研究者データベース

山本 順司(ヤマモト ジユンジ)
総合博物館
准教授

基本情報

所属

  • 総合博物館

職名

  • 准教授

学位

  • 博士(理学)(東京大学)

ホームページURL

科研費研究者番号

  • 60378536

ORCID ID

J-Global ID

研究キーワード

  • マントル捕獲岩   流体包有物   ラマン分光   分光分析   質量分析器   管状加熱炉   マントルウェッジ   物質循環系   還元実験   同位体分析   炭素同位体   地質圧力計   マントル   沈み込み帯   マグマ   脱水反応   炭素同位体組成   地下温度構造   蛍光X線   海洋プレート   海洋地殻   ラマン分光分析   電気伝導度構造   非破壊分析   地殻熱流量   岩石・流体相互作用   ホットスポット   プチスポット   プレート内火山   微量成分   

研究分野

  • 自然科学一般 / 固体地球科学
  • 自然科学一般 / 宇宙惑星科学
  • 自然科学一般 / 固体地球科学

職歴

  • 2012年04月 - 現在 北海道大学 総合博物館 准教授
  • 2003年12月 - 2011年03月 京都大学 理学研究科 助教
  • 2003年01月 - 2003年12月 東京工業大学 理工学研究科 日本学術振興会 特別研究員(SPD)
  • 2002年04月 - 2002年12月 東京大学 理学系研究科 日本学術振興会 特別研究員(PD)
  • 2001年04月 - 2002年03月 東京大学 理学系研究科 非常勤講師

学歴

  • 1998年04月 - 2001年03月   東京大学   理学系研究科   地球惑星科学科
  • 1996年04月 - 1998年03月   東京大学   理学系研究科   地質学科
  • 1992年04月 - 1996年03月   広島大学   理学部   地球惑星システム学科

所属学協会

  • The Geochemical Society   American Geophysical Union   日本環境教育学会   日本地学教育学会   東京地学協会   日本鉱物科学会   日本地球惑星科学連合   日本地球化学会   

研究活動情報

論文

  • Yuuki Hagiwara, Kenta Yoshida, Akira Yoneda, Junji Torimoto, Junji Yamamoto
    Chemical Geology 559 119928 - 119928 2021年01月
  • Junji Yamamoto, Naoto Hirano, Mark D. Kurz
    Earth and Planetary Science Letters 552 116611 - 116611 2020年12月
  • Takeshi Hanyu, Junji Yamamoto, Katsunori Kimoto, Kenji Shimizu, Takayuki Ushikubo
    Chemical Geology 557 119855 - 119855 2020年12月
  • Yuuki Hagiwara, Junji Torimoto, Junji Yamamoto
    JOURNAL OF RAMAN SPECTROSCOPY 51 6 1003 - 1018 2020年06月 [査読有り][通常論文]
     
    Dependence of residual pressures of fluid inclusions on their size and host mineral species provides valuable information related to the depth provenance and P-T-t path of the rocks. Although Raman-based barometry is an effective method for ascertaining the internal pressure of H2O-CO2 fluid inclusions, few studies have elucidated Raman spectral features of CO2 in a system of high-pressure H2O-CO2. New experiments using a high-pressure optical cell in this binary system with compositions of 100, 75 +/- 2, and 60 +/- 2 mol% CO2 were conducted for this study to verify the availability of Raman CO2 barometers for use in assessing the temperature and pressure conditions of approximately 22 degrees C and 17.3-141.4 MPa. Our results demonstrate that the existence of H2O does not affect the relation between Fermi diad splits (Delta, cm(-1)) and total pressure of pure CO2. These results suggest that the Delta-total pressure relation obtained from pure CO2 is also applicable to H2O-CO2 systems, even at high pressure. However, unlike Delta, because the peak positions of the Fermi diad in the system of H2O-CO2 shift to a higher wavenumber than those of pure CO2 at given pressure higher than 30 MPa, the peak positions are not very suitable for the pressure scale in an H2O-CO2 system. Additionally, we confirmed the availability of bandwidths of CO2 as an indicator of compositions that can identify the presence of very small amounts of H2O (at least 0.3 mol% H2O), even at room temperature.
  • J. Yamamoto, N. Takahata, Y. Sano, M. Yanagita, S. Arai, V.S. Prikhod'ko
    Earth and Planetary Science Letters 534 116109 - 116109 2020年03月 [査読有り][通常論文]
  • Lena Yokokura, Yuuki Hagiwara, Junji Yamamoto
    JOURNAL OF RAMAN SPECTROSCOPY 2020年03月 [査読有り][通常論文]
     
    Micro-Raman spectroscopy can find the carbon isotopic ratio of CO2 fluid from the ratio of intensity or area of a (CO2)-C-13 peak to that of a (CO2)-C-12 peak. We examined the precisions of carbon isotopic ratios (delta C-13) of CO2 at constant room temperature and pressure of 10-150 MPa. Measurement of the intensity ratio has precision of 2.8-8.7 parts per thousand, which is better than that of the area ratio of 4.5-14.7 parts per thousand. We also investigated the pressure dependence of the Raman intensity ratios and area ratio by changing fluid pressure. When changing fluid pressure from 10 to 150 MPa, the ratios of intensity and area both show negative correlation with fluid pressure (CO2 density). Pressures of two types affect the Raman spectrum of CO2 peaks, affecting the peak position and peak shape. To evaluate effects on the peak position, we repeatedly measured the intensity ratio at constant CO2 pressure (10 MPa) with movement of the grating center position, which is defined as the center value of the analyzed wave number range. Although we moved the grating center position from 1,248.5 to 1,251.5 cm(-1), no significant correlation was observed for either ratio of intensity or area. The pressure effect on the ratios can be corrected by ascertaining the CO2 pressure. Combination with the Raman spectroscopic barometry for CO2 enables analyses of delta C-13 of CO2 respectively using the intensity ratio and the area ratio of CO2 Raman peaks within 8.7 and 14.7 parts per thousand.
  • ERUPTION AGE OF KANNABE VOLCANO USING MULTI-DATING: IMPLICATIONS FOR AGE DETERMINATION OF YOUNG BASALTIC LAVA FLOW
    YORINAO SHITAOKA, TAKESHI SAITO, JUNJI YAMAMOTO, MASAYA MIYOSHI, HIDEMI ISHIBASHI, TSUTOMU SODA
    Geochronometria 46 49 - 56 2019年04月 [査読有り][通常論文]
  • J. Yamamoto, T. Yoshino, D. Yamazaki, Y. Higo, Y. Tange, J. Torimoto
    Journal of Materials Science 54 1 139 - 148 2019年01月 [査読有り][通常論文]
  • Yoshihiro Nakamura, Hidemi Ishibashi, Atsushi Yasuda, Natsumi Hokanishi, Junji Yamamoto
    LITHOS 324 315 - 324 2019年01月 [査読有り][通常論文]
     
