyzing REE concentration in garnet, in order to increase analytical precision and detection limit, and to reduce the measurement time. -from Authors
  • K MATSUMOTO, H YURIMOTO, K KOSAKA, K MIYATA, T NAKAMURA, S SUENO
    IEEE TRANSACTIONS ON ELECTRON DEVICES 40 1 82 - 85 1993年01月 [査読有り][通常論文]
     
    This paper describes a new area detector for secondary ion mass spectrometry (SIMS) ion microscope, and its performance. The operational principle is based on detecting the change in potential of a floating photodiode caused by the ion-induced secondary-electron emission and the incoming ion itself. The experiments demonstrated that 10(1)-10(5) aluminum ions per pixel can be detected with good linear response. Moreover, relative ion sensitivities from hydrogen to lead were constant within a factor of 2. The performance of this area detector provides the potential for detection of kiloelectronvolt ion images with current ion microscopy.
  • Hisayoshi Yurimoto, Yoshiharu Mori, Hironori Yamamoto
    Review of Scientific Instruments 64 5 1146 - 1149 1993年 [査読有り][通常論文]
     
    A small, compact negative-ion source based on plasma sputtering has been developed for secondary-ion mass spectrometry (SIMS). It can make precise measurements of the oxygen isotope ratios in minerals. From a copper sputter target, a high-density 63Cu- ion beam of 3 mA cm -2 has been obtained as the primary-ion beam with a size of 100 μm in diameter. The mass distribution of the ion beam is 99% Cu- and 1% Cu-2 ions; other ionic species comprise less than 0.1%. A typical beam stability for 10 min has been achieved at 0.4% (σ). These performances of the negative-ion source are useful to perform in situ analyses of insulator materials in SIMS. As an application, the high-mass resolution spectra for three isotopes of oxygen secondary ions from an insulator sample bombarded by the 63Cu- ion beam was studied.
  • Isao Sakaguchi, Hisayoshi Yurimoto, Shigeho Sueno
    Journal of the American Ceramic Society 75 12 3477 - 3480 1992年12月 [査読有り][通常論文]
     
    Diffusion profiles of Sr in single‐crystal MgO at 1473 to 1843 K have been determined by a depth‐profiling technique using secondary ion mass spectrometry. The diffusion experiments were performed using a focusing infrared furnace. The temperature dependences of lattice and dislocation diffusion are D 1 = 2.6 × 10 −11 exp(–268.2/RT [kJ/mol])[m 2 .s ‐1 ], D d = 1.7 × 10 4 exp(–562.3/RT), respectively. The present lattice diffusion coefficients are three orders of magnitude smaller than those previously reported. Si diffused with Sr in MgO over 1583 K, and the diffusion coefficients of Si were also determined. The results of Si diffusion were equivalent to those of our previous study. Copyright © 1992, Wiley Blackwell. All rights reserved
  • Isao Sakaguchi, Hisayoshi Yurimoto, Sigeho Sueno
    Solid State Communications 84 9 889 - 893 1992年12月 [査読有り][通常論文]
     
    Self-diffusion of 26Mg in single crystal MgO has been investigated at low temperature side (1573-973 K). The lattice and dislocation diffusion coefficients were determined from diffusion penetration which was measured by SIMS. The dislocation pipe diffusion was 4-5 orders faster than the lattice diffusion at the same temperature. © 1992.
  • Isao Sakaguchi, Hisayoshi Yurimoto, Sigeho Sueno
    Materials Science and Engineering B 13 3 L1 - L4 1992年04月 [査読有り][通常論文]
     
    Tracer diffusion of Li+, Na+, Si4+ and P5+ in single-crystal MgO has been performed. The lattice and dislocation diffusion coefficients were determined from diffusion penetration measured by SIMS. Temperature dependence of the lattice and dislocation diffusion among these ions was argued to connect with the property of ions. © 1992.
  • Isao Sakaguchi, Hisayoshi Yurimoto, Shigeho Sueno
    Journal of the American Ceramic Society 75 3 712 - 715 1992年03月 [査読有り][通常論文]
     
    The lattice and dislocation diffusion coefficients for Ca 2+ in single‐crystal MgO have been determined in the temperature range 1743 to 1293 K from the diffusion penetration determined using secondary ion mass spectrometry. The dislocation diffusion coefficients were 4 to 5 orders of magnitude larger than the lattice diffusion coefficients in the same temperature range. The activation energy of Ca 2+ lattice diffusion was comparable to that of ionic conductivity. The diffusion mechanism of Ca 2+ is related to Mg vacancies. Copyright © 1992, Wiley Blackwell. All rights reserved
  • Hisayoshi Yurimoto, Eiji Ohtani
    Geophysical Research Letters 19 1 17 - 20 1992年01月03日 [査読有り][通常論文]
     
    The secondary ion mass spectrometry (SIMS) was applied to measure the trace element abundances in majorite and the ultramafic liquid equilibrating at high pressure and temperature for the first time, and was proved to be useful for the high pressure experimental petrology. The analysis by SIMS was made to determine the abundance of 15 lithophile elements (Li, Be, B, Sc, Ti, V, Cr, Mn, Y, Zr, La, Sm, Gd, Yb, and Hf), one siderophile (Co), and two chalcophile elements (Cu, Zn). The electron microprobe (EPMA) analysis was also made to obtain the major element abundance. Some lithophile elements (Al, Be, and V) are enriched in majorite, whereas the lithophile elements (Li, B, Na, K, Ca, Ti, Zr, Y, La, Sm, Gd, and Hf), and siderophile and chalcophile elements (Co, Cu, Zn) are favored in the liquid. These results give important constraint for the genesis of komatiites and chemical heterogeneity in the Archean mantle. Copyright 1992 by the American Geophysical Union.
  • Hisayoshi Yurimotc, Masana Morioka, Hiroshi Nagasawa
    Geochemical Journal 26 4 181 - 188 1992年 [査読有り][通常論文]
     
    Diffusion profiles of l8O tracer in single crystals of forsterite following anneals at 1100° and 1200'C have been determined by a depth profiling technique using secondary ion mass spectrometry. The diffusion penetration profiles showed error function forms with developed tails. The profiles were analyzed in terms of diffusion in the forsterite lattice together with a contribution from dislocation. The present results of lattice diffusion lie in the range of the extrapolation of lines on Arrhenius plots reported previously for intracrystalline diffusion in forsterite. The dislocation diffusion coefficients are about 104 times faster than the lattice diffusion at the same temperature. Diffusion along the dislocations takes place within a pipe with radius of about 0.1 nm surrounding the dislocation line. Based on the above results, O diffusion along high diffusivity paths, such as dislocations and grain boundaries, play an important role on the diffusional creep in olivine under laboratory condition. © 1992, GEOCHEMICAL SOCIETY OF JAPAN. All rights reserved.
  • M. Kurosawa, H. Yurimoto, S. Sueno
    Annual Report - University of Tsukuba, Institute of Geoscience 18 83 - 88 1992年 [査読有り][通常論文]
     
    This study shows examples of the SIMS quantitative analysis of trace H, Ni and Ca in mantle olivine crystals. Secondary ion intensities of the elements were correlated to absolute concentration by three kinds of standard materials: 1) fused glass rock standards, 2) natural olivine standards, and 3) ion implanted standards. The concentration gave good agreement with the result determined by EPMA (Ca, Ni) and the previous study (H). -from Authors
  • Hisayoshi YURIMOTO, Isao SAKAGUCHI, Norimasa NISHIDA, Shigeho SUENO
    Geostandards Newsletter 15 1 155 - 159 1991年04月 [査読有り][通常論文]
     
    Trace level determination of nickel in silicate rock samples has been achieved using secondary ion mass spectrometry (SIMS) with kinetic energy filtering. Standard rock references, issued by the Geological Survey of Japan, were fused into glass and used as standards for the SIMS analysis. Due to interferences from the glass matrix, the secondary ion of mass 60 was only useful for Ni, although the secondary ion was interfered mainly by CaO+. The contributions of these molecular ions were deconvolved by a least squares regression. Good linear correlation between results after the deconvolution and the Ni concentration in the glass standards was obtained. The uncertainties of the SIMS analysis depend strongly on the degree of contribution of CaO+ molecular ion. Such a method of SIMS analysis is especially useful to study the detailed behavior of Ni on a micro‐scale in Ca‐poor materials. Copyright © 1991, Wiley Blackwell. All rights reserved
  • Hisayoshi Yurimoto, E. F. Duke, J. J. Papike, C. K. Shearer
    Geochimica et Cosmochimica Acta 54 7 2141 - 2145 1990年07月 [査読有り][通常論文]
     
    All 14 stable rare earth elements (REEs) in biotite-muscovite granite and tourmaline-rich granite of the Harney Peak Granite, Black Hills, South Dakota, USA, have been analyzed using inductively coupled plasma mass spectrometry. Chrondrite-normalized REE patterns of the tourmaline-rich granites are discontinuous between Nd and Sm. The discontinuity was modeled successfully by the fractional crystallization of monazite from a biotite-muscovite granite initial composition. This explanation may also apply to the development of such discontinuous patterns in other highly evolved rocks. © 1990.
  • C. K. Shearer, J. J. Papike, S. B. Simon, N. Shimizu, H. Yurimoto, S. Sueno
    Geochimica et Cosmochimica Acta 54 3 851 - 867 1990年03月 [査読有り][通常論文]
     
    The major element geochemistry of picritic lunar glass beads indicates that they represent primary basaltic liquid compositions and, as such, provide unique information concerning the origin of mare basalts and characteristics of the lunar interior. This study used ion microprobe techniques for trace element analysis of individual glass beads representing seven compositionally distinct types of picritic glass beads from the Apollo 14 site [high-Ti glasses (17-11% TiO2): Red/Black, Orange; intermediate-Ti glasses (5-4% TiO2): Yellow; low-Ti glasses (2.8% TiO2): LAP (low alkali, picritic; Papike et al., 1989); very low-Ti glasses (<1% TiO2): Green A, VLT, Green B]. The Green B, Green A, VLT, and LAP glasses are typically LREE enriched. The total REE abundance of Green A, VLT, and LAP overlap (Ce = 30 to 80 × chondrite) whereas the REE abundances of the more MgO-rich Green B are substantially lower (Ce = 8 to 18 × chondrite). The trace element signature [REE patterns and abundances, ( Ba Sr) > 1] of these glasses are different from low-Ti mare basalts at other sites but are similar to crystalline basalts at the Apollo 14 site. The intermediate to high-Ti picritic glasses exhibit a flat to slightly positive LREE slope and a negative HREE slope. The Orange glass has a higher total REE abundance and a slightly larger negative Eu anomaly than the Red/Black and Yellow glasses. Relative to the Apollo 17 high-Ti glasses, Apollo 14 high-Ti glasses are enriched in REE, LREE/HREE, Y, V, Zr, Sr, Ba, and Ba Sr and are similar in alkali elements (Li, Rb), Co, and Sc. Trace element modeling, within the context of liquid lines of descent and major element characteristics, indicates that the picritic glass beads at the A-14 site are not related by low pressure fractional crystallization to each other or to crystalline basalts at the Apollo 14 or other landing sites. A possible exception is the relationship between LAP and basalts of the high-Al basalt suite. The wide range of primary magma compositions and the lack of petrogenetic linkage (via crystal fractionation) to crystalline basalts indicates that either a wide compositional range of evolved mare basalts has not yet been sampled or a unique mechanism is selectively tapping these picritic magmas directly from their mantle source region. The wide range of major and trace element characteristics of the volcanic glass beads is consistent with derivation from mineralogically distinct sources which consist of varying proportions of olivine + orthopyroxene ± clinopyroxene ± ilmenite ± plagioclase ± KREEP component. The evolved KREEP component may have been incorporated into these primary picritic magmas by either assimilation-fractional crystallization-type processes (AFC) or by hybridization of the mantle source. The former appears less likely due to the general systematic increase in incompatible elements relative to Ti concentration and the apparent lack of crystallization that is required in AFC-type models. The hybridization processes may be the result of "sinker" mechanisms as proposed by Ringwood and Kesson (1976), a manifestation of original mantle inhomogeneities, or a magma ocean stirred by large impacts. © 1990.
  • Hisayoshi Yurimoto, Masana Morioka, Hlroshi Nagasawa
    Geochimica et Cosmochimica Acta 53 9 2387 - 2394 1989年09月 [査読有り][通常論文]
     
    Diffusion profiles of 18O tracer in single crystals of gehlenite and åkermanite following annealing at 1000°-1300°C have been determined by a depth-profiling technique using secondary ion mass spectrometry. From the 18O depth profiling the lattice diffusion coefficients for oxygen along the crystallographic axes in gehlenite and åkermanite, D1geh//c, D1·ak//a and D1·ak//c, respectively, are given by: D1geh//c = 4.36 × 10-12 exp(- 186 ± 16 [kJ mol-1] RT) [m2sec-1]D1 a ̇k//a = 6.96 × 10-6 exp(- 300 ± 37 [kJ mol-1] RT) [m2sec-1]D1 a ̇k//c = 9.41 × 10-10 exp(- 215 ± 51 [kJ mol-1] RT) [m2sec-1] Present results are two to four orders of magnitude lower than those previously reported for melilite solid solutions (HAYASHl and Muehlenbachs, 1986). These high diffusion rates in melilite solid solutions and the heterogeneous distribution of O isotopes in the Allende Ca, Al-rich inclusions (CAIs) have been examined considering the contribution of fast diffusion along dislocations and possible changes in diffusion rate with gehlenite-åkermanite ratios in melilite. For this purpose, diffusion coefficients of O along dislocations were calculated by analyzing "tailing" of the O-diffusion profiles. From the effective diffusion rate in melilite solid solution obtained by lattice and dislocation diffusion rates, it is unlikely that the O-isotope differences in the Allende CAI minerals are the result of diffusion processes during a postcrystallization thermal event. © 1989.
  • Hisayoshi Yurimoto, Masanori Kurosawa, Shigeho Sueno
    Geochimica et Cosmochimica Acta 53 3 751 - 755 1989年03月 [査読有り][通常論文]
     
    Microanalysis of hydrogen in quartz crystals and quartz glasses has been developed by secondary ion mass spectrometry (SIMS). The secondary ion intensities of hydrogen are proportional to the hydrogen contents determined by infrared (IR) absorption over the range of 5 to 3000 ppma H/Si. The correlation between SIMS and IR results indicates that secondary ion yields of hydrogen are independent of crystal structure. This SIMS method could reveal correlations between hydrogen distribution and hydrolytic weakening at the microscopic level. © 1989.
  • Hisayoshi Yurimoto, Aya Yamashita, Shigeho Sueno, Norimasa Nishida
    Geochemical Journal 23 5 215 - 236 1989年 [査読有り][通常論文]
     
    Glasses prepared from JA-1, JA-2, JA-3, JB-1, JB-1a, JB-2, JB-3,JGb-1, JR-1 and JR-2 rock standards were found to be homogeneous standards appropriate for SIMS micro-analysis. Simultaneous micro-analysis of major, minor and trace elements in ng samples is made possible by use of the glass standards. This method uses energy filtering and, for REE’s and Hf, the contribution of simple oxide ions were corrected. Using specific SIMS operating conditions, linear calibration curves have been established for 38 elements (Li, Be, B, Na, Mg, Al, P. K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Cu, Rb, Sr, Y, Zr, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Hf). The typical accuracy of the analyses are within 10% of the recommended values for the elements over 1 ppm. Complications were encountered as described below: (1) Secondary ion yield for Na was enhanced in JF-, JG- and JR-series glasses which have relatively higher Si concentrations than the other standard glasses, whereas the yield of REE was reduced on JR-series glasses. The results demonstrate that systematic errors occur among silicates with different Si abundances for these elements. (2) Energy filtering was ineffective in removing interferences on the P and Sc peaks. The detection limits of these elements are controlled by the background level of the masses. Despite these problems, the empirical relationships obtained in this study are still useful for the application of quantitative SIMS to geological samples. © 1989, GEOCHEMICAL SOCIETY OF JAPAN. All rights reserved.
  • Matsukazu Kamo, Hisayoshi Yurimoto, Yoichiro Sato
    Applied Surface Science 33-34 C 553 - 560 1988年09月 [査読有り][通常論文]
     
    The growth features of diamond from the gas phase have been studied using (111), (110) and (100) planes of diamond as substrates. The deposition layers were studied by reflection electron diffraction, Raman spectroscopy, scanning electron microscopy, secondary ion mass spectroscopy and absorption spectroscopy. Epitaxial growth on these planes was observed for the various crystallographic orientations. The growth rate decreases in the order (111) ≅ (110) > (100). Epitaxially grown layers on the (111) and (110) planes were obtained in the temperature range from 820 to 950°C. On the other hand, the layer on the (100) plane was only observed at 820°C. The investigation of the properties of the deposited layers suggests that the layers can be contaminated by elements present in the substrate holder which may arise from the impact of plasma particles, and that the grown diamond belongs to Type IIa diamond, the purest form of natural diamond. © 1988.
  • Mutsukazu Kamo, Hisayoshi Yurimoto, Yoichiro Sato, Nobuo Setaka
    Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films 6 3 1818 - 1819 1988年05月 [査読有り][通常論文]
  • Hisayoshi Yurimoto, Shigeho Sueno
    Geochemical Journal 21 3 85 - 104 1987年 [査読有り][通常論文]
     
    Partition coefficients for — 1, -2, —3, +1, +2, +3, +4 and +5 valent ions between the groundmass of boninite and coexisting phenocrysts, bronizite, protoenstatite, augite and chrome spinel, from Bonin Island, Japan have been determined by secondary ion mass spectrometry (SIMS). The SIMS method could reveal the equilibria between the phenocrysts and the groundmass glass. The method has been useful in determining the partition coefficient for trace elements of the rock. The present anion and cation partitioning strongly supports the “crystal structure control” mechanism (Onuma et al., 1968; Yurimoto and Sueno, 1984a). Each of the crystallographic site gives rise to a parabola-shaped peak on partition coefficient vs. ionic radius diagram. On the diagrams for three kinds of pyroxene, sharpness of their peaks is consistent with geometrical flexibility of the corresponding coordination polyhedra, and relative height between the partition curves for homovalent ions is controlled by electrostatic charge balancing their crystallographic sites. © 1987, GEOCHEMICAL SOCIETY OF JAPAN. All rights reserved.
  • Hisayoshi Yurimoto, Shigeho Sueno
    GEOCHEMICAL JOURNAL 18 2 85 - 94 1984年 [査読有り][通常論文]
     
    Partition coefficients for —1, -2, -3, +1, +2, +3, +4 and +5 valent ions between the groundmass of tholeiite basalt and coexisting olivine and plagioclase phenocrysts from the Mid-Atlantic Ridge have been determined by secondary ion mass spectrometry. The present cation partitioning strongly supports the “crystal structure control” mechanism, The partition coefficient for an anion is also under control of the crystal structure, so that each of the cation and anion positions in the crystal structure gives rise to a parabola-shaped peak on the partition coefficient vs. ionic radius diagram. © 1984, GEOCHEMICAL SOCIETY OF JAPAN. All rights reserved.

MISC

  • 矢田 達, 安部 正真, 岡田 達明, 中藤 亜衣子, 与賀田 佳澄, 宮﨑 明子, 西村 征洋, 坂本 佳奈子, 畠田 健太朗, 熊谷 和也, 古屋 静萌, 岩前 絢子, 吉武 美和, 人見 勇矢, 副島 広道, 長島 加奈, 金丸 礼, 山本 大貴, 林 佑, 深井 稜汰, 管原 春菜, 鈴木 志野, 橘 省吾, 臼井 寛裕, 圦本 尚義, 藤本 正樹, 澤田 弘崇, 岡崎 隆司, 高野 淑識, 三浦 弥生, 矢野 創, Trevor Ireland, 杉田 精司, 長 勇一郎, 湯本 航生, 矢部 佑奈, 森 晶輝, Jean-Pierre Bibring, Cedric Pilorget, Rosario Brunetto, Lucie Riu, Damian Loizeau, Lionel Lourit, Vincent Hamm, 中澤 暁, 田中 智, 佐伯 孝尚, 吉川 真, 渡邊 誠一郎, 津田 雄一 遊・星・人 = Planetary people : 日本惑星科学会誌 31 (2) 153 -164 2022年06月
  • 鈴村明政, 川崎教行, 圦本尚義, 伊藤正一 日本地球惑星科学連合大会予稿集(Web) 2022 2022年
  • 癸生川陽子, DARTOIS E., QUIRICO E., BONAL L., ENGRAND C., DUPRAT J., MATHURIN J., DAZZI A., DENISET-BESSEAU A., 薮田ひかる, 圦本尚義, 中村智樹, 野口高明, 岡崎隆司, 奈良岡浩, 坂本佳奈子, 橘省吾, 橘省吾, 渡邊誠一郎, 津田雄一 日本地球化学会年会要旨集(Web) 69th 2022年
  • 永島一秀, 川崎教行, 坂本直哉, 中村智樹, 野口高明, 岡崎隆司, 薮田ひかる, 奈良岡浩, 坂本佳奈子, 渡邊誠一郎, 津田雄一, 橘省吾, 圦本尚義 日本地球化学会年会要旨集(Web) 69th 2022年
  • 猪裕太, 猪裕太, 田中智, 田中智, 小野寺圭祐, 小野寺圭祐, 川村太一, 嶌生有理, 中嶋大輔, 岩田隆浩, 岩田隆浩, 中村智樹, 森田朋代, 菊入瑞葉, 天野香菜, 加川瑛一, 圦本尚義, 野口高明, 岡崎隆司, 薮田ひかる, 奈良岡浩, 坂本佳奈子, 橘省吾, 橘省吾, 渡邊誠一郎, 津田雄一 日本地球惑星科学連合大会予稿集(Web) 2022 2022年
  • 三河内岳, 吉田英人, 中村智樹, ZOLENSKY Michael E., 中嶋大輔, 萩谷健治, 菊入瑞葉, 森田朋代, 天野香菜, 加川瑛一, 圦本尚義, 野口高明, 岡崎隆司, 薮田ひかる, 奈良岡浩, 坂本佳奈子, 橘省吾, 渡邊誠一郎, 津田雄一 日本鉱物科学会年会講演要旨(Web) 2022 2022年
  • 松本恵, 松野淳也, 土山明, 土山明, 中村智樹, 三河内岳, 安武正展, 上杉健太朗, 竹内晃久, 延寿里美, 奥村翔太, 三津川到, MINGQI S., 榎戸祐馬, 三宅亮, 圦本尚義, 野口高明, 岡崎隆司, 薮田ひかる, 奈良岡浩, 坂本佳奈子, 橘省吾, 渡邊誠一郎, 津田雄一 日本鉱物科学会年会講演要旨(Web) 2022 2022年
  • 松野淳也, 三宅亮, 松本恵, 中村智樹, 高橋嘉夫, 山田真也, 土山明, 延寿里美, 圦本尚義, 野口高明, 岡崎隆司, 薮田ひかる, 奈良岡浩, 坂本佳奈子, 橘省吾, 渡邊誠一郎, 津田雄一 日本鉱物科学会年会講演要旨(Web) 2022 2022年
  • 石崎拓也, 長野方星, 田中智, 坂谷尚哉, 中村智樹, 藤田涼平, ALASLI Abdulkareem, 岡田達明, 森田朋代, 菊入瑞葉, 天野香菜, 加川瑛一, 圦本尚義, 野口高明, 岡崎隆司, 薮田ひかる, 奈良岡浩, 坂本佳奈子, 橘省吾, 橘省吾, 渡邊誠一郎, 津田雄一 日本惑星科学会秋季講演会予稿集(Web) 2022 2022年
  • 石崎拓也, 長野方星, 田中智, 坂谷尚哉, 中村智樹, 藤田涼平, ALASLI Abdulkareem, 森田朋代, 菊入瑞葉, 天野香菜, 加川瑛一, 圦本尚義, 野口高明, 岡崎隆司, 薮田ひかる, 奈良岡浩, 坂本佳奈子, 橘省吾, 橘省吾, 渡邊誠一郎, 津田雄一 Thermophysical Properties (CD-ROM) 43rd 2022年
  • 小松睦美, 小松睦美, 薮田ひかる, 癸生川陽子, BONAL Lydie, QUIRICO Eric, 圦本尚義, 中村智樹, 野口高明, 岡崎隆司, 奈良岡浩, 坂本佳奈子, 橘省吾, 橘省吾, 渡邊誠一郎, 津田雄一 日本惑星科学会秋季講演会予稿集(Web) 2022 2022年
  • 佐藤雅彦, 木村勇気, 田中智, 畠山唯達, 杉田精司, 中村智樹, 橘省吾, 奥住聡, 渡邊誠一郎, 圦本尚義, 野口高明, 岡崎隆司, 薮田ひかる, 奈良岡浩, 坂本佳奈子, 矢田達, 西村征洋, 中藤亜衣子, 宮崎明子, 与賀田佳澄, 安部正真, 岡田達明, 臼井寛裕, 吉川真, 佐伯孝尚, 照井冬人, 中澤暁, 津田雄一 日本惑星科学会秋季講演会予稿集(Web) 2022 2022年
  • 圦本尚義 地学雑誌 131 (2) 163 -177 2022年 
    Determining the elemental abundances of the Earth is one of the fundamental interests of the Earth and planetary sciences. The elemental abundances of the bulk solar system, chondrites and bulk Earth are reviewed. The elemental abundances of the bulk solar system resemble those of chondrites, with the exception of atmophile elements. CI chondrite may be most resemblant, but significant improvements in solar photosphere spectroscopy are necessary to reject other chondrites. Volatilities of elements control chemical variations among chondrites. These variations may reflect global thermal structures in the proto-solar disk. Alternatively, the variations may correspond to accretion ratios of chondrite-forming components, which are refractory inclusions, chondrules, and matrix, into the parent bodies. The elemental abundances of bulk silicate Earth can be empirically estimated without referring those of the bulk solar system and chondrites if we use chemical variations of mantle rocks. However, the chemical composition of bulk Earth remains largely uncertain because it is difficult to estimate the chemical compositions of the central core and the lower mantle without formation models of the Earth.
  • 圦本尚義 応用物理 91 (3) 2022年
  • 太田明緒, 井上徹, 野田昌道, 柿澤翔, 川添貴章, 佐藤友子, 新名亨, 入舩徹男, 坂本直哉, 圦本尚義 日本鉱物科学会年会講演要旨(Web) 2021 2021年
  • 圦本尚義 技術と経済 (653) 2021年
  • 大槻悠太, 馬上謙一, 圦本尚義 質量分析総合討論会講演要旨集 69th 2021年
  • 大槻悠太, 馬上謙一, 圦本尚義 Journal of the Mass Spectrometry Society of Japan 69 (6) 2021年
  • 和田壮平, 馬上謙一, 圦本尚義 日本地球化学会年会要旨集(Web) 68th 2021年
  • 圦本 尚義, 馬上 謙一 レーザー研究 = The review of laser engineering : レーザー学会誌 48 (8) 441 -446 2020年08月
  • 和田壮平, 川崎教行, 圦本尚義, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2020 2020年
  • 川崎教行, 伊藤正一, 坂本直哉, SIMON Steven B., 圦本尚義, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2020 2020年
  • 鈴村明政, 川崎教行, 瀬戸雄介, 圦本尚義, 圦本尚義, 伊藤正一 日本地球惑星科学連合大会予稿集(Web) 2020 2020年
  • 山本大貴, 橘省吾, 川崎教行, 上林海ちる, 圦本尚義 日本鉱物科学会年会講演要旨(Web) 2020 2020年
  • 永田康祐, 馬上謙一, 三友秀之, 三友秀之, 藤田龍介, 上原亮太, 上原亮太, 居城邦治, 居城邦治, 圦本尚義 日本分子生物学会年会プログラム・要旨集(Web) 43rd 2020年
  • 矢田達, 安部正真, 中藤亜衣子, 与賀田佳澄, 宮崎明子, 岡田達明, 西村征洋, 熊谷和也, 吉武美和, 古屋静萌, 岩前絢子, 林佑, 山本大貴, 橘省吾, 橘省吾, 臼井寛裕, 圦本尚義, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2020 2020年
  • S. Ishikubo, S. Tachibana, N. Kawasaki, D. Yamamoto, M. Kuroda, H. Yurimoto METEORITICS & PLANETARY SCIENCE 54 2019年08月
  • D. Yamamoto, S. Tachibana, N. Kawasaki, M. Kamibayashi, H. Yurimoto METEORITICS & PLANETARY SCIENCE 54 2019年08月
  • 柿澤翔, 柿澤翔, 井上徹, 井上徹, 井上徹, 阿部遼太郎, 黒田みなみ, 黒田みなみ, 坂本直哉, 圦本尚義, 圦本尚義, 圦本尚義 日本地球化学会年会要旨集(Web) 66th 2019年
  • 鈴村明政, 川崎教行, 瀬戸雄介, 圦本尚義, 圦本尚義, 伊藤正一 日本地球化学会年会要旨集(Web) 66th 2019年
  • 和田壮平, 川崎教行, 圦本尚義, 圦本尚義 日本地球化学会年会要旨集(Web) 66th 2019年
  • 川崎教行, 和田壮平, PARK C., 坂本直哉, 圦本尚義, 圦本尚義 日本地球化学会年会要旨集(Web) 66th 2019年
  • 川崎教行, PARK Changkun, 坂本直哉, 圦本尚義, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2019 2019年
  • 和田壮平, 川崎教行, 圦本尚義, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2019 2019年
  • 磯野雄生, 坂本直哉, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2019 2019年
  • 矢田達, 安部正真, 中藤亜衣子, 与賀田佳澄, 坂本佳奈子, 西村征洋, 岡田達明, 中埜夕希, 吉武美和, 熊谷和也, 岩前絢子, 古屋静萌, 橘省吾, 橘省吾, 圦本尚義, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2019 2019年
  • 坂本直哉, 阿部光太郎, 圦本尚義 実験医学 36 (20) 3426‐3427 2018年12月15日 [査読無し][通常論文]
  • 安部正真, 安部正真, 圦本尚義, 圦本尚義 日本惑星科学会誌 遊・星・人 27 (2) 92‐95 -95 2018年06月25日 [査読無し][通常論文]
     