    Ultra-magnesian igneous olivine is thought to crystallize from ultramafic melts and can therefore provide information about physicochemical conditions and the geochemistry and lithology of the source in the context of extremely hot mantle activity. This study focuses on the petrology and mineralogy of the Shizuoka meimechites, a series of ultra-magnesian olivine-bearing ultramafic lava blocks embedded in middle Eocene-early Miocene accretionary sediments at Shizuoka, Japan. Olivine phenocrysts within the Shizuoka meimechites have Fo compositions of ca. 81-92.8 mol%, where Fo = 100 Mg/(Mg + Fe). These ultra-magnesian olivines have trace-element compositions that are indicative of derivation from ultramafic melts that were in equilibrium with peridotitic mantle olivine. Al-in-olivine geothermometry yielded crystallization temperatures of similar to 1450 degrees C for Fo(92.5-92.8) olivine, higher than the potential temperature of present-day mid-ocean ridge basalt source mantle material and similar to the potential temperatures of some large igneous provinces and ocean island basalts. Primary melt compositions in equilibrium with Fo(92.5-92.8) olivine were estimated using the whole-rock compositions of the ultramafic lavas and are meimechitic, with MgO concentrations of similar to 21.4-27.0 wt% and SiO2 concentrations of 45.4-44.5 wt%. The potential temperature of the source mantle region for these meimechites (T-p) is estimated to be similar to 1486 degrees C-1705 degrees C, which is consistent with the Al-in-olivine geothermometry when considering adiabatic cooling during magma ascent. The relationship between T-p and Al-in-olivine temperature estimates for these lavas is consistent with global examples of ultra-magnesian olivine-bearing lavas. These lavas provide evidence of hitherto unknown Late Cretaceous-early Miocene deep mantle activity beneath the western Pacific region. (C) 2018 Elsevier B.V. All rights reserved.
  • J. Yamamoto, T. Kawano, N. Takahata, Y. Sano
    Earth and Planetary Science Letters 497 139 - 148 2018年09月 [査読有り][通常論文]
  • Yuki Sato, Naoto Hirano, Shiki Machida, Junji Yamamoto, Masao Nakanishi, Teruaki Ishii, Arashi Taki, Kazutaka Yasukawa, Yasuhiro Kato
    International Geology Review 60 10 1231 - 1243 2018年07月27日 [査読有り][通常論文]
     
    The stress field of oceanic lithosphere controls the distribution of submarine petit-spot volcanoes. However, the eruption sites of these petit-spot volcanoes are considered to be limited to concavely flexed regions of lithosphere off the outer rise. Here, we present new data for a recently identified petit-spot lava field on a convexly flexed section of the lithosphere adjacent to the subduction zone offshore of northeast Japan in an area containing more than 80 volcanoes. This area is marked by strongly alkaline lavas that were erupted on the convexly flexed region. As for the concavely flexed region where the petit-spots previously reported, the base of the lithosphere beneath the eruption sites is under extension, whereas the upper part of the lithosphere is under compression. This change in the stress field, from the lower to upper lithosphere, causes ascending dikes to stall in the mid-lithosphere, leading to metasomatic interaction with the surrounding peridotite. The new geochemical data of rocks and xenocrysts presented in this study indicate that strongly alkaline magmas erupted on the convexly flexed region would have ascended more rapidly through the mid-depth of lithosphere because of the extensional regime of the upper lithosphere and decreasing the degree of metasomatic reaction with the surrounding mantle peridotite. The results indicate that the degree of metasomatism and the compositional variations of petit-spot magmas are controlled mainly by the stress field of the lithosphere.
  • CO2 Raman thermometer improvement: comparing hot band and Stokes and anti-Stokes Raman scattering thermometers
    Hagiwara Y, Takahata K, Torimoto J, Yamamoto J
    Journal of Raman Spectroscopy 49 1776 - 1781 2018年07月 [査読有り][通常論文]
  • クラウドファンディングを利用した展示制作
    山本順司, 徳永彩未
    博物館学雑誌 44 55 - 65 2018年04月 [査読有り][通常論文]
  • Kenya Ono, Yuya Harada, Akira Yoneda, Junji Yamamoto, Akira Yoshiasa, Kazumasa Sugiyama, Hiroshi Arima, Tohru Watanabe
    PHYSICS AND CHEMISTRY OF MINERALS 45 3 237 - 247 2018年03月 [査読有り][通常論文]
     
    We determined elastic constants of a single-crystal chromian spinel at temperatures from -15 to 45 A degrees C through the Rectangular Parallelepiped Resonance method. The sample is a natural chromian spinel, which was separated from a mantle xenolith. Elastic constants at an ambient temperature (T = 24.0 A degrees C) are C (11) = 264.8(1.7) GPa, C (12) = 154.5(1.8) GPa and C (44) = 142.6(0.3) GPa. All the elastic constants decrease linearly with increasing temperature. The temperature derivatives are dC (11)/dT = -0.049(2) GPa/A degrees K, dC (12)/dT = -0.019(1) GPa/A degrees K and dC (44)/dT = -0.020(1) GPa/A degrees K. As an implication of the elastic constants, we applied them to the correction of a fluid inclusion geobarometry, which utilizes residual pressure of fluid inclusion as a depth scale. Before entrainment by a magma, the fluid inclusions must have the identical fluid density in constituent minerals of a xenolith. It has been, however, pointed out that fluid density of fluid inclusions significantly varies with host mineral species. The present study elucidates that elastic constants and thermal expansion coefficients cannot explain the difference in fluid density among mineral species. The density difference would reflect the difference in the degree of plastic deformation in the minerals.
  • 岩脈形成過程を観察する教材の教育実践と体系的解説
    下岡順直, 三好雅也, 西村光史, 石橋秀巳, 山本順司
    地球環境研究 20 95 - 102 2018年02月 [査読有り][通常論文]
  • Hagiwara Y, Sogo Y, Takahata K, Yamamoto J
    GEOCHEMICAL JOURNAL 52 4 379 - 383 2018年 [査読有り][通常論文]
  • 複数の年代測定法による噴火活動年代の推定−神鍋スコリア丘への適用−
    下岡順直, 齋藤武士, 山本順司, 石橋秀巳, 三好雅也, 早田 勉
    号外地球 69 174 - 181 2018年 [査読無し][通常論文]
  • Yusuke Shibano, Kohei Takahata, Jun Kawano, Tsuyoshi Watanabe, Daisuke Enomoto, Hiroyuki Kagi, Natsumi Kamiya, Junji Yamamoto
    JOURNAL OF RAMAN SPECTROSCOPY 48 12 1755 - 1761 2017年12月 [査読有り][通常論文]
     