    サンプルリターンミッションは惑星探査の最終形態のひとつであり，今後も新たなサンプルリターンミッションが世界中の惑星探査計画において実施されることが予想される．JAXAでも，はやぶさ，はやぶさ２の帰還試料受入れを通して，設備や受け入れ態勢が強化されつつある．本稿では，これまでの経緯を含めJAXAにおけるサンプルリターンミッションからの試料受入れの現在，過去，未来について紹介する．
  • 久我ゆかり, WU Ting-Di, WU Ting-Di, 永田康祐, 坂本直哉, GUERQUIN-KERN Jean-Luc, GUERQUIN-KERN Jean-Luc, 勝山千恵, 圦本尚義 日本土壌微生物学会講演要旨集 2018 2018年
  • 柿澤翔, 井上徹, 井上徹, 井上徹, 阿部綾太郎, 黒田みなみ, 坂本直哉, 圦本尚義, 圦本尚義, 圦本尚義 高圧討論会講演要旨集 59th 2018年
  • 川崎教行, 圦本尚義 日本地球化学会年会要旨集(Web) 65th 2018年
  • 野々山貴行, 鈴木裕貴, 木山竜二, WANG Lei, 津田真寿美, 安田和則, 田中伸哉, 永田康祐, 藤田龍介, 坂本直哉, 圦本尚義, GONG Jian Ping 日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM) 31st 2018年
  • 山本大貴, 上林海ちる, 川崎教行, 橘省吾, 圦本尚義, 圦本尚義 日本鉱物科学会年会講演要旨(Web) 2018 2018年
  • 黒田みなみ, 橘省吾, 坂本直哉, 圦本尚義, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2018 2018年
  • 川崎教行, PARK Changkun, 坂本直哉, PARK Sun Young, KIM Hyun Na, 黒田みなみ, 圦本尚義, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2018 2018年
  • 山本大貴, 黒田みなみ, 橘省吾, 橘省吾, 坂本直哉, 圦本尚義, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2018 2018年
  • 伊藤元雄, 松本純, 癸生川陽子, 青木順, 河井洋輔, 渡邊元樹, 池田峻太, 久保勇貴, 岡田達明, GRAND Noel, BUCH Arnaud, 横田勝一郎, 圦本尚義, 圦本尚義, 豊田岐聡, 森治 日本惑星科学会秋季講演会予稿集(Web) 2018 2018年
  • 矢田達, 与賀田佳澄, 坂本佳奈子, 吉武美和, 古屋静萌, 西村征洋, 西村征洋, 熊谷和也, 熊谷和也, 岡田達明, 岡田達明, 安部正真, 圦本尚義, 圦本尚義 日本惑星科学会秋季講演会予稿集(Web) 2018 2018年
  • 矢田達, 安部正真, 岡田達明, 坂本佳奈子, 吉武美和, 中埜夕希, 松本徹, 川崎教行, 熊谷和也, 西村征洋, 松井重雄, 圦本尚義, 圦本尚義, 藤本正樹, 藤本正樹 日本地球惑星科学連合大会予稿集(Web) 2018 ROMBUNNO.PPS03‐P10 (WEB ONLY) 2018年 [査読無し][通常論文]
  • T. Yada, K. Sakamoto, M. Yoshitake, Y. Nakano, K. Kumagai, M. Nishimura, S. Matsui, T. Matsumoto, N. Kawasaki, T. Okada, M. Abe, H. Yurimoto, M. Fujimoto METEORITICS & PLANETARY SCIENCE 52 A393 -A393 2017年08月 [査読無し][通常論文]
  • H. Yurimoto, A. Tonotani, K. Bajo, C. T. Olinger, D. Reisenfeld, A. J. G. Jurewicz, S. Itose, I. Sakaguchi, M. Ishihara, K. Uchino, D. S. Burnet METEORITICS & PLANETARY SCIENCE 52 A401 -A401 2017年08月 [査読無し][通常論文]
  • 黒田みなみ, 橘省吾, 坂本直哉, 圦本尚義 日本鉱物科学会年会講演要旨(Web) 2017 2017年
  • 岡田達明, 岡田達明, 癸生川陽子, 青木順, 伊藤元雄, 河井洋輔, 矢野創, 岡本千里, 薮田ひかる, 圦本尚義, 圦本尚義, 横田勝一郎, 寺田健太郎, 豊田岐聡, 中村良介, 岩田隆浩, 松本純, 森治, BIBRING Jean-Pierre, ULAMEC Stephan, JAUMANN Ralf 日本惑星科学会秋季講演会予稿集(Web) 2017 2017年
  • 癸生川陽子, 伊藤元雄, 青木順, 岡田達明, 岡田達明, 河井洋輔, 松本純, 寺田健太郎, 豊田岐聡, 薮田ひかる, 圦本尚義, 圦本尚義, 矢野創, 中村良介, COTTIN Herve, GRAND Noel, 森治 日本惑星科学会秋季講演会予稿集(Web) 2017 2017年
  • 安部正真, 岡田達明, 矢田達, 坂本佳奈子, 吉武美和, 中埜夕希, 松本徹, 川崎教行, 熊谷和也, 松井重雄, 西村征洋, 圦本尚義, 圦本尚義 日本惑星科学会秋季講演会予稿集(Web) 2017 2017年
  • 益田 晴恵, 圦本 尚義 地球化学 51 (4) i -i 2017年 [査読無し][通常論文]
  • 矢田達, 安部正真, 岡田達明, 吉武美和, 坂本佳奈子, 松本徹, 中埜夕希, 川崎教行, 西村征洋, 熊谷和也, 松井重雄, 圦本尚義, 圦本尚義, 藤本正樹, 藤本正樹 日本地球惑星科学連合大会予稿集(Web) 2017 ROMBUNNO.PPS02‐P27 (WEB ONLY) 2017年 [査読無し][通常論文]
  • 川崎教行, SIMON Steven B, GROSSMAN Lawrence, 坂本直哉, 圦本尚義, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2017 ROMBUNNO.PPS10‐29 (WEB ONLY) 2017年 [査読無し][通常論文]
  • 松本徹, 長谷川直, 圦本尚義, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2017 ROMBUNNO.PPS10‐07 (WEB ONLY) 2017年 [査読無し][通常論文]
  • 殿谷梓, 馬上謙一, OLINGER Chad T, JUREWICZ Amy J G, 坂口勲, 鈴木拓, BURNETT Donald S, 糸瀬悟, 石原盛男, 内野喜一郎, 圦本尚義, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2017 ROMBUNNO.PPS10‐04 (WEB ONLY) 2017年 [査読無し][通常論文]
  • 久我 ゆかり, Ting-Di Wu, Jean-Luc Guerquin-Kern, 永田 康祐, 坂本 直哉, 圦本 尚義, 勝山 千恵 日本菌学会大会講演要旨集 61 (0) 109 -109 2017年 [査読無し][通常論文]
  • 岡田達明, 癸生川陽子, 伊藤元雄, 青木順, 河井洋輔, 寺田健太郎, 豊田岐聡, 岡本千里, 中村良介, 矢野創, 松岡彩子, 横田勝一郎, 岩田隆浩, 松本純, 森治, 圦本尚義, BIBRING Jean‐Pierre, COTTIN Herve, PALOMBA Ernesto, HELBERT Joern, ULAMEC Stephan, JAUMANN Ralf 宇宙科学技術連合講演会講演集(CD-ROM) 61st ROMBUNNO.2G19 2017年 [査読無し][通常論文]
  • 圦本 尚義 地球化学 51 (2) 49 -59 2017年 [査読無し][通常論文]
     

    Oxygen is the third most abundant element in the Universe and the most abundant element of the terrestrial planets. The presence of oxygen in gaseous, ice and dust phases makes oxygen isotopes important tracers of various fractionation processes to form a protoplanetary accretion disk, which are essential for understanding the evolution of building blocks for planet formation. Photodissociation of CO isotopologues in cold interstellar environments forms H2O ice with depletion of 16O component relative to the interstellar CO, but with heritage 17O/18O ratio from the interstellar CO. Dynamic evolution of protoplanetary disk generates H2O enrichments inside snowline of the disk to change from 16O-rich to 16O-poor gaseous environments. Thermodynamics during heating processes reset oxygen isotopic compositions of dust in the disk to the gaseous oxygen isotope values. Therefore, building blocks of planet show oxygen isotope variations with variable 16O component, but with similar 17O/18O ratio each other. Oxygen isotopic compositions of outer planets would be 16O-poor in order of increasing distance from the Sun if outer planet formation started from icy planetesimal accretion.

  • 圦本 尚義 地球化学 = Geochemistry 51 (2) 49 -59 2017年 [査読無し][通常論文]
  • 久我ゆかり, 山田博之, 田代智子, 勝山千恵, 中村仁, 坂本直哉, 圦本尚義 日本土壌微生物学会講演要旨集 2016 9 2016年06月06日 [査読無し][通常論文]
  • 浅井恵, 兼平裕也, 伊藤哲平, 屋代充, 園生智弘, 小林幸雄, 居城邦治, 圦本尚義, 重松隆, 木村(須田)廣美 日本骨形態計測学会雑誌 26 (1) S160 -S160 2016年06月05日 [査読無し][通常論文]
  • 安部正真, 安部正真, 圦本尚義, 圦本尚義, 矢田達, 岡田達明, 岡田達明, 坂本佳奈子, 吉武美和, 中埜夕希, 松本徹, 川崎教行, 熊谷和也, 松井重雄, 西村征洋 日本惑星科学会秋季講演会予稿集(Web) 2016 2016年
  • 低温光化学反応による分子雲での有機物形成・進化
    Piani Laurette, 橘 省吾, 羽馬 哲也, 菅原 いよ, 大場 康弘, 田中 秀和, 木村 勇気, 三宅 亮, 松 野 淳也, 土山 明, 圦本 尚義, 香内 晃 日本地球惑星科学連合2016年大会 2016年 [査読無し][通常論文]
  • 圦本 尚義 日本地球化学会年会要旨集 63 (0) 135 -135 2016年 [査読無し][通常論文]
     

    はやぶさ２以降の宇宙物質サンプルリターンミッションを推進するため，JAXA宇宙研に地球外物質研究グループが2015年度に組織化された．この新グループは，初代はやぶさの時の地球外物質キュレーション施設が行っていた研究者への試料供給サービスに加え，地球外物質を研究する組織を宇宙研内に芽吹かせることを志向している．そのため，世界の類似の組織の模倣ではない，サンプル分析以外の(を超える)研究特徴を持つ世界オンリーワンの地球外物質研究グループ育成を目指す．その対策として，世界のアカデミアコミュニティーとのより強い連携に加え，民間企業との有機的な連携を模索している．本発表では，そのマスタープランを皆様に披露し，皆様からのご意見をいただきたい．

  • 橋口未奈子, 小林幸雄, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2016 ROMBUNNO.PPS12‐15 (WEB ONLY) 2016年 [査読無し][通常論文]
  • 殿谷梓, 馬上謙一, 糸瀬悟, 石原盛男, 内野喜一郎, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2016 ROMBUNNO.MTT28‐P03 (WEB ONLY) 2016年 [査読無し][通常論文]
  • 吉成耕一, 馬上謙一, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2016 ROMBUNNO.SGL38‐P05 (WEB ONLY) 2016年 [査読無し][通常論文]
  • 川崎教行, 伊藤正一, 坂本直哉, 圦本尚義, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2016 ROMBUNNO.PPS12‐04 (WEB ONLY) 2016年 [査読無し][通常論文]
  • 矢田達, 安部正真, 岡田達明, 圦本尚義, 上椙真之, 唐牛譲, 中藤亜衣子, 橋口未奈子, 松本徹, 西村征洋, 熊谷和也, 松井重雄, 藤本正樹 日本地球惑星科学連合大会予稿集(Web) 2016 ROMBUNNO.PCG10‐03 (WEB ONLY) 2016年 [査読無し][通常論文]
     
    第49回月・惑星シンポジウム (2016年7月20-21日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)), 相模原市, 神奈川県著者人数: 17名資料番号: SA6000059007
  • 圦本 尚義 日本地球化学会年会要旨集 63 (0) 102 -102 2016年 [査読無し][通常論文]
     

    今，あなたが解き明かしたい地球化学は，あなたの実験室の分析装置でできそうですか？どこかの実験室に行けばできそうですか？それとも全く新しい分析装置の発明が必要ですか？この発表では最後の質問に「はい」と答える方と議論したい． なぜ最先端分析装置を越える新しい分析装置を発明したいのか？それは，最先端分析装置を発展させるだけでは解き明かせない新しい地球化学を発見しているからだ．新しい分析装置の開発は，新しい物理と新しい化学のコラボレーションで始まり，発明へと進展する．地球化学の発見が分析装置の発明によりなされることがあることを，同位体顕微鏡を例にして議論する．地球化学の難題は，分析装置発明の原動力になりそうだ．

  • 井上徹, 柿澤翔, CAI Nao, 藤野清志, 栗林貴弘, 長瀬敏郎, GREAUX Steeve, 肥後祐司, 阪本直哉, 圦本尚義, 服部高典, 佐野亜沙美 高圧討論会講演要旨集 56th 45 2015年10月27日 [査読無し][通常論文]
  • 坪井香奈子, 長谷川智香, 本郷裕美, 圦本尚義, 小林幸雄 Clin Calcium 25 (10) 1505-1511,1428 -1511 2015年09月28日 [査読無し][通常論文]
     
    骨細胞の細胞突起は三次元的複雑な分布をし、骨細胞・骨細管系と呼ばれる細胞性ネットワークを形成している。今回我々は構造化照明顕微鏡法(SIM)や集束イオンビーム走査電子顕微鏡(FIB-SEM)を用いて骨細胞・骨細管系の三次元微細構造を観察し、細胞突起の走行の様子を詳細に観察した。また、同位体顕微鏡システムを用いて骨基質へのカルシウム沈着やミノドロン酸の骨組織内部での局在を検索したところ、新たな知見を得ることができた。さまざまな顕微鏡をその試料に応じて適切に選択することで、今まで明らかとならなかった種々の事象を解明することができると思われる。(著者抄録)
  • 柿澤翔, 井上徹, 栗林貴弘, 圦本尚義 日本鉱物科学会年会講演要旨集 2015 109 2015年09月18日 [査読無し][通常論文]
  • 黒田みなみ, 橘省吾, 奥村聡, 中村美千彦, 坂本直哉, 圦本尚義 日本鉱物科学会年会講演要旨集 2015 5 2015年09月18日 [査読無し][通常論文]
  • N. Kawasaki, N. Sakamoto, H. Yurimoto METEORITICS & PLANETARY SCIENCE 50 2015年08月 [査読無し][通常論文]
  • J. Bollard, N. Kawasaki, N. Sakamoto, K. Larsen, D. Wielandt, M. Schiller, J. Connelly, H. Yurimoto, M. Bizzarro METEORITICS & PLANETARY SCIENCE 50 2015年08月 [査読無し][通常論文]
  • S. Tachibana, L. Piani, L. Dessimoulie, T. Hama, Y. Kimura, Y. Endo, K. Fujita, S. Nakatsubo, H. Fukushi, S. Mori, T. Chigai, H. Yurimoto, A. Kouchi METEORITICS & PLANETARY SCIENCE 50 2015年08月 [査読無し][通常論文]
  • 山本淳博, 川崎教行, 坂本直哉, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2015 ROMBUNNO.PPS22‐12 (WEB ONLY) 2015年 [査読無し][通常論文]
  • 川崎教行, 加藤千図, 伊藤正一, 若木重行, 伊藤元雄, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2015 ROMBUNNO.PPS22‐13 (WEB ONLY) 2015年 [査読無し][通常論文]
  • 殿谷梓, 馬上謙一, 圦本尚義 日本地球惑星科学連合大会予稿集(Web) 2015 ROMBUNNO.MTT44‐02 (WEB ONLY) 2015年 [査読無し][通常論文]
  • 柿澤翔, 井上徹, 圦本尚義 高圧討論会講演要旨集 55th 127 2014年11月10日 [査読無し][通常論文]
  • 井上徹, 矢吹智美, 柿澤翔, 藤野清志, 圦本尚義, 栗林貴弘, 長瀬敏郎 高圧討論会講演要旨集 55th 10 2014年11月10日 [査読無し][通常論文]
  • 芳野極, 櫻井萌, 坂本直哉, 圦本尚義 高圧討論会講演要旨集 55th 6 2014年11月10日 [査読無し][通常論文]
  • 井上徹, 矢吹智美, 柿澤翔, 藤野清志, 圦本尚義, 栗林貴弘, 長瀬敏郎 日本鉱物科学会年会講演要旨集 2014 114 2014年09月10日 [査読無し][通常論文]
  • 久我ゆかり, 坂本直哉, 圦本尚義 日本土壌肥料学会講演要旨集 60 36 2014年09月09日 [査読無し][通常論文]
  • N. Kawasaki, C. Kato, S. Itoh, M. Ito, S. Wakaki, H. Yurimoto METEORITICS & PLANETARY SCIENCE 49 A198 -A198 2014年09月 [査読無し][通常論文]
  • C. Park, K. Nagashima, S. Wakaki, N. Sakamoto, S. Kobayashi, H. Yurimoto METEORITICS & PLANETARY SCIENCE 49 A315 -A315 2014年09月 [査読無し][通常論文]
  • L. Piani, S. Tachibana, T. Hama, Y. Endo, K. Fujita, S. Nakatsubo, H. Fukushi, S. Mori, T. Chigai, H. Yurimoto, A. Kouchi METEORITICS & PLANETARY SCIENCE 49 A318 -A318 2014年09月 [査読無し][通常論文]
  • M. Bizzarro, M. Olsen, S. Itoh, N. Kawasaki, M. Schiller, L. Bonal, H. Yurimoto METEORITICS & PLANETARY SCIENCE 49 A43 -A43 2014年09月 [査読無し][通常論文]
  • ミノドロン酸の同位体顕微鏡を用いた骨組織分布の観察と骨の細胞群に対する影響(Localization of 15N-minodronate by isotope microscopy and histochemical assessment for the biological effects of minodronate in mice)
    佐々木 宗輝, 本郷 裕美, 小林 幸雄, 圦本 尚義, 網塚 憲生 Journal of Oral Biosciences Supplement 2014 106 -106 2014年09月 [査読無し][通常論文]
  • ミノドロン酸の同位体顕微鏡を用いた骨組織分布の観察と骨の細胞群に対する影響(Localization of 15N-minodronate by isotope microscopy and histochemical assessment for the biological effects of minodronate in mice)
    佐々木 宗輝, 本郷 裕美, 小林 幸雄, 圦本 尚義, 網塚 憲生 Journal of Oral Biosciences Supplement 2014 144 -144 2014年09月 [査読無し][通常論文]
  • 木村(須田)廣美, 伊藤哲平, 金沢恭祐, 小林幸雄, 居城邦治, 圦本尚義 日本腎臓学会誌 56 (3) 327 -327 2014年05月25日 [査読無し][通常論文]
  • 佐々木宗輝, 本郷裕美, 小林幸雄, 織田公光, 圦本尚義, 網塚憲生 日本骨形態計測学会雑誌 24 (2) S112 -S112 2014年05月19日 [査読無し][通常論文]
  • 小笠原希実, 坂本直哉, 伊藤利章, 内藤哲, 高野順平, 圦本尚義 日本顕微鏡学会関東支部講演会予稿集 38th 41 2014年03月08日 [査読無し][通常論文]
  • 久我 ゆかり, 坂本 直哉, 圦本 尚義 土と微生物 68 (1) 36 -36 2014年 [査読無し][通常論文]
  • 久我 ゆかり, 坂本 直哉, 圦本 尚義 日本土壌肥料学会講演要旨集 60 (0) 36 -36 2014年 [査読無し][通常論文]
  • 日高 洋, 寺田 健太郎, 圦本 尚義 日本地球化学会年会要旨集 61 (0) 129 -129 2014年 [査読無し][通常論文]
     
    宇宙化学分野からは惑星探査，探査によってもたらされるリターンサンプルのキュレーション体制の強化，新しい分析手法の開発を伴うリターンサンプルのキャラクタリゼーション等を包含する大型研究計画を提案する。
  • 井上徹, 林晃平, 圦本尚義 高圧討論会講演要旨集 54th 69 2013年10月30日 [査読無し][通常論文]
  • 井上 徹, 林 晃平, 圦本 尚義 日本鉱物科学会年会講演要旨集 2013 8 -8 2013年09月05日 [査読無し][通常論文]
  • 圦本 尚義 日本鉱物科学会年会講演要旨集 2013 257 -257 2013年09月05日 [査読無し][通常論文]
     
    私たちはイオンマイクロプローブ，同位体顕微鏡の開発を行ってきており，現在，同位体ナノスコープの開発に挑戦している．これらの分析法は相補的な効果があり，総合して活用することにより宇宙物質の成因が包括的に科学できる．今後は分光法による外惑星の軽元素の分光法による同位体分析の開発が必要である．また，ケロジェンの全構造解析のために，放射光の種々の分光分析・質量分析・NMR・クロマトグラフィーの分析技術とそれらを融合する新しいバイオインフォマティクスを開発するプロジェクトが重要である．
  • 圦本尚義, 馬上謙一, 石原盛男, 内野喜一郎, 糸瀬悟, 松谷幸, 工藤政都 質量分析総合討論会講演要旨集 61st 16 2013年09月02日 [査読無し][通常論文]
  • 馬上謙一, 圦本尚義 質量分析総合討論会講演要旨集 61st 134 2013年09月02日 [査読無し][通常論文]
  • ミノドロン酸の同位体顕微鏡を用いた骨組織分布と破骨細胞に対する影響
    佐々木 宗輝, 本郷 裕美, 小林 幸雄, 圦本 尚義, 網塚 憲生 Journal of Oral Biosciences Supplement 2013 135 -135 2013年09月 [査読無し][通常論文]
  • ミノドロン酸の同位体顕微鏡を用いた骨組織分布と破骨細胞に対する影響
    佐々木 宗輝, 本郷 裕美, 小林 幸雄, 圦本 尚義, 網塚 憲生 Journal of Oral Biosciences Supplement 2013 146 -146 2013年09月 [査読無し][通常論文]
  • 小笠原希実, 坂本直哉, 伊藤利章, 圦本尚義, 内藤哲, 高野順平 日本植物学会大会研究発表記録 77th 167 2013年08月20日 [査読無し][通常論文]
  • 大竹翼, 坂本佑樹, 伊藤正一, 圦本尚義, 掛川武 資源地質学会年会講演会講演要旨集 63rd 34 2013年06月26日 [査読無し][通常論文]
  • 久我ゆかり, 坂本直哉, 圦本尚義 日本土壌微生物学会講演要旨集 2013 23 2013年06月19日 [査読無し][通常論文]
  • 佐々木宗輝, 本郷裕美, 小林幸雄, 圦本尚義, 網塚憲生 日本骨形態計測学会雑誌 23 (1) S81 -S81 2013年06月10日 [査読無し][通常論文]
  • 圦本尚義 分析化学討論会講演要旨集 73rd 24 2013年05月04日 [査読無し][通常論文]
  • 小笠原希実, 坂本直哉, 伊藤利章, 圦本尚義, 内藤哲, 高野順平 日本植物生理学会年会要旨集 54th 335 2013年03月14日 [査読無し][通常論文]
  • 佐々木宗輝, 本郷裕美, 小林幸雄, 圦本尚義, 網塚憲生 Journal of Oral Biosciences Supplement (Web) 2013 ROMBUNNO.O‐112 (WEB ONLY) 2013年 [査読無し][通常論文]
  • 北村 啓太朗, 海野 進, 金山 恭子, 石塚 治, 坂本 直哉, 圦本 尚義 日本火山学会講演予稿集 2013 (0) 2013年 [査読無し][通常論文]
  • 圦本尚義 日本地球化学会年会講演要旨集 60th 200 2013年 [査読無し][通常論文]
  • 北村啓太朗, 海野進, 金山恭子, 石塚治, 坂本直哉, 圦本尚義 日本火山学会講演予稿集 2013 91 2013年 [査読無し][通常論文]
  • 伊藤 正一, 柳井 佳穂里, サラ ラッセル, ジム グリーンウッド, 圦本 尚義 日本地球化学会年会要旨集 60 (0) 3 -3 2013年 [査読無し][通常論文]
     
    隕石母天体内での流体（H2O)のふるまいは，これまで全く不明瞭であった．これら流体のふるまいに制約を与えるため，近年，リン酸塩鉱物の岩石学的，同位体的研究が盛んに行われてきた（e.g., Jones et al., 2011; Yanai et al., 2012). 本講演では，系統的に，熱変成度の異なるLL4-6のリン酸塩鉱物に含まれる微量結晶水の定量及び水素同位体組成を報告する予定である．
  • 馬上 謙一, 坂口 勲, 鈴木 拓, 糸瀬 悟, 松谷 幸, 工藤 政都, 石原 盛男, 内野 喜一郎, 圦本 尚義 日本地球化学会年会要旨集 60 (0) 8 -8 2013年 [査読無し][通常論文]
     
    Nagao et al. (2011) によるはやぶさ試料の希ガス同位体分析は太陽風照射とそれに伴う太陽風起源He/Ne間の分別を明らかにした．しかし，希ガス分析は粒子一粒ごとの結果でありSTEM観察との直接比較を行うには希ガス分析事前にSTEM観察を行うなど，分析方法の工夫が必要である．そこで，我々が開発したポストイオン化二次イオン質量分析装置LIMAS(Laser Ionization Mass Nanoscope)を用いることで，希ガス同位体分析を数十nmスケールの空間分解能で行うことが可能となり得る．本発表では新しい局所希ガス同位体分析手法をもとに，イトカワ表層での太陽風照射の履歴に関して期待される結果について述べる．
  • 北村 啓太朗, 海野 進, 金山 恭子, 石塚 治, 坂本 直哉, 圦本 尚義 日本火山学会講演予稿集 2013 (0) 91 -91 2013年 [査読無し][通常論文]
  • 吉村 俊平, 中村 美千彦, 圦本 尚義 日本鉱物科学会年会講演要旨集 2012 (0) 29 -29 2012年09月15日 [査読無し][通常論文]
     
    ピストンシリンダ型高温高圧発生装置を用い，1200 &deg;C・10 kbarの条件における花崗岩質メルトとCO<sub>2</sub>に富む流体との間の炭素同位体分別実験を行った．気体質量分析計を用いて同位体組成を分析した結果，&Delta;<sub>f-m=</sub> +0.8&permil;の同位体分別が認められた．また，赤外分光分析により，メルト中のCO<sub>2</sub>溶存化学種としては，CO<sub>2</sub>分子とCO<sub>3</sub><sup>2-</sup>の両方が確認された．炭素同位体分別は，CO<sub>2</sub>分子の寄与とCO<sub>3</sub><sup>2-</sup>の寄与の線形結合によってあらわされた．
  • M. Inoue, S. Itoh, H. Yurimoto, M. Kimura, N. Nakamura METEORITICS & PLANETARY SCIENCE 47 A207 -A207 2012年07月 [査読無し][通常論文]
  • 圦本 尚義, 坂本 直哉 顕微鏡 = Microscopy 47 (2) 92 -97 2012年06月30日 [査読無し][通常論文]
     

    太陽系の起源の研究法として宇宙物質を実験室で分析する方法がある．宇宙物質は微細な組織を持っているため顕微鏡法が非常に有効な手段である．また，宇宙においては物質間の同位体組成の違いが顕著である場合が多いため，同位体は物質の起源や進化のトレーサーとして有効である．同位体は質量分析法により測定されるが微細構造を持つ物質には適用が限られていた．最近，同位体顕微鏡という装置が開発され質量分析法と顕微鏡法が融合した．それにより，同位体をトレーサーとして微細組織の形成を可視化し，解析できるようになった．本稿では，同位体顕微鏡により初めて明らかになった太陽系最古の物質，恒星の残骸物質，分子雲の氷の化石の研究について解説する．

  • 圦本尚義 応用物理学関係連合講演会講演予稿集(CD-ROM) 59th ROMBUNNO.15P-B11-1 2012年02月29日 [査読無し][通常論文]
  • 坂口勲, 坂本直哉, 圦本尚義, 大橋直樹, 菱田俊一 セラミックス基礎科学討論会講演要旨集 50th 21 2012年01月12日 [査読無し][通常論文]
  • 橋口 未奈子, 小林 幸雄, 圦本 尚義 日本地球化学会年会要旨集 59 (0) 267 -267 2012年 [査読無し][通常論文]
     
    本発表では，始原的隕石中の有機物の水素・窒素同位体組成，そして有機物の形状について報告する．マーチソン隕石 (CM2)とNWA 801隕石 (CR2)マトリックスから，マトリックスの同位体比よりDまたは15Nに富む有機物を発見した． マーチソン隕石とNWA 801隕石におけるDに富む有機物と15Nに富む有機物の割合から，水質変質の進行によってマーチソン隕石では有機物のDの過剰が優先的に消失したことが考えられた．Dまたは15Nに富む有機物の形状は，複数の粒子の集合体 (アグリゲイト)または単独の粒子であり，マーチソン隕石とNWA 801隕石の有機物には， (アグリゲイト/単独の粒子)比に違いが見られた．形状からDに富む有機物と15Nに富む有機物を判別することは出来ず，隕石中の有機物がその形成時に同位体比が一定の値であったとすると，(アグリゲイト/単独の粒子)比の違いは，隕石母天体周囲の環境あるいは集積プロセスの違いを反映している可能性がある．
  • 若木 重行, 伊藤 正一, 田中 剛, 圦本 尚義 日本地球化学会年会要旨集 59 (0) 280 -280 2012年 [査読無し][通常論文]
     
    CAIとコンドリュールは、原始太陽系星雲内で異なる時間に異なる条件で溶融したと考えられているが、これらの物質の溶融を引き起こした物理的プロセスが同一であるか、その物理的プロセスの詳細は明らかになっていない。本研究では、CAI-コンドリュール複合物質の形成年代および溶融条件を明らかにする事を目的として、SIMSによるAl-Mg系同位体分析を行った。複合物質のオリビンと斜長石は、CAI形成後3.4Myに相当するisochronを形成した。一方で溶融残渣と考えられるスピネルは上記isochronとCanonical isochronとの中間に分布し、そのMg同位体組成は複合物質形成イベントによって不完全に(45-98%程度)リセットされたと考えられる。スピネルのみが溶け残る温度条件は岩石学的に1380-1480℃と見積もれる。スピネル中のMg拡散モデルから、溶融時間は50s-7hと見積もられた
  • 馬上 謙一, 工藤 政都, 江端 新吾, 藤岡 修, 坂口 勲, 圦本 尚義, 内野 喜一郎, 石原 盛男, 糸瀬 悟, 松谷 幸 日本地球化学会年会要旨集 59 (0) 286 -286 2012年 [査読無し][通常論文]
     
    二次イオン質量分析は高い空間分解能と多元素の高感度な定量が出来るため微小領域の同位体分析において重用されている。しかしながら希ガスはイオン化ポテンシャルが高いことと含有量が微量であることから、天然試料のSIMSでの分析は不可能であった。そこで我々はLaser Ionization MAss nanoScopeを用いて希ガス同位体分析を天然試料に適応するための開発を行っている。この装置は一次イオンビームによりスパッタされた希ガス原子をフェムト秒レーザーによりポストイオン化させることが可能である。従来の希ガス局所分析の空間分解能は100 μm程度であったが、LIMASではサブミクロン(最高空間分解能10 nm)で分析が可能である。この装置を用いてレゴリスブレッチャの太陽風起源希ガスの2次元分布を分析することにより、小惑星表層を覆うレゴリスの形成過程を明らかにすることが本研究の主題である。
  • 吉村 俊平, 中村 美千彦, 圦本 尚義 日本鉱物科学会年会講演要旨集 2012 (0) 28 -28 2012年 [査読無し][通常論文]
     
    ピストンシリンダ型高温高圧発生装置を用い，1200 °C・10 kbarの条件における花崗岩質メルトとCO2に富む流体との間の炭素同位体分別実験を行った．気体質量分析計を用いて同位体組成を分析した結果，Δf-m= +0.8‰の同位体分別が認められた．また，赤外分光分析により，メルト中のCO2溶存化学種としては，CO2分子とCO32-の両方が確認された．炭素同位体分別は，CO2分子の寄与とCO32-の寄与の線形結合によってあらわされた．
  • Zhang Aicheng, 伊藤 正一, 坂本 直哉, 圦本 尚義, Wang Rucheng 日本地球化学会年会要旨集 59 (0) 269 -269 2012年 [査読無し][通常論文]
     
    We report mineralogy， oxygen isotopic and rare-earth-element compositions of a sapphirine-bearing Al-rich chondrule (SARC) from the Dar al Gani (DaG) 978 ungrouped carbonaceous chondrite. Our results indicate that the precursor of SARC included Group II CAIs as components. Assimilation of incompletely melted amoeboid olivine aggregate also occurred during formation of the ferromagnesian rim in SARC.
  • 圦本 尚義 現代化学 (489) 23 -28 2011年12月 [査読無し][通常論文]
  • 圦本 尚義, 石原 盛男, 内野 喜一郎, 江端 新吾 應用物理 80 (11) 979 -982 2011年11月10日 [査読無し][通常論文]
     

    小惑星はやぶさが持ち帰った宇宙試料を分析するために，Gaイオン粒子でスパッタされた2次中性粒子をフェムト秒レーザーでイオン化する質量分析法を開発してきた．質量分析には多重周回飛行時間型質量分析器を用いている．現在，サンプル上で40nmの空間分解能とHeなどの希ガスを含む全元素のポストイオン化に成功している．本分析法を宇宙試料に適用することにより，太陽系誕生時の太陽活動の記録や太陽系誕生以前に形成した微粒子の年代測定が可能になると考えられる．

  • 井上徹, 矢吹智美, 圦本尚義 高圧討論会講演要旨集 52nd 25 2011年10月25日 [査読無し][通常論文]
  • 圦本 尚義, 中村 智樹, 伊藤 正一, 坂本 直哉, 阿部 憲一, 橋口 未奈子, 片山 樹里, 加藤 千図, 川崎 教行, 小林 幸雄, 女池 竜二, 朴 昌根, 武井 将志, 若木 重行, 山本 広佑, 橋爪 光, 土山 明, 瀬戸 雄介, 長尾 敬介, 野口 高明, 海老原 充, 奈良岡 浩, 北島 富美雄, 岡崎 隆司, Ireland T.R., Zolensky M.E., 阿部 正真, 藤村 彰夫, 川口 淳一郎, 向井 利典, 上椙 真之, 矢田 達, 吉川 真 日本惑星科学会秋期講演会予稿集 2011 15 -15 2011年10月23日 [査読無し][通常論文]
  • 海老原 充, 関本 俊, 白井 直樹, 浜島 靖典, 山本 政儀, 熊谷 和也, 大浦 泰嗣, Ireland Trever, 北島 富美雄, 長尾 敬介, 中村 智樹, 奈良岡 浩, 野口 高明, 岡崎 隆司, 土山 明, 上椙 真之, 圦本 尚義, Zolensky Michael, 安部 正真, 藤村 彰夫, 向井 利典, 矢田 達 日本惑星科学会秋期講演会予稿集 2011 (2011) 16 -16 2011年10月23日 [査読無し][通常論文]
     
    本文データは学協会の許諾に基づきCiNiiから複製したものである
  • 土山 明, 上椙 真之, 松島 亘志, 道上 達弘, 門野 敏彦, 中村 智樹, 上杉 健太朗, 中野 司, Sandford Scott A., 野口 遼, 松本 徹, 松野 淳也, 永野 崇, 今井 悠太, 竹内 晃久, 鈴木 芳生, 大神 稔皓, 片桐 淳, 海老原 充, Ireland Trevor, 北島 富美雄, 長尾 敬介, 奈良岡 浩, 野口 高明, 岡崎 隆司, 圦本 尚義, Zolensky Michael, はやぶさキュレーションチーム 日本惑星科学会秋期講演会予稿集 2011 18 -18 2011年10月23日 [査読無し][通常論文]
  • 長尾 敬介, 岡崎 隆司, 中村 智樹, 三浦 弥生, 大澤 崇人, 馬上 謙一, 松田 伸太郎, 海老原 充, Ireland Trevor R., 北島 富美雄, 奈良岡 浩, 野口 高明, 土山 明, 上椙 真之, 圦本 尚義, Zolensky Michael E., 白井 慶, 安部 正真, 矢田 達, 石橋 之宏, 藤村 彰夫, 向井 利典, 上野 宗孝, 岡田 達明, 吉川 真, 川口 淳一郎 日本惑星科学会秋期講演会予稿集 2011 19 -19 2011年10月23日 [査読無し][通常論文]
  • 井上 徹, 矢吹 智美, 圦本 尚義 日本鉱物科学会年会講演要旨集 2011 228 -228 2011年09月05日 [査読無し][通常論文]
     
    地球内部に存在可能な相の含水量を明らかに知ることは、地球内部の状態や物性を推定する上で重要となる。水は鉱物の融点を下げる以外に、各種物性に大きく影響を及ぼすからである。このような理由から現在までにカンラン石、輝石、ザクロ石などのいわゆるnominally anhydrous minerals、及び高圧含水相の含水量が明らかにされてきている。さらにAl3+はH+とのカップリングによって鉱物中の含水量を増加させる傾向があることが想定され、その効果も研究されてきている。本研究では、pyrope – enstatite – H2O 系において660 km不連続面付近に相当する温度圧力条件でどのような相が生成されるかを明らかにし、その生成されたAlに富む鉱物中の含水量を測定した。
  • 木村(須田)廣美, 梶原誠, 坂本直哉, 小林幸雄, 居城邦治, 圦本尚義, 大和英之 J Oral Biosci 53 (Supplement) 84 -84 2011年09月01日 [査読無し][通常論文]
  • 木村 須田 廣美, 桑原 三恵子, 日高 公介, 金沢 恭祐, 本間 教嗣, 坂内 堅二, 菅野 三喜男, 梶原 誠, 大西 晃宏, 小林 幸雄, 坂本 直哉, 居城 邦治, 圦本 尚義, 大和 英之 バイオイメージング 20 (2) 95 -96 2011年08月10日 [査読無し][通常論文]
  • 木村(須田, 廣美, 桑原三恵子, 日高公介, 金沢恭祐, 本間教嗣, 坂内堅二, 菅野三喜男, 梶原誠, 大西晃宏, 小林幸雄, 坂本直哉, 居城邦治, 圦本尚義, 大和英之 バイオイメージング 20 (2) 95 -96 2011年08月10日 [査読無し][通常論文]
  • 木村 廣美, 須田, 桑原 三恵子, 日高 公介, 金沢 恭祐, 本間 教嗣, 坂内 堅二, 菅野 三喜男, 梶原 誠, 大西 晃宏, 小林 幸雄, 坂本 直哉, 居城 邦治, 圦本 尚義, 大和 英之 バイオイメージング 20 (2) 95 -96 2011年08月 [査読無し][通常論文]
  • K. Nagao, R. Okazaki, T. Nakamura, Y. N. Miura, T. Osawa, K. Bajo, S. Matsuda, M. Ebihara, T. R. Ireland, F. Kitajima, H. Naraoka, T. Noguchi, A. Tsuchiyama, M. Uesugi, H. Yurimoto, M. E. Zolensky, K. Shirai, M. Abe, T. Yada, Y. Ishibashi, A. Fujimura, T. Mukai, M. Ueno, T. Okada, M. Yoshikawa, J. Kawaguchi METEORITICS & PLANETARY SCIENCE 46 A171 -A171 2011年07月 [査読無し][通常論文]
  • H. Yurimoto, K. Abe, M. Abe, M. Ebihara, A. Fujimura, M. Hashiguchi, K. Hashizume, T. R. Ireland, S. Itoh, J. Katayama, C. Kato, J. Kawaguchi, N. Kawasaki, F. Kitajima, S. Kobayashi, T. Meike, T. Mukai, K. Nagao, T. Nakamura, H. Naraoka, T. Noguchi, R. Okazaki, C. Park, N. Sakamoto, Y. Seto, M. Takei, A. Tsuchiyama, M. Uesugi, S. Wakaki, T. Yada, K. Yamamoto, M. Yoshikawa, M. E. Zolensky METEORITICS & PLANETARY SCIENCE 46 A260 -A260 2011年07月 [査読無し][通常論文]
  • 圦本 尚義 Isotope news (686) 17 -21 2011年06月01日 [査読無し][通常論文]
  • 日高公介, 桑原三重子, 金沢恭祐, 大西晃宏, 坂内堅二, 菅野三喜男, 小林幸雄, 圦本尚義, 大和英之, 木村(須田)廣美 高分子学会予稿集(CD-ROM) 60 (1 Disk1) ROMBUNNO.1PB148 2011年05月10日 [査読無し][通常論文]
  • 圦本 尚義 理大科学フォーラム 28 (5) 40 -44 2011年05月 [査読無し][通常論文]
  • MIYAWAKI RITSURO, SHIMAZAKI HIDEHIKO, SHIGEOKA MASAKO, YOKOYAMA KAZUMI, MATSUBARA SATOSHI, YURIMOTO HISAYOSHI, YANG ZHUMING, ZHANG PEISHAN Clay science 15 (1) 13 -18 2011年03月01日 
    Two new species of F-mica, fluorokinoshitalite (BaMg_3Al_2Si_2O_<10>F_2) and fluorotetraferriphlogopite (KMg_3Fe^<3+>Si_3O_<10>F_2) occur in Bayan Obo, Inner Mongolia, China. They form subhedral to euhedral platy crystals in metamorphosed carbonate rocks. They are associated with phlogopite, yangzhumingite, and rare earth minerals such as bastnasite-(Ce), cordylite-(Ce), monazite-(Ce), fluorbritholite-(Ce) and huanghoite-(Ce). Fluorokinoshitalite is transparent and colorless with white streak and pearly luster. Cleavage is perfect on {001}. The calculated density is 3.235g cm^<-3>. Fluorotetraferriphlogopite is brown in color with white to pale brown streak. It is transparent showing pearly luster and perfect cleavage on {001}. The hardness is 3-4 on the Mohs scale. The calculated density is 2.966g cm^<-3>. This mineral is optically biaxial (-) with n=1.576 (min.)-1.582 (max.). It shows reverse pleochroism (Z'=colorless, X'=light brown). Electron microprobe analyses with SIMS for Li gave empirical formulae (based on 12 anions); (Ba_<0.56>Na_<0.25>K_<0.06>)(Mg_<2.76>Fe^<2+>_<0.14>Ti_<0.01>) (Si_<2.73>Al_<1.15>Fe^<3+>_<0.12>)O_<10>[F_<1.72>(OH)_<0.28>] and (K_<0.94>Na_<0.02>Ba_<0.01>)(Mg_<2.62>Li_<0.15>Fe^<+2>_<0.14>_Mn_<0.01>)(Si_<3.33>Fe^<3+>_<0.66>Al_<0.01>)O_<10>[F_<1.65>(OH)_<0.35>] for fluorokinoshitalite and fluorotetraferriphlogopite, respectively. The lattice parameters were refined in the monoclinic system (C2/m) with the XRD data obtained with an IP-Gandolfi camera as; a=5.3161 (11), b=9.2082(15), c=10.044(2) Å, β=100.158(18)°, V=483.97(17) Å^3 (fluorokinoshitalite) and a=5.325(3), b=9.217(5), c=10.192(7) Å, β=100.03(5)°, V=492.6(5) Å^3 (fluorotetraferriphlogopite).
  • 奈良岡浩, 三田肇, 浜瀬健司, 斎藤香織, 福島和彦, 藪田ひかる, 北島富美雄, SANDFORD Scott, 岡崎隆司, 野口高明, 中村智樹, 長尾敬介, 海老原充, 圦本尚義, 土山明, 安部正真, 白井慶, 上野宗孝, 矢田達, 石橋之宏, 岡田達明, 藤村彰夫, 向井利典, 吉川真, 川口淳一郎 日本惑星科学会秋季講演会予稿集(Web) 2011 2011年
  • 北島富美雄, 小嗣真人, 大河内拓雄, 奈良岡浩, 石橋之宏, 安部正真, 藤村彰夫, 岡崎隆司, 矢田達, 中村智樹, 野口高明, 長尾敬介, 土山明, 圦本尚義, 海老原充, 向井利典, SANDFORD Scott A., 岡田達明, 白井慶, 上野宗孝, 吉川真, 川口淳一郎 日本惑星科学会秋季講演会予稿集(Web) 2011 2011年
  • 圦本尚義, 伊藤正一, 坂本直哉, 小林幸雄, 橋爪光, 土山明, 瀬戸雄介, IRELAND T. R, ZOLENSKY M, 中村智樹, 野口高明, 長尾敬介, 海老原充, 奈良岡浩, 岡崎隆一, 北島富美雄, 向井利典, 藤村彰夫, 安部正真, 矢田達, 上椙真之, 吉川真, 川口淳一郎 日本地球化学会年会講演要旨集 58th 179 -171 2011年 [査読無し][通常論文]
     
    太陽系形成期の研究は，主に隕石を参照することにより検証がおこなわれ，進展して来た．隕石は小惑星の破片であるといわれているが，母天体となる小惑星が確認されている隕石は一つもない．小惑星イトカワにタッチダウンした惑星探査機はやぶさが，昨年，小惑星イトカワの表面物質を地球に持ち帰った．採取された試料は，最大で数百ミクロンの微粒子であるが，これらの試料を分析することにより，小惑星と隕石との関係の一部が初めて明らかになっていくことが期待される． 本講演では，酸素同位体組成，マグネシウム同位体組成戸26Al，微量元素組成について報告する．
  • 橋口 未奈子, 小林 幸雄, 圦本 尚義 日本地球化学会年会要旨集 58 (0) 290 -290 2011年 [査読無し][通常論文]
     
    始原的隕石中の重水素に富む有機物と水素同位体異常を示さない有機物に対し，ラマン分光分析を行った．重水素に富む有機物とマトリックスのラマンスペクトルには，どちらも，Gバンド (約1580 cm-1)とDバンド (約1370 cm-1)が見られた．これは，隕石有機物が示す典型的なラマンスペクトルである．また，重水素に富む有機物の方が，水素同位体異常を示さない有機物と比較してDバンドの半値幅, DバンドとGバンドの強度比が小さいことが分かった．この結果は，重水素に富む有機物と水素同位体異常を示さない有機物とでは構造が異なることを示唆しており，前者の方が少し構造が単純であると考えられる．
  • 伊藤 正一, サイモン スティーブン, グロスマン ローレンス, 圦本 尚義 日本地球化学会年会要旨集 58 (0) 223 -223 2011年 [査読無し][通常論文]
     
    本講演では，部分溶融を経験している二つのTypeB CAI（Golfball, TS34)の酸素同位体組成及びAl-Mg同位体組成を組み合わせ，部分溶融による鉱物アイソクロンへの影響を議論する．これまで，分析精度の制約により，低いAl-Mg比をもつ鉱物のアイソクロンは不明瞭であったため，本研究では，二次イオン質量分析計による高精度局所同位体分析により，結晶化時期が異なると考えられている低いAl/Mg比をもつ各鉱物のアイソクロンを含めた鉱物アイソクロンを議論し，CAIの部分溶融と年代の関係を議論する．
  • 片山 樹里, 伊藤 正一, 圦本 尚義 日本地球化学会年会要旨集 58 (0) 179 -179 2011年 [査読無し][通常論文]
     
    Fluffy Type A CAI (FTA)の3つのメリライト単結晶中の逆累帯構造にともなう酸素同位体組成変化を評価した．各結晶コア部の酸素同位体組成は異なり，累帯構造に伴う酸素同位体組成の変化の大きさやそのゾーニングの幅も異なっていた．本講演では，累帯構造に対応して単結晶内に存在した酸素同位体組成の変化に着目し，Fluffy Type A CAIの形成環境を評価する．
  • 川崎 教行, 坂本 直哉, 圦本 尚義 日本地球化学会年会要旨集 58 (0) 178 -178 2011年 [査読無し][通常論文]
     
    本研究では，エフレモフカCV3コンドライト中のFluffy Type A CAIの岩石学的記載と，累帯構造を持つメリライト結晶の固溶体組成および酸素同位体組成の分析を行った．本CAIは，内部にWark-Loveringリムの断片のような構造があり，領域によって岩石学的特徴が異なることから，大きく4つのドメインに分類できる．各ドメインはその構造，鉱物組合せなどが異なり，特に2つのドメインのメリライトの固溶体組成と酸素同位体組成に違いが見られた．各ドメインの境界は大部分はWark-Loveringリムやその断片のような構造で区切られており，各ドメインは別々に形成され集合したものであると考えられる．
  • 馬上 謙一, 江端 新吾, 内野 喜一郎, 石原 盛男, 糸瀬 悟, 松谷 幸, 工藤 政都, 圦本 尚義 日本地球化学会年会要旨集 58 (0) 177 -177 2011年 [査読無し][通常論文]
     
    二次イオン質量分析は高い空間分解能と多元素の高感度な定量が出来るため微小領域の同位体分析において重用されている。しかしながら希ガスはイオン化ポテンシャルが高いことと、含有量が極微量であることから二次イオン質量分析での分析は不可能であった。そこで発表者らは新たに開発された超高感度極微量質量分析システムを用いて希ガス同位体分析を試みている。このシステムでは一次イオンビームによりスパッタされた希ガス原子を高光子密度のレーザーを照射することにより希ガス原子をイオン化させることができる。発表者らは隕石中の太陽風起源希ガスに注目して実験を行っており、今後はSolar-gas-rich 隕石から太陽風起源希ガス同位体の検出を試みる予定である。
  • 江端 新吾, 馬上 謙一, 内野 喜一郎, 石原 盛男, 糸瀬 悟, 松谷 幸, 工藤 政都, 圦本 尚義 日本地球化学会年会要旨集 58 (0) 176 -176 2011年 [査読無し][通常論文]
     
    サンプルリターンミッションは宇宙地球科学に多数の新知見をもたらした．しかし，サンプルリターンミッションにより得られる試料は極微量であり，詳細に分析するには微小領域を高感度で分析可能な装置が必要である．我々は超高感度極微量質量分析システムLIMAS（Laser Ionization Mass Nanoscope）の開発を行なってきた．本発表ではLIMASの現時点での性能と今後の展望について報告する．
  • 圦本 尚義, 中村 智樹, 野口 高明, 長尾 敬介, 海老原 充, 奈良岡 浩, 岡崎 隆一, 北島 富美雄, 向井 利典, 藤村 彰夫, 安部 正真, 伊藤 正一, 矢田 達, 上椙 真之, 吉川 真, 川口 淳一郎, 坂本 直哉, 小林 幸雄, 橋爪 光, 土`山 明, 瀬戸 雄介, T. R. Ireland, M. Zolensky 日本地球化学会年会要旨集 58 (0) 171 -171 2011年 [査読無し][通常論文]
     
    太陽系形成期の研究は，主に隕石を参照することにより検証がおこなわれ，進展して来た．隕石は小惑星の破片であるといわれているが，母天体となる小惑星が確認されている隕石は一つもない．小惑星イトカワにタッチダウンした惑星探査機はやぶさが，昨年，小惑星イトカワの表面物質を地球に持ち帰った．採取された試料は，最大で数百ミクロンの微粒子であるが，これらの試料を分析することにより，小惑星と隕石との関係の一部が初めて明らかになっていくことが期待される． 本講演では，酸素同位体組成，マグネシウム同位体組成戸26Al，微量元素組成について報告する．
  • 土山 明, 野口 遼, 松本 徹, 松野 淳也, 永野 崇, 今井 悠太, 竹内 晃久, 鈴木 芳生, 大神 稔皓, 片桐 淳, 海老原 充, 上椙 真之, アイルランド トレバー, 北島 富美雄, 長尾 敬介, 奈良岡 浩, 野口 高明, 岡崎 隆司, 圦本 尚義, ゾレンスキー マイケル, はやぶさ キュレーションチーム, 松島 亘志, 道上 達弘, 門野 敏彦, 中村 智樹, 上杉 健太朗, 中野 司, スコット サンドフォード 日本地球化学会年会要旨集 58 (0) 169 -169 2011年 [査読無し][通常論文]
     
    はやぶさ探査機が採取した粒子は小惑星イトカワのレゴリス粒子であると考えられる。これらの粒子の初期分析として、粒子の３次元構造と外形をSPring-8においてX線マイクロCTにより求めた。これより求めた粒子全体の鉱物モード組成や密度はLLコンドライトのものと類似していた。粒子には、月レゴリスのアグルーチネートのような融解組織は見られなかった。粒子のサイズ分布や３次元形状分布も、月レゴリスとは異なるものであった。これらのデータより、イトカワ表面でのレゴリス粒子の生成と進化について議論する。
  • 井上 徹, 矢吹 智美, 圦本 尚義 日本鉱物科学会年会講演要旨集 2011 (0) 224 -224 2011年 [査読無し][通常論文]
     
    地球内部に存在可能な相の含水量を明らかに知ることは、地球内部の状態や物性を推定する上で重要となる。水は鉱物の融点を下げる以外に、各種物性に大きく影響を及ぼすからである。このような理由から現在までにカンラン石、輝石、ザクロ石などのいわゆるnominally anhydrous minerals、及び高圧含水相の含水量が明らかにされてきている。さらにAl3+はH+とのカップリングによって鉱物中の含水量を増加させる傾向があることが想定され、その効果も研究されてきている。本研究では、pyrope – enstatite – H2O 系において660 km不連続面付近に相当する温度圧力条件でどのような相が生成されるかを明らかにし、その生成されたAlに富む鉱物中の含水量を測定した。
  • 土`山 明, 野口 遼, 松本 徹, 松野 淳也, 永野 崇, 今井 悠太, 竹内 晃久, 鈴木 芳生, 大神 稔皓, 片桐 淳, 海老原 充, 上椙 真之, アイルランド トレバー, 北島 富美雄, 長尾 敬介, 奈良岡 浩, 野口 高明, 岡崎 隆司, 圦本 尚義, ゾレンスキー マイク, 向井 利典, 安部 正真, 松島 亘志, 矢田 達, 藤村 彰夫, 吉川 真, 川口 淳一郎, 道上 達弘, 門野 敏彦, 中村 智樹, 上杉 健太朗, 中野 司, サンドフォード スコット 日本地質学会学術大会講演要旨 2011 (0) 1 -1 2011年 [査読無し][通常論文]
  • 大谷 栄治, 木村 淳, 高橋 幸弘, 中島 健介, 中本 泰史, 三好 由純, 小林 憲正, 山岸 明彦, 並木 則行, 小林 直樹, 出村 裕英, 倉本 圭, 大槻 圭史, 今村 剛, 寺田 直樹, 渡部 重十, 荒川 政彦, 伊藤 孝士, 圦本 尚義, 渡部 潤一 日本惑星科学会誌遊星人 20 (4) 349 -365 2011年 [査読無し][通常論文]
     
    「月惑星探査の来たる10年」検討では第一段階で5つのパネルの各分野に於ける第一級の科学について議論した.そのとりまとめを報告する.地球型惑星固体探査パネルでは,月惑星内部構造の解明,年代学・物質科学の展開による月惑星進化の解明,固体部分と結合した表層環境の変動性の解明,が挙げられた.地球型惑星大気・磁気圏探査パネルは複数学会に跨がる学際性を考慮して,提案内容に学会間で齟齬が生じないように現在も摺り合わせを進めている.本稿では主たる対象天体を火星にしぼって第一級の科学を論じる.小天体パネルでは始原的・より未分化な天体への段階的な探査と,発見段階から理解段階へ進むための同一小天体の再探査が提案された.木星型惑星・氷衛星・系外惑星パネルは広範な科学テーマの中から,木星の大気と磁気圏探査,氷衛星でのハビタブル環境の探査,系外惑星でも生命存在可能環境と生命兆候の発見について具体的な議論を行った.アストロバイオロジーパネルでは現実的な近未来の目標として火星生命探査を,長期的な目標として氷衛星・小天体生命探査を目指した観測装置開発が検討された.これらのまとめを元に「月惑星探査の来たる10年」検討は2011年7月より第二段階に移行し,ミッション提案・観測機器提案の応募を受け付けた.
  • 江端新吾, 石原盛男, 公文代康介, 身深亮, 内野喜一郎, 圦本尚義 日本惑星科学会誌 遊・星・人 19 (4) 295 -304 2010年12月25日 [査読無し][通常論文]
  • 阿部憲一, 坂本直哉, 圦本尚義 日本惑星科学会誌 遊・星・人 19 (4) 268 -272 2010年12月25日 [査読無し][通常論文]
  • 阿部 憲一, 坂本 直哉, 圦本 尚義 遊・星・人 : 日本惑星科学会誌 19 (4) 268 -272 2010年12月25日 [査読無し][通常論文]
     
    <特集>初期太陽系物質科学の最前線
  • 江端 新吾, 石原 盛男, 公文代 康介, 身深 亮, 内野 喜一郎, 圦本 尚義 遊・星・人 : 日本惑星科学会誌 19 (4) 295 -304 2010年12月25日 [査読無し][通常論文]
     
    <特集>初期太陽系物質科学の最前線
  • 土山 明, 海老原 充, 北島 冨美雄, 長尾 敬介, 中村 智樹, 奈良岡 浩, 野口 高明, 岡崎 隆司, 上椙 真之, 圦本 尚義, 初期分析メンバー 日本鉱物科学会年会講演要旨集 2010 65 -65 2010年09月23日 [査読無し][通常論文]
  • 圦本 尚義, 杉田 精司, 橘 省吾 日本鉱物科学会年会講演要旨集 2010 69 -69 2010年09月23日 [査読無し][通常論文]
  • 甕 聡子, 永井 隆哉, 岨 康輝, 渡邊 剛, 坂本 直哉, 圦本 尚義 日本鉱物科学会年会講演要旨集 2010 84 -84 2010年09月23日 [査読無し][通常論文]
  • 瀬戸 雄介, 藤 昇一, 坂本 直哉, 圦本 尚義 日本鉱物科学会年会講演要旨集 2010 157 -157 2010年09月23日 [査読無し][通常論文]
  • 宮脇律郎, 島崎英彦, 重岡昌子, 横山一己, 松原聰, 圦本尚義, 楊主明 粘土科学討論会講演要旨集 54th 58 -59 2010年09月07日 [査読無し][通常論文]
  • 宮脇 律郎, 島崎 英彦, 重岡 昌子, 横山 一己, 松原 聰, 圦本 尚義, 楊 主明 粘土科学討論会講演要旨集 (54) 58 -59 2010年09月07日 [査読無し][通常論文]
  • 山本広佑, 坂本直哉, 西尾崇, 居城邦治, 圦本尚義 日本分析化学会年会講演要旨集 59th 168 2010年09月01日 [査読無し][通常論文]
  • 木村(須田)廣美, 梶原誠, 坂本直哉, 小林幸雄, 居城邦治, 圦本尚義, 大和英之 高分子学会予稿集(CD-ROM) 59 (2 Disk1) ROMBUNNO.2PE123 2010年09月01日 [査読無し][通常論文]
  • C. Park, S. Wakaki, H. Yurimoto METEORITICS & PLANETARY SCIENCE 45 A162 -A162 2010年07月 [査読無し][通常論文]
  • H. Yurimoto, S. Itoh, M. E. Zolensky, M. Kusakabe, A. Karen METEORITICS & PLANETARY SCIENCE 45 A222 -A222 2010年07月 [査読無し][通常論文]
  • B. G. Choi, K. Ziegler, J. T. Wasson, E. Young, S. Itoh, H. Yurimoto METEORITICS & PLANETARY SCIENCE 45 A35 -A35 2010年07月 [査読無し][通常論文]
  • M. Hashiguchi, S. Kobayashi, H. Yurimoto METEORITICS & PLANETARY SCIENCE 45 A78 -A78 2010年07月 [査読無し][通常論文]
  • J. P. Greenwood, S. Itoh, N. Sakamoto, E. P. Vicenzi, H. Yurimoto METEORITICS & PLANETARY SCIENCE 45 A68 -A68 2010年07月 [査読無し][通常論文]
  • 山崎 大輔, HEGODA Chamathni, DOHMEN Ralf, 圦本 尚義, CHAKRABORTY Sumit, 桂 智男 日本鉱物科学会年会講演要旨集 2009 199 -199 2010年04月07日 [査読無し][通常論文]
  • 小林 幸雄, 永島 一秀, 殿谷 梓, 坂本 直哉, 伊藤 正一, RUSSELL S. S., KROT Alexander N., 圦本 尚義 日本鉱物科学会年会講演要旨集 2009 223 -223 2010年04月07日 [査読無し][通常論文]
  • 阿部 憲一, 坂本 直哉, 小島 秀康, KROT A. N., RUSSELL S. S., 圦本 尚義 日本鉱物科学会年会講演要旨集 2009 224 -224 2010年04月07日 [査読無し][通常論文]
  • 伊藤 正一, SIMON S. B., GROSSMAN L., 圦本 尚義 日本鉱物科学会年会講演要旨集 2009 225 -225 2010年04月07日 [査読無し][通常論文]
  • 若木 重行, 伊藤 正一, 田中 剛, 圦本 尚義 日本鉱物科学会年会講演要旨集 2009 226 -226 2010年04月07日 [査読無し][通常論文]
  • 坂本 直哉, 青山 聡, 川人 祥二, 圦本 尚義 日本鉱物科学会年会講演要旨集 2009 236 -236 2010年04月07日 [査読無し][通常論文]
  • 宮脇 律郎, 島崎 英彦, 重岡 昌子, 横山 一己, 松原 聰, 圦本 尚義, 楊 主明 粘土科学討論会講演要旨集 54 (0) A11 -A11 2010年 [査読無し][通常論文]
     
    世界有数の希土類元素の鉱床である白雲鄂博の標本から，yangzhumingite[KMg2.5Si4O10F2]に続いて，フッ素雲母の新種が２種，確認された。これらはtetraferriphlogopite[KMg3Fe3+Si3O10(OH)2]と木下雲母[BaMg3(Si2Al2)O10(OH)2]のフッ素置換体に相当し，このたび国際鉱物学連合・新鉱物命名分類委員会から新鉱物として承認された。
  • 圦本尚義 宇宙航空研究開発機構特別資料 JAXA-SP- (10-001(CD-ROM)) DOITAINOIMEJINGU 2010年 [査読無し][通常論文]
  • 木村(須田)廣美, 梶原誠, 坂本直哉, 小林幸雄, 居城邦治, 圦本尚義, 大和英之 日本骨代謝学会学術集会プログラム抄録集 28th 163 -163 2010年 [査読無し][通常論文]
  • 山口紀子, 井上淳, 杉山真二, 小林幸雄, 圦本尚義, 平舘俊太郎 日本ペドロジー学会大会講演要旨集 49th 27 2010年 [査読無し][通常論文]
  • 瀬戸 雄介, 藤 昇一, 坂本 直哉, 圦本 尚義 日本鉱物科学会年会講演要旨集 2010 (0) 153 -153 2010年 [査読無し][通常論文]
     
    炭素質コンドライトAcfer 094のマトリックスに存在する異常な酸素同位体組成を持つ物質COS試料について透過電子顕微鏡(TEM)による原子スケールの詳細な観察を行い、その生成条件を検討した。観察の結果、構成鉱物であるmagnetiteとpyrrhotiteは100nm程度のオーダーで虫食い状に入り組んだ組織を示していた。magnetiteとpyrrhotiteの界面は直線的ではなくスムースな曲線(面)であり、界面に非晶質相が存在せず直に接触している。構成結晶や界面の方向はランダムで結晶学的に意味のある方位関係は見られなかった。このような微細結晶が互いに入り組んだ構造は、単なる機械的な混合過程では説明が難しいため、どちらかが母相でもう一方の子相が化学的に侵食したか、あるいは両方の結晶が同時期に成長した共晶組織である可能性が高い。
  • 土`山 明, 圦本 尚義, 初期分析 チーム, 海老原 充, 北島 冨美雄, 長尾 敬介, 中村 智樹, 奈良岡 浩, 野口 高明, 岡崎 隆司, 上椙 真之 日本鉱物科学会年会講演要旨集 2010 (0) 64 -64 2010年 [査読無し][通常論文]
     
    「はやぶさ」探査機は2005年11月に小惑星イトカワに着陸し、その表層サンプルの採取を試みた[1]。サンプリングは予定どおりにはおこなわれなかったが、大きさ数十ミクロンの少数の粒子が採集されたと期待されている。サンプルカプセルは2010年6月に地球に無事帰還し、現在開封作業がおこなわれている。サンプル粒子が存在すれば、最初の１年間での初期分析とその後の公募研究がおこなわれる予定である。これにより（a）イトカワの表面物質（反射スペクトルから推定された平衡LLコンドライトであるか）、（b）前世代天体での諸過程とイトカワへの集積過程（角礫化の有無、衝撃の程度など）、（c）宇宙環境との相互作用（宇宙風化の実証、太陽風酸素同位体組成など）、（d）小惑星表面へ降り注ぐ物質（例えば、地球上で汚染されていない有機物など）が明らかされるであろう。
  • 圦本 尚義, 杉田 精司, 橘 省吾 日本鉱物科学会年会講演要旨集 2010 (0) 68 -68 2010年 [査読無し][通常論文]
     
    はやぶさ」の成功により，計画中の始原的天体，および，火星へのサンプルリターンミッションが現実的である事が証明された．計画中のこれらのミッションは，太陽系の起源研究や初期惑星進化の物質科学的研究の新しい手段である事はいうまでもない．一般的に惑星探査は大型科学の典型の一つであるため，その成功には，個々の研究室を越えた組織作りが必要不可欠である．図１は，我々が提案するサンプルリターンミッション創成のための組織案である．本組織の従来と大きく異なる点は，産業界の参入を積極的に導入する点である．これにより，惑星科学・地球科学コミュニティーに工学的な要素を取り込み，ものつくりができる科学者を養成するとともに，宇宙物質という非日常的な試料を取り扱う新技術開発により新しい産業イノベーションのシーズを創出し産業界にフィードバックする．この観点は10年を越える長いサンプルリターンミッションのタイムスパンにおいて，その間ずっと研究者の科学・工学アクティビティーを高くするために必要な仕掛けでもある．
  • 甕 聡子, 永井 隆哉, 岨 康輝, 渡邊 剛, 坂本 直哉, 圦本 尚義 日本鉱物科学会年会講演要旨集 2010 (0) 82 -82 2010年 [査読無し][通常論文]
     
    造礁性サンゴ骨格はaragonite(CaCO3)から形成される．骨格に含まれる微量元素及び同位体比等は骨格生成時の周辺環境を反映し変動するとされ，この変動を用いて古環境復元が試みられている．しかし，古環境復元の精度に関係すると考えられるサンゴ骨格の形成メカニズムはいまだ解明されていない．そこで，サンゴ骨格中のnm～μmスケールの微小領域における鉱物組織・形態の観察から，サンゴ骨格を形成する鉱物相とその成長過程について鉱物学的な検討を行った．
    試料として現生の塊状サンゴ(Porites lobata)と樹枝状サンゴ(Acropora nobilis)を用いた．各薄片を光学顕微鏡で観察した後、TEMを用いて結晶形態観察と鉱物同定， FE-SEMを用いて元素濃度分布観察を行った．
  • 片山 樹里, 伊藤 正一, 圦本 尚義 日本地球化学会年会要旨集 57 (0) 266 -266 2010年 [査読無し][通常論文]
     