    We investigated the relation between Sr# [=100Sr/(Sr+Ca) in mol] of calcites and their Raman spectra for Sr-doped calcite samples with Sr# of 0-13.2. We selected 3 major Raman peaks observed at 150-155cm(-1) (peak A), 274-282cm(-1) (peak B), and 710-712.5cm(-1) (peak C). With increasing Sr#, the peaks shifted monotonously to lower wavenumbers. We obtained a linear expression for peak B as Sr#=-1.734(B)+76.93, where (B) is a separation between peak B and a neon emission line of 237.07cm(-1) in Raman shift. The present spectroscopic analysis can ascertain Sr# of calcite with precision of +/- 1.26 in the range of Sr# of 0-13.2.
  • 江田 真毅, 山本 順司
    博物館研究 = Museum studies 52 9 30 - 33 日本博物館協会 2017年09月 [査読無し][通常論文]
  • Junji Yamamoto, Hidemi Ishibashi, Koshi Nishimura
    Geochemical Journal 51 6 457 - 467 2017年 [査読有り][通常論文]
     
    Geothermometry is fundamentally important to explore thermal processes within the Earth. An extremely popular geothermometer is the two-pyroxene thermometer, which is based on the temperature dependence of elemental partitioning between pyroxenes in a rock. This technique is ambiguous in terms of its responsiveness to change in the temperature of the system. We performed a numerical simulation of one-dimensional calcium diffusion in a clinopyroxene using Ca- Mg inter-diffusion coefficients. While applying the simulation to rock bodies with various temperature conditions and both heating and cooling rates, we investigated the time scale for the re-equilibration of elemental partitioning between enstatite and diopside. Those results enable us to evaluate the responsiveness of the two-pyroxene thermometer to change in temperature. For heating processes up to 1300∞C, chemical zoning is not well developed at a heating rate faster than 10∞C/yr because the duration for the diffusion is insufficient. In addition, at a heating rate 10-4∞C/yr and > 1200∞C, the simulated diffusion profiles show no chemical zoning. This occurs because the chemical equilibrium between the pyroxenes is achieved via elemental diffusion. For cooling processes, a rock body will cool down to closure temperature before making an observable zoning at a high cooling rate such as 100∞C/yr. In addition, no detectable zoning of Ca in clinopyroxene developed under high temperature (> ∼1100∞C) and a slow cooling rate (< ∼10-4∞C/yr) down to 700∞C, properly reflecting temperature without detectable zoning of Ca. In contrast, for a rock body with detectable chemical zoning, it is difficult to ascertain the appropriate pyroxene temperature. Model diffusion profiles reflect conditions of changing temperature. Therefore, a graphic representation of diffusion profiles under various initial temperatures and different rates of temperature change would be useful to estimate the thermal history of rock bodies.
  • 異分野展示の融合:天体シミュレーターソフトウェアを用いた宇宙展示は異分野融合の架け橋となるか?
    田中公教, 山本順司, 安藤卓人, 増田彩乃, 三嶋渉, 岩波連, 山下俊介
    博物館学雑誌 印刷中 2017年 [査読有り][通常論文]
  • 級化組織の形成機構を理解するための補助教材の開発 ー媒体の粘性による影響を体感するー
    山本順司, 徳永彩未, 田中公教, 高畑幸平, 田島貴裕, 三嶋渉
    地学教育 70 31 - 41 2017年 [査読有り][通常論文]
  • 凍結融解による岩石の風化を理解させるためのモデル実験におけるモルタルの利用可能性
    三嶋渉, 山本順司, 在田一則, 加藤義典, 田中公教, 鳥本淳司, 高畑幸平, 日下葵, 寺西辰郎
    地学教育 70 15 - 22 2017年 [査読有り][通常論文]
  • Norikatsu Akizawa, Akihiro Tamura, Keisuke Fukushi, Junji Yamamoto, Tomoyuki Mizukami, Marie Python, Shoji Arai
    LITHOS 263 66 - 87 2016年10月 [査読有り][通常論文]
     
    Reaction products between hydrothermal fluids and uppermost mantle harzburgite-lowermost crustal gabbro have been reported along Wadi Fizh, northern Oman ophiolite. They are named mantle diopsidite (MD) or crustal diopsidite (CD) depending on the stratigraphic level. They construct network-like dikes crosscutting structures of the surrounding harzburgite or gabbro. The MD is mainly composed of diopsidic clinopyroxene, whereas the CD is of diopsidic clinopyroxene and anorthitic plagioclase. Here, we report a new reaction product, crustal anorthosite (CA), from the lowermost crustal section. The CA is always placed in the center of the CD network, and mainly consists of anorthitic plagioclase with minor titanite and chromian minerals such as chromite and uvarovite. Aqueous fluid inclusions forming negative crystals are evenly distributed in minerals of the CA. The fluid inclusions contain angular-shaped or rounded daughter minerals as calcite or calcite-anhydrite composite, which were identified by Raman spectroscopic analysis. We estimated their captured temperature at 530 degrees C at least by conducting microthermometric analysis of the fluid inclusions. Furthermore, we examined their chemical characteristics by direct laser-shot sampling conducted by laser ablation-inductively coupled plasma mass spectrometer (LA-ICP-MS). The results indicate that the trapped aqueous fluids contain an appreciable amount of Na, but no K and Cr. Hydrothermal fluids involved in the CA formation transported Cr, which was probably taken up from chromite seams in the uppermost mantle section. Cr got soluble by forming complexes with anions as SO42-, CO32- and Cl-. In addition, these hydrothermal fluids transported Fe, Mg and trace elements (Ti, Sr, Y, Zr and rare-earth elements) governing whole-rock chemical compositions of the MDs, CDs and CAs. Our estimation for the condition of CA formation yielded rather low temperatures (530-600 degrees C), which indicates a later stage production of the CA than the MD and CD (similar to 800 degrees C). A series of high-temperature hydrothermal events had been significantly contributed to the chemical flux occurring around the Moho, boundary between the mantle and crustal sections. (C) 2016 Elsevier B.V. All rights reserved.
  • Eruption age of Sakurajima-Satsuma tephra using thermoluminescence dating
    Shitaoka, Y, Moriwaki, H, Akai, F, Nakamura, N, Miyoshi, M, Yamamoto, J
    地球環境研究 19 125 - 128 立正大学 2016年03月 [査読有り][通常論文]
  • 歯舞群島と色丹島の地質資料と岩石試料の重要性
    平野直人, 油谷拓, 山本順司
    東北アジア研究 20 61 - 74 2016年 [査読無し][通常論文]
  • Eruption age of Sakurajima-Satsuma tephra using thermoluminescence dating
    Shitaoka Y, Moriwaki H, Akai F, Nakamura N, Miyoshi M, Yamamoto J
    Bulletin of Geo-Environmental Science 18 29 - 35 2016年 [査読有り][通常論文]
  • 減災教育を意識した液状化現象実験観察の実践例
    下岡順直, 山本圭香, 山本順司
    地球環境研究 18 89 - 96 2016年 [査読有り][通常論文]
  • 天文シミュレーターMitakaを用いたプログラム公演と大学博物館展示の連携:化石展示との連携を事例して
    田中公教, 三嶋渉, 高畑幸平, 榊山匠, 山本順司
    地学教育 68 145 - 153 2016年 [査読有り][通常論文]
  • 田中公教, 岩波連, 神田いずみ, 山本順司, 福澄孝博
    Computer & Education 39 80 - 85 2016年 [査読有り][通常論文]
  • 三嶋渉, 山本順司, 在田一則, 鳥本淳司, 田中公教, 酒井実
    地学教育 68 59 - 67 2015年 [査読有り][通常論文]
  • 山本順司, 高畑幸平, 鳥本淳司, 石橋秀巳
    地学雑誌 124 429 - 443 2015年 [査読有り][招待有り]
  • Kohei Takahata, Junji Torimoto, Junji Yamamoto
    CHEMISTRY LETTERS 43 12 1924 - 1925 2014年12月 [査読有り][通常論文]
     
    We improved Raman spectroscopic densimetry for a CO2 fluid using a micro-Raman spectrometer with high spectral resolution. For precise determination of CO2 density, we obtained A, the separation of wavenumbers between two main peaks of the CO2 Raman spectrum, with a precision of +/- 0.006 cm(-1) (1 sigma). This precision will be enhanced to +/- 0.003 cm(-1) by increasing counts, corresponding to a density precision of +/- 0.0009 g cm(-3), which is approximately one order of magnitude less than that reported in earlier studies.
  • Junji Yamamoto, Jun Korenaga, Naoto Hirano, Hiroyuki Kagi
    GEOLOGY 42 11 967 - 970 2014年11月 [査読有り][通常論文]
     
    Young basaltic knolls have been discovered on the old oceanic lithosphere, namely petit-spot volcanoes. Based on their geochemical signatures, they have presumably originated from partial melts in the asthenosphere. However, there is no direct information on the depth provenance of petit-spot formation. Here we report new geothermobarometric data of rare mantle xenoliths discovered from petit-spot lavas exhibiting a geotherm much hotter than expected for the ca. 140 Ma seafloor on which petit-spots were formed. Such an anomalously hot geotherm indicates that melt porosity around the lithosphere-asthenosphere boundary (LAB) must be as high as a few percent. Such high melt porosity would be possible by continuous melt replenishment. Excess pressure induced by the outer-rise topography enables horizontal melt migration along the LAB and sustains a continuous melt supply to petit-spot magmatism. Given the general age-depth relationship of ocean basins, a melt-rich boundary region could also be a global feature.
  • Yoshitaka Kumagai, Tatsuhiko Kawamoto, Junji Yamamoto
    CONTRIBUTIONS TO MINERALOGY AND PETROLOGY 168 4 DOI:10.1007/s00410-014-1056-9  2014年10月 [査読有り][通常論文]
     
    Lherzolite xenoliths containing fluid inclusions from the Ichinomegata volcano, located on the rear-arc side of the Northeast Japan arc, may be considered as samples of the uppermost mantle above the melting region in the mantle wedge. Thus, these fluid inclusions provide valuable information on the nature of fluids present in the sub-arc mantle. The inclusions in the Ichinomegata amphibole-bearing spinel-plagioclase lherzolite xenoliths were found to be composed mainly of CO2-H2O-Cl-S fluids. At equilibrium temperature of 920 degrees C, the fluid inclusions preserve pressures of 0.66-0.78 GPa, which correspond to depths of 23-28 km. The molar fraction of H2O and the salinity of fluid inclusions are 0.18-0.35 and 3.71 +/- 0.78 wt% NaCl equivalent, respectively. These fluid inclusions are not believed to be fluids derived directly from the subducting slab, but rather fluids exsolved from sub-arc basaltic magmas that are formed through partial melting of mantle wedge triggered by slab-derived fluids.
  • Yorinao Shitaoka, Masaya Miyoshi, Junji Yamamoto, Tomoyuki Shibata, Tsuneto Nagatomo, Keiji Takemura
    GEOCHRONOMETRIA 41 1 30 - 35 2014年03月 [査読有り][通常論文]
     
    We determined the eruption age of basaltic rocks by application of thermoluminescence (TL) method, which is often used for TL dating, to quartz. Mafic magma only rarely includes quartz because of their mutual disequilibration. The basaltic lavas reported herein include quartz as xenocrysts, as corroborated by their rounded or anhedral shape. The basaltic lava used for this study is from the Oninomi monogenetic volcano in northern Kyushu, Japan. The volcano eruption was estimated as occurring 7.3-29 ka because the lava exists between two widespread tephras: Aira-Tanzawa ash (26-29 ka) and Kikai-Akahoya ash (7.3 ka). We succeeded in collecting ca. 200 mg of quartz by decomposition of 30 kg of the lava samples. TL measurements for the lava indicate the eruption age as 15.8 +/- 2.5 ka, which is fairly consistent with the stratigraphical estimation. Although the TL method has played a considerable part in constraining the timescale of Quaternary events, its application has been limited to silicic samples. The present result demonstrates the availability of quartz for dating even of mafic rock.
  • Preliminary report on post-IR IRSL dating of poly-mineral semi-fine grains extracted from Myojin volcanic body
    Shitaoka Y, Miyoshi M, Yamamoto J, Takemura K
    Annual Report of Institute for Geothermal Sciences (FY2013) 14 Kyoto University 2014年 [査読無し][通常論文]
  • 下岡順直, 本庄眞, 渡辺克裕, 河原真菜, 山本順司, 三好雅也, 中野英之, 平賀章三, 竹村恵二
    環境教育 24 85 - 91 2014年 [査読有り][通常論文]
  • Masaya Miyoshi, Taro Shinmura, Hirochika Sumino, Takashi Sano, Yasuo Miyabuchi, Yasushi Mori, Hirohito Inakura, Kuniyuki Furukawa, Koji Uno, Toshiaki Hasenaka, Keisuke Nagao, Yoji Arakawa, Junji Yamamoto
    Chemical Geology 352 202 - 210 2013年08月16日 [査読有り][通常論文]
     
    We investigated the K-Ar ages and the petrological and geochemical features of lava units from lateral cones and lava distributed around the Aso caldera in central Kyushu, Japan, in order to constrain the spatial range of lateral magma intrusion during the caldera-forming stage. The results of the K-Ar age determination showed that most of the analyzed lava units erupted almost simultaneously with the Aso caldera-forming pyroclastic eruptions (266 to 89. ka). In addition, the petrography, major and trace element compositions, and Sr isotope ratios of these lava units are indistinguishable from the caldera-forming pyroclastic products. The contemporaneous activities of compositionally similar magmas inside and outside of the caldera presumably indicate the occurrence of a lateral intrusion of caldera-forming magma, which had accumulated in a huge magma chamber beneath the caldera system. Our results suggest that a total of 6.3. vol.% of caldera-forming magma in the Aso volcano migrated more than 20. km along the faults from the center of the caldera. © 2013 Elsevier B.V.
  • 温泉熱源における時間情報の解読II:姫島明神山火山岩片のルミネッセンス年代測定
    下岡順直, 三好雅也, 山本順司
    大分県温泉調査研究会報告 64 25 - 32 2013年 [査読無し][通常論文]
  • 東日本大震災に対する環境教育の応答性を探るーサイエンスカフェを例にー(東日本大震災後の環境教育)
    徳永彩未, 山本順司
    日本の環境教育 1 86 - 93 2013年 [査読有り][通常論文]
  • Tomoyuki Kobayashi, Junji Yamamoto, Takao Hirajima, Hidemi Ishibashi, Naoto Hirano, Yong Lai, Vladimir S. Prikhod'ko, Shoji Arai
    JOURNAL OF RAMAN SPECTROSCOPY 43 8 1126 - 1133 2012年08月 [査読有り][通常論文]
     