    Fluffy TypeA CAIのメリライト結晶の鉱物学的組織を解析し，固溶体成分の累帯構造に基づき，酸素同位体非平衡を再検討したので報告する．逆累帯構造をもつメリライト結晶を8個発見し，どの結晶も連続的にオケルマナイト成分(ak5)が3-25%の範囲で変化していた．Wark-Lovering (WL)リムに接していない鉱物間では，それぞれ異なるak組成範囲を示していたが，鉱物間の酸素同位体組成は，分析誤差範囲内でどれもほぼ均一な組成を示した．一方，WLリムに接している結晶３個は、鉱物内に酸素同位体非平衡な分布を示した（Δ17O= -20~ -5‰）。本講演では，累帯構造に基づいて単結晶内に存在した酸素同位体分布の変化に注目し， Fluffy Type A CAIの成因を評価していく。
  • 圦本尚義 日本分析化学会年会講演要旨集 58th 451 2009年09月10日 [査読無し][通常論文]
  • 宮脇 律郎, 島崎 英彦, 重岡 昌子, 横山 一己, 松原 聰, 圦本 尚義 粘土科学討論会講演要旨集 (53) 18 -19 2009年09月10日 [査読無し][通常論文]
  • 圦本尚義 臨床化学 38 (3) 272 -279 2009年07月31日 [査読無し][通常論文]
  • S. Itoh, S. B. Simon, L. Grossman, H. Yurimoto METEORITICS & PLANETARY SCIENCE 44 A98 -A98 2009年07月 [査読無し][通常論文]
  • K. Nagashima, A. N. Krot, G. R. Huss, H. Yurimoto METEORITICS & PLANETARY SCIENCE 44 A152 -A152 2009年07月 [査読無し][通常論文]
  • S. Ebata, H. Yurimoto METEORITICS & PLANETARY SCIENCE 44 A65 -A65 2009年07月 [査読無し][通常論文]
  • K. Abe, N. Sakamoto, H. Kojima, A. N. Krot, H. Yurimoto METEORITICS & PLANETARY SCIENCE 44 A15 -A15 2009年07月 [査読無し][通常論文]
  • N. Sakamoto, S. Aoyama, S. Kawahito, H. Yurimoto METEORITICS & PLANETARY SCIENCE 44 A181 -A181 2009年07月 [査読無し][通常論文]
  • S. Wakaki, S. Itoh, T. Tanaka, H. Yurimoto GEOCHIMICA ET COSMOCHIMICA ACTA 73 (13) A1401 -A1401 2009年06月 [査読無し][通常論文]
  • Y. Tasai, T. J. Fagan, S. Itoh, H. Yurimoto GEOCHIMICA ET COSMOCHIMICA ACTA 73 (13) A1316 -A1316 2009年06月 [査読無し][通常論文]
  • 坂本直哉, 青山聡, 川人祥二, 圦本尚義 日本鉱物科学会年会講演要旨集 2009 236 2009年 [査読無し][通常論文]
  • 圦本尚義 日本地球化学会年会講演要旨集 56th XII 2009年 [査読無し][通常論文]
  • 宮脇 律郎, 島崎 英彦, 重岡 昌子, 横山 一己, 松原 聰, 圦本 尚義 粘土科学討論会講演要旨集 53 (0) 1 -1 2009年 [査読無し][通常論文]
     
    新種のカリウム四ケイ素フッ素雲母，yangzhumingite (楊主明雲母)が中華人民共和国内モンゴル自治区白雲鄂博より発見され、国際鉱物学連合・新鉱物命名分類委員会から承認された。EPMAの分析結果から導かれる実験式は (K0.70Li0.30Na0.01)(Mg2.48Fe0.06)(Si3.96Al0.03)O10[F1.92(OH)0.08]となる。単斜晶系で空間群C2/mの格子定数は、a = 5.249(4), b = 9.095(5), c = 10.142(5) Å, β = 99.96(6)˚, V = 476.9(5)Å3, Z = 2である。
  • 伊藤 正一, スティーブン サイモン, ローレンス グロスマン, 圦本 尚義 日本地球化学会年会要旨集 56 (0) 69 -69 2009年 [査読無し][通常論文]
     
    Allende隕石中のGolfball typeB CAIは、岩石学的研究から、少なくとも２回の溶融イベントを経験していることがいわれている。本研究では、このCAIについて、溶融時期の異なるスピネル結晶及びメリライト結晶の酸素同位体組成とAl-Mg同位体組成を明らかにし、個々の液の形成時期とその酸素同位体組成の変化を評価することを試みた。スピネル結晶の酸素同位体組成は、deltaO-18で-50 から-40perimlに分布した。岩石学的特徴に対応してメリライト結晶の酸素同位体組成は、異なる分布を示し、ゲーレナイト成分に富むコア部は、deltaO-18で-20~-10permilに分布し、リム部で~0permilとなった。Al-Mg同位体組成も岩石学的特徴及び酸素同位体組成に対応して異なる２本のアイソクロンにそれぞれの結晶が分布し、コア部のゲーレナイト成分に富むメリライトは、26Al/27Al初生比で4.9±0.8 x 10-5、リム部のメリライトで1.9±1.2 x 10-5となり、その年代差は、約百万年となった。以上から、このCAIの形成過程について議論する。
  • 山崎 大輔, Chamathni Hegoda, Ralf Dohmen, 圦本 尚義, Sumit Chakraborty, 桂 智男 日本鉱物科学会年会講演要旨集 2009 (0) 193 -193 2009年 [査読無し][通常論文]
     
    高温高圧下でのフォルステライト中のSi自己拡散係数の決定を行った。実験的に拡散係数を決定するために、川井型高圧装置による高圧実験と2次イオン質量分析計(SIMS)による同位体濃度分析を行った。高圧実験の出発試料には、研磨表面に29Siに富んだMg2SiO4をコーティングした合成単結晶フォルステライトを用いた。拡散実験中の最表面の同位体組成を一定に保つために、コーティング層を200-300 nmの厚みにした。圧力3、8、13 GPa、温度1600, 1800 Kで一定時間拡散させた後、結晶表面から深さ方向への同位体濃度プロファイルをSIMSにより測定した。予備的な解析結果では、拡散係数D=7×10-21m2/sとなる。
  • 小林 幸雄, 永島 一秀, 殿谷 梓, 坂本 直哉, 伊藤 正一, Russell S. S., Krot A. N., 圦本 尚義 日本鉱物科学会年会講演要旨集 2009 (0) 217 -217 2009年 [査読無し][通常論文]
     
    化学的グループや母天体変成変質の程度が異なる炭素質コンドライトと普通コンドライトに対し，2次元その場同位体分析法を用いてプレソーラー粒子の探索を行った．FE-SEM-EDSを用いてプレソーラー粒子の形状，サイズ，化学組成を調べた．合計で56個の炭素同位体異常と125個の酸素同位体異常をもつ粒子を発見した．これらはSiCとグラファイト，酸化物とケイ酸塩であり，多くのケイ酸塩はFeを多く含むオリビン的組成であった．炭素質コンドライト中の存在度からは，母天体における水質変質と熱変成によるプレソーラーケイ酸塩の破壊や同位体的痕跡の消失が示唆される．変成度が小さい普通コンドライト中の低いケイ酸塩存在度は，普通コンドライト形成領域では，星雲プロセスにより，プレソーラーケイ酸塩が失われていたことを示唆する．
  • 阿部 憲一, 坂本 直哉, 小島 秀康, Krot A. N., Russell S. S., 圦本 尚義 日本鉱物科学会年会講演要旨集 2009 (0) 218 -218 2009年 [査読無し][通常論文]
     
    炭素質コンドライトAcfer 094は最も始原的なコンドライトの一つだと考えられている。そのマトリックスはプレソーラー粒子の存在度が高く、唯一宇宙シンプレクタイトが発見されている。Acfer 094のユニークな点はマトリックスの化学組成にあると考えられる。本研究では、Acfer 094と様々な炭素質コンドライトグループ間で細粒なマトリックス物質の化学組成の比較を行った。その結果、コンドライトグループ間でマトリックスのAl、S、Ca含有量に大きな変動が見られた。Acfer 094は他のコンドライトグループとは異なり、S/Al比とCa/Al比が両方とも高い値を示した。この違いは水質変質や熱変成によりマイクロメートルスケールでの元素の再分配の結果生じたと思われる。このアプローチは始原的なマトリックスを持つコンドライトを分類する指標になるかもしれない。
  • 伊藤 正一, Simon Steven, Grossman Lawrence, 圦本 尚義 日本鉱物科学会年会講演要旨集 2009 (0) 219 -219 2009年 [査読無し][通常論文]
     
    Allende隕石中のGolfball typeB CAIは、岩石学的研究から、少なくとも２回の溶融イベントを経験していることがいわれている。本研究では、このCAIについて、溶融時期の異なるスピネル結晶及びメリライト結晶の酸素同位体組成とAl-Mg同位体組成を明らかにし、個々の液の形成時期とその酸素同位体組成の変化を評価することを試みた。スピネル結晶の酸素同位体組成は、deltaO-18で-50 から-40perimlに分布した。岩石学的特徴に対応してメリライト結晶の酸素同位体組成は、異なる分布を示し、ゲーレナイト成分に富むコア部は、deltaO-18で-20∼-10permilに分布し、リム部で∼0permilとなった。Al-Mg同位体組成も岩石学的特徴及び酸素同位体組成に対応して異なる２本のアイソクロンにそれぞれの結晶が分布し、コア部のゲーレナイト成分に富むメリライトは、26Al/27Al初生比で4.9±0.8 x 10-5、リム部のメリライトで1.9±1.2 x 10-5となり、その年代差は、約百万年となった。以上から、このCAIの形成過程について議論する。
  • 若木 重行, 伊藤 正一, 田中 剛, 圦本 尚義 日本鉱物科学会年会講演要旨集 2009 (0) 220 -220 2009年 [査読無し][通常論文]
     
    本研究では、Allende隕石より見いだされたCAI-chondrule複合物質に対して、岩石学的観察、REE分析および構成鉱物の局所O同位体分析を行い、その形成過程を考察した。その結果分析したCAI-chondrule複合物質は、以下のように異なる環境下で複数回の溶融を経て形成された事がわかった：1)16Oに富む星雲ガスから前駆CAIが凝縮、2) 複数回の不完全溶融によるspinelの形成、3) 16Oに僅かに富む星雲ガスの下でCAIとChondrule物質が共存し溶融によって混合、4) 16Oに僅かに富む星雲ガスの下で溶融したchondrule物質が中心部に付着しリムを形成。
  • 坂本 直哉, 青山 聡, 川人 祥二, 圦本 尚義 日本鉱物科学会年会講演要旨集 2009 (0) 230 -230 2009年 [査読無し][通常論文]
     
    リアルタイムにイオン検出可能な新しいイオンイメージャを開発している．このイメージャは25万個の独立したイオン検出器である画素から構成される．各画素のイオンに対する応答性は，画素キャパシタを小さくすることで従来の5倍となる150 µV/イオンに向上した．高速駆動時の読み出しノイズを低減するために，画素に蓄積した信号電荷を複数回サンプリングして積分することで相対的にノイズを低減する多重サンプリング機構を組み込み，16回積分した時の読み出しノイズは250 µV（1.7イオン相当）であった．イメージの読み出し速度は1回積分時で12.5フレーム/秒，16回積分時で8.3フレーム/秒を達成し，読み出しノイズは速度に依存しないことが分かった．全てのパラメータを最適化してノイズを低減できれば，リアルタイムにシングルイオンの検出が可能になると期待される．
  • 圦本 尚義, 三浦 弥生 地球化学 43 (4) 115 -116 2009年 [査読無し][通常論文]
     
    This special issue of "Chikyu Kagaku" contains five papers from three sessions for cosmochemistry, "Cosmochemistry of extraterrestrial materials: From presolar history to early solar history", "Origin and evolution of Moon, Mars and small bodies in the solar system", and "Analytical technique, analytical organization and the scientific results of a new age of sample return mission", in the annual meeting of the Geochemical Society of Japan 2008. The five papers cover several topics on formation of water molecules in circum stellar environments, noble gas compositions of individual chondrules, discovery of chondrules from a comet sample, new analytical technique of extraterrestrial organics, and advances of lunar science under the cosmochemical view. These papers should be helpful to understand the trends of current research subjects of cosmochemistry. We hope this special issue could act as useful media for the cosmochemical community and the new comers to this research field.
  • 圦本 尚義 臨床化学 38 (3) 272 -279 2009年 [査読無し][通常論文]
  • 圦本尚義 金属 78 (11) 1024 -1028 2008年11月01日 [査読無し][通常論文]
     
    特集 : 複雑な物質・材料解析への新たなアプローチ 最近、隕石中に太陽系誕生以前の物質が含まれていることが明らかになった。この物質は化学組成からでは判別することができず、同位体組成によってのみ特定できる。この物質の研究を進めることにより、太陽系の起源でとぎれていた我々の歴史が宇宙史の中に位置づけられる日が来るだろう。
  • 圦本 尚義 金属 78 (11) 1024 -1028 2008年11月 [査読無し][通常論文]
     
    特集 : 複雑な物質・材料解析への新たなアプローチ
  • 圦本 尚義 日本地質学会学術大会講演要旨 115 27 -27 2008年09月15日 [査読無し][通常論文]
  • B. -G. Choi, S. Itoh, H. Yurimoto, A. E. Rubin, J. T. Wasson, J. N. Grossman METEORITICS & PLANETARY SCIENCE 43 (7) A32 -A32 2008年07月 [査読無し][通常論文]
  • Y. Seto, N. Sakamoto, K. Fujino, H. Yurimoto METEORITICS & PLANETARY SCIENCE 43 (7) A143 -A143 2008年07月 [査読無し][通常論文]
  • Hisayoshi Yurimoto, Alexander N. Krot, Byeon Gak Choi, Jerome Aléon, Takuya Kunihiro, Adrian J. Brearley Reviews in Mineralogy and Geochemistry 68 141 -186 2008年 [査読有り][通常論文]
     
    We review the oxygen isotopic compositions of chondrite components (refractory inclusions, chondrules, and matrix) and their inter- and intra- crystalline oxygen isotopic distributions. Primary oxygen isotopic compositions, acquired before planetesimal accretion, are easily disturbed by parent-body processes such as aqueous alternation and thermal metamorphism. Primary or original oxygen isotopic compositions of refractory inclusions (Ca-, Al-rich inclusions and amoeboid olivine aggregates) distribute along a slope-1 line on the three-oxygen isotope diagram over the range of -60‰ < δ 17O ≈ δ18O < +10‰. The variations suggest that oxygen isotopic compositions of the solar nebular gas temporally and spatially varied between 16O-rich and 17O-, 18O-rich during refractory inclusion formation. On the other hand, primary minerals of most chondrules have small isotopic variations and are enriched in 17O and 18O relative to refractory inclusions, suggesting that chondrule formation occurred in 17O-, 18O-rich nebular gas. However, rare 16O-rich chondrules have been found, suggesting some overlap in the timing of formation of chondrules and refractory inclusions in the solar nebula. Oxygen isotopic compositions of matrix grains distribute along the slope-1 line over the same range as refractory inclusions and chondrules. The similarity in oxygen isotopic distributions suggests that matrix was originally a mechanical mixture of nebular dusts co-generated with chondrules and refractory inclusions. Presolar grains with oxygen isotopic compositions that are clearly distinct from those of solar nebular materials are a trace component of chondrite matrices. Based on these oxygen isotopic characteristics, more than 99.5% of the solid materials in the nebula formed locally in the solar nebula, and the remainder formed in interstellar space. The astrophysical setting of chondrite component formation in the early Solar System is also discussed. Refractory inclusions and 16O-rich matrix dusts formed around the inner edge of the solar nebula. On the other hand, most chondrules and 17O-, 18O-rich matrix dusts seem to have formed elsewhere in the solar nebula. Efficient, large-scale radial mixing of the solar nebular materials may have been an essential process in the formation of chondritic planetesimals. Copyright © Mineralogical Society of America.
  • 伊藤正一, 圦本尚義 日本地球化学会年会講演要旨集 55th 409 2008年 [査読無し][通常論文]
  • 瀬戸雄介, 坂本直哉, 藤野清志, 圦本尚義 日本鉱物科学会年会講演要旨集 2008 212 2008年 [査読無し][通常論文]
  • 圦本尚義 質量分析総合討論会講演要旨集 56th 228 -229 2008年 [査読無し][通常論文]
  • 石原盛男, 公文代康祐, 身深亮, 内野喜一郎, 圦本尚義 質量分析総合討論会講演要旨集 56th 36 -37 2008年 [査読無し][通常論文]
  • 圦本尚義 パリティ 23 (1) 62 -64 2008年01月01日 [査読無し][通常論文]
     
    太陽系起源論の物質科学における最大の謎である太陽系の酸素同位体異常が発見されて，今年で35年を迎える。この酸素同位体異常は，その後の研究が進んでも，発見当時の単純な規則性はそのままである。そして，太陽系の起源を語るうえで最大の謎の1つとして，依然としてわれわれを悩ませ続けている。2007年に筆者たちのグループは，この35年間の枠組みを打ち破る大きな同位体異常をもつ物質を隕石中に発見した。その物質中の酸素は，従来報告されていたものと正反対の異常をもち，しかも酸素同位体異常の単純な規則性の延長上にあった。われわれはこの物質中の酸素が，太陽系形成当時の水(始原水)の名残であると結論づけた。この始原水の発見は，力学系で議論されることが多かった従来の太陽系起源論が，原子分子レベルからの物質進化を加えた総合的な汎惑星系起源論へと発展する契機となるだろう。
  • 圦本 尚義, 藤本 久美子, 江端 新吾, 伊藤 正一 日本地球化学会年会要旨集 55 (0) 378 -378 2008年 [査読無し][通常論文]
     
    原始太陽の酸素同位体組成は惑星の卵による太陽への汚染が太陽系進化過程において顕著ではなかった事を示す．また．原始太陽の酸素同位体比は太陽大気から求めた元素存在度が太陽系の平均元素存在度である事を保証している．
  • 伊藤 正一, 圦本 尚義 日本地球化学会年会要旨集 55 (0) 377 -377 2008年 [査読無し][通常論文]
     
    CaとAlに富む包有物（CAI）は、太陽系初期の時代から保存された物質であり、様々な複数回急加熱イベントを通じて、それより前に存在していた固体の熱加工により形成した。しかし，その間隔や期間は，不明瞭であった。本講演では、CAI構成鉱物に対して，約１０ミクロン領域の短寿命核種26Alを用いた高精度年代測定の結果を報告する。個々のCAI形成期間は多様であり(10-50万年)，16O-richな星雲ガス環境と16O-poorな星雲ガス環境が変動し，数万年以内でスイッチングしていた場合の存在した。
  • 江端 新吾, 坂本 直哉, 圦本 尚義 日本地球化学会年会要旨集 55 (0) 375 -375 2008年 [査読無し][通常論文]
     
    プレソーラー粒子は太陽系形成以前に存在した太陽系を作る材料粒子であり、単独でマトリックス中に埋まっている。2007年江端らによってカンラン石や金属鉄とともにFeSで囲まれていたプレソーラーSiC粒子（SEC_ALH07）がEH3コンドライトから発見された。本研究では、周囲の組織の起源を解明する事を目的とし周囲を取り囲んでいるFeSの硫黄同位体組成分析を行った。‹BR›FeSの硫黄同位体組成は、δ‹SUP›33‹/SUP›S=-71±45‰, δ‹SUP›34‹/SUP›S=-48±56‰, δ‹SUP›36‹/SUP›S=27±173‰（誤差1σ）であった。δ‹SUP›34‹/SUB›S, δ‹SUP›36‹/SUP›Sの同位体組成は2 σの誤差内で太陽系の同位体組成と同じである事を示す。また、江端らの酸素同位体測定の報告によると内包されているカンラン石は太陽の同位体組成と同じであった。これらの結果は、周囲の硫化物はプレソーラーSiC粒子を核としてカンラン石や金属鉄と共に原始太陽系内において形成されたものである事を示唆する。
  • 瀬戸 雄介, 坂本 直哉, 藤野 清志, 圦本 尚義 日本鉱物科学会年会講演要旨集 2008 (0) 206 -206 2008年 [査読無し][通常論文]
     
    始原的炭素質コンドライトAcfer094のマトリックス中の酸素同位体異常物質"COS"について、放射光X線回折実験および透過電子顕微鏡観察から詳細な鉱物学的記載を行い、その生成条件を検討した。Ni含有量の高いもの(High-Ni COS)と低いもの(Low-Ni COS)を観察した結果、次のような相違点、類似点が見られた。(1)High-Ni COSはmagnetiteとpentlanditeから成るが、Low-Ni COSはmagnetiteとpyrrhotiteから成る。(2)High-Ni COSはmagnetiteとpentlanditeが入り組んだシンプレクタイトのような組織を示すが、Low-Ni COSは比較的等粒状のmagnetiteとpyrrhotiteの集合物である。(3)High-Ni COS中のmagnetiteは電子線回折において3倍周期の超構造を示すが、Low-Ni COS中のmagnetiteには超構造が見られない。(4) 両試料ともX線回折ではpentlanditeの明瞭な回折ピークが観察されるが、電子線では回折スポットが検出できない。いずれのCOSも酸化鉄と硫化鉄(+Ni)から構成されており、金属鉄(+Ni)の酸化・硫化による反応性生物である可能性が高い。High- / Low-Ni COSの組織、鉱物相の相違は、酸化・硫化反応以前のNi含有量の相違を反映していると考えられる。
  • 甕 聡子, 永井 隆哉, 坂本 直哉, 岨 康輝, 渡邊 剛, 圦本 尚義 日本鉱物科学会年会講演要旨集 2008 (0) 175 -175 2008年 [査読無し][通常論文]
     
    造礁性サンゴはアラゴナイトによってその骨格を形成し、その骨格に含まれる酸素同位体比、あるいは微量元素量が古環境復元に利用されている。例えば、アラゴナイト中のSr/Ca比の変動は、骨格形成時の海水温度と相関を持つとされ、過去の海水温度復元に用いられている。これは、骨格に含まれているSr（Porites sp.であれば約7000ppm）が全てアラゴナイトに固溶し、固溶割合の変動が鉱物生成時の温度の違いに起因するものであると考えられているからである。しかし、近年になりサンゴ骨格中にアラゴナイト以外の鉱物相の存在が示唆された。例えば、Greegor et al.(1997)はXANES、EXAFSを用いた実験で、Srの60％程度はアラゴナイト中に固溶しているが、残りの40％はアラゴナイト構造を持つSrCO3端成分として存在していると報告した。この報告が信頼できるとすると、Sr/Ca比を海水温度計として使うには注意が必要となる。一方Finch et al(2003a, 2003)は放射光を使ったmicro-EXAFSを用いての観察の結果、Srは全てアラゴナイト固溶体として存在するとGreegorとは異なった報告している。しかしながらいずれの報告もSrの配位環境やSr-O結合距離からの考察であり、これまで直接的な鉱物同定は行われていない。
  • 圦本 尚義 日本地質学会学術大会講演要旨 2008 (0) 52 -52 2008年 [査読無し][通常論文]
  • 圦本 尚義 パリティ 23 (1) 62 -64 2008年01月 [査読無し][通常論文]
     
    太陽系起源論の物質科学における最大の謎である太陽系の酸素同位体異常が発見されて，今年で35年を迎える。この酸素同位体異常は，その後の研究が進んでも，発見当時の単純な規則性はそのままである。そして，太陽系の起源を語るうえで最大の謎の1つとして，依然としてわれわれを悩ませ続けている。2007年に筆者たちのグループは，この35年間の枠組みを打ち破る大きな同位体異常をもつ物質を隕石中に発見した。その物質中の酸素は，従来報告されていたものと正反対の異常をもち，しかも酸素同位体異常の単純な規則性の延長上にあった。われわれはこの物質中の酸素が，太陽系形成当時の水(始原水)の名残であると結論づけた。この始原水の発見は，力学系で議論されることが多かった従来の太陽系起源論が，原子分子レベルからの物質進化を加えた総合的な汎惑星系起源論へと発展する契機となるだろう。
  • 勝田雅典, 井上徹, 入舩徹男, 圦本尚義 高圧討論会講演要旨集 48th 103 2007年11月11日 [査読無し][通常論文]
  • 圦本 尚義 日本鉱物学会・学術講演会,日本岩石鉱物鉱床学会学術講演会講演要旨集 2007 6 -6 2007年09月22日 [査読無し][通常論文]
     
    New technology of mass spectrometry for isotope analyses has been greatly advanced for recent years. The advances are especially for improvements of precision and for microanalysis. Precisions of isotope ratios have been improved by using an inductively coupled plasma mass spectrometer with multiple ion collectors. Capabilities of microanalysis have been improved by secondary ion mass spectrometry. These advances introduce new insights for origin of the Solar System and evolution of the Earth.
  • 瀬戸 雄介, 坂本 直哉, 圦本 尚義, 藤野 清志 日本鉱物学会・学術講演会,日本岩石鉱物鉱床学会学術講演会講演要旨集 2007 77 -77 2007年09月22日 [査読無し][通常論文]
  • N. Sakamoto, Y. Seto, S. Itoh, K. Kuramoto, K. Fujino, K. Nagashima, A. N. Krot, H. Yurimoto METEORITICS & PLANETARY SCIENCE 42 A134 -A134 2007年08月 [査読無し][通常論文]
  • Y. Seto, N. Sakamoto, K. Fujino, H. Yurimoto METEORITICS & PLANETARY SCIENCE 42 A140 -A140 2007年08月 [査読無し][通常論文]
  • S. Ebata, T. J. Fagan, H. Yurimoto METEORITICS & PLANETARY SCIENCE 42 A38 -A38 2007年08月 [査読無し][通常論文]
  • S. Itoh, K. Makide, H. Yurimoto METEORITICS & PLANETARY SCIENCE 42 A75 -A75 2007年08月 [査読無し][通常論文]
  • K. Makide, S. Itoh, S. Maruyama, M. Yoshitake, H. Yurimoto METEORITICS & PLANETARY SCIENCE 42 A95 -A95 2007年08月 [査読無し][通常論文]
  • 身深亮, 栗原伸治, SAFWAT Hassaballa, 内野喜一郎, 圦本尚義, 戸所竜太郎, 公文代康祐, 石原盛男 質量分析総合討論会講演要旨集 55th 342 -343 2007年05月01日 [査読無し][通常論文]
  • 戸所竜太郎, 公文代康祐, 身深亮, 栗原伸治, 内野喜一郎, 圦本尚義, 石原盛男 質量分析総合討論会講演要旨集 55th 284 -285 2007年05月01日 [査読無し][通常論文]
  • 圦本尚義 日本顕微鏡学会北海道支部学術講演会プログラム・予稿集 2006 7 2007年02月 [査読無し][通常論文]
  • 渡邊剛, 岨康輝, 坂本直哉, 圦本尚義 日本地球化学会年会講演要旨集 54th 239 2007年 [査読無し][通常論文]
  • 瀬戸 雄介, 坂本 直哉, 圦本 尚義, 藤野 清志 日本鉱物科学会年会講演要旨集 2007 (0) 75 -75 2007年 [査読無し][通常論文]
     
    最近、炭素質コンドライトAcfer094中に17,18Oに富む物質が発見された。この物質は"New-PCP"と呼ばれ、これまで報告されている惑星物質の中でもっとも17,18Oの値が高い物質である。本研究ではこの物質の詳細な鉱物学的記載をおこなった。実験の結果、この物質は直径100-300nm程度の大きさの粒子で構成されており、その粒子の内部にはマグネタイトとペントランダイトの虫食い状組織が形成されていた。この組織は金属鉄の硫化、酸化反応によって形成されたと考えられる。
  • 渡邊 剛, 岨 康輝, 坂本 直哉, 圦本 尚義 日本地球化学会年会要旨集 54 (0) 219 -219 2007年 [査読無し][通常論文]
     
    熱帯・亜熱帯域のサンゴ礁に生息する造礁性サンゴの骨格は、過去数百年間の環境変化が連続的に記録されており、環境変動を復元する強力なツールとして注目されてきた。サンゴ骨格のバイオミネラリゼーション（生物鉱化作用）はまだよく理解されておらず、まだこの問題の解明には石灰化が起こっている微小領域における生物地球化学的な情報が必要である。
  • 勝田雅典, 井上徹, 入舩徹男, 圦本尚義 高圧討論会講演要旨集 47th 133 2006年10月30日 [査読無し][通常論文]
  • 中村佳太, 加藤真理子, 丹所良二, 藤本正樹, 井田茂, 圦本尚義 日本天文学会年会講演予稿集 2006 135 2006年08月20日 [査読無し][通常論文]
  • K. Nagashima, H. Yurimoto GEOCHIMICA ET COSMOCHIMICA ACTA 70 (18) A440 -A440 2006年08月 [査読無し][通常論文]
  • M. Yoshitake, H. Yurimoto METEORITICS & PLANETARY SCIENCE 41 (8) A195 -A195 2006年08月 [査読無し][通常論文]
  • 圦本 尚義 顕微鏡 41 (2) 134 -137 2006年07月31日 [査読無し][通常論文]
  • 圦本 尚義 遊・星・人 : 日本惑星科学会誌 15 (2) 43 -43 2006年06月25日 [査読無し][通常論文]
  • 圦本 尚義 学術月報 59 (3) 173 -178 2006年03月 [査読無し][通常論文]
  • 圦本 尚義 学術月報 59 (3) 173 -178 2006年03月 [査読無し][通常論文]
  • 圦本尚義 日本地球化学会年会講演要旨集 53rd 265 2006年 [査読無し][通常論文]
  • 地球・大陽系の起源を探る-石になった星-
    学術月報 59 173 -178 2006年 [査読無し][通常論文]
  • 倉本 圭, 圦本 尚義 遊・星・人 : 日本惑星科学会誌 14 (4) 193 -200 2005年12月25日 [査読無し][通常論文]
  • AN Krot, H Yurimoto, MI Petaev, ID Hutcheon, DA Wark, G Libourel, L Tissandier, JM Paque METEORITICS & PLANETARY SCIENCE 40 (9) A87 -A87 2005年09月 [査読無し][通常論文]
  • 留岡 和重, 土山 明, 圦本 尚義 岩石鉱物科学 34 (3) 96 -97 2005年05月30日 [査読無し][通常論文]
  • Katayama, I, S Nakashima, H Yurimoto, S Maruyama GEOCHIMICA ET COSMOCHIMICA ACTA 69 (10) A651 -A651 2005年05月 [査読無し][通常論文]
  • AN Krot, H Yurimoto GEOCHIMICA ET COSMOCHIMICA ACTA 69 (10) A749 -A749 2005年05月 [査読無し][通常論文]
  • リタソフ コンスタンチン, 圦本 尚義, リタソフ ユーリ, ラスカゾフ セルゲイ, マルコベッツ ウラジミル, 谷口 宏充 東北アジア研究 9 159 -178 2005年03月28日 [査読無し][通常論文]
     
    Trace element chemistry of clinopyroxene in the mantle xenoliths from melanephelinites of the Burkal volcanic group has been studied. The Burkal group is composed of several local outcrops of 5-8 Ma melanephelinites within the Khentey domal uplift near the Russia/Mongolia boundary. Cr-diopside group xenoliths include garnet and spinel lherzolite, spinel harzburgite and dunite, and garnet and spinel pyroxenites. Hydrous minerals were not detected, however shallow mantle feldspatic metasomatism is present. Clinopyroxene from garnet lherzolites has high TiO_2, Al_2O_3, and Na_2O relative to clinopyroxene from spinel lherzolites. Olivine has composition of Fo_<90-92>. Spinel has Mg#=60-80 and contains 10-46 wt.% Cr_2O_3. Clinopyroxene from garnet lherzolites has REE patterns typical for fertile peridotites. Trace element patterns of clinopyroxene from depleted spinel peridotites show progressive depletion in HREE and HFSE and enrichment in LREE toward more depleted varieties of harzburgites and dunites. REE patterns of clinopyroxene in harzburgites are strongly U-shaped and have (La/Sm)n=5-36 and (Sm/Yb)n=0.4-2.1. Clinopyroxene in harzburgites has also extremely low Zr content (0.4-3.4ppm) and high Ti/Zr ratio ranged in 190-240. The patterns of clinopyroxene in depleted peridotites are indicative of significant partial melting (up to 15-20%) of the primary substrate followed by cryptic metasomatic enrichment by silicate or carbonatitic melt. Estimation of T-P parameters for garnet lherzolites reveals equilibration at 17-23 kbar (60-90km depths) and 1050-1150℃. T-estimations for harzburgites and dunites indicate, that they may form veins at 50-70km depth, whereas shallow mantle (low-T) depleted peridotites were not detected. The uppermost mantle may be composed of fertile spinel lherzolites.
  • 太陽系における不均質な酸素同位体組成の分子雲起源説
    遊星人 14 193 -200 2005年 [査読無し][通常論文]
  • 留岡 和重, 土山 明, 圦本 尚義 日本鉱物学会・学術講演会,日本岩石鉱物鉱床学会学術講演会講演要旨集 2004 167 -167 2004年09月22日 [査読無し][通常論文]
  • 下宿 彰, 久保 友明, 大谷 栄治, 圦本 尚義 日本鉱物学会・学術講演会,日本岩石鉱物鉱床学会学術講演会講演要旨集 2004 181 -181 2004年09月22日 [査読無し][通常論文]
     