    To assess the ability of densimetry for CO2 fluid in CO2 inclusions, we compare two methods, microthermometry and Raman microspectroscopic densimetry for CO2. The comparative experiment was performed for nine CO2 inclusions in three mantle xenoliths. The results are as follows: (1) microthermometry precisely determines CO2 density with the range of 0.65 to 1.18?g/cm3 compared with Raman microspectroscopic densimetry; (2) CO2 density obtained by Raman microspectroscopic densimetry is fairly consistent with that by microthermometry; (3) it is hard to determine CO2 density in CO2 inclusion with diameter of less than around 3 mu m using microthermometry; and (4) microthermometry can be applied only to the CO2 inclusion whose CO2 density ranges from around 0.65 to 1.18?g/cm3, whereas the Raman microspectroscopic densimetry is applicable to CO2 density ranging from 0.1 to 1.24?g/cm3. The above features carry the potential for estimation of depth origin of mantle-derived rocks. The depth where the rocks were trapped by host magma can be estimated using both geothermometric data and CO2 fluid density in CO2 inclusions in the rocks. Typical precisions of density of CO2 in CO2 inclusions obtained by the Raman microspectroscopic densimetry (similar to 0.01?g/cm3) and by the microthermometry (< 0.001?g/cm3) correspond to uncertainties in the depth origin of 2.4?km and?<?1.7?km, respectively, at 1000?+/-?50?degrees C. In case of the mantle under 7501250?degrees C and 1?GPa, the CO2 fluid has a density ranging from 1.06?g/cm3 to 1.21?g/cm3, which are well measured by the Raman microspectroscopic densimetry. Combination of both densimetries for CO2 in mantle minerals elucidates the deep structure of the Earth. Copyright (c) 2012 John Wiley & Sons, Ltd.
  • Junji Yamamoto, Koshi Nishimura, Hidemi Ishibashi, Hiroyuki Kagi, Shoji Arai, Vladimir S. Prikhod'ko
    TECTONOPHYSICS 554 74 - 82 2012年07月 [査読有り][通常論文]
     
    Based on pressure and temperature (P-T) information of mantle-derived xenoliths, this report describes a geotherm in Far Eastern Russia, which is situated in the backarc of volcanic chains in eastern Asia. The mantle xenoliths have abundant CO2 fluid inclusions. Accurate determination of the internal pressure of the CO2 fluid inclusions enables estimation of the depth provenance of the mantle xenoliths. The depth provenances obtained from five mantle xenoliths are correlated with equilibrium temperatures estimated using a geothermometer. Assuming that the correlation reflects the geotherm in this region, it corresponds to heat flow of around 100 mW/m(2), which is comparable to the surface heat flow in the volcanic arc. Such high heat flow implies a thin lithosphere and high temperature of the shallower upper mantle. Backarc areas are universally characterized by both high surface heat flow and the occurrence of recent volcanic activities. Furthermore low seismic velocity anomaly is widely observed in the shallower upper mantle in the backarc, especially in eastern Asia. The present xenolith geotherm suggests that the seismic anomaly arises from high temperature of the shallower upper mantle. It would be direct evidence for warming of the lithospheric mantle and subsequent lithospheric thinning, which is likely attributable to asthenospheric upwelling. (C) 2012 Elsevier B.V. All rights reserved.
  • 下岡 順直, 三好 雅也, 山本 順司, 三好 まどか, 竹村 恵二
    地学教育 65 2 51 - 61 日本地学教育学会 2012年03月25日 [査読無し][通常論文]
  • Hidemi Ishibashi, Masashi Arakawa, Junji Yamamoto, Hiroyuki Kagi
    JOURNAL OF RAMAN SPECTROSCOPY 43 2 331 - 337 2012年02月 [査読有り][通常論文]
     
    The relationship between Mg# [ = 100 Mg/(Mg + Fe) in mol] and the Raman shift was analyzed precisely for olivine [(Mg, Fe)2SiO4] samples with Mg# between 100 and 62.8. Two prominent peaks at 826820 cm-1 (peak 1) and 858849 cm-1 (peak 2) and three subordinate peaks at 883881 cm-1 (peak 3), 920914 cm-1 (peak 4), and 967951 cm-1 (peak 5) were observed to shift monotonously to lower wavenumbers with decreasing Mg#. The ?Mg#( = Mg#ref - Mg#) versus ??(= ?ref - ?) can be linearly regressed for each peak as ?Mg# = A ??, where ? is a peak wavenumber of olivine with Mg# ranging from 100 to 62.8, and ?ref is that of olivine with a reference value of Mg#, namely, Mg#ref. We set Mg#ref as 100 (i.e.pure forsterite Mg2SiO4) whereas A is a regression parameter (5.789, 4.294, 12.34, 6.348, and 2.09, respectively,for peaks 1, 2, 3, 4, and 5). This equation enables us to avoid small inter-laboratory differences of wavenumber calibration. The equation for peak 2 yields estimations of Mg# in geologically satisfactory precision, +/- 1 Mg# (1s) in the Mg# range of 10062.8. Copyright (C) 2011 John Wiley & Sons, Ltd.
  • 温泉熱源における時間情報の解読:熱ルミネッセンス法による鬼箕単成火山の噴火活動年代の推定
    下岡順直, 山本順司
    大分県温泉調査研究会報告 63 47 - 53 2012年 [査読無し][通常論文]
  • 山本順司, 徳永彩未, 下岡順直
    環境教育 21 64 - 73 2012年 [査読有り][通常論文]
  • 山本順司, 石橋秀巳
    地球化学 46 243 - 255 2012年 [査読有り][招待有り]
  • Chiaki Toyama, Yasuyuki Muramatsu, Junji Yamamoto, Shun'ichi Nakai, Ichiro Kaneoka
    GEOCHEMICAL JOURNAL 46 1 45 - 59 2012年 [査読有り][通常論文]
     
    Strontium-Neodymium isotopes and 28 elements for Kimberlites from China (Shandong and Liaoning) and from South Africa (Kimberley area) have been measured to estimate their chemical characteristics and magma sources. The epsilon Sr and epsilon Nd values for Chinese kimberlites were, respectively, +1.0 to +93.0 and -4.3 to +0.2. The isotopic signature for all Shandong samples revealed very similar to those of Group I kimberlites (South African samples), whereas the Liaoning samples were categorized as Transitional. Although primitive mantle-normalized trace element patterns of the mean values of Group I Shandong and South African samples all resembled those of other Group 1 kimberlites, their HREE concentrations differed slightly. Shandong samples were depleted in HREEs. Our model calculation demonstrated that the kimberlites would be produced by partial melting with degree of less than 1%. Furthermore, Shandong samples were possibly generated from source rock in which the mineral contents differed slightly (specifically the proportion of garnet) from those of other regions.
  • Junji Yamamoto, Kazuhiko Otsuka, Hiroaki Ohfuji, Hidemi Ishibashi, Naoto Hirano, Hiroyuki Kagi
    EUROPEAN JOURNAL OF MINERALOGY 23 5 805 - 815 2011年10月 [査読有り][通常論文]
     