    Diffusion experiments of mantle minerals are important for understanding the rheological properties of the Earth's mantle and subducting slab, because the atomic diffusion in the crystals controls plastic deformation in silicate minerals. Wadsleyite is a major constituent mineral in the mantle transition zone. Hence experimental examination of the diffusion rates is essential for debating the rheology of mantle transition zone. In this study, Si self-diffusion rates in wadsleyite were measured at 18 GPa, 1703-1903 K and the viscosity of wadsleyite deformed by diffusion creep was calculated. Our results imply some portions in cold subducting slabs, where the grain size reduces to less than 1 micron after the olivine-spinel transformation, become weaker than the surrounding mantle.
  • 伊藤 正一, 圦本 尚義 月刊地球 26 (9) 576 -580 2004年09月 [査読無し][通常論文]
  • S Itoh, SS Russell, H Yurimoto GEOCHIMICA ET COSMOCHIMICA ACTA 68 (11) A766 -A766 2004年06月 [査読無し][通常論文]
  • Yohei Shimizu, Shoji Arai, Tomoaki Morishita, Hisayoshi Yurimoto, Fernando Gervilla Special Paper of the Geological Society of America 389 265 -276 2004年 [査読有り][通常論文]
     
    Felsic and related veins within mantle-derived peridotite xenoliths from Tallante, Spain, were examined in order to understand the mantle-wedge processes related to the behaviour of Si-rich melt. The thickest part of the vein has a quartz diorite lithology, and is composed mainly of quartz and plagioclase, with pyroxenes, hydrous mineral, apatite, zircon and rutile present as minor phases. The thinner parts are free of quartz and predominantly composed of plagioclase. Orthopyroxene always intervenes between the internal part (plagioclase ± quartz) and host peridotite, indicating that it is a product of interaction between silica-oversaturated melt and olivine. This indicates that a sufficiently high melt/wall rock ratio enabled the melt to retain its silica-oversaturated character. The quartz diorite part has adakite-like geochemical signatures, except for negative Ba, Rb Eu and Sr anomalies, and positive Th and U anomalies. These negative anomalies indicate that fractionation of plagioclase and hydrous minerals was achieved between the upper most mantle and the slab melting zone. The shape of the rare-earth element (REE) pattern of clinopyroxene in quartz diorite is strikingly similar to that of clinopyroxene phenocrysts from Aleutian adakites. However, the former has one order higher REE contents than the latter, except for Eu which shows a prominent negative spike. This feature was caused by the precipitation of large amounts of plagioclase and small amounts of clinopyroxene from a fractionated adakitic melt before and during solidification. This adakitic melt was produced by partial melting of a detached and sinking slab beneath the Betic area in the Tertiary.
  • 留岡 和重, 土`山 明, 圦本 尚義 日本鉱物学会年会講演要旨集 2004 (0) 146 -146 2004年 [査読無し][通常論文]
     
    太陽系始原物質とは，コンドライト隕石に代表される太陽系で最も始原的な物質であり，「45.6億年前の太陽系の始まり」を我々に直接伝えてくれるロゼッタストーンだと言えよう。これまでの膨大な始原物質研究の成果は，現在の太陽系の起源・進化のモデルの構築に大きな役割を果たしてきた。いまや物質科学は惑星科学を支える重要な一分野である。今回のシンポジウムでは，始原物質科学の最前線で活躍しておられる研究者の方々をお招きし，ご自分の研究を紹介していいただく。このシンポジウムの目的は，普段，惑星科学とは直接関係の薄い鉱物科学者たち（とくに若い人たち）に太陽系始原物質科学の最前線に触れていただき，その面白さ，意義を知っていただくことである。そして，私たちは，願わくは鉱物科学者と惑星科学者がお互いの接点を見出し，新たな研究テーマを創出するきっかけがつくれればいいと思っている。
  • 伊藤 正一, ラッセル サラ, 圦本 尚義 日本地球化学会年会要旨集 51 (0) 169 -169 2004年 [査読無し][通常論文]
     
    セマルコナLL3.0コンドライト隕石からAmoeboid olivine aggregates (AOAs)を発見した．これまで普通コンドライト中の細粒CAIsの報告はあるがAOAsの報告はない．AOAsの岩石学的研究と同位体組成を組み合わせ、従来の炭素質コンドライト中のAOAsの結果と合わせて議論する．
  • 圦本 尚義 日本地球化学会年会要旨集 51 (0) 17 -17 2004年 [査読無し][通常論文]
     
    惑星固体物質の成因は化学組成の変化を用いた元素組織学により主に議論されてきた。最近のその場局所同位体分析は同位体による組織学を構築できるレベルにまで進歩しつつある。そもそも同位体組織と元素組織は整合的であるべきだが，太陽系最古の物質といわれるCAIにおいて元素組織学による成因と同位体組織学による成因が甚だしい不一致を示すことが少なくない。本発表では固体物質の成因の完全理解のためにすべての元素とその同位体の分析と解析をどのように活用すべきか，その指針を論じたい。
  • 吉武 美和, 圦本 尚義 日本地球化学会年会要旨集 51 (0) 170 -170 2004年 [査読無し][通常論文]
     
    CHコンドライトに分類されるAcfer 214中のコンドリュールの酸素同位体組成を，マルチコレクター付随型二次イオン質量分析計（東京工業大学）を用いて高精度分析を行った。 その結果，Acfer 214中のコンドリュールはAllende隕石のコンドリュールの酸素同位体を内包し、重い同位体側に広がっているということがわかった。 このことより、CHコンドライトはCVコンドライトより多様性のある環境下で形成されたコンドリュールを集積していることを示す。
  • 永島 一秀, クロット アレキサンダー, サラ ラッセル, 圦本 尚義 日本地球化学会年会要旨集 51 (0) 171 -171 2004年 [査読無し][通常論文]
     
    我々は，イオンビームなど荷電粒子に感度がある二次元半導体素子SCAPSを開発してきた。今回，SCAPSを投影型SIMSに装着した顕微同位体分析法により始源的コンドライトのマトリックス物質の同位体分布を二次元的にサーベイした．その結果，始源的コンドライト中には太陽系の材料となった星くず（プレソーラー粒子）が，わずかであるが，生き残っていることが判明した．講演では，種々のコンドライトにおけるプレソーラー粒子の存在度の評価結果を報告する．
  • 小林 幸雄, 殿谷 梓, 永島 一秀, クロット アレキサンダー N., 圦本 尚義 日本地球化学会年会要旨集 51 (0) 172 -172 2004年 [査読無し][通常論文]
     
    プレソーラー粒子は太陽系とは大きく異なる同位体組成により同定される．本研究では始源的な隕石であるCOコンドライトYamato81025とALHA77307の薄片から，その場同位体面分析によりプレソーラー粒子の同定を目指した．プレソーラー粒子の発見には東京工業大学の同位体顕微鏡システムを用いた．発見した粒子はSEM-EDSを用いて組織と化学組成を決定した． 発表では，同定した個々のプレソーラー粒子についてと，異なる隕石間における存在度の違いについて議論する．
  • 巻出 健太郎, 小林 幸雄, 圦本 尚義 日本地球化学会年会要旨集 51 (0) 249 -249 2004年 [査読無し][通常論文]
     
    Acfer214中の酸素同位体組成は、個々のCAI中で均一であるが、異なるCAI間に16O-richから16O-poorに至る約50‰の巾に分布している(Kobayashi et.al,2003)。本研究は26Alの存在と酸素同位体組成の不均一の相関を明らかにするため、Acf214中の酸素同位体組成の異なる６つのCAIについて二次イオン質量分析計(Cameca ims-1270)を用いてAl-Mg年代測定を行った。結果すべてのCAIについて26Mgの過剰はなく、26Alの存在と酸素同位体異常の程度に相関はなかった。これらの結果は原始太陽系円盤進化に次のような制約を課す。(1)Al-Mgシステムが時計として働くのであれば、CAI形成は原始太陽系円盤において300万年以上継続しその間酸素同位体不均一が円盤内に残っていた。もしくは、(2) 26Alと酸素同位体の不均一が円盤内に存在してこの両者の分布は相関がなかった。
  • Litasov Konstantin, 圦本 尚義, Litasov Yury 東北アジア研究 (9) 159 -178 2004年 [査読無し][通常論文]
  • Y Matsunami, K Nagashima, H Nagasawa, H Yurimoto GEOCHIMICA ET COSMOCHIMICA ACTA 67 (18) A281 -A281 2003年09月 [査読無し][通常論文]
  • S Itoh, H Yurimoto GEOCHIMICA ET COSMOCHIMICA ACTA 67 (18) A179 -A179 2003年09月 [査読無し][通常論文]
  • K Nagashima, Y Takeda, S Itoh, H Yurimoto GEOCHIMICA ET COSMOCHIMICA ACTA 67 (18) A321 -A321 2003年09月 [査読無し][通常論文]
  • TJ Fagan, AN Krot, K Keil, H Yurimoto GEOCHIMICA ET COSMOCHIMICA ACTA 67 (18) A89 -A89 2003年09月 [査読無し][通常論文]
  • AN Krot, MI Petaev, S Itoh, TJ Fagan, H Yurimoto, SS Russell GEOCHIMICA ET COSMOCHIMICA ACTA 67 (18) A237 -A237 2003年09月 [査読無し][通常論文]
  • 清水 洋平, 荒井 章司, 圦本 尚義, Gervilla Fernando 日本岩石鉱物鉱床学会 学術講演会 講演要旨集 2003 (0) 80 -80 2003年 [査読無し][通常論文]
     
    (はじめに)
    斜長石かんらん岩は地殻の薄く地温勾配の高い海洋底マントルにおいて一般に存在すると考えられている。海洋底から得られるかんらん岩中の斜長石の起源については、サブソリダス下での反応ではなく、トラップメルトからの晶出が大半であるらしい(Dick, 1989) 。南東スペイン、タジャンテにおけるかんらん岩捕獲岩にも斜長石かんらん岩が存在する。本発表では、タジャンテのかんらん岩における斜長石かんらん岩の起源について議論する。
    (かんらん岩について)
    スペイン南東部タジャンテ周辺域には中新世にカルクアルカリ火山活動が、それに引き続き鮮新世にマントル捕獲岩を包有したアルカリ玄武岩が噴出した。超苦鉄質捕獲岩類は、Frey and Prinz (1978)でいうところの、Group I（レールゾライトからハルツバージャイト）と、母岩と同じマグマソースを持つとGroup II(クライノパイロクシナイト)に分けられる。これらの岩石は複合捕獲岩(Irvine, 1975)を形成することがある。Group Iの岩石は鉱物組み合わせにより、スピネルかんらん岩と斜長石かんらん岩の2つに分類される。Group Iにはしばしば斜方輝石-斜長石脈が観察され、最も太い脈では石英を伴い、その起源としてはスラブ起源のSiに富むメルトが考えられている(Arai et al. 2003)。Group IIと複合捕獲岩を形成するGroup Iの岩石、または斜方輝石-斜長石脈を含む岩石では斜長石が多く観察されるが、それらと無関係の独立した捕獲岩でも斜長石が見出される。
    (鉱物化学組成について)
    かんらん石のFo値とスピネルのCr#(=Cr/(Cr+Al)原子比)の関係において、スピネル、斜長石かんらん岩とほぼ同じスピネルCr#（0.15-0.22）をもつが，後者の方がより低いFo値をもつ（スピネルかんらん岩：Fo90.5-91、斜長石かんらん岩Fo89.8-90.8）。また、単斜輝石のAl2O3、Cr2O3量を比較するとスピネルかんらん岩は斜長石かんらん岩より高く，TiO2wt%は斜長石かんらん岩のほうが高い。東工大に設置されているSIMSにより求められた単斜輝石中の微量元素存在量のうち、La/Yb比はスピネルかんらん岩、斜長石かんらん岩はそれぞれ1.32-1.99、0.70-1.84であるのに対し、斜方輝石-斜長石脈を含むサンプルにおいては1.57-4.71と比較的高い値を示す。REEパターンにおいてはスピネル、斜長石かんらん岩は、後者がEuの負異常を持つ点を除いて、ほぼ似たいようなフラットなパターンを示すのに対し、脈を持つサンプルはLREEにエンリッチしたパターンを示す。
    (議論＆まとめ)
    スピネルかんらん岩は圧力低下に伴い斜長石かんらん岩へとサブソリダス変化することが知られている(Kushiro and Yoder, 1966)。しかしながら、この反応は系のCr/Al比に影響を受け、Cr/Al比が高い岩石ほどこの反応曲線はより低圧側へと移動することが知られている。一連の様々な枯渇度を有するスピネルかんらん岩が減圧した後、高枯渇度の部分はそのままで、低枯渇度の部分にのみ斜長石が形成されることが起こり得る。タジャンテでは一見これが起きているように思える。そのことは微量元素の検討からも指示され、スピネル、斜長石かんらん岩はほぼ同じようなREEパターン、La/Yb比を持つのに対し、外界からのメルトの影響を受けたサンプルはLREEにエンリッチしたパターンに変化したことが明瞭である。したがって、タジャンテの斜長石かんらん岩は外部からのメルトの侵入を受けて形成されたものではなく、サブソリダス変化によってもたらされたと結論づけられる。
  • 久保 友明, 下宿 彰, 大谷 栄治, 圦本 尚義 日本鉱物学会年会講演要旨集 2003 (0) 29 -29 2003年 [査読無し][通常論文]
     
    オリビンの高圧相であるwadsleyiteは，地球内部のマントル遷移層における主要構成鉱物であり，wadsleyite中の原子の拡散速度を測定することは，マントル遷移層のレオロジーやダイナミクス，電気伝導度を議論するうえで重要である。本研究では15-18.5GPa, 1473-1973Kにおいてwadsleyite中のMg-Feの相互拡散実験を無水と含水条件下で、またSiの自己拡散実験を無水条件下で行った。それらの結果からマントル遷移層の含水量と電気伝導度，およびマントル遷移層のレオロジーに関して考察を行う。
    高圧実験は東北大学理学部設置の3000 ton 川井型高圧発生装置（MAP-3000）を用いて行った。Mg-Fe相互拡散実験では、Mg#90とMg#100のwadsleyite多結晶体を接合し、酸素分圧はNi-NiOバッファーで制御しながら実験を行った。FTIR測定により、無水条件下では0.01 wt.%以下、含水条件下では0.02-0.23 wt. %のH2Oがwadsleyite多結晶体中に含まれていることがわかった。拡散実験後， EPMAを用いて拡散プロファイルを測定し拡散係数を算出した。wadsleyite中のMg-Fe相互拡散には組成依存性があり，Boltzmann-Matanoの解析法を用いて拡散係数を求めた結果，Fe 成分が多いほど拡散速度は速くなることがわかった。無水条件下ではMg-Fe相互拡散の活性化エネルギーは156kJ/molと求められた。16 GPa, 1200 °C における wadsleyite中のMg-Fe 相互拡散係数は，無水条件下で1.85×10-14 m2/s, 含水条件下で5.53×10-13 m2/s と求められた． wadsleyite中のMg-Fe 相互拡散係数は，0.02-0.23 wt. %のH2Oの存在下で約3倍速くなる。また含水量が多いwadsleyiteについては，粒界拡散の寄与も認められた。Schultz et al. (1993) による地球内部の電気伝導度観測とMg-Fe相互拡散係数から計算した電気伝導度を比較した場合，マントル遷移層には約0.2 wt. %程度のH2Oが存在する可能性がある。
    Si自己拡散実験では、出発物質としてwadsleyite多結晶体表面に拡散源となる29Siに富んだSiO2を蒸着したものを用いた。拡散実験後，東京工業大学設置の二次イオン質量分析計(SIMS)によるDepth profile法を用いて29Siの拡散プロファイルを作成し，拡散係数を算出した。拡散プロファイルは粒内拡散と粒界拡散が寄与している二つの領域からなる。粒内拡散が寄与している領域について薄膜状拡散源に対する解法をもちいて粒内拡散係数(Dv)を求め、粒界拡散が寄与している領域についてはLe Claire（1963）による解法を用いて粒界拡散係数(_Dgb)を求めた。Si自己拡散の活性化エネルギーは、粒内拡散の場合273kJ/mol、粒界拡散の場合254kJ/mol と推定された。Wadsleyite中のSiの拡散速度は，Mg-Feの相互拡散速度と比較して約6桁遅い。また，Dohmen et al. (2002) によるオリビン中のSiの拡散速度よりも1桁程度高くYamazaki et al. (2000) によるペロブスカイト中のSiの拡散速度と同程度であった。得られた拡散係数を用いてwadsleyiteが拡散クリープによって変形した際の粘性率を計算した。また，転位クリープによって変形した際の粘性率をKarato et al. (2001) によるクリープパラメーターを用いて計算した。それらの結果と地球物理学的観測による粘性値を比較して，マントル遷移層では拡散クリープおよび転位クリープの両方の変形メカニズムが卓越する可能性がある。また沈み込むスラブの低温条件では拡散クリープが卓越していることが予想され，この場合は相転移に伴う結晶粒径の細粒化によってプレートが軟化する可能性がある。
  • 井上 徹, 和田 智之, 佐々木 瑠美, 入舩 徹男, 圦本 尚義 日本鉱物学会年会講演要旨集 2003 (0) 15 -15 2003年 [査読無し][通常論文]
     
    （はじめに）
    水は地球表層に大量に存在する主要な揮発性成分の1つであり、その水がスラブの沈み込みによって常に地球内部に供給され、鉱物の物性や溶融温度に大きく影響を与えることが明らかにされてきている。特にマントルの主要構成鉱物はカンラン石であり、その高圧相のwadsleyite, ringwooditeには3wt%ものH2Oが結晶構造中に含まれうることが明らかにされてきてはいるが、実際の水の存在割合を議論する場合、それらの鉱物間の水の分配が重要で、マントル中のどの層に相対的にどれぐらい水が存在可能かということを知る必要がある。現在までolivine-wadsleyite間（Chen et al.,2003）、及びwadsleyite-ringwoodite間（Kawamoto et al., 1996）でこのようなデータが報告されているが、特に後者ではデータは１点だけである。本研究ではオリビンの高圧相転移のwadsleyite-ringwoodite、及びringwoodite-perovskite間における水の分配を明らかにし、上部マントル、マントル遷移層、及び下部マントル間の水の分配を明らかにした。
    （実験方法）
    本研究の含水系の出発物質には(Mg0.8Fe0.2)2SiO4+16wt%H2OになるようにFe2SiO4, Mg(OH)2, SiO2の混合粉末試料を、無水系には(Mg0.8Fe0.2)2SiO4になるようにFe2SiO4, MgO, SiO2の混合粉末試料を用意した。実験装置は愛媛大学設置のマルチアンビル型高圧発生装置を使用し、wadsleyite-ringwoodite間の水の分配を求める実験は14.6～17.0GPa、1400℃の条件下で、ringwoodite-perovskiteの水の分配を求める実験は～23.5GPa、1600℃の条件下で行った。今回の実験は含水量測定に耐え得る大きな共存結晶を得ることを目的としているので、比較的大きい含水量を選択し、また温度も含水ソリダス直上になるよう設定した。実験は目的の圧力まで加圧、圧力を一定に保ちながら加熱した後、急冷減圧し回収した。回収試料は顕微ラマン分光装置、及び反射電子像により相の同定を、さらにエネルギー分散型電子顕微鏡により化学組成を測定した。また含水量は東京工業大学設置の二次イオン質量分析計により測定した。
    （実験結果）
    含水系で含水量測定に耐え得る50μm以上のwadsleyite及びringwooditeの共存結晶、及びringwoodite及びperovskiteの共存結晶を合成することに成功し、この共存結晶間での水の分配が明らかにできた。Wadsleyiteとringwoodite間の水の分配係数は５点で制約できたが約2程度となり、これはKawamoto et al.(1996)での値(2.5)と近い値を示した。またringwooditeとperovskite間の水の分配係数は約10かそれ以上となった。我々の以前の研究（Chen et al.,2003）によりwadsleyiteとolivine間の水の分配係数は約5程度と明らかにされているので、410km以浅の上部マントル、410-520km及び520-660km間のマントル遷移層、及び660km以深の下部マントル間での水の分配は4:20:10:1ということになる。すなわち、マントル遷移層に極めて高濃度に水が保持され、地球内部の水の貯蔵庫となっていることが考えられる。
  • 永島 一秀, 竹田 裕, 伊藤 正一, 圦本 尚義 日本地球化学会年会要旨集 50 (0) 37 -37 2003年 [査読無し][通常論文]
     
    CRコンドライトのMg-richコンドルールのコアおよび，リムの酸素同位体分布について報告する．リムの酸素同位体組成分布は，同位体マッピングを行うことで評価した．その結果，およそ半分のオリビン粒子が16Oに富む組成をもち，その他の半分のオリビンや他の粒子は16Oに乏しい組成を持つことが分かった．16Oに富むオリビンの存在は，コンドルールリムは，起源の異なる物質が，コンドルールに集積することによって形成されたことを示唆する．
  • 伊藤 正一, 圦本 尚義 日本地球化学会年会要旨集 50 (0) 38 -38 2003年 [査読無し][通常論文]
     
    Y81020 CO3.0 chondriteからO-16-poorなコンドルールを内包するO-16-richなigneous CAIを発見した。さらに、O-16-poorなmelilite coreをO-16-richなigneous CAIが取り囲んでいた。結果、コンドルールとCAIの形成は空間的、時間的に重なっていたことを示した。酸素同位体の結果からから、初期太陽系における固体物質は循環しながら進化したことを示した。
  • 松濤 誠之, 永島 一秀, 長沢 宏, 圦本 尚義 日本地球化学会年会要旨集 50 (0) 39 -39 2003年 [査読無し][通常論文]
     
    炭素質隕石を初めとする始源的隕石は太陽系初期に形成された。これら隕石中には太陽系形成以前に存在した恒星の放出物から形成された微粒子が太陽系形成時の加熱による蒸発，溶融をのがれ，それら隕石中にごく少量含まれている．これらは一般にプレソーラーグレインとよばれる。 従来プレソーラーグレインの分離回収にはシカゴ大学のグループが開発した酸を用いて隕石を分解する方法が広く用いられている(Amari et al., 1994)．シカゴグループの方法はシリケイト成分をフッ酸を用いて除去し，その残査からプレソーラーグレインを見つけ出す方法である．現在までに報告されているプレソーラーグレインのほとんどがこの方法で分離，回収された物である．本研究ではNaOHを用いた岩石融解法(Chan et al., 1983)を用いて炭素質コンドライト中のシリケイト成分を融解し，その残渣を同位体分析しプレソーラーグレインを分離する方法の開発を行った．異なった方法でシリケイト成分を除去することにより，今までの結果を独立に検証することができ，また新しい組成や形状のプレソーラーグレインを発見することが期待できる．
  • J Chen, T Inoue, H Yurimoto, DJ Weidner GEOCHIMICA ET COSMOCHIMICA ACTA 66 (15A) A135 -A135 2002年08月 [査読無し][通常論文]
  • K Makide, Y Fukasawa, H Yurimoto, H Nagasawa METEORITICS & PLANETARY SCIENCE 37 (7) A92 -A92 2002年07月 [査読無し][通常論文]
  • H Yurimoto, K Kuramoto METEORITICS & PLANETARY SCIENCE 37 (7) A153 -A153 2002年07月 [査読無し][通常論文]
  • TJ Fagan, H Yurimoto, AN Krot, K Keil METEORITICS & PLANETARY SCIENCE 37 (7) A45 -A45 2002年07月 [査読無し][通常論文]
  • 伊藤 正一, 永島 一秀, 国広 卓也, 圦本 尚義 日本地球化学会年会要旨集 49 (0) 110 -110 2002年 [査読無し][通常論文]
     
    南極産炭素質隕石Y81020 (CO3.0)中に見つかった粗粒CAIは内部がメリライトとファッサイトからなりWork-Loveringリムに囲まれている。このCAIを同位体顕微鏡を用いて空間分解能2ミクロンの酸素同位体分布マップを得ることに成功した。本発表ではその分析装置と分析法を示し、その結果の信頼性を吟味する。
  • 永島 一秀, 伊藤 正一, 国広 卓也, 圦本 尚義 日本地球化学会年会要旨集 49 (0) 111 -111 2002年 [査読無し][通常論文]
     
    同位体顕微鏡による酸素同位体分布マップとEPMAによる元素分布マップを比較することにより南極産炭素質隕石Y81020 (CO3.0)中に見つかった粗粒CAIの鉱物内の同位体不均一が鉱物の結晶成長に伴いどのようにして導入されたのかが議論された。酸素同位体以上は単一プロセスでCAI中に記録されたのではなく、非平衡状態における鉱物の溶融と結晶成長によるものであった。
  • 圦本 尚義, 倉本 圭 日本地球化学会年会要旨集 49 (0) 112 -112 2002年 [査読無し][通常論文]
     
    隕石中の酸素同位体異常の存在から, 原始太陽系星雲中には酸素同位体異常が存在していたことは広く知られているが, その起源については未だに謎である。今回, 分子雲が原始惑星系円盤に進化したとき, 分子雲で発生していた非質量依存性の酸素同位体分別がどのような変化をするのか考察した。その結果, 同位体異常は原始惑星系円盤内部領域において普遍的に起こる現象かもしれないという結果を得た。
  • 阿部 なつ江, 荒井 章司, 松影 香子, 二ノ宮(田中) 小満, Shcheka Sergei, 圦本 尚義 日本地質学会学術大会講演要旨 2002 (0) 2002年 [査読無し][通常論文]
  • 高柳 功, 中村 淳一, Fossum Eric R., 永島 一秀, 国広 卓也, 圦本 尚義 映像情報メディア学会技術報告 26 (0) 7 -12 2002年 [査読無し][通常論文]
     
    荷電粒子検出用イメージセンサの読み出しノイズを低減するため、新しい画素構造を導入した積層型CMOSイメージセンサを試作、評価した。画素内の読み出しトランジスタのホットキャリア効果を抑圧することで、低温動作時の暗電流ドリフトをほぼ検知限界以下の5×10^<-8>V/sまで低減することができた。また暗電流ノイズ低減と併せて、開口率の改善とチャネル雑音の低減を行い、さらにリセット雑音を非破壊読み出し(Non-Destructive Read Out-CDS: NDRO-CDS)で抑圧することで、感度を大幅に改善した。今回の素子を二次イオン質量分析装置に組み込んで評価した結果、10keVのAlイオン撮像実験において、トータルノイズフロア3ion/pixelかつダイナミックレンジ84dBを達成した。
  • 阿部 なつ江, 荒井 章司, 松影 香子, 二ノ宮(田中) 小満, Shcheka Sergei, 圦本 尚義 日本地質学会学術大会講演要旨 2002 (0) 9 -9 2002年 [査読無し][通常論文]
  • Y Higo, T Inoue, T Irifune, H Yurimoto GEOPHYSICAL RESEARCH LETTERS 28 (23) 4415 -4415 2001年12月 [査読無し][通常論文]
  • 井上 徹, 圦本 尚義 月刊地球 23 (7) 504 -506 2001年07月 [査読無し][通常論文]
  • In istu investigation for the origin of the interplanetary dust particles
    H. Kobatake, K. Tsukamoto, E. Yokoyama, H. Satoh, H. Yurimoto Lunar and Planetary Science XXXII 1550 2001年 [査読無し][通常論文]
  • 伊藤 元雄, 圦本 尚義 地學雜誌 109 (6) 836 -844 2000年12月01日 [査読無し][通常論文]
     
    Petrography or observation of petrographic texture is one of the most basic techniques for microanalysis of natural samples. Secondary ion mass spectrometry (SIMS) has been applied to isotope and trace element analyses in micron-size minerals in various natural samples evaluated by conventional petrography, e.g., search for the oldest rock, mineral and life, and for presolar grains. However, elemental texture and isotopic texture often indicate a different evidence of origin and evolution of the sample. In this paper, we reviewed SIMS history in cosmo-and geo-chemistry from a viewpoint from point-analysis to area-analysis. Here we propose that promotion of isotopic texture research, isotopography, is an important future trend of cosmo-and geo-chemistry. We also propose that further diffusion study in minerals under various Pressure-Temperature conditions is necessary. The analysis of isotopography by diffusion gives a quantitative scale of geospeedmetry of natural samples.
  • 国広 卓也, 永島 一秀, 高柳 功, 中村 淳一, 小坂 光二, 圦本 尚義 日本惑星科学会秋期講演会予稿集 2000 31 -31 2000年10月31日 [査読無し][通常論文]
  • M Ito, H Yurimoto, H Nagasawa METEORITICS & PLANETARY SCIENCE 35 A81 -A81 2000年09月 [査読無し][通常論文]
  • JT Wasson, AE Rubin, H Yurimoto METEORITICS & PLANETARY SCIENCE 35 A166 -A167 2000年09月 [査読無し][通常論文]
  • H Yurimoto, JT Wasson METEORITICS & PLANETARY SCIENCE 35 A175 -A176 2000年09月 [査読無し][通常論文]
  • 圦本 尚義 天文月報 93 (3) 121 -133 2000年02月20日 [査読無し][通常論文]
  • Direct observation of evaporation and condensation from silicate melts
    H. Kobatake, K. Tsukamoto, H. Yurimoto, C. Kaito, E. Yokoyama Antactic Meteorites XXV 50 -52 2000年 [査読無し][通常論文]
  • 伊藤 元雄, 圦本 尚義 地學雜誌 109 (6) Plate5a -Plate5a 2000年 [査読無し][通常論文]
  • 永島 一秀, 国広 卓也, 高柳 功, 中村 淳一, 小坂 光二, 圦本 尚義 映像情報メディア学会技術報告 24 (0) 13 -18 2000年 [査読無し][通常論文]
     
    Output characteristics of two-dimensional solid-state detector for charged particles has been analyzed by ion irradiation with keV level energy. The detector was designed by CMOS rule and constructed as stacked CMOS-device[1]. The detector was operated under nondestructive readout mode due to correction of fixed pattern noises among pixels and reset noise of a pixel. The output signals of a pixel correlated linearly with incoming ions over the range of four orders of magnitude. Non-linear effects of the output is about 10% over the whole dynamic range of a pixel. The dominant effects of the non-linear components are reset voltage drop down by overlap capacitance. After correction of the drop down effect the nonlinearity reduced to percent level, the percent level nonlinearity was due to voltage dependence of pixel capacitance with ion irradiation.
  • 長嶋 剣, 塚本 勝男, 小畠 秀和, 佐藤 久夫, 圦本 尚義 日本結晶成長学会誌 27 (1) 55 -55 2000年 [査読無し][通常論文]
  • 小畠 秀和, 塚本 勝男, 長嶋 剣, 横山 悦郎, 圦本 尚義, 佐藤 久夫 日本結晶成長学会誌 27 (1) 56 -56 2000年 [査読無し][通常論文]
  • 高柳 功, 中村 淳一, 杁本 尚義, 国広 卓也, 永島 一秀, 小坂 光二 電子情報通信学会技術研究報告. EID, 電子ディスプレイ 99 (374) 7 -12 1999年10月21日 [査読無し][通常論文]
  • 高柳 功, 中村 淳一, 圦本 尚義, 国広 卓也, 永島 一秀, 小坂 光二 電子情報通信学会技術研究報告. EID, 電子ディスプレイ 99 (374) 7 -12 1999年10月21日 [査読無し][通常論文]
     
    積層型荷電粒子検出用CMOSイメージセンサを開発した。本センサを2次イオン質量分析装置に導入し、80dBの広いダイナミックレンジと、良好な線形性を有する荷電粒子像検出システムを実現した。画素のノイズを評価した結果、CMOSセンサの特長である非破壊読み出しを利用してリセットノイズを抑圧できれば、将来的に100dBを超えるダイナミックレンジの実現も可能であると考えられる。
  • 高柳 功, 中村 淳一, 圦本 尚義 電子情報通信学会技術研究報告 99 (374) 7 -12 1999年10月21日 [査読無し][通常論文]
  • 圦本 尚義 表面科学 20 (9) 658 -664 1999年09月10日 [査読無し][通常論文]
  • 高岡 宣雄, 土山 明, 古宇田 亮一, 圦本 尚義 鉱物学雜誌 = Journal of the Mineralogical Society of Japan 28 (3) 93 -94 1999年08月01日 [査読無し][通常論文]
  • 圦本 尚義 ぶんせき 291 219 -228 1999年03月05日 [査読無し][通常論文]
  • H Yurimoto SCIENCE 283 (5410) 2102 -2102 1999年03月 [査読無し][通常論文]
  • H Yurimoto SCIENCE 283 (5398) 35 -35 1999年01月 [査読無し][通常論文]
  • 上野 雄一郎, 磯崎 行雄, 丸山 茂徳, 圦本 尚義 日本地質学会学術大会講演要旨 1999 (0) 1999年 [査読無し][通常論文]
  • N. Abe, M. Takami, H. Yurimoto Ofioliti 24 (1 A) 47 -47 1999年 [査読有り][通常論文]
     