    To assess the capacity of fluid inclusions in mantle minerals for CO2 retention, annealing experiments were conducted for two mantle xenoliths with CO2 inclusions for 8 days at 1000 degrees C under atmospheric pressure and fO(2) of 10(-11) MPa. The results show no marked decrease in the CO2 density of the CO2 inclusions for any examined minerals - olivine, orthopyroxene, clinopyroxene, or spinel. The CO2 density of CO2 inclusions in olivine in the present mantle xenoliths is lower than that in pyroxenes or spinel. Results of previous studies indicate that the low CO2 density in olivine is attributable to plastic deformation of olivine around CO2 inclusions during annealing in ascending magma. Results of this study present fundamental implications for deformation mechanisms that arise from internal pressure of fluid inclusions in silicate minerals. We calculated the stress field in minerals having a CO2 inclusion. Results show a steep stress gradient in the host around the inclusion. Such local stress in the mineral induces a local rise in the density of dislocations around the CO2 inclusions. The orthopyroxene used for this study showed a sparse distribution of dislocations around a CO2 inclusion, whereas olivine showed dense dislocations around CO2 inclusions, implying that the low CO2 density of the CO2 inclusions in olivine results from volume expansion of the CO2 inclusions through plastic deformation of the host mineral during annealing of the xenoliths in ascending magma. In this respect, constancy of CO2 density during the annealing experiments for all minerals is an interesting finding. Regarding olivines, the reduction of internal pressure of the CO2 inclusions or interaction of the dense dislocations possibly inhibits decrepitation or further volume expansion of the CO2 inclusions during annealing experiments. However, pyroxenes and spinel show higher and similar CO2 density, which reflects the resistance to plastic deformation and which indicates the effectiveness of CO2 inclusions in these minerals as a depth probe for mantle xenoliths.
  • 下岡 順直, 三好 雅也, 馬渡 秀夫, 吉川 慎, 山本 順司, 渡辺 克裕, 齋藤 武士, 杉本 健, 山田 誠, 三好 まどか, 竹村 恵二
    地学教育 64 3 53 - 69 日本地学教育学会 2011年05月25日 [査読無し][通常論文]
  • M. Yoshikawa, T. Kawamoto, T. Shibata, J. Yamamoto
    Geological Society Special Publication 337 153 - 175 2010年 [査読有り][通常論文]
     
    Ultramafic xenoliths from Mont Briançon, Ray Pic and Puy Beaunit in the French Massif Central show variable mineral compositions that indicate a residual origin after various degrees of partial melting of a fertile peridotite. Furthermore, trace element and Sr-Nd isotopic variations of clinopyroxenes indicate mixing processes between depleted mantle and enriched components such as asthenospheric melt and silicate carbonatite melt. Pyroxene geothermometer and CO2 geobarometer estimates are 860-1060°C at 0.92-1.10 GPa for Mont Briançon, 930-980 oC at 0.89-1.04 GPa for Ray Pic and 840-940 oC at 0.59-0.71 GPa for Puy Beaunit. From south to north, the xenoliths show the following trends: (1) deeper to shallower origin (2) more depleted mineral compositions, suggesting higher degrees of partial melting and (3) more enriched isotopes and trace elements, indicating a mixing process with a silicate-rich carbonatite melt characterized by high H2O and K2O, possibly during Variscan subduction. © The Geological Society of London 2010.
  • 平野直人, 阿部なつ江, 町田嗣樹, 山本順司
    地質学雑誌 116 1 - 12 2010年 [査読有り][通常論文]
  • Petrology and Sr-Nd isotopic geochemistry of ultramafic xenoliths from the French Massif Central
    Yoshikawa M, Kawamoto T, Shibata T, Yamamoto J
    Geological Society of London, Special Publications 337 153 - 175 2010年 [査読有り][通常論文]
  • Takaharu Yasuzuka, Hidemi Ishibashi, Masashi Arakawa, Junji Yamamoto, Hiroyuki Kagi
    JOURNAL OF MINERALOGICAL AND PETROLOGICAL SCIENCES 104 6 395 - 400 2009年12月 [査読有り][通常論文]
     
    We measured the Raman spectra of Fe-Mg olivine grains with Mg# [= 100 x Mg/(Mg + Fe)] values ranging from 80-100 under a pressure Of LIP to 4 GPa using a diamond anvil cell (DAC). We focused oil a relatively weak peak at around 547 cm(-1), denoted as peak 0, and two intense peaks at around 825 cm(-1) (peak 1) and 857 cm(-1) (peak 2). The peak position (K) of each peak shifted upward linearly as Mg# and pressure increased; the Mg# derivatives (partial derivative kappa/partial derivative Mg#) for peak 0, peak 1, and peak 2 under ambient pressure were 0.496, 0.184, and 0.227 cm(-1)/Mg#, respectively. The pressure derivatives (partial derivative kappa/partial derivative P) for peak 0, peak 1, and peak 2 were 1.558-2.08, 3.38-3.46, and 3.20-3.35 cm(-1)/GPa, respectively. The value of partial derivative kappa/partial derivative P for peak 0 decreased as Mg# increased, whereas those for peak I and peak 2 were almost constant against Mg#. The peak positions of peak 0, peak 1, and peak 2 were formulated as functions of Mg# and pressure based oil the results. We found that when the ranges of Mg# and pressure are limited to 85-100 and 0-1 GPa, the combination of peak 0 and peak I reproduced the original observed data with an error of +/- 0.9 for Mg# and an error of +/- 0.09 GPa for residual pressure. We applied these functions to a natural olivine inclusion in a diamond obtained From Internationalnaya pipe, Yakutia, Siberia, Russia, and obtained reasonable values of Mg# and pressure-91.6 +/- 0.6 Mg# and 0.32 +/- 0.05 GPa, respectively.
  • Junji Yamamoto, Naoto Hirano, Natsue Abe, Takeshi Hanyu
    CHEMICAL GEOLOGY 268 3-4 313 - 323 2009年11月 [査読有り][通常論文]
     