    There are some localities of residual peridotite xenoliths from western edge arcs of the Circum-Pacific Ocean. Abe (1997) and Abe et al. (1998; 1999) show that the peridotite xenoliths from those arcs underwent wedge mantle metasomatism with some influx from subducted slab. We report the petrological and geochemical characteristics of the ultramafic xenoliths in the Cenozoic alkali-olivine basalts of Oki-Dogo island, another locality reported by Abe (1997) and Abe et al. (1998; 1999) in the Japan Sea. Both Group I and II ultramafic xenoliths (classification by Frey and Prinz (1978), equivalent to Wilshire and Shervais (1975) Cr-diopside and Al-augite series, respectively) come from Oki-Dogo island. Preliminary data on the petrology of the ultramafite, and also mafic xenoliths are in Yamaguchi (1964), Aoki (1977) and Takahashi (1978). We present here their mineral chemistry, especially the abundance of trace-elements in clinopyroxenes of Group I peridotite and the metasomatism by Group II ultramafic xenoliths suite. Oki-Dogo Island is located at the northern end of the Southwest Honshu Arc in the Japan Sea. Extensive alkalic volcanism (mugearite, hawaiite, trachy-andesite, trachyte and alkali rhyolite) took place from late Miocene to early Pliocene in this island. Alkali-olivine basalts with a subordinate amount of basanites were extruded from many vents situated inside of the supposed magma chamber. These basalts were monogenetic in most cases and their extrusion started at least 3.6 Ma and lasted at least until 0.8 Ma (Kaneoka et al., 1977). Most of these alkali basalts are fresh and contain 2 to 15 percent normative nepheline. Ultramafic and mafic inclusions are commonly found in most of the monogenetic lava flows. According to Takahashi (1978), those xenoliths are classified into five groups: spinel lherzolite, banded spinel peridotite, banded plagioclase peridotite, gabbro and granulite groups. The rocks of the banded spinel peridotite group are cumulates formed by fractional crystallization of basic magmas in a pressure range between about 10 and 20 kb, and recrystallized at the same depth. Some of the spinel lherzolite group are cumulates from basic magmas in the upper mantle during the partial melting of the preexisting lherzolite. Group I peridotite, which was classified as spinel lherzolite group by Takahashi (1978), has very low-Cr spinel. The Cr (=Cr/(Cr+Al) atomic ratio) of chromian spinel is less than 0.3. Their Fo content of olivine varies from 90 to 83, while their NiO content is rather constant (0.25 to 0.40 wt%). Clinopyroxene grains in polished thin sections were analyzed in situ for abundances of REE, Ti, Sr, Y, Zr with the secondary ion mass spectrometer (SIMS; Cameca IMS-3f) at Tokyo Institute of Technology. The chondrite normalized REE patterns of clinopyroxene in Oki-Dogo Group I xenoliths are flat to U-shaped LREE-depleted. HREE contents, however, almost same level, which suggests that those peridotites have the same degree of melt extraction. The evidence from their REE patterns and trace-element contents suggest that the Group I peridotites underwent Fe-rich mantle metasomatism by the alkaline magma. The continental type mantle metasomatism as well as arc type metasomatism suggested by Abe (1997) occurs in mantle wedge.
  • 圦本 尚義 表面科学 20 (9) 658 -664 1999年 [査読無し][通常論文]
     
    Stratigraphy of oxygen isotope anomaly in Ca-Al-rich inclusions (CAIs) in primitive meteorites has been determined by secondary ion mass spectrometry. The results show that the CAIs have experienced multiple heating event in the protoplanetary disk as well as in vacuum. The oxygen isotope anomaly in CAIs was introduced by isotopic exchange reaction between the 16O-rich melt and the surrounding 16O-poor gas during the heating. A proposed energy source for the multiple heating would be flares of active protosun. The proto-CAIs generated near the protosun were launched into the meteorite forming region in the protoplanetary disk by bipolar out flow.
  • 圦本 尚義, 国広 卓也, 永島 一秀, 高柳 功, 小坂 光二 映像情報メディア学会技術報告 23 (0) 19 -23 1999年 [査読無し][通常論文]
     
    Charged particles such as ion and electrons with keV order kinetic energy are important for probes and signals for surface analyses. Many detection systems have been developed for measurement of two-dimensional distribution for the particles. However, capabilities of solid-state area detector are not sufficient for quantitative analysis for the charged particles, although solid-state imager such as charge coupled device has been great succeeded to photon detection for optical spectroscopy. This paper discussed performance and characteristics of a novel solid-state imager for charged particles. This device is useful to charged particle detection such as mass spectrometry and electron microscopy.
  • 上野 雄一郎, 磯崎 行雄, 丸山 茂徳, 圦本 尚義 日本地質学会学術大会講演要旨 1999 (0) 175 -175 1999年 [査読無し][通常論文]
  • 圦本 尚義, 倉本 圭 科学 68 (8) 637 -645,649〜650 1998年08月 [査読無し][通常論文]
  • M Ito, H Yurimoto, H Nagasawa METEORITICS & PLANETARY SCIENCE 33 (4) A74 -A75 1998年07月 [査読無し][通常論文]
  • S Maruyama, H Yurimoto, S Sueno METEORITICS & PLANETARY SCIENCE 33 (4) A98 -A98 1998年07月 [査読無し][通常論文]
  • 圦本 尚義 遊・星・人 : 日本惑星科学会誌 7 (1) 9 -10 1998年03月25日 [査読無し][通常論文]
  • CAI related spinel in a compound chondrule: evidence of O isotope
    Seiji Maruyama, Hisayoshi Yurimoto, Shigeho Sueno Lunar and Planetary Science XXIX (XXIX) 1342 1998年 [査読無し][通常論文]
  • 上野 雄一郎, 磯崎 行雄, 丸山 茂徳, 圦本 尚義 日本地質学会学術大会講演要旨 1998 (0) 143 -143 1998年 [査読無し][通常論文]
  • 国広 卓也, 永島 一秀, 小坂 光二, 平田 岳史, 圦本 尚義 日本惑星科学会秋期講演会予稿集 1997 38 -38 1997年09月15日 [査読無し][通常論文]
  • 圦本 尚義 科学 67 (7) 560 -566 1997年07月 [査読無し][通常論文]
  • 圦本 尚義, 松本 一哉 分析化学 = Japan analyst 45 (6) 493 -500 1996年06月 [査読有り][通常論文]
     
    数keVオーダーのエネルギーを持つイオン粒子や電子線は,固体の表面分析や表面改質のためのプローブや信号として,よく用いられる粒子線である.そのため,これらの二次元分布を定量的に測定するためにいろいろな検出システムが考案されてきた.しかし,粒子線に対する検出器として,光学分野で画期的に成長した電荷結合素子(CCD)のような固体撮像素子の開発・実用化は遅れている.著者らのグループでは,粒子線の積分型二次元検出器として,電極を積層した増幅型固体撮像素子(AMI)を開発中である.今回は,積層型AMIの構造と動作原理及びkeVオーダーのエネルギーを持つイオン粒子を照射した場合の特性を報告する.
  • 平田 岳史, 圦本 尚義 日本地質学会学術大会講演要旨 1996 (0) 1996年 [査読無し][通常論文]
  • 角替 敏昭, 圦本 尚義 日本地質学会学術大会講演要旨 1996 (0) 1996年 [査読無し][通常論文]
  • 平田 岳史, 圦本 尚義 日本地質学会学術大会講演要旨 1996 (0) 21 -21 1996年 [査読無し][通常論文]
  • 角替 敏昭, 圦本 尚義 日本地質学会学術大会講演要旨 1996 (0) 312 -312 1996年 [査読無し][通常論文]
  • 小野 秀史, 広瀬 敬, 圦本 尚義, 丸山 茂徳 日本地質学会学術大会講演要旨 1995 (0) 251 -251 1995年 [査読無し][通常論文]
  • 宮城 磯治, 圦本 尚義 火山 40 (5) 349 -355 1995年 [査読無し][通常論文]
     
    日本を含む島弧の火山では,しばしば爆発的な噴火が見られる.マグマ中の揮発性成分(主に水)の飽和・発泡・膨張にともなうマグマの急激な放出が,それらの要因である.火山噴火の理解の為には,マグマ含水量,マグマヘの水の溶解度,そして噴火時の脱水過程を理解する必要がある.しかし,噴出時の脱水のため,噴出前の含水量を火山岩から読みとることはきわめて困難である.これまでのところ,斑晶中のガラス包有物の含水量を分析することが,マグマ含水量を見積もるための最も有効な手段であると考えられる.ただし,斑晶中のガラス包有物の大きさは通常直径100μm以下であるため,微小領域の正確な含水量測定法が必要である.そこで本研究では,二次イオン質量分析計を用いた含水量分析の手法を開発した.これまでの研究により,ガラスの組成が異なると水素の二次イオン生成率も変化することが知られており,この手法の問題点であった.しかし本研究では,ガラスのシリカ濃度を用いてその生成率が補正できることを示し,この問題点を克服した.これにより玄武岩質〜流紋岩質ガラスの微小部分(半径約5μm)の含水量を正確(約±0.5wt.%)に分析する手法が確立された.この手法の応用として姶良カルデラの約2万2千年前の噴出物から取り出した斑晶メルト包有物の分析を行ったところ,5～7wt.%の含水量が示された.これはAramaki(1971)の水熱合成実験により得られている水分圧と水の溶解度から推定される含水量と良く一致する.
  • 圦本尚義 固体惑星物質科学の基本的手法と応用 67 -80 1994年
  • 宮城 磯治, 圦本 尚義, 高橋 栄一 日本火山学会講演予稿集 1994 (0) 113 -113 1994年 [査読無し][通常論文]
  • 王 五一, 栗田 敬, 末野 重穂, 圦本 尚義, 高橋 栄一 日本火山学会講演予稿集 1994 (0) 163 -163 1994年 [査読無し][通常論文]
  • 黒沢 正紀, 圦本 尚義, 松本 一哉 鉱物学雑誌 22 (2) p63 -68 1993年04月 [査読無し][通常論文]
  • 圦本 尚義 ぶんせき 219 190 -194 1993年03月05日 [査読無し][通常論文]
  • 圦本尚義 実験化学講座13(丸善) 439 -451 1993年
  • Fe-Mg zoning in olivines of Allende chondrule
    Seiji Maruyama, Hisayoshi Yurimoto, Shigeho Sueno, Kei Kurita Antarctic Meteorites XVIII 110 -113 1993年 [査読無し][通常論文]
  • 黒沢 正紀, 圦本 尚義, 松本 一哉 鉱物学雜誌 22 (2) 63 -68 1993年 [査読無し][通常論文]
     
    The abundance of hydrogen in olivines has been determined by secondaryion mass spectrometry (SIMS). Hydrogen implanted olivines were prepared for SIMSmeasurements as standards. A linear relationship was obtained between the relative hydrogen intensity ratio against the silicon and hydrogen concentrations overthe range of 100 to 25000 ppm H/Si.
  • 角替 敏昭, 圦本 尚義, 宮野 敬 日本地質学会学術大会講演要旨 1993 (0) 738 -738 1993年 [査読無し][通常論文]
  • 角替 敏昭, 圦本 尚義, 宮野 敬 日本地質学会学術大会講演要旨 1992 (0) 598 -598 1992年 [査読無し][通常論文]
  • 虎谷 秀穂, 圦本 尚義 日本結晶学会誌 29 (3) 234 -235 1987年 [査読無し][通常論文]
  • 圦本 尚義, 末野 重穂 日本結晶学会誌 29 (4) 259 -269 1987年 [査読無し][通常論文]
     
    Application of Secondary ion mass spectrometry (SIMS) to the study of chemical analyses of insulated materials is described. A simple working curve method is useful for the quantitative analyses of SIMS data. The sensivity acheaved is suffietient to concentration levels from ppm to ppb. This is demonstrated for the partition coefficients between olivine and magma and for the impuriry destribution in diamond thin film. A blieaf description of two demensional analyses is also made.
  • 松浦 茂, 末野 重穂, 圦本 尚義 日本結晶学会誌 26 (0) 13PB -3-13PB-3 1984年 [査読無し][通常論文]

書籍等出版物

所属学協会

  • 日本地球化学会   日本学術振興会第141委員会   日本鉱物学会   Meteoritical Society   

共同研究・競争的資金等の研究課題

  • 日本学術振興会：科学研究費助成事業 基盤研究(S)
    研究期間 : 2021年07月 -2026年03月 
    代表者 : 圦本 尚義
     
    本研究の目的は，前主系列星期から現在に至る46億年間の太陽活動の変遷を解明することである．そのために，46億年前に太陽風照射されたガスリッチ炭素質隕石；40億年前，30億年前，20億年前，10億年前，1億年前に太陽風照射された月面レゴリス；百万年前に太陽風照射された小惑星イトカワ粒子の分析を行う．これらの分析結果から解析されるkeVレベルからMeVレベルに至る運動エネルギーをもつ粒子放射スペクトルの比較により，太陽活動の経年変化を解明する．本研究は未踏の新規研究分野であり，その成果は恒星の進化を探るのみならず，原始惑星系円盤進化，惑星進化，宇宙風化，宇宙天気などの理解に向けて大きな意味を持つ．本年度は以下の研究成果が得られた． 1. 同位体ナノスコープによる希ガスの組成分析・同位体分析 本研究では，世界唯一の希ガス局所分析が可能な同位体ナノスコープを用い，地球外物質の固体粒子局所表面の希ガス濃度・同位体分布より太陽風の照射量とエネルギー分布を決定することにより，過去の太陽活動を解析している．同位体ナノスコープの周回イオン軌道中に挿入する誘電電荷検出器を考案し，電荷増幅器による誘導電荷検出システムの設計を完了した．また，同位体ナノスコープの広領域イメージング化の装置開発を完了した． この装置を用い，Heに加え，新たにNe, Arの分析法の開発を進めている． 2. 月粒子中に記録される太陽活動 1億年前までの太陽活動をNASA APOLLO探査機が持ち帰った月粒子（71501）から解読したHeの深さ方向分布を測定し，太陽風照射量を求めた． 3. 隕石中に記録される太陽活動 前主系列星期の太陽活動を解析するためにガスリッチ炭素質隕石NWA 801を分析した．開発した広領域イメージング装置によりこの隕石中の太陽風希ガスの濃集箇所を特定した．今後，太陽風起源He, Ne, Ar分布を明らかにする.
  • 日本学術振興会：科学研究費助成事業 特別推進研究
    研究期間 : 2021年05月 -2026年03月 
    代表者 : 廣瀬 敬, 太田 健二, 坂本 直哉, 梅本 幸一郎, 圦本 尚義, Alfred Baron
     
    本研究の鍵となる水素を含む鉄合金系の実験を集中的に行った。Fe-FeH系はFukai (1992)以来、連続固溶体系と考えられていた。しかし本研究により、Fe-FeH系の融解開始温度が端成分FeHの融解温度よりも十分低いことが明らかとなり、>40GPaでは共融系であることが初めてわかった。さらにFe-FeH系の共融点組成（水素濃度）ならびに固体-液体鉄間の水素の分配を見積もることに成功した。共融点の水素濃度は外核中の水素量の上限を与える、外核-内核間の水素の分配が計算可能になるという意味で、これらは極めて重要な成果と言える。Fe-FeH系の共融点組成が得られたことにより、外核が軽元素に乏しい内核を結晶化するための条件が厳しくなった。そして、この条件を満たす組成範囲と、外核で観測される密度・縦波速度を説明する組成範囲がほとんど重ならない（この２つの制約を満たす組成範囲がかなり狭い）ことがわかった。さらには、本研究の技術開発の目玉であるクライオSIMSの開発に成功し、高圧下でコア（金属鉄）-マントル（シリケイト）間で水素の同位体が大きく分別する結果が得られた。これにより、地球全体の水素同位体比が推定できた上、隕石のデータと比較して地球の炭素／水素比を得ることができた。軽元素同士の大きな相互作用を考慮した、超高圧下での固体鉄（内核）と液体鉄合金（外核）の間の軽元素の分配係数も明らかになった。これらの結果を基に、外核・内核それぞれの軽元素組成を狭い範囲に絞り込むことに成功した。その他、液体鉄合金の密度・速度の測定、リキダス相関係の決定、固体鉄・鉄合金の密度・速度決定、金属-シリケイト間の軽元素分配などを精力的に進めた。
  • 日本学術振興会：科学研究費助成事業 学術変革領域研究(A)
    研究期間 : 2020年11月 -2025年03月 
    代表者 : 橘 省吾, 瀧川 晶, 奈良岡 浩, 薮田 ひかる, 岡崎 隆司, 松本 恵, 圦本 尚義
     
    太陽系も他の惑星系と同様，原始太陽の周囲に原始太陽系円盤がつくられることで誕生した．原始太陽系円盤も，電波天文観測で捉えられている惑星系形成領域の多様な化学環境のいずれかを初期状態とし，地球を含む惑星に至るまで進化したと考えられる．分子で観測される惑星系形成領域の化学的多様性に，太陽系の初期状態がどのように位置づけられ，太陽系がその形成時にどのような化学過程を経たのか，を明らかにすることが本課題の目的である．中間温度・中間密度環境で様々な化学反応が起こりうる惑星系形成領域での多様な化学を理解するためには，観測や分析の結果のみから推定するのではなく，原子・分子レベルでの素過程に立ち戻り，新たな学理を構築する必要がある．本領域で物理・化学分野との協働で進める素過程の解明に基づき，惑星系形成領域の化学的多様性を理解し，太陽系の初期化学状態をその中に位置づけることを目的とする．当該年度は小惑星探査機「はやぶさ2」が持ち帰った近地球C型小惑星リュウグウ試料の初期分析をおこない，無機化学（元素，同位体）・鉱物学・岩石学・有機化学（固体有機物，可溶性有機分子）の観点から，その詳細を明らかにし，既存の隕石との比較をおこなった．また，リュウグウに存在する鉱物のひとつである炭酸塩の真空分解実験をおこない，分解速度をもとにして，リュウグウが近地球側小惑星として経験した最も太陽に近い軌道条件の制約をおこなった．
  • 日本学術振興会：科学研究費助成事業 基盤研究(A)
    研究期間 : 2021年04月 -2024年03月 
    代表者 : 圦本 尚義, 馬上 謙一
     
    本研究の目的は，原始星太陽と主系列星太陽との間の太陽活動の違いを解明することである．そのために，46億年前に太陽風照射されたガスリッチ炭素質隕石； 1億年前に太陽風照射された月面レゴリス；百万年前に太陽風照射された小惑星イトカワ粒子の分析を行う．これらの分析結果から解析された粒子放射(太陽風)スペクトルの対比により，前主系列星期と主系列星期の太陽活動の特徴を解明する．本研究は未踏の新規研究分野であり，その成果は，恒星の進化を探るのみならず，原始惑星系円盤進化，惑星進化，宇宙風化，宇宙天気などの理解に向けて大きな意味を持つ．本年度は以下の研究を開始し，基盤S研究に引き継がれた． 1. 同位体ナノスコープによる希ガスの組成分析・同位体分析 希ガス超局所分析(空間分解能：縦800nm横800nm深5nm)が可能な同位体ナノスコープを用い，地球外物質の固体粒子局所表面の希ガス濃度・同位体分布より太陽風の照射量とエネルギー分布を決定する．今年度は，1辺100umを超える試料表面の広領域イメージングを可能にするための一段階として，真空ゲートバルブを購入し，改造にとりかかった．この改造は，新規に採択された基盤S研究に引き継がれた． 2. 小惑星イトカワ粒子中に記録される太陽活動 百万年前までの太陽活動をJAXA はやぶさ探査機が持ち帰った小惑星イトカワ粒子から解読する．イトカワ粒子の分析を行い，粒子の表面から太陽風Heの3次元濃度分布(nmスケールの分解能)の測定を開始し，Heは粒子表面下50nm付近に多く存在しているのを確認した．これは低速太陽風(keV/核子)の照射が多かったことを示す．今後は本研究課題を引き継いだ基盤S研究において，深さ400nm以深のHeを分析し，百keV/核子のエネルギーを持つコロナ質量放出の検出と定量を目指す．
  • 日本学術振興会：科学研究費助成事業 基盤研究(A)
    研究期間 : 2021年04月 -2024年03月 
    代表者 : 廣瀬 敬, 太田 健二, 坂本 直哉, 梅本 幸一郎, 圦本 尚義
     
    結果的に１ヶ月半という期間となった本課題について、以下の７つの研究を進めた。１）SPring-8のビームラインBL43LXUにおけるX線非弾性散乱法を使った液体FeOの縦波速度測定に関し、過去の測定データの解析と６月のビームタイムに向けた実験準備を行った。また２）同じくSPring-8のビームラインBL10XUにおけるX線回折測定によって、超高圧高温まで 固体Feの格子体積を求め、状態方程式を決定するためのデータを解析した。さらに３）固体FeHの高圧高温下における体積データから高温の状態方程式を作成するとともに、４）Fe-FeH系の高圧高温実験を行って、状態図の作成を試みた。クライオ二次イオン質量分析法を使って、回収試料の三次元水素濃度マッピングを行い、水素の定量分析法の開発を進めた。５）Fe-Si系の実験も200万気圧までやり直し、共融点の化学組成の圧力変化を正確に見積もった。６）コア形成時の金属-シリケイト分配についても二次イオン質量分析法を使った定量を行い、水素（水）が系に含まれることにより、硫黄と炭素の分配係数が大きく変化する（メタルに分配されにくくなる）ことを見つけた。最後に、７）沈み込んでいく海洋プレート（スラブ）は水をコアーマントル境界まで輸送し、その高温環境下で脱水した水はコアの金属鉄と化学反応を起こして、鉄水酸化物などを作ると従来考えられていた。ところが今回二次イオン質量分析法を使って行った、含水SiO2相の含水量を定量する実験によって、スラブが運んだ水は脱水せず、コアーマントル境界域に水を供給しないことが明らかになった。
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2020年04月 -2023年03月 
    代表者 : 中井 泉, 由井 宏治, 圦本 尚義, 寺田 靖子, 阿部 善也
     
    本研究の目的は、リュウグウ小惑星試料の化学組成を非破壊蛍光X線分析により明らかにすることである。本年度は，その目的のために開発した①から⑤の手法を用いて実資料を分析し、⑥の成果を得て目的を達成した。 ①粉末試料を加圧成型せず波長分散型蛍光X線装置（WDXRF）の真空系へ導入し，定量分析を行う技術を確立し，実試料の分析に適用した。約0.03gの微量試料に対して炭素，酸素を含む23元素の定量分析を行った。酸素を単独の成分として定量することで，含水粉末試料に対してXRF単独で水の影響も考慮した分析値が得られることを示した意義は大きい。②エネルギー分散蛍光X線分析（ED-XRF）によりCからZnまでの元素を定量した。新SDD検出器を導入し、C専用の検量線を作成することで定量分析が可能になった。③高エネルギー蛍光X線分析（HE-SR-XRF）では、SPring-8のBL37XU（37.5 keV）、BL08W（116.0 keV）で単色化した放射光X線を励起光として、ZnからNdまで計18元素を定量した。④SPring-8 BL37XUにてリュウグウ試料の放射光状態分析を行った。Feの状態分析の結果は試料が炭素質コンドライトに分類されることを支持した。⑤小惑星試料表面に点在する水質変性による二次鉱物（炭酸塩など）を中心にラマン分光分析した。試料表面に水熱作用による変質が認められ、リュウグウがCI型隕石の一つの母天体であることを強く示唆するだけでなく、かつて存在した水の環境を推定する上で重要な手がかりを得た。 ⑥炭素質隕石はC型小惑星の破片と考えられている。はやぶさ２が採取したリュウグウ試料の全岩化学組成を決定した。試料は炭素質コンドライト隕石，特にCIコンドライトに含まれる物質から構成されていた。本試料は人類が手にしている天然試料の中で最も太陽大気の元素存在比を保持している試料である。
  • 日本学術振興会：科学研究費助成事業 基盤研究(A)
    研究期間 : 2019年04月 -2023年03月 
    代表者 : 橘 省吾, 瀧川 晶, 川崎 教行, 圦本 尚義
     
    太陽系の原材料となったダストは，太陽より前世代の恒星周囲でつくられたダスト（恒星周ダスト）や，星間空間で破壊され，再生産されたダスト（星間再生産ダスト）と考えられる．恒星周ダストは，特異な同位体組成を持つ微粒子として隕石や彗星塵などに僅かに発見される．一方，星間再生産ダストは，太陽と同じ同位体組成を持つはずであるが，ダストの集積でつくられた地球や隕石の酸素同位体組成は，太陽とは異なっている．本研究では，太陽系原材料となった「太陽型ダスト（恒星周ダストと星間再生産ダスト）」が，太陽系最初期にダストとガスとの酸素同位体交換反応を経て，地球や隕石の材料である「地球型ダスト」へと変身する過程に注目する．ダストとガスとの酸素同位体交換反応を実験で明らかにし，酸素同位体交換反応に必要な原始太陽系円盤の物理化学条件を定量的に決定し，隠された太陽系原材料物質を始原隕石中に発見することにより，太陽系での同位体交換過程を解明する．今年度は，非晶質エンスタタイトとH2Oの酸素同位体交換は，非晶質フォルステライトに比べて，1/30程度と小さく，初期太陽系での酸素同位体交換には非晶質フォルステライトに比べて，約100 K高温が必要であることがわかった．非晶質フォルステライトとCOガスとの酸素同位体交換実験では，同位体交換速度がH2Oガスとの交換に比べて小さいことがわかった．また，酸素同位体交換反応実験の前段階として，FeOの入った非晶質かんらん石，非晶質酸化アルミニウム，遷移アルミナ相の結晶化実験を開始した．
  • 日本学術振興会：科学研究費助成事業 基盤研究(S)
    研究期間 : 2016年05月 -2021年03月 
    代表者 : 圦本 尚義, 橘 省吾
     
    太陽系形成の最初期に内側太陽系で高温ガスからの固体凝縮プロセスや加熱による固体溶融プロセスがあったことは，始源的隕石中の難揮発性包有物（CAIやAOA）の存在から明らかである．惑星材料物質が経験したこの高温プロセスは，原始星や原始惑星系円盤の天文観測でも観測されておらず，その物理化学環境はいまだにはっきりとしない．本研究では，難揮発性包有物の同位体岩石学・鉱物学的研究に，室内実験による難揮発性包有物の再現実験を組み合わせ，太陽系最初期の高温プロセスの物理化学環境を定量的に制約する．特に本研究により，原始惑星系円盤内縁領域の圧力条件，水蒸気分圧とガス／ダスト比が新規決定できることが期待される．本年度は以下の研究成果が得られた． 低水素圧条件での模擬CAIの溶融・結晶化実験について水素圧力，加熱時間を系統的に変化させた実験をおこない，CAI模擬物質の組織，構成鉱物化学組成に対する蒸発の影響を求めた．また，低水蒸気圧下でのCAI模擬物質の溶融体と水蒸気間の酸素同位体交換実験を開始した．これまでの実験結果と溶融CAIの鉱物学岩石学・酸素同位体分布の観察・分析とから原始惑星系円盤CAI形成領域のガス圧力を見積もった． Vigarano (CV3) 隕石中のCAI V2-01鉱物学岩石学・酸素同位体分布の観察・分析を行った．このCAIは高温ガスから凝縮でつくられたと考えられた．メリライトは逆累帯構造を示した．もし1400 Kの定温下で結晶成長したと仮定すると，この観察結果は，メリライトの結晶成長中に原始太陽系星雲ガスの圧力が，3E-4barから1E-4barに減少したことを示す．また，Al-Mg年代測定により形成の時間スケールを求めた.
  • 日本学術振興会：科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2018年04月 -2020年03月 
    代表者 : 圦本 尚義
     
    本研究の目的は，人類観測史上最大の太陽フレアである2003年ハロウィン太陽嵐のコロナ質量放出（CME）成分を，NASA Genesis探査機によりサンプルリターンされた太陽風の中から同定し，その速度分布を物質科学的に決定することである．本研究では，太陽を構成する第2最大成分であるヘリウムに着目し，Genesisが回収した基板への太陽風ヘリウムの注入深さ分布を測定することにより，ハロウィン太陽嵐当時の太陽風の速度分布を決定する．そして，それを太陽観測衛星の結果と比較し，ハロウィン太陽嵐のフラックスを検証する．この研究成果は，ハロウィン太陽嵐に限らず，CMEの原子放出メカニズム，CME放出原子の惑星間空間伝播メカニズム，地球磁気圏と太陽嵐との相互作用の解明のために貢献すると思われる．本年度は以下の研究成果が得られた． 同位体ナノスコープLIMASによる太陽風のその場分析を，NASA Genesis探査機が持ち帰った太陽風回収試料について行った．バルク太陽風が照射されたGenesis試料中の太陽風ヘリウムの分析では，特に，深さ100 nm以深へのヘリウムの注入分布を明らかにした．このヘリウム注入分布を，多数の異なる運動エネルギーを仮定したヘリウムの飛程分布曲線に分解することにより，太陽風の深さ方向分布曲線を太陽風の速度分布曲線に変換した．この回収試料から得られた速度分布曲線とACE/SWICS探査機により得られた速度分布曲線を比較することにより，SWICS分析器のキャリブレーション因子について議論した．以上の実験をCME太陽風だけが照射された回収試料についても実施し，太陽風ヘリウムの速度分布を正確に求める方法を確立した．その結果，バルク太陽風とCME太陽風の両方の試料においてハロウィン太陽嵐起源のCMEヘリウムの速度分布が一致することを示した．
  • 日本学術振興会：科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2015年11月 -2018年03月 
    代表者 : 香内 晃, 橘 省吾, 永原 裕子, 深澤 倫子, 山本 智, 圦本 尚義, 奈良岡 浩
     
    宇宙分子進化の研究成果を，大型国際共同研究（ALMA，「はやぶさ２」などの始原的小惑星からのサンプルリターンプロジェクト）との連携に生かし，積極的に海外に発信し，さらに，これらの活動を通じて若手研究者を育成することが主たる目的である．このために，指導的研究者から若手研究者までの派遣および招聘を実施した．その結果，拠点研究機関同士の研究交流が活発におこなわれ，国際連携研究が当初の想定以上に展開され，優れた研究結果が多数生み出された．これらの研究活動を通じて，次世代の指導者たる人材を育成することができた．
  • 日本学術振興会：科学研究費助成事業 基盤研究(A)
    研究期間 : 2014年04月 -2018年03月 
    代表者 : 井上 徹, 肥後 祐司, 栗林 貴弘, 丹下 慶範, 大藤 弘明, 圦本 尚義, 蔡 闹, 末次 秀規, 柿澤 翔, 徐 超文, 野田 昌道
     
    最先端の高圧合成実験技術、放射光X線その場観察実験技術、及び中性子散乱実験技術を駆使して、地球深部における水の存在可能性を探索する研究を行った。結果、下部マントルの主要構成鉱物であるブリッジマナイトに有意に水が含まれうること、そしてその根拠を化学組成変化、単結晶X線構造解析による水素の存在可能性及び格子定数変化、赤外分光法によるOH振動ピークの検出、中性子回折による水素の存在位置の検出、及び体積弾性率等の物性定数の変化の立場から明らかにした。さらに、他の高圧含水相であるsuperhydrous phase Bやphase Dにおいても、同様な置換が起こりうることを明らかにした。
  • 日本学術振興会：科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2013年06月 -2018年03月 
    代表者 : 香内 晃, 橘 省吾, 深澤 倫子, 山本 智, 永原 裕子, 深澤 倫子, 山本 智, 圦本 尚義, 奈良岡 浩, 渡部 潤一
     
    宇宙分子進化研究を実験，観測，理論，分析等の多様な手法で推進し，さらに，これらを学際的な連携・融合研究として展開させることが主たる目的である．このために，全体集会，ワークショップ，国際シンポジウム等を開催するとともに，若手研究者の育成にも努めた．その結果，計画班同士および計画班と公募研究者の連携研究が，当初の想定以上に活発に展開され，優れた研究結果が多数生み出された．それらの研究活動を通じて，次世代の指導者たる人材を育成することができた．さらに，領域のホームページや多種多様な方法でのアウトリーチ活動もおこなった．
  • 日本学術振興会：科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2013年06月 -2018年03月 
    代表者 : 圦本 尚義, 三田 肇, 濱瀬 健司, 奈良岡 浩, 伊藤 正一, 高野 淑識
     
    本研究は，分子雲と原始惑星系の宇宙有機物の生成過程と分子構造との関係を解明することを目的とした．超高質量分解能液体クロマトグラフ質量分析計を導入し，合成模擬分子雲有機物と隕石より抽出した可溶性有機物に対し網羅的に高分解能質量スペクトルを取得した．その精密質量とスペクトルパターンから宇宙有機物はいくつかの同族体有機化合物として分類することが有効であることが判明した．この解析により，アルデヒドとアンモニアが分子雲分子から隕石有機物分子の進化をリンクする新しい鍵となるマーカー分子・マーカー官能基であることを突き止めた．
  • 日本学術振興会：科学研究費助成事業 基盤研究(A)
    研究期間 : 2016年04月 -2017年03月 
    代表者 : 圦本 尚義, 馬上 謙一
     