    We measured noble gas isotopic compositions of mantle xenoliths and xenocrystic olivines sampled from seamounts-so-called petit-spot volcanoes-on the 135-million-year-old northwestern Pacific Plate. The xenoliths are spinel lherzolites originating from suboceanic lithospheric mantle. The samples' He-3/He-4 ratios are 7.0-8.5 Ra, where Ra signifies atmospheric He-3/He-4. The Ar-40/Ar-36 ratios are as high as 7000. These observations suggest that the noble gas isotopic compositions of suboceanic lithospheric mantle resemble those of mid-ocean ridge basalt (MORB). A mantle source with a He/U ratio as high as an assumed value for MORB source is necessary to maintain the MORB-like He-3/He-4 over 135 million years, implying that melt extraction at mid-ocean ridges only slightly alters the He/U ratio of the oceanic upper mantle. The He-4/Ar-40* ratios of the samples described herein are much lower than the theoretical radiogenic production ratio, where an asterisk denotes correction for atmospheric contribution. The low He-4/Ar-40* is inferred to result from kinetic fractionation in the mantle. When magma migrates through a mantle source, lighter noble gases in the mantle source diffuse selectively into magma channels. The MORB generation does not cause low He-4/Ar-40*, however. If a mantle source is depleted in lighter noble gases during ancient MORB generation, then noble gas isotopic compositions of the mantle source are affected over time by accumulation of radiogenic nuclides. Thereby, the mantle source adopts a radiogenic or nucleogenic noble gas isotopic composition. Recent kinetic fractionation contributes to the low He-4/Ar-40* in the samples. Based on the diffusive fractionation model, more than 100 years are necessary to produce a residual mantle source with He-4/Ar-40*, as observed in the samples. However, petit-spot volcanoes. found as small knolls, seem to erupt within a short period. The low He-4/Ar-40* of the samples implies prior volcanism in this region. No recent volcanism has occurred near this region aside from petit-spot volcanism, indicating that petit-spot volcanoes are polygenetic with a long active period. Petit-spot volcanoes are regarded as common magmatism on the subducting oceanic plate. Consequently, the thermal structure and temperature-dependent physical properties of the oceanic plate are, at least partly, affected by remnant heat of the magmatism. (C) 2009 Elsevier B.V. All rights reserved.
  • Yuji Sano, Ayano Kameda, Naoto Takahata, Junji Yamamoto, Junichi Nakajima
    CHEMICAL GEOLOGY 266 1-2 50 - 56 2009年08月 [査読有り][通常論文]
     
    In the Kinki district of southwestern Japan, anomalously high (3)He/(4)He ratios (high Ra) are observed in the frontal arc region. This globally unique phenomenon is called the "Kinki Spot." These high-Ra values are not attributable to dehydration of the young, warm subducting Philippine Sea slab based on the magma aging effect. A recent study reported that the source melt generated below the plate may penetrate a large slab tear fissure and arrive at the shallow crust by upwelling flow. To verify this hypothesis, we collected 25 gas and water samples from hot springs in the northern district and measured the (3)He/(4)He and (4)He/(20)Ne ratios of these samples. The geographical distribution of high-Ra values revealed not a spot but a region extending parallel to the extinct spreading center in the Shikoku Basin. More precisely, the distribution is shaped like a backwards letter "L," suggesting that the subducted spreading center may have been a mid-ocean ridge with a transform fault. This hypothesis is supported by seismic tomography results and is consistent with the geometry of the subducting slab deduced from seismic isodepth contours as well as that of a young magnetic anomaly in the region. Thus, the high (3)He emanation may trace an extinct ridge-transform-ridge type spreading center in a subduction zone. (C) 2008 Elsevier B.V. All rights reserved.
  • Masako Yoshikawa, T. Kawamoto, T. Shibata, J. Yamamoto
    GEOCHIMICA ET COSMOCHIMICA ACTA 73 13 A1486 - A1486 2009年06月 [査読有り][通常論文]
  • Junji Yamamoto, Koshi Nishimura, Takeshi Sugimoto, Keiji Takemura, Naoto Takahata, Yuji Sano
    EARTH AND PLANETARY SCIENCE LETTERS 280 1-4 167 - 174 2009年04月 [査読有り][通常論文]
     
    By crushing olivine and pyroxene phenocrysts in volcanic rocks from Kyushu Island, Japan, we determined (3)He/(4)He of 3-7 Ra and (40)Ar/(36)Ar of up to 1750. These values are lower than those of MORB. (4)He/(40)Ar* (down to 0.1) is much lower than the production ratio of (4)He/(40)Ar* (1-5), where an asterisk denotes correction for the atmospheric contribution. Such values are typical of mantle-derived samples from the island arcs and active continental margins. Although the origin of the low (3)He/(4)He and (40)Ar/(36)Ar of subcontinental mantle has been widely discussed, low (4)He/(40)Ar* has been given little attention. Actually, (3)He/(4) He and (4)He/(40)Ar* of phenocrysts overlap with those of subcontinental mantle xenoliths. Although noble gas compositions of phenocrysts are affected considerably by diffusive fractionation in ascending magma, they have little effect on the noble gases in the mantle xenoliths because it takes 100 years for He/Ar fractionation of ca. 15% for a mantle xenolith with 5 cm diameter. Therefore, the low (4)He/(40)Ar* of the mantle xenoliths is inferred to result from another kinetic fractionation in the mantle. During generation and migration of magma in the mantle, lighter noble gases diffuse rapidly out into the magma. This diffusive fractionation can explain low (4)He/(40)Ar* and somewhat low (3)He/(4)He in the residual mantle. Furthermore, the combination of the diffusive fractionation and subsequent radiogenic ingrowth explain the fact that data from subcontinental mantle xenoliths have extremely low (3)He/(4)He and various (4)He/(40)Ar*. Consequently, (4)He/(40)Ar* and (3)He/(4) He in mantle-derived materials are proposed as indicators of the degree of noble gas depletion of the source mantle. (C) 2009 Elsevier B.V. All rights reserved.
  • Junji Yamamoto, Shun'ichi Nakai, Koshi Nishimura, Ichiro Kaneoka, Hiroyuki Kagi, Keiko Sato, Tasuku Okumura, Vladimir S. Prikhod'ko, Shoji Arai
    ISLAND ARC 18 1 225 - 241 2009年03月 [査読有り][通常論文]
     
    Based on both major and trace element chemistry, the occurrence of the intergranular component in mantle-derived xenoliths from far eastern Russia has been constrained. Whole-rock trace element measurements of one xenolith show apparent negative anomalies in Ce, Th, and high field strength elements on normalized trace element patterns. The trace element pattern of the whole rock differs from those of constituent minerals, indicating that the anomalies in the whole rock are attributable to the presence of an intergranular component. That assumption was confirmed using in situ analysis of trace elements in the intergranular substance and melt inclusion using laser ablation inductively coupled plasma-mass spectrometry. Both the intergranular component and the melt inclusions have identical trace element patterns, which mean that these materials are a cognate metasomatizing agent. The anomalies are regarded as mantle metasomatism related to an aqueous fluid. Hydrous minerals were observed on the wall of the melt inclusions using micro-Raman spectroscopy, indicating that the melt inclusions contained a large amount of water. Thus, this study reveals a trace element composition of a hydrous metasomatizing agent in the mantle.
  • Geochemical and Sr-Nd isotopic characteristics and P-T estimates of mantle xenoliths from the French Massif Central: evidence for melting and multiple metasomatism by silicate-rich carbonatite and asthenospheric meltsr
    Yoshikawa, M, Kawamoto, T, Shibata, T, Yamamoto, J
    Journal of Geological Society of London 2009年 [査読有り][通常論文]
  • Hidemi Ishibashi, Masashi Arakawa, Shugo Ohi, Junji Yamamoto, Akira Miyake, Hiroyuki Kagi
    JOURNAL OF RAMAN SPECTROSCOPY 39 11 1653 - 1659 2008年11月 [査読有り][通常論文]
     