    本研究の目的は，宇宙空間において太陽風の直接照射を受けている固体微粒子表面直下の希ガス３次元分布を解析し，照射当時の太陽活動，すなわち，太陽風のエネルギー分布を決定することである．さらにこの分析を微粒子表面全体にわたり行い，天体上における微粒子の運動状態を特定することである．従来，このようなナノメーター空間分解能を持った希ガス分析は不可能であったが，申請者たちが開発した同位体ナノスコープが実現可能とした．人類は，現在，太陽風が直接照射された３種類の物質を宇宙から持ち帰っている．月，はやぶさ，Genesis試料である．これらは順に数十億年，数百～千年，現在の太陽風を記録しているので，太古代から現在に至る太陽活動の経時変化の情報が期待できる．また，試料表面に照射された太陽風の不均質性から月とイトカワとの天体サイズの違いによる小天体表面の粒子運動テクトニクスの理解が進むことが期待される．初年度は，Genesisターゲットの太陽風希ガスその場分析を重点的に行い，太陽活動と固体表面に打ち込まれた希ガス分布との対応，特に，フレア現象の記録の発見を目指した．そのため次の実験を行った．定常太陽風と太陽フレアを模擬したエネルギーを持つ希ガスイオンをGenesisターゲットにイオン注入することにより模擬試料を作成した．太陽フレア起源のHeをGenesisターゲットから検出した． 小天体表面のダイナミックスを解明するための分析をするために，現状の希ガス測定時間を短くする必要がある．この分析時間のボトルネックは大容量の飛行時間質量スペクトルのメモリーへの転送速度である．この転送速度を向上させるアルゴリズムを開発した．
  • 日本学術振興会：科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2015年04月 -2017年03月 
    代表者 : 圦本 尚義, 馬上 謙一
     
    (U-Th)/He系は閉鎖温度が低いので，山脈形成過程のような低温領域の地球史復元に有効な年代測定法であるため，鉱物中におけるその場He局所分析が期待されている．しかしながら，Heの局所分析は，現在のところ，最高で数十μm領域に限られていて，α粒子リコイルロスの飛程を超えられていない．二次中性粒子質量分析法を用い，ジルコン中に含まれるU, Thの放射壊変元素Heの局所その場分析法を開発した．1 ppm以上のHeをα粒子リコイルロスの飛程を超える空間分解能7μmで分析できることを初めて示した．
  • 日本学術振興会：科学研究費助成事業 基盤研究(C)
    研究期間 : 2014年04月 -2017年03月 
    代表者 : 中沢 祐一, 圦本 尚義, 出穂 雅実, 赤井 文人, 直江 康雄, ベガ・マエソ クリスティーナ
     
    異なる気候帯にある地域や遺跡単位で、黒曜石水和層法が年代測定法としてどの程度の有効性をもつかを検討した。日本列島の暖温帯域～亜寒帯、大西洋の温帯域に属する先史遺跡をとりあげ、遺跡から得られた黒曜石を用いた石器に形成された水和層の観察と計測を実施した。計測方法は従来の偏光顕微鏡下での観察と計測を基本とし、一部のサンプルについては、二次イオン質量分析法を用いて水和層を形成する水素イオンの濃度分布を比較検討した。推定される水和層の発達程度は気候帯によって異なるのみではなく、黒曜石の産地、産地内の含水量の違いなどの内的条件に応じて水和層の発達程度が異なることが明らかとなった。
  • 日本学術振興会：科学研究費助成事業 基盤研究(A)
    研究期間 : 2013年04月 -2016年03月 
    代表者 : 圦本 尚義
     
    本研究の目的は，原始太陽におけるスーパーフレアのような高エネルギー現象の規模やエネルギーレベルを推定し，活発な原始太陽活動に関する新しいパラダイム構築をすることである．本研究では，太陽風Heの微小領域分布を定量分析する分析法を確立した．次に，この分析法をNASAの太陽風回収ミッションであるGenesisミッションに適用し，太陽風と物質との間の相互作用の物理を解明した．また，JAXAはやぶさミッションにより回収された小惑星イトカワ微粒子に太陽風Heが３次元的に不均一分布している様子を定量的に決定した．以上の成果を用い，隕石中の太陽風Heの検出を試みたが，有意な信号をまだ検出できていない．
  • 日本学術振興会：科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2013年04月 -2015年03月 
    代表者 : 圦本 尚義
     
    鉱物中の流体包有物は，その鉱物が晶出時の母液を取り込んだもので地下深部流体を直接分析できる貴重なサンプルである．流体には水素，酸素，炭素，窒素等の元素が含まれておりその同位体組成は流体の起源を探る鍵として使われている．本研究では，流体包有物を凍結して，研磨を行い，流体を表面に露出させた後，二次イオン質量分析法で流体構成元素の同位体分析を行う試料作成法を開発した．
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2010年04月 -2014年03月 
    代表者 : 久我 ゆかり, 和崎 淳, 齋藤 雅典, 圦本 尚義, 早川 慎二郎, 中村 仁, 山中 高史, 増野 和彦
     
    植物の根域生態系におけるCおよびNの生物間の受け渡しを細胞・組織・生態レベルで明らかにする新規手法を確立した．細胞・組織レベルでは，安定同位体をトレーサーとして植物との真菌の共生である菌根を用い，樹脂切片法-同位体顕微鏡観察法により元素の流れを解析した．また，土壌微生物間機能解析系は，果樹類白紋羽病の温水処理による抑止現象を用い，菌糸圏土壌細菌作用の関与を明らかにし，環境中のDNAによる菌糸圏細菌群の分析法，分離株による加温処理を組み合わせた発病抑止試験，細胞レベルでの生死判定および抗菌活性試験法を確立した．
  • 科学技術振興機構：産学が連携した研究開発成果の展開 研究成果展開事業 先端計測分析技術・機器開発プログラム 一般領域 開発成果の活用・普及促進
    研究期間 : 2011年 -2013年 
    代表者 : 圦本 尚義
     
    【装置】 本プログラム「プロトタイプ実証・実用化タイプ」において開発した「レーザーイオン化質量分析ナノスコープ(LIMAS) 装置」を開放(共同利用)します。この装置は、探査衛星が持ち帰った惑星上の物質や宇宙塵などに代表される、その量が極めて限られた貴重なサンプルを分析するために、ポストイオン化や高速の質量分析として新しい手法を導入し、より高感度化を狙ったものです。 【内容】 本装置を開放(共用)することにより、はやぶさ採取試料を含む宇宙試料の全元素分析や年代測定が可能となり、世界の宇宙科学の最先端分析を先導することが期待されます。
  • 日本学術振興会：科学研究費助成事業 特別研究員奨励費
    研究期間 : 2011年 -2012年 
    代表者 : 圦本 尚義, ZHANG Aicheng, AICHENG Zhang
     
    地球の水が何処から来たのかは,地球惑星科学における重要な未解決問題の一つである.地球の水の起源は太陽系の水の起源へと直接結びついている.近年,コンドライト母天体のような太陽系始原天体における水の起源が酸素や水素の同位体研究により考察することができる様になってきた.また,始原天体に取り込まれる前の原始太陽系星雲中の水蒸気の同位体的性質も受入研究者のグループにより解明されつつある.これら一連の研究の進展によると,太陽系始原水の研究は,従来の粘土鉱物の研究に加え,リンと酸素と硫黄に富む物質の研究が重要であることがわかってきた. 本研究の意義は,このリンと酸素と硫黄に富む物質のうちリンと酸素に富む硫化物に注目して,その同位体的性質とナノメーターレベルの結晶学的組織を解明することにより,太陽系の水の起源と進化を明らかにする事である.この包有物は,申請者により,炭素質隕石中に発見されたものであり,新物質である可能性がある.この新物質の成因を解明するために,酸素同位体組成とナノスケールレベルの結晶構造と組織解析を行い,このリンと酸素に富む包有物の成因を解明することにより,初期太陽系に存在していた始原水の解明を行う.本年度は以下の研究成果が得られた。 (1)リンと酸素に富む硫化物の岩石組織を,フィールドエミッション型走査顕微鏡(FE-SEM)により観察した. (2)同位体顕微鏡を用いたリンと酸素に富む硫化物の酸素同位体比測定法の開発を行った. (3)以上の結果をまとめ,リンと酸素に富む硫化物の起源と成因を解析した. (4)以上と平行してコンドリュールとCAIが結合したオブジェクトの分析を行いその成因を決定した. (5)第44回月惑星科学会議(米国ヒューストン)において発表を行った.
  • 日本学術振興会：科学研究費助成事業 特別推進研究
    研究期間 : 2008年 -2012年 
    代表者 : 圦本 尚義, 橘 省吾, 伊藤 正一, 坂本 直哉, 大槻 かおり
     
    同位体顕微鏡による隕石の解剖学を実施し,隕石のいわゆる『解体新書』を作成した.その成果に基づき,太陽系創世時代とそれに直接つながる先太陽系時代の物質進化を解明し,物質に刻まれた証拠に立脚する宇宙における太陽系の特殊性と一般性を区分した新しい太陽系起源論を構築した.
  • 科学技術振興機構：産学が連携した研究開発成果の展開 研究成果展開事業 先端計測分析技術・機器開発プログラム 一般領域 要素技術タイプ
    研究期間 : 2006年 -2008年 
    代表者 : 圦本 尚義
     
    荷電粒子を高精度・高分解能で2次元検出する技術はイオン顕微鏡や電子顕微鏡において必要不可欠であり、また、質量分析、電子線分光・回折においても有用です。本開発では分光・投影した荷電粒子の二次元イメージを空間分解能10μmで検出できる半導体素子を開発します。この半導体検出器は二次電子放出の原理を利用し分解能あたり数10万個分までの荷電粒子を電荷として蓄積します。この蓄積電荷を統計誤差の定量性で読み出す技術も確立します。
  • 日本学術振興会：科学研究費助成事業 基盤研究(S)
    研究期間 : 2005年 -2008年 
    代表者 : 圦本 尚義, 榎森 啓元, 倉本 圭
     
    最近,申請者達は『太陽系固体惑星の起源物質(Nature 428,921:2004)』,『酸素同位体的に不均一な太陽系の謎(Science 305,1763:2004)』,『太陽系の形成順序(Nature 423,728;2003)』を解明する重要な発見や仮説を提唱し,太陽系の新しい起源論を展開し始めた。本研究では,これらの発見に対応する太陽系創成期とそれに直接つながる先太陽系史に焦点を当て,これらの発見を進展させるための新しい証拠を隕石から探索する。この探索結果を取り入れ,現在提唱中の仮説を検証・発展させることにより新しい太陽系起源論を構築することを目的とする。 今年度は以下の研究を行い,今年度より採択された特別推進研究に研究を発展させた。 ●隕石中における先太陽系物質の系統的な探査 1.同位体顕微鏡を用いて隕石研磨片のマトリックス中の同位体異常を精査した。 2.同位体異常があった領域を電界放出型走査電子顕微鏡によりナノメートル分解能で観察し,同位体異常を持つ物質を同定した。 3.同定粒子を現有の分析走査電子顕微鏡により化学分析し,鉱物名と組成を決定した。 4.隕石の種類毎に先太陽系物質の特徴および存在度についてデータベースを作成した。 ●太陽系内の酸素同位体異常の起源と大きさ 1.隕石試料の中に含まれている46億年前の太陽風成分酸素の同位体比を同位体顕微鏡により測定した。 2.測定値に数値計算による補正を加え,46億年前誕生時の太陽の酸素同位体比を決定した。 ●始原隕石構成物質の形成と進化 1.先太陽系物質の系統的な探査のため作成した隕石試料から難揮発性包有物(CAI)とコンドリュールを選別した。 2.選別したCAIとコンドリュールに短寿命核種を用いた年代測定を同位体顕微鏡により行った。 3.色々な隕石毎のCAI,コンドリュール形成時期と形成期間をデータベース化した。
  • 日本学術振興会：科学研究費助成事業 学術創成研究費
    研究期間 : 2004年 -2008年 
    代表者 : 石原 盛男, 豊田 岐聡, 植田 千秋, 内野 喜一郎, 倉本 圭, 松本 拓也
     
    まず新規に開発する超高感度極微量質量分析システムの構想決定を行い,その検討結果をもとに装置の製作を行った。その後,質量分析部,1次イオン照射系,レーザーイオン化について,それぞれ装置性能評価を行った。
  • 日本学術振興会：科学研究費助成事業 基盤研究(S)
    研究期間 : 2003年 -2007年 
    代表者 : 丸山 茂徳, 中嶋 悟
     
    本研究を要約すると以下のようになる。 (1)一連の記載研究と精密分析(論文数;丸山32、磯崎9、中嶋8、圦本8)。 (2)総合化(丸山:Dynamics of plumes and superplumes through time,in Superplumes;Beyond Plate Tectonics,Springer,441-502,2007、磯崎:Plume Winter Scenario for Biosphere Catastrophe,ibid,409-439,Springer)。 (3)P/T境界の精密解析(磯崎:掘削試料;6)と化石(太古代1、原生代末1、古生代末5)の記載。 (4)35.6億年前(世界最古生命化石)のSIMSスポット分析(δ^<13>C)と化石の認定基準(圦本、発表準備中)。 (5)化石認定の新しい指標の開発と応用(中嶋;1、実験結果と認定の新基準(古細菌か真性細菌か)の提案図については投稿準備中)。 以上の成果は、これまでの地球史標準モデルを更に精密化し、誕生後徐々に冷却してきた地球システムが起こす物理的必燃として説明しうるが、新たな原因として、銀河内部で起きた3回のスターバーストとの緊密な関係が浮かび上がってきた。これらは日本のみならず世界最前線の研究を更にリードするものである。これらは、地球惑星科学の中の諸分野へ大きな影響を与えるが、地球惑星科学以外の分野である天文学、ゲノム生物学、分子生物学、生命進化学、更に気象学にも大きな影響を与えるだろう。
  • 日本学術振興会：科学研究費助成事業 基盤研究(A)
    研究期間 : 2001年 -2004年 
    代表者 : 圦本 尚義, 井田 茂, 藤本 正樹, 倉本 圭, 榎森 啓元
     
    惑星や隕石の平均化学組成は太陽系平均組成とすこしずつ異なり、それぞれ独自の値をもつことが知られている。この隕石や惑星の化学組成の変動は、原始惑星系円盤において太陽近傍まで落下したダストが太陽系外縁部に還流した結果であると考えられる。本研究では、この原始太陽系中心から外縁部まで達する原始太陽系における物質大循環に関するモデルを、隕石中の物質の分析結果と惑星系円盤中の電磁気学的・力学的・化学的シミュレーションを結合させ、定量化することにある。 この研究では数値シミュレーションと隕石中の同位体分布の研究を発展させ,以下のような成果を得た。 1.太陽系の酸素同位体異常の起源が母星間雲におけるCOの自己遮蔽効果を起源とすることを決定した。 2.母星間雲の酸素同位体異常は星間ガスと氷成分により相分離され,原始惑星円盤中に導入されることを決定した。 3.惑星の酸素同位体組成は原始惑星系円盤中のダスト濃縮と氷の蒸発により支配されることを突き止めた。 4.原始惑星系のガス・ダスト比が変化すると形成される木星型惑星の質量,軌道半径分布がどのように変わるか数値シミュレーションにより求めた。その結果は天体観測による系外惑星の存在確率をよく説明した。これは,円盤ガス量は星形成プロセスで決まるが惑星形成はガス・ダスト比により支配されることを意味している。 5.宇宙空間を満たすプラズマ中における大規模渦の振舞いを数値計算で調査した。渦が巻上がるにつれてその内部で電子慣性効果が発動し、その結果、出現した小渦が元の大渦の素早い崩壊をひきおこすことを発見した。これは、宇宙空間において従来よりも効率よく物質混合が起きていることを示唆する。
  • 日本学術振興会：科学研究費助成事業 特別研究員奨励費
    研究期間 : 2001年 -2002年 
    代表者 : 圦本 尚義, FAGAN Timothy Jay, FAGAN T. J.
     
    本研究の目的は炭素質コンドライト中の難揮発性包有物における^<16>O成分に欠乏したメリライトの成因をアメーバー状カンラン石集合体による酸素同位体局所分析結果に基づき解明することである。地球などの惑星を生み出した原始太陽系円盤中の酸素同位体比は^<16>O成分に富んでいたと考えられている。一方地球型惑星の酸素同位体比は^<16>O成分に乏しい。これは原始太陽系円盤中で酸素同位体比が変化したことを示している。本研究では、太陽系でもっとも普遍的な鉱物からなるアメーバー状カンラン石集合体中の酸素同位体分布をミクロンスケールで分析することにより、酸素同位体変化の起源を解明する。 炭素質コンドライトは始原的で未分化の隕石であり、原始太陽系円盤に漂っていたチリの集合体と考えられているが、天体形成後の水成変質作用により元々の鉱物が新しい鉱物に変化していることが申請者たちの研究により明らかになってきた。今年度はエフレモフカ隕石に加え,変質作用がもっとも小さい炭素質コンドライトであるレオビル隕石とヴィガラノ隕石を材料にして酸素同位体比分布を以下の手順で解析した。 1.各隕石から研磨薄片を作成し、X線分析装置付走査電子顕微鏡を用いて、アメーバ状カンラン石集合体の探索と岩石学的記載を行い、局所酸素同位体分析を行う個所を決定した。 2.次イオン質量分析法を用い3つのアメーバ状カンラン石集合体の構成鉱物(μmサイズ)すべての酸素同位体比を決定した。 3.すべての隕石においてアメーバ状カンラン石集合体を構成する全ての初生鉱物は^<16>O成分に約4%富んでいる(地球に比較して)ことが判明した。 4.これらのアメーバー状かんらん石集合体は原始太陽系星雲中における直接凝縮物であり,隕石中に普遍的に存在することが明らかになった。 今後は^<16>O成分に乏しいメリライトと^<16>O成分に富むメリライトの成因上の関連について母天体の変成作用の観点を加え研究を進めていく。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2000年 -2002年 
    代表者 : 河村 雄行, 廣瀬 敬, 圦本 尚義, 丸山 茂徳, 神崎 正美, 加藤 工
     
    本研究では世界最古の岩体であるカナダのアカスタかこう岩体の地質調査を行い、ジルコンを用いた年代測定と地質構造上の関係から、岩体の形成史をあきらかにした。またオーストラリアのピルバラ地塊の調査により、太古代中期30-35億年前の中央海嶺や沈み込み帯における火成活動や熱水活動をあきらかにした。その結果当時の海水中には多量の二酸化炭素が含まれており、熱水活動により炭酸塩が多量に地殻に生成され、さらに沈み込みにより地球深部へ多くの炭素が運ばれていたことを明らかにした。また太古代に特徴的なコマチアイトマグマ中のメルト包有物の測定を行った結果、太古代のプルームマントル中には多くの水が含まれていたことがわかった。またマルチアンビルプレスを用いた高圧高温実験により、下部マントル上位におけるマントルかんらん岩と玄武岩の融解実験を行い、融解相関係や微量元素分配を決定した。さらにこの結果から現在進行中のコア・マントル境界における融解現象において、微量元素分配はCaSiO3ペロブスカイトに支配されることを示した。実験結果から期待される特徴的な微量元素の濃度パターンは現在のプルームマントル中の捕獲岩に残されていることから、ハワイや南太平洋のプルームはコア・マントル境界由来である可能性を指摘した。本研究ではダイヤモンドセルを用いたマントル最下部までの条件の超高圧高温実験をも行った。その結果、SiO2相は下部マントル中で2回の相転移を起こし、マントル最下部ではα-PbO2相が安定であることなどがあきらかになった。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2000年 -2001年 
    代表者 : 矢田 慶治, 伊藤 敦, 篠原 邦夫, 渡邊 誠, 圦本 尚義, 本田 捷夫
     
    1.本研究は、光電子にX線が当たって形成される光電子増を電子光学的に拡大し、MCPもしくは能動型半導体素子(積層APS)で検出・記録する空間分解能50nm程度の2次元検出装置を試作することを目的としている。初年度では透過電子線による拡大像の分解能が60nmまで向上したが、同時に、X線ターゲットを用いて実験室に於いてX線励起による光電子増を50倍程度まで蛍光板上で観察できた。これにMCPを備えて実験を推進すると共に、放射光施設での実験を3回行った。 2.以下に現状と問題点を述べる。 (1)加速電圧15kVで、電子線像の分解能は、適切な対物絞りとステグマトールを用いて40nmまで向上した。 (2)上の状態でもターゲットからのX線で励起して結像する場合には分解能がかなり悪くなる。それでも珪藻土の撮影で1μ前後の小孔は分解できた。 (3)SOR光を用いた実験では、分光したX線の照射で生物試料HeLa細胞をホトカウンティングモードで撮影できた。10時間の長時間撮影でも安定で、波長による像の内部構造の違いを確認できた。像質は浜ホトのズーミング管の最良の物と同程度それより幾分良い程度であった。珪藻土の像から分解能は0.3〜0.4μmと推定された。 (4)試料前面の電界強度を上げることで分解能が改善できることが確認された。 3.最終目標の高分解能を得るために、試料前面の電界強度を大幅に上げること、非点収差の完全な補正、積層APSの有効利用が行われている。将来的には像のフィルタリングが必要と思われるので、ウィーンフィルターを検討している。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 1999年 -2000年 
    代表者 : 石原 盛男, 圦本 尚義, 長尾 敬介, 交久瀬 五雄, 豊田 岐聡, 伊藤 啓行, 松田 准一, 齋藤 義文
     
    我々は小型で高分解能を達成できる多重周回タイプの飛行時間型質量分析装置の開発を行ってきており、世界最高の質量分解能35万をすでに達成した。しかしその装置はQレンズを多用したため、イオン光学的に複雑であり、惑星探査用としては簡略化が求められていた。本研究では、その目的のためにまずQレンズを用いないイオン光学系をさがした。その結果完全収束条件を満たした上で多重周回軌道をイオンビームが安定に周回できるイオン光学系を見出した。このイオン光学系は先に分解能35万を達成した装置のイオン光学系と同等の性能を持つことが期待できるものである。 さらにそのイオン光学系を搭載するための真空装置(真空箱、バルブ、ポンプ等)や架台などの機械設計を行い、実際に製作を行った。また内部に搭載する小型の垂直加速型イオン源の試作実験も試みた。さらに多用な試みが可能なように検出部に小型のイオンミラーを搭載すべくその設計を行った。設計したイオンミラーは新しく製作した装置に実際に組み込んだ。 多重周回型の装置では各電極に適当なタイミングでパルス的に電圧を供給する必要があるが、そのためのタイミング回路と制御プログラムまた高速で信号を取り込むためのシステムも構築した。現在予備的な動作確認の段階である。
  • 文部科学省：科学研究費補助金(基盤研究(A))
    研究期間 : 1998年 -2000年 
    代表者 : 圦本 尚義, 松本 一哉, 高柳 功, 平田 岳史
     
    最近の急速な分析法の進歩により,微小な鉱物間および鉱物内の地球科学的・年代学的情報を引き出すことが可能になりつつある。それにより太陽系形成や惑星形成初期の物質科学的な進化過程が明らかになりつつある。特に,固体地球試料のミクロンサイズの局所表面分析から精密同位体情報を引き出す分析法の実用化により,鉱物の形成・進化過程についての詳細な環境情報並びに時間情報が同時に得られるようになり,従来の地球科学観はまさに一変されつつあるといっても過言ではない(圦本尚義 科学67,1997)。これらの局所・表面同位体分析に対して,二次イオン質量分析法(SIMS)は主導的役割を担っている。しかしながら,太陽系形成時を遡り,太陽系を構成する原子が星間雲であった時代を読み取るためには,隕石等の地球外物質中のサブミクロンサイズの結晶から同位体情報を得る必要がある。また,地球深部を探る超高圧実験も下部マントル以深の条件では合成された結晶の大きさはミクロンサイズを下回る。この様に地球惑星科学のフロンティア領域では素部ミクロンからナノ領域における新しい分析法の確立が要請されている。本研究は,以上の学術的要請に応えるために,我々が独自に開発してきたミクロン領域のSIMS法を発展させ,ナノ領域まで分析可能な質量分析装置(同位体ナノスコープ)の開発と実用化を目的とした。この実現のために,我々の開発した二次元半導体荷電粒子検出素子の能力を大幅に向上させ,Stacked-CMOS active sensor (SCAPS)を完成させた。今回完成した同位体ナノスコープは高分解能SIMSとSCAPSが組み合わしたシステムである。本同位体ナノスコープにより隕石中の酸素同位体分布を測定しその性能を検証した。本研究で達成した性能は100ミクロンの試料領域上で空間分解能1ミクロン,同位体精度0.1%の分解能を持つ同位体比の定量イメージを世界で初めて得ることができた
  • 文部科学省：科学研究費補助金(基盤研究(B))
    研究期間 : 1997年 -1999年 
    代表者 : 圦本 尚義, 平田 岳史
     
    隕石中の星間物質は太陽系誕生以前の歴史を探る唯一の手がかりである.この星間物質を太陽系物質と見分けるためには,同位体比を測定し,太陽系の同位体比とは異なることを証明する以外にない.この観点から,本研究では隕石中の鉱物1粒1粒毎の同位体比組成とその形態・結晶構造との関係を明らかにすることにより,星間物質から惑星系への進化論を実証的に構築することを目的とした.そのため,二次イオン質量分析法を用いた酸素同位体比のミクロンスケールの局所分析法を新たに開発した.その分析法を適用した結果,太陽系最古の物質であるアエンデ隕石中の難揮発性包有物(CAI)に含まれるメリライト単結晶中に酸素同位体比の不連続的なゾーニングを初めて発見した.この事実は,原始太陽系星雲中では,ダストと気体成分との間において,酸素同位体比が異なる値を持ち,原始太陽系星雲中における複数回のダスト成分の加熱作用により太陽系の固体成分が進化していったことが証明された.今回見つかったゾーニングは加熱時の固体と気体間における同位体交換現象を凍結している例であると考えられる.この固体成分と気体成分間の酸素同位体比均一はコンドリュールの形成時代まで保存されていたことも明らかになった.これらの新しい事実を説明するため,双極流という原始星段階に特異的な現象を利用した新しい太陽系進化シナリオを構築した.本シナリオにおいて太陽系の固体物質は,それらがダストであった段階に,双極流により原始太陽系円盤の内側から外側に環流された.原始太陽系円盤中のダストは中心星に向かい定常的に落下しているので,原始太陽系円盤において大規模な物質大循環と混合が起こっていたことになる.このシナリオは従来知られていた事実も矛盾なく説明できる.これにより,わずか数百万年間の間〓現在観測される惑星間の平均組成や同位体比の差が決定してしまったことが判明した.
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 1996年 -1998年 
    代表者 : 磯崎 行雄, 谷本 俊郎, 平田 岳史, 圦本 尚義, 丸山 茂徳, 中村 保夫
     
    現在の環太平洋地域では、いずれも海洋プレートが大陸プレートの下に沈み込んでおり、典型的なプレート沈み込み帯型の造山帯をなしている。本研究計画の前半では、その造山帯成長を司る二つの主要なプロセス、すなわち付加体の形成と花崗岩帯の形成についての地質学的研究がなされ、日本列島に分布する顕生代の付加型造山帯の基本構造と形成過程が解明された。また、そこで開発された研究手法は、日本列島からみると太平洋の対岸にあたる北米西岸のカリフォルニア州のコルディレラ造山帯においても適用され、新たな成果をあげた。この一般的な造山帯形成過程に対して、都城型造山運動と命名した。これは超海洋の誕生から消滅に及ぶ一つのウイルソンサイクルの中での一般的プロセスと理解される。 一方、これらのプレート沈み込み型造山帯の基本的体制が何時成立したのかについては従来不明であったが、本研究後半では、本邦における最古期岩石群の特徴に着目し、それらの起源が約7-6億年前に超大陸ロディニアが分裂した時に出現したリフト帯にあったことを明らかにした。すなわち、日本列島の成長核になる揚子地塊の海洋側に産する5億8千万年前のオフィオライト(西九州および北上山地)が太平洋の最古断片を代表することをつきとめた。この事実は、先に解明した付加型造山帯の成長極性と調和的で、揚子地塊の太平洋側大陸縁が、もともとの受動的なものから、約4.5億年前に活動的大陸縁に転換したことを示す。 一つの超大陸の分裂から大海洋が生まれ、同時にそれをとりまく新しい大陸縁辺のグループが生じる。その海洋が面積を拡大していゆくと、やがて地球の反対側で別の海洋が開き始める頃には、もとの大陸縁はプレート収束帯に進化してゆくという大陸縁造山帯の一般的成長プロセスが、日本列島の研究から導かれたことになる。
  • 文部科学省：科学研究費補助金(基盤研究(A))
    研究期間 : 1996年 -1997年 
    代表者 : 圦本 尚義, 丸山 茂徳, 松本 一哉, 平田 岳史
     
    本研究では、ジルコン試料から高精度年代情報を引き出すという高い学術的要求を実現するために、レーザーサンプリング法を用いた超高精度同位体分析法(以下レーザー質量分析法と略記)の開発を行った。まず、50ミクロン以下の微小ジルコン結晶を分析対象とするため、固体試料の局所部分から試料をサンプリングできる新しいレーザーシステムの開発を行った。レーザー光学レンズ系の改良(被写界深度の向上)と、長時間安定性の向上により、年代測定に重要なウランと鉛の定量性を高めることができた。また、レーザービームの微小化にともない、質量分析計内に導入される試料量が小さくなるため、質量分析計の高感度化を行った。これは、イオン光学系の改良(真空度の向上、イオン加速レンズの改良)と、高感度イオン検出器の開発により達成した。その結果、従来の質量分析法と比較して、少なくとも10倍以上の元素検出感度を達成することができた。特に、二次元固体撮像素子を用いたイオン検出器は、実用化に向けた基礎データの取得も進み、現時点では、イオンを直接検出できる最も有力な高感度イオン検出器であると結論でき、今後、様々な質量分析法に応用される可能性があることがわかった。これらの分析法の開発により、ジルコン結晶からウラン-鉛年代の決定が可能となった。得られた年代は、従来の分析法で得られたものとよい一致を示し、データの信頼性が確認できた。また、これまで分析が困難であった若い試料(年代1億年以下のジルコン)についても再現性のより年代データが得られることがわかり、ジルコン結晶の適用範囲が広がったことも本研究の特筆すべき成果だといえる。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 1995年 -1997年 
    代表者 : 高橋 裕子, 小澤 一仁, 圦本 尚義
     
    初期太陽系星雲の高温過程における固体鉱物の蒸発にともなう元素および同位体の分別を温度.圧力に依存する時間の関数として解明するため,フォルステライトとかんらん石(Fo92)をもちいた蒸発実験をおこなった.結晶軸に平行な定方位に切り出した箱型とした出発物質を用いた実験の結果、鉱物は蒸発に関し強い異方性をもつことが明らかとなった.表面は方位ごとに固有の微細構造を示し,転位密度に応じて固有の表面組織を示す.かんらん石はかんらん石構造を保ったまま蒸発するため,部分蒸発の結果,表面はよりMg,Caに富むようになる。一方Fe,Niは初生値より低くなる。表面組成は中心部に未反応部分が残っているかぎり一定時間の経過後定常状態に達し,初生値との比が固相・気相分別係数を求めることが可能となった。内部は拡散プロファイルを示し、蒸発が拡散に支配されていることを示している。蒸発による界面後退をともなう拡散方程式により実験結果を解析した結果、蒸発速度と拡散係数を求めることができた。拡散係数はMisner(1974)による低温での結果の外挿値よりやや大きい。この値の原因は (1)高温では拡散のモードが低温とは変化するためintrinsicな値として正しい、(2)真空中の蒸発では表面に空孔が発生して拡散速度が増大する、(3)蒸発速度の推定値が不正確でその結果拡散速度も誤差を含んでいる、 という3つの可能性がある。今回用いた方法は従来実験技術上の制約から困難であった拡散係数を求める上で画期的なものである。さらに、拡散をともなう蒸発における元素分別の一般的な関係を定式化することに成功したため、太陽系星雲における元素分別を温度、圧力、時間の関数として記述することが可能となった。
  • 文部科学省：科学研究費補助金(重点領域研究)
    研究期間 : 1996年 -1996年 
    代表者 : 圦本 尚義
     
    最近,本研究代表者を中心とするグループでSIMSの発展型である同位体顕微鏡の開発が進行しつつある.同位体顕微鏡とは同位体比組成の分布をミクロンオーダーの空間分解能で観察できる分析装置である.開発中の同位体顕微鏡は負重イオン源+二次イオン質量分析装置+二次元イオン検出装置からなるシステムをもつ.本申請は同位体顕微鏡システムをさらに発展させることにより,地質学的試料中に保存されている同位体比の縞縞の読み取りを目的とする.本申請期間内に明らかにしたい点は:独自に開発した同位体顕微鏡を用いて天熱物質中の同位体比の空間変動を実際に読みとり、解読することにより、全地球史解読の新手法の有効性と証明する。この独創的な装置を縞縞解析に適用することにより,ジルコンの結晶成長年輪や貝殻・有孔虫・ストラマトライトの酸素同位体変動の連続的な分布を測定できるようになるものと予想される.この結果は,地殻のリサイクルの速度や過去の気候の季節変動を定量的に読み取る方法を確立する基礎研究となる.本年度行った研究は以下の通りである。1.負重イオン源の改造。2.AMIのイオン粒子に対する基礎的特性の評価。3.本装置を縞縞解析に適用のための,ジルコンの結晶・貝殻・放散虫・ストラマトライトのサンプルを同位体顕微鏡で検鏡できるように加工。4.ジルコン結晶のゾーニングがSIMSにより分析することにより各ゾーンの晶出年代を求めその拡散プロファイルを解析することにより地殻の上昇過程とジルコンのリサイクル過程の定量化。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 1995年 -1996年 
    代表者 : 平田 岳史, 松本 一哉, 圦本 尚義
     
    質量分析法において多重検出方式(マルチコレクション)は、同位体分析精度を高める最も有効な手段であるといえる。多重検出方式としては、これまでファラデー検出器が広く用く用いられてきた。しかし、高精度同位体分析に適したファラデー検出器は、イオン検出感度が低く(二次電子増倍管などの手法の1,000分の一程度)、微量元素の同位体分析を行う上で問題となっていた。そこで本研究では、高精度同位体分析を目的とした新しい高感度イオン検出器の開発を試みた。 本研究で開発した検出器は、AMI(Amplified MOS Imager)とよばれる固体撮像素子であり、250,000画素(単一ピクセルの大きさは5μmX10μmで全体の大きさは8mmX6mm)からなり、イオンビーム強度の二次元分布を調べることができる。つまり、一つのAMI検出器で複数のファラデー検出器の役割を果たすことができる。AMI検出器は、1)イオン(荷電粒子)を直接検出できる唯一の固体素子である、2)素子内部に信号増幅回路をもっているためS/N比が高い、3)検出器が積分型であるため微弱な信号についても正確な強度情報が読み取れる、などの特長を有しており、イオン検出感度の向上には最も有力な検出法だといえる。本研究では、このAMI検出器をICP質量分析計にとりつけ、様々な質量数および強度のイオンの計測を行い、基本的な特性評価を行うとともに、質量数180〜210amuの分析元素(ハフニウム、ダングステン、鉛、タリウム)について、3つの同位体信号を同時検出・計測することに成功した。またAMI検出器は、テレビカメラのようにリアルタイムでイオンビーム強度をモニターすることも可能であり、質量分析計のイオンレンズの調整や分析条件の最適化が容易となり、従来複雑であった質量分析計の調整が格段に容易となったことも特筆すべき成果といえる。現段階では、検出器のノイズレベルが理論値と比較して10倍程度残っており、実用的なダイナミックレンジとしては4桁程度しか得られていないが、同位体分析の繰返し再現性(測定精度)としては0.01%程度が得られており、当初目標としていた基本性能は達成できたといえる。
  • 文部科学省：科学研究費補助金(重点領域研究)
    研究期間 : 1995年 -1995年 
    代表者 : 圦本 尚義, 平田 岳史
     
    本研究の目的は隕石中の鉱物1粒1粒の同位体比組成と形態・結晶構造との関係を明らかにすることにより,太陽系外物質(星間物質)を同定することである.本研究の特色・独創的な点は,従来,別々の隕石において行なわれているLi, B, O, Mg, Si, Ti, Feの各同位体比存在度の決定を同一の試料において系統的に行なうことである.特に,星間物質の進化の関数として,同位体比の変化を追跡する.得られた分析結果は,星間物質の起源となる元素合成のプロセスを解析する基礎データとなる.対象とする隕石は炭素質隕石や普通隕石といった始原的なタイプの隕石でありコンドライト隕石と総称されている.コンドライト隕石は46億年前の太陽系形成初期に形成されて依頼,そのままの状態で現在まで保存されている隕石である.今年度行った研究は(1)コンドライト隕石を同位体顕微鏡を用いサーベイし,酸素同位体異常のある部分をチェックした.(2)コンドライト隕石中のLiとBの濃度分布と同位体比を測定した.今後は,測定された同位体異常分布,主成分濃度と形態的特徴と岩石組織を関連づけ,各粒子を構成する元素合成の元となった恒星のタイプを決定し,宇宙におけるLiとBの存在度の過剰を解明するための基礎データを完備する予定である。
  • 文部科学省：科学研究費補助金(重点領域研究)
    研究期間 : 1995年 -1995年 
    代表者 : 圦本 尚義
     
    天然においてある元素の同位体比の変動をおこす原因は,主に次の2つの過程がある:(1)放射性元素の壊変,(2)熱による同位体分別.これらの現象は,地球科学分野の研究において,それぞれ,年代測定や古気温(古水温)の決定に応用されている.しかしながら,従来の質量分析法では,最新の二次イオン質量分析法(SIMS)を用いたとしても数十ミクロンの平均的な領域の値を測定できるにすぎなかった.最近,本研究代表者を中心とするグループでSIMSの発展型である同位体顕微鏡の開発を行った.今年度はイオン顕微鏡型SIMSに同位体分析の定量性を付加する新しいタイプの二次元イオン検出器を試作した.この検出器には我々が開発した固体素子を使用した.以下に具体的内容を示す.1.同位体顕微鏡システムの目といえる二次元イオン撮像素子(以後AMIと呼ぶ)を用いた二次元イオン検出装置の調整を行った.2.AMIのイオン粒子に対する基礎的特性の評価を行った.3.本装置を縞縞解析に適用ための,ジルコンのサンプルを同位体顕微鏡で検鏡できるように加工した.4.測定するジルコンサンプルはその拡散プロファイルを解析することにより地殻の上昇過程とジルコンのリサイクル過程の定量化の両方を解析した.
  • 文部科学省：科学研究費補助金(試験研究(B))
    研究期間 : 1994年 -1995年 
    代表者 : 圦本 尚義, 松本 一哉
     
    本研究において、数keVオーダーのエネルギーを持つイオン粒子や電子線のような荷電粒子線の積分型二次元検出器を新しく開発した。この粒子線検出器はシリコン半導体の上に電極を積層した増幅型固体撮像素子AMIである.また,この粒子線撮像素子を投影型の二次イオン質量分析装置の搭載した同位体顕微鏡システムのプロトタイプを完成した.この同位体顕微鏡の性能は,空間分解能が最大1μmであり,512 x 250ピクセルの同位体画像を得ることが可能である.また,1ピクセルあたりのダイナミックレンジは4桁におよぶ.撮像領域は二次イオン質量分析装置のイオン光学系の倍率により25-400μmまで可変である.現在,この同位体顕微鏡を用い隕石中の同位体比分布の分析が進行中である.この分析により,原始太陽系の進化と我々を構成する元素の起源を探るための重要な証拠が得られることが期待される.しかも,この開発による波及効果として,半導体検出器CCDが光学分野の研究手法を革新的に変革したように,同様な効果が粒子線検出を手段とする科学工学分野においても急速に波及していくと思われる.
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 1993年 -1995年 
    代表者 : 大谷 栄治, 佐々木 晶, 丸山 茂徳, 兼岡 一郎, 牧嶋 昭夫, 圦本 尚義
     
    本研究においては、初期地球を含めて地球史の中でマグマの果たした役割に関して初期地球におけるマグマオーシャンの実体を解明すること、マグマの形成による初期地殻の形成過程とマントルの進化過程を明らかにすること、マグマの生成によるマントル内部の不均質と大循環を解明することの三つを目的として研究を行った。 マグマオーシャンの実体を解明する研究では珪酸塩多成分系(Mg2SiO4-Fe2SiO4,MgO-Al2O3-SiO2系)などの高圧下での溶融関係が実験的に明らかにされ、マグマオーシャンの組成、初期地球で生成したコマチアイトマグマの起源が解明された。またマグマオーシャンの形成にともなう地球核の形成過程を解明するために高圧下における金属鉄と珪酸塩融液間の元素分配の実験的研究が行われた。実験結果とマントルのNiやCoなどの親鉄元素の存在度を比較することによって、下部マントルに達する深いマグマオーシャン中での鉄と珪酸塩の平衡でマントルの親鉄元素存在度が説明できることが明らかになった。 マグマの形成による初期地殻の形成とマントルの進化に関しては、イスア、ピルパラなど世界各地の始生代の地質体お綿密な調査と採取した岩石試料の化学分析が行われ、コマチアイトマグマの起源が明らかになり、始生代に於いてもプレートテクトニクスが働いていたことが明らかになった。また、始生代の玄武岩マグマを作るマントルが現在に比較して鉄に富んでいたらしいことが明らかになった。 マグマの生成によるマントル内部の不均質お大循環の研究においては、高温高圧下でのマグマの密度測定が行われ、15-20GPa付近にマグマとダイヤモンドの密度逆転が存在することが実験的に明らかになった。また、マントル内部でのマグマと鉱物間の密度関係が明らかになった。これによるとカンラン石とマグマの密度逆転は予想に反して上部マントルの大部分の深さにおいて生じないようである。マントル内部における水の循環に関する研究が行われ、下部マントルでにおいて存在する高密度含水鉱物であるG相が合成され、単結晶構造解析がなされた。この相は水を15-18%も含みSiが6配位の席を占める点で特異な相であることが明らかになった。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 1993年 -1994年 
    代表者 : 高橋 裕子, 田近 英一, ゆり本 尚義, 小澤 一仁, 森岡 正名, 久城 育夫
     
    かんらん石を真空および低圧の水素ガスフロー中で、実験時間のみ変化させて蒸発程度を変化させた場合の蒸発速度を実験的に調べた結果、蒸発速度は水素ガス圧力に大きな依存性があることがわかった。10^<-6>気圧以下の低圧では蒸発速度は圧力依存性はみられず、真空中での蒸発速度に等しく、10^<-6>気圧から10^<-4>気圧の間では水素圧に対して1乗の依存性をもち、それ以上の高圧ではふたたび依存性は小さくなる。10^<-6>気圧以下での関係はj=0.33P_

    +8×10^<-7>として示される。ただしjは蒸発速度である。水素圧に対し1乗の依存性をもつことから、固体表面における1モルのかんらん石を1モルの水素分子がアタックする、という素反応が考えられる。 この結果を用いて一様なサイズのかんらん石粒子が太陽系元素存在度比の水素-炭素-酸素からなるガス中で急速に加熱、高温に保持された場合のライフタイムについて考察した。蒸発速度は始めは真空中における速度でおこるが、蒸発の進行とともに小さくなる。かんらん石粒子のサイズ変化、蒸発成分のフラックスを、無次元数hの関数として求めた。hはガスに対する固体成分の濃集の度合いとみなすことができる。hが3より小さい場合はかんらん石は完全に蒸発してしまい、その速度は真空中でのそれに等しい。h が3より大きい場合は系が平衡に到達し、蒸発は途中でストップする。平衡にいたる時間はhが大きくなるにつれ小さくなる。h が3近傍では完全蒸発、平衡到達ともきわめて長い時間を要する。太陽系星雲における h の値は0.1程度から数100 であり、ダストの濃集の程度が大きい場合は星間ダストは星雲の加熱に対し生きのび、一方ダストがあまり濃集していない場合は星間ダストは完全に蒸発してしまい、系は均質化しうることが明らかとなった。

  • 日本学術振興会：科学研究費助成事業
    研究期間 : 1992年 -1994年 
    代表者 : 末野 重穂, STEPHENS P.W, LIEBERMANN R, VAUGHAN M.T., WEIDNER D.J., PARISE J.B., 鍵 裕之, 圦本 尚義, 栗田 敬, 大嶋 建一, 高野 薫, 若槻 雅男, PARISIE J.B., 中井 泉, WEIDNER D J, PARISE J B
     
    本研究の目的は、地球深部造岩物質を主とする無機物資についての高温高圧状態下における振舞いを研究し、地球内部の物質移動における結晶構造と化学組成の変化を読み取り、地球の生成と変化の過程について諸問題の解明に役立てることにある。研究に際しては、筑波大学及びニューヨーク州立大学ストーニ-ブルック校(SUNY-SB)間の20年間に渉る緊密な協力体制とで研究実績の基に、両校がそれぞれ得意とする合成及び分析などの実験技術、野外調査で協力しつつ、広い学問分野からの理論考察を統合して学際的に結晶構造と結晶組織・安定領域、相転移、組成変化・メルト-結晶間の元素分配などの観点から研究するものである。高温高圧下における物質の挙動の詳細は物性物理学的にも、材料科学上の新物質の探索と開発でも重要な問題であり、火山や地震についてもこれらの物質の高温高圧における諸性質を熟知しないと理解できない問題が累積している現在では、本研究のような総合的研究は重要な意義がある。 本年度の研究内容としては、地球科学的に重要な地球深部における水の存在に関する研究とダイヤモンドその他の炭素各相の研究を行ない、地球深部における水素の存在量の推定とその形態について詳細と、工業的にもまた地球科学的にも重要な炭素の物質科学的振舞いを明らかにすることを試みた。また、高温高圧下で合成された試料のおける微量化学成分の分配の解明のために高エネルギーイオン線を利用した微量元素分析法の開発に精力を注いだ。 本年度は本研究の最終年度でもあり、これまでの3年間に渉る本共同研究で得た成果について、代表者及び両校の分担者及び研究協力者が全員が集まって議論する合宿制の合同研究会を開催することは、問題点を明確にする上でも、また今後の共同研究の推進のためにも重要なことである。 合同研究会は、(1)両大学からの距離、(2)経済面、(3)ハワイ大学の協力(宿舎・会議室など)などの利点を考慮して、12月中旬にハワイ島ヒロ市で開催した。またハワイ島は、地球の深部からのマグマが湧き出るホットスポットにあたり、深部物質の試料採集と溶岩の観測も行える利点がある。 研究会での、講演者とその内容は次の通りである。 12月10日(21:00-22:00) J.B.Parise(SUNY・分担者):SORX線による微小結晶による結晶構造解析 D.J.Weidner(SUNY・分担者):上部マントル下部での含水相 12月11日(9:00-12:00) 鄭貞仁(筑波大学・研究協力者):水を含有した場合の深部物質の溶融温度変化 J.Zhan(SUNY・研究協力者):MgCO3などの炭酸塩のマントルでの状態 末野重穂(研究代表者):高エネルギーイオン線による微量元素分析法 M.T.Vaughan(SUNY・分担者):Hydrogen bondの評価 12月11日(14:00-17:00) 高野薫(筑波大学・分担者):サファイヤアンビルによる高圧下分光研究 近藤忠(東大・研究協力者):ダイヤモンドアンビルによる高圧物質研究 山本一樹(筑波大学・研究協力者):極超短波長X線による結晶構造解析 大嶋建一(筑波大学・分担者):X線散漫散乱による物質研究 Y.Wang(SUNY・研究協力者):Caペロブスカイトの状態方程式 王五一(筑波大学・研究協力者):ダイヤモンド中の包有物による地球深部研究 田浦弘史(筑波大学・研究協力者):高圧下でのメルト-結晶間元素分配研究 栗田 敬(筑波大学・分担者):地球深部物質研究への新しい提案 12月11日(20:00-21:00) C.T.Prewitt(招待研究者:カ-ネギ-地球物理学研究所所長):高圧力研究の将来 以上の研究発表会の前後に火山研究所の訪問、マントル物質試料の採集、火山巡検を行ったが、12月12日には火山の溶岩が噴出するという事態が発生し、火山研究所所長の特別許可を得て、間近で溶岩を観測するという絶好の機会に恵まれた。 研究自体の成果も大きかったが、両校の若手研究者が互いに理解し合い、今後の協力態勢が生まれたことは素晴らしいことであった。
  • 文部科学省：科学研究費補助金(重点領域研究)
    研究期間 : 1993年 -1993年 
    代表者 : 圦本 尚義, 末野 重穂
     
    本研究では,2次イオン分析法(SIMS)による酸素同位体比のその場測定という新しい手法を用いアレンデ隕石中の粗粒白色包有物中の酸素同位体比を測定した。また,酸素同位体比の局所分布と鉱物の結晶成長に対応する形態的特徴とその分布をむすびつけるため走査電子顕微鏡とEPMAにより元素組成分析を平行して行った。その結果,酸素同位体比は鉱物間で異なる値をもっているが,鉱物内ではほぼ均一に分布しており,化学組成のゾーニングとは独立した分布をしていることが明らかになった。この結果は,従来の白色包有物の成因説の全てと矛盾している。つまり,包有物が固結後,太陽系星雲内の加熱による酸素の固体内拡散を通じた同位体比交換の証拠はなかった。したがって包有物を構成している全ての鉱物種を結晶化した環境は異なる同位体比組成をもっていたことが判明した。これらの事実を総合すると,次のような白色包有物の成因が推定される:太陽系のとなりの星の囲りで星間塵が形成された。その星間塵は,太陽系星雲ガスと化学反応をおこし,異なる同位体比をもつダストの集合体となった。この期間はおよそ100万年間である。その後太陽系星雲よりメルトが凝縮し、太陽系の同位体組成の鉱物が形成された。この最後のプロセスは数日の期間内におこった。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 1992年 -1992年 
    代表者 : 熊沢 峰夫, 藤井 敏嗣, 圦本 尚義, 阿部 豊, 栗田 敬, 小河 正基
     
    物質科学グループでは,2次イオン質量分析計の周辺装置の拡充をはかり,ビームの高輝度化などによって面分析とその高精度化ゐ実現した.これによって,超高圧力(5-27GPa)高温(900-2000C)条件のもとで平衡処理した珪酸塩と鉄の試料の分析を行ない,地球核とマントルの間におけるニッケルなど27元素の分配係数を精密に求めた.また,これらの分配係数に対する圧力効果,酸素分圧の効果,硫黄の組性効果など,従来は分からなかった効果を解明しつつある.これらの結果を用いると,マントル中のモリブデン,タングステン濃度のデータから,核の中の主要軽元素は硫黄ではないらしい,という重要な結果が得られる.また,鉄-水素2成分系の状態方程式の研究では,核内の軽元素として重要な水素の固液間の分配係数が0.8という結果をえた.これは内核生長による外核対流の物質駆動について,従来の評価を見直すべきことを示す重要な結果である. 流体力学グループでは,マグマオーシャン,すなはち,金属と珪酸塩の分離を伴いつつ対流する2相系の挙動を「あぶく対流」の理論と実験によって,また,熱物質対流の流れ場,温度場,プリュームの型などを液晶をもちいた2次元可視化実験によって研究し,重力場における物質分化とそれらの基本的性質を明らかにした. シミュレイショングループでは上の2グループの成果の他,最近の核に関する研究成果を総合して,地球核の形成進化におけるエネルギー物質収支の大局的描像を導くことができた.核の初期密度成層がもつ大きな重力エネルギーを補償して対流とダイナモが生ずるための条件として,地球潮汐と核内の慣性重力振動の共鳴現象が28億年にあり,核の物質分布,熱的状態,ひいてはマントルの活動と月地球形の力学進化にも大きな異変をもたらした.また,内核の生長のダイナミックスについての詳しい研究によって観測的にチェックできる核の層構造とその構造進化モデルを創った. 総括すると,今まで単に単純な一定の構造を持つ定常的な存在としてのイメージしかなかった地球中心核について,具体的な物理的プロセスの連鎖相互作用の結果として,その生成,生長,変動,進化する動的な描像を得ることができた,といえよう.
  • 文部科学省：科学研究費補助金(一般研究(C))
    研究期間 : 1991年 -1992年 
    代表者 : 圦本 尚義, 末野 重穂
     
    本研究ではアレンデ隕石中の白色包有物を対象として太陽系外物質の存在の有無を重点的に探査した。その成果は以下の様にまとめられる。(1)白色包有物中の元素濃度を1μmの分解能で定量マッピングを行い、分布図を作成した。その結果、各構成鉱物の結晶成長の様式が明らかになった。(2)酸素同位体比を精密測定するために、新しくカスプ型負重イオン源を設計・製作し、2次イオン質量分析計に取りつけた。(3)カスプ型負重イオン源から発生する金の負イオンを1次イオンビームとして用いることにより、鉱物試料中の酸素同位体比の局所分析法を確立した。(4)この酸素同位体比局所分析法を白色包有物中の各鉱物種の分析に適用した。その結果どの鉱物種においてもその粒内の酸素同位体比は一定の値で均一であることが判明した。しかしながら、異なる鉱物種の間では同位体比は異なっている。つまり、各鉱物種はその鉱物独自の酸素同位体比を有しており、その間の関係は化学平衡により説明することができない。(5)(1)と(4)の結果より、白色包有物の成因は次の様に考えられる。A.起新星爆発した星の囲りで、スピネルがまず結晶化する。B.そのスピネルが原始太陽系星雲に近づいたとき、輝石が結晶化を始めた。C.輝石とスピネルが完全に太陽系星雲にとり込まれた後、その囲りに液滴が凝縮をはじめ、その液体からメリライトと針長石が品出をはじめた。(6)以上の結果より、白色包有物中のスピネルは、太陽系外物質であると結論できる。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 1991年 -1991年 
    代表者 : 熊沢 峰夫, 藤井 敏嗣, 圦本 尚義, 阿部 豊, 栗田 敬, 小河 正基
     
    本研究は手法を異にする3つの研究グル-プより成っている。物質科学グル-プでは筑波大学の2次イオン質量分析計の周辺装置の拡充をはかり、元素分配解析の精密化を試みている。重点的に拡充した部分は、イオン源の高輝度化・高信頼性化、面分析用ディテクタ-でありこれにより同位体比測定まで含めた高精度化、微量元素の分析が可能になった。また面分析ディテクタ-の導入により分配係数の決定に不可欠な2次元分析に道を開いた。本年度はこれらの基礎的性能の整備に費やされたために、高圧実験試料をもちいた金属・シリケイト間の分配係数の決定などの決定は次年度にもちこされている。核形成にひき続いておきたマグマオ-シャンでの分化を調べるために従来の装置を用いてシリケイト・メルト間の元素の分配係数が決定された。流体力学グル-プでは組成対流が外核の流体運動に果たす役割を中心に研究を進めた。又熱対流の流れ場、温度場の基本的な性質が数値実験、室内実験の両者から調べられた。シミュレ-ショングル-プでは核形成初期の流体の密度成層構造をとりあげ、地球初期史に果たした役割が調べられた。鉄・ニッケル以外の第3成分の混入による外核の密度成層構造の形成はダイナモ運動やマントルカップリングに極めて重要な役割を果たしたと考えられる。 個別の研究成果とは別に本研究で明らかになった問題点をより明確化し中心核全体に関わる問題としてとらえるために他の研究グル-プとセミナ-を開催した。1つは核の流体運動に関するサマ-セミナ-で組成対流、密度成層構造のふるまいがダイナモグル-プとの間で議論された。2番目のセミナ-は地球初期史に関するセミナ-で地球初期のマグマオ-シャンの形成が物質科学、超高圧グル-プ、シュミレ-ショングル-プを集めて核形成に関連して議論された。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 1989年 -1991年 
    代表者 : 若槻 雅男, WEIDNER D.J., VAUGHAN M.T., PARISE J.B., 圦本 尚義, 中井 泉, 高野 薫, 栗田 敬, 福谷 博仁, 大嶋 建一, 青木 貞雄, 藤井 保彦, 末野 重穂, PARISE John, WEIDNER Dona, CHU Benjamin, 浜谷 望
     
    筑波大学とState University of New York at Stony Brook(SB校)は微小粒子と微小結晶の成長過程に関する研究を双方の得意とする実験及び理論で相互に協力しながら進めた。そのために初年度から互いに2名から4名の研究者を派遣または招聘し、共同実験、講演、討論を重ねながら広い分野間のつながりを広げ、また個々の研究者間の信頼と協力の精神を培った。共同における研究題目と交流は次のようである。 (a)高温高圧物質探査:高温高圧物質の研究は工業的及び宇宙・惑星科学的に重要であるが、SB校と筑波大学では共にこの研究が盛んである。特に合成実験ではSB校のLiebermann,Weidner,Vaughan教授等と本校の若槻教授(物質工学系)、栗田助教授(地球科学系)が技術と情報の交換を行なっている。特に放射光による高圧下での結晶成長の直接観察実験はつくば市の高エネルギ-研究所の実験施設が世界的に群を毅いているためSB校からは多くの招聘研究者が訪れ、ここで共同実験を行なった。ここ数年間でSB校の高圧実験施設は交流の成果もあり、実績を重ねて米国における高圧実験のセンタ-となったことは喜ばしい。 (b)単結晶の構造解析および組成分析実験も両校共に優れた実績を持っているが、互いに試料の提供や解析結果と実験手法の交流など重ねた。合成及び天然物質の構造・組成評価研究はSB校のParise助教授、Ko研究員、筑波大学の末野教授(地球科学系)藤井教授(物質工学系)、中井講師(化学系)が協力しつつ放射光を始めとするX線的研究を発展させてきた。SB校で合成された結晶を筑波大学のSIMSによる微量元素解析を行なうなどの新しい発展を見せており、両者の得意とする分野で互いに研究を補いつつ理想的な共同研究を推進している。 (c)小角散乱実験:SB校のChu教授はこの分野の第一人者であり、特に末野教授が開発を進めていたCCD検出器による小角散乱実験及び回折強度測定における応用についての共同研究と討論を行った。 (d)微小結晶からのX線回折強度測定:大政助教授(物質工学系、現在姫路工業大学)が開発したサブミクロンの微小結晶X線回折実験は、他に例を見ない実験技術であり、Chu教授やParise助教授が深い関心を示し、各々の分野におけるそ応用について討論と研究打ち合せが行なわれた。特に細いビ-ムを作る法や試料結晶の保持法について検討し,SUNY(Chu)がcollimatorを作成することになった。Chu教授が開発中の広領域の小角散乱装置は本研究の目的に重要であると考えられる。 (e)EXAFS実験:BNLにある測定システムを用いてParise助教授と中井講師は放射光を利用したX線分光分析法による非晶質物質中の金属元素の状態分析とEXAFS法による構造解析を行い、多くの有用な知見を得た。 (f)X線顕微鏡:放射光の平行性と偏光性を利用したX線顕微鏡に関する開発研究は物質科学において重要であるが、SB校のKirz教授と本校の青木助教授(物理工学系)が、永年にわたりNSLS(米国)と高エネ研の放射光を利用して共同研究を行なった。 (g)相転移とX線散漫散乱研究:NSLS(米国)と高エネ研の放射光を利用してSB校のStephens教授と大嶋助教授(物理工学系)が金属のマルテンサイト変態などに関する共同研究を行なった。 (h)講演会・研究会:両校の研究者が相手校を訪問した際には、講義またはゼミナ-ル形式で講演会・研究会を開催して互いに情報の交換と研究上の意見とアイディアを討論している。特に、Chu教授による講演会(題目:Recent advance in laser light scattering)は広く関心を集め、つくば市の各研究所からの研究者が参集した。 昭和60年に締結した交流協定も本科学研究費により交流が本格化し、お蔭で両校の研究者間に共同作業に対する違和感や不信感が取れ、親密にフランクに意見やアイディアの交換がなされ、両校の交流が定常的に行なうことが出来、共同研究に一層のはずみが附いたことが将来に亙って最大の成果であると考える。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 1988年 -1989年 
    代表者 : 末野 重穂, 紀本 靜雄, 圦本 尚義, 紀本 静雄
     
    本研究では、高分解能で研磨試料面上の微小領域の同位体元素の二次元的分布、又は深さ方向分析との併用によって三次元分析を観察するため、CAMECA社製3f型二次イオン質量分析計(SIMS)に装着して使用するCCDを応用した二次元イオン検出システムを設計・試作した。本システムは次のような構成になっている。(1)CCD検出器部、(2)CCD冷却デュワ-部、(3)CCDドライブ部、(4)CCD制御部、(5)CCDモニタ-部、(6)制御コンピュ-タ部、(7)カラ-モニタ-部。CCD検出器部は、マイクロチャネルプレ-ト、蛍光体フィルムとCCD(日本TI社:VID272型:6×9ミリ:798×242画素)からなり、二次イオンは電子に増幅変換される。このシステムにおいて高いS/N比を得るには、闇電流を削除することが最も重要であることが見いだされ、そのためCCD部は-60℃に液体窒素で冷却され、このことにより微弱イオン像の計測と長時間露出が可能となった。測定デ-タはノイズを除去した後、各種の画像処理(ブライトネス処理、コントラスト処理、蓄積時間処理、MCP感度補正処理、画像ひずみ補正)をほどこす。 本システムはアレンドコンドライト隕石中の酸素同位体( ^<16>Oと^<18>O)の二次元分布の観測に応用され、 ^<18>Oの分布の二次元像の計測に世界で初めて成功した。この実験結果から、250×250μmの試料画上の分布を一度の一次イオン照射により測定可能であり、非常に弱いイオン像(数百カウント/秒: ^<18>Oの場合)の測定も可能であることが判った。現在のところ、多くの改良すべき問題もあるが、本システムの高感度性は実用上充分であることが証明された。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 1985年 -1988年 
    代表者 : 末野 重穂, 圦本 尚義, 熊沢 峰夫
     
    本研究では、従来定量分析が困難であった鉱物・岩石及び無機化合物中における水素、ほう素等の軽元素の定量分析と酸素同位体比分析、及び稀土類元素を含んだ微量元素の定量分析を二次イオン質量分析計を用いて行なった。これまで鉱物試料にSIMSの適用が遅れ、成果が少ない最大の理由は、(1)絶縁体である、(2)組成が複雑である、という鉱物のもつ二つの性質に起因する。(1)は帯電による二次イオンの安定性を抑制、(2)は質量スペクトルを複雑にする原因となる。本研究では(1)は金の薄膜の蒸着と^<16>O^-を一次ビームに用いる事で解決し、(2)は設備備品として購入した一次イオンを精製するマスフィルターを用いる事とスペクトルを高分解能で分解する事で解決した。本研究における始めの数年間は以上の手法の開発のために基礎研究を行なった。そして完成された測定手法は深さ方向分析能を組合せることで、以下の様な成果を挙げる事ができた。期間中になされた主要な課題と内容の概略を下に示す。 【○!1】マグマ〜結晶間(輝石、斜長石、クロムスピネル)における陰・陽イオンの挙動の研究を行ない、イオンの元素分配は結晶構造によって制御される事を陰イオンについても確認した。 【○!2】標準岩石をガラス化させた試料について軽〜重元素に至る微量元素をSIMSにより検量線法を用いて定量的に分析する方法を開発した。 【○!3】各種のメリライト鉱物中に^<18>O^-を1000ー1300℃で拡散させ、拡散プロファイルを測定し、酸素自己拡散での格子拡散と転位拡散速度を精密に解析した。 【○!4】パリクレース(MgO)など無機物質中における微量元素の拡散速度の測定を行ない、一つの拡散プロファイルから格子拡散と転位拡散速度を解析する事に成功した。 【○!5】気相合成されたダイヤモンド膜中の微量ほう素の深さ方向プロファイルを測定した。 以上の成果の外にX線結晶構造解析により、酸化物超伝導体その他の酸化物中の酸素含有量と構造の解明も行なった。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 1987年 -1987年 
    代表者 : 圦本 尚義
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 1986年 -1986年 
    代表者 : 末野 重穂, 圦本 尚義
     
    以下に箇条書する新たな知見・成果が得られた。 1.従来、我々の実験室で使用していた酸素の1次イオンには、【^(16)O】,【^(17)O】,【^(18)O】の同位体の他に、【O_2】,【H_2】O,N,【N_2】,【CO_2】,CN,Ar,Cl等の不純物イオンが存在していたことが判明した。しかし、これらの不純物イオンは1次イオンビーム質量分析装置を使用することにより完全に除去可能となった。現在では同位体的にも純粋な【_(16)O_-】の1次イオンビームを使用可能となった。 2.その結果、鉱物中の酸素の分析・酸素同位体の分析が初めて可能になった。鉱物から発生する酸素の2次イオンのうち、【^(16)O】は30〜40%の1次イオンの混入が避けられないが、【^(17)O】,【^(18)O】は妨害フリーの2次イオンで、鉱物中の酸素を直接反映する。 3.この酸素分析技術を、メリライト中の酸素の自己拡散の研究に適用した。得られた拡散プロファィルには、従来知られていた格子拡散によるものに加えて、転位を利用した高速拡散のプロファイルが存在していた。これは、酸素の自己拡散が、酸化物中で、転位により促進されることを示した初めての証拠である。 4.1次イオンビーム中に極微量含有されていたFe,Niイオンも除去可能となったため、重元素の分析限界が約4桁向上した。 5.ペリクレース中の不純物の拡散係数を2次イオン分析法を用いた深さ方向分析法により求めた。この方法は1μmの拡散パスから拡散係数を算出可能である。そのため従来の限界より2桁遅い拡散係数も容易に測定可能となった。 6.ペリクレース中の不純物の拡散においても、転位による拡散の促進が重要な役割を演じていることが明かになった。
  • 太陽系の起源と進化
    研究期間 : 1980年
  • Origin of the solar system
    研究期間 : 1980年

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