    The relationship between Raman spectra and crystallographic orientation was examined for single crystals of Fo(89)Fa(11) olivine [(Mg(0.89)Fe(0.11))(2)SiO(4)]. Raman spectra were obtained for chemically homogeneous olivine grains with various orientations on a thin section of mantle-derived rock (dunite) using micro-Raman equipment and an unpolarized exciting laser. Crystallographic orientations of each olivine grain were determined using an electron backscattered diffraction (EBSD) method. Five apparent peaks at 822 (peak 1), 854 (peak 2), 880 (peak 3), 917 (peak 4), and 959 cm(-1) (peak 5) were observed in the spectral range of 700-1050 cm(-1). Intensity ratios of peak i to peak 2, I(i)/I(2), for i = 1, 4, and 5 were formulated empirically as functions of crystallographic orientations: I(i)/I(2) = (a(1i) theta(2)/pi(2) + a(2i) theta/pi + a(3i)) sin(2) phi + (b(1i) theta(2)/pi(2) + b(2i) theta/pi + b(3i)) sin phi + c(i) where a(1i), a(2i), a(3i), b(1i), b(2i), b(3i), c(i) are constants. 0 is the angle between the [100] axis and the incident direction of the laser, and 0 is the angle between the [0011 axis and the incident direction of laser projected on the {100} plane. These equations well describe the relationships between 142 and crystallographic orientation. The obtained empirical equations enable Raman spectroscopic determination of the crystallographic orientation of olivine. Copyright (C) 2008 John Wiley & Sons, Ltd.
  • Junji Yamamoto, Hiroyuki Kagi
    EUROPEAN JOURNAL OF MINERALOGY 20 4 529 - 535 2008年07月 [査読有り][通常論文]
     
    Micro-Raman spectroscopy enables precise non-destructive analyses of CO(2) density in a very small volume. By applying this method to CO(2) fluid inclusions in minerals, a contrast is apparent in the CO(2) density specific to mineral species in a mantle-derived spinel lherzolite xenolith entrained by ascending magma. The rock investigated in this study comprises four mineral species: olivine, orthopyroxene (opx), clinopyroxene (cpx), and chromian-spinel (spinel). The CO(2) densities in the fluid inclusions in these minerals are 1.006-1.035, 1.148-1.154, 1.150-1.154 and 1.189-1.194 g/cm(3), respectively. During transport of the rock by magma and subsequent cooling, the CO(2) fluid inclusions change their volume due to both elastic and plastic properties of the host mineral, which are sensitive to differential pressure between internal pressure of the CO(2) fluid inclusion, and stress in surrounding crystal lattice. We tested the possibility that the Volume Of CO(2) fluid inclusion changes by the differential pressure. Existing models dealing with the volume change of fluid inclusion in response to deformation of host mineral do not explain the density gradation, particularly that between pyroxenes and spinel. We propose that combination of precise determination of fluid density in mantle-derived minerals and observation of microstructure in the host mineral provides a deep insight into the deformation mechanism of natural minerals under high differential pressure and temperature.
  • Junji Yamamoto, Jun-ichi Ando, Hiroyuki Kagi, Toru Inoue, Akihiro Yamada, Daisuke Yamazaki, Tetsuo Irifune
    PHYSICS AND CHEMISTRY OF MINERALS 35 5 249 - 257 2008年06月 [査読有り][通常論文]
     
    Using in situ strength measurements at pressures up to 10 GPa and at room temperature, 400, 600, and 700 degrees C, we examined rheological properties of olivine, orthopyroxene, and chromian-spinel contained in a mantle-derived xenolith. Mineral strengths were estimated using widths of X-ray diffraction peaks as a function of pressure, temperature, and time. Differential stresses of all minerals increase with increasing pressure, but they decrease with increasing temperature because of elastic strain on compression and stress relaxation during heating. During compression at room temperature, all minerals deform plastically at differential stress of 4-6 GPa. During subsequent heating, thermally induced yielding is observed in olivine at 600 degrees C. Neither orthopyroxene nor spinel shows complete stress relaxation, but both retain some stress even at 700 degrees C. The strength of the minerals decreases in the order of chromian-spinel approximate to orthopyroxene > olivine for these conditions. This order of strength is consistent with the residual pressure of fluid inclusions in mantle xenoliths.
  • Masashi Arakawa, Junji Yamamoto, Hiroyuki Kagi
    CHEMISTRY LETTERS 37 3 280 - 281 2008年03月 [査読有り][通常論文]
     
    Raman spectra of CO2 fluids were measured at 288-329 K and densities of 0.81-1.16g/cm(3). The peak area ratios of hot bands at 1265 and 1408 cm(-1) and Fermi doublet peaks at 1388 and 1285 cm(-1) were correlated linearly with temperature. The peak area ratios are correlated with density. Calculation of the relationship between the peak area ratio, temperature, and density was achieved. Micro-Raman analysis enabled in situ temperature measurement of CO2 fluid with high spatial resolution.
  • 西尾 嘉朗, 山本 順司
    日本地球化学会年会要旨集 55 0 66 - 66 一般社団法人日本地球化学会 2008年 [査読有り][通常論文]
     
    マントル捕獲岩中のCPXをより微小単位でLiとSr同位体と微量元素濃度を同時に測定して,大きな同位体不均質の存在するLi同位体との相関の有無から,大きなLi同位体変動の原因を明らかにすることを試みる。
  • Masashi Arakawa, Junji Yamamoto, Hiroyuki Kagi
    APPLIED SPECTROSCOPY 61 7 701 - 705 2007年07月 [査読有り][通常論文]
     
    We investigated the applicability of micro-Raman spectroscopy for determining carbon isotopic compositions (C-13/C-12) of minute CO2 fluid inclusions in minerals. This method is nondestructive and has sufficiently high spatial resolution (1 mu m) to measure each fluid inclusion independently. Raman spectra Of CO2 fluid have (CO2)-C-12-origin peaks at about 1285 cm(-1) and 1389 cm(-1) (v(-)([12]) and v(+)([12])) and a (CO2)-C-13-origin peak at about 1370 cm(-1) (v(+)([13])). The relationship between carbon isotopic compositions and peak intensity ratios of v(+)([12]), and v(+)([13]), was calibrated. Considering several factors affecting the peak intensity ratio, the error in obtained carbon isotopic composition was 2% (20 parts per thousand). The reproducibility of the intensity ratio under the same experimental environment was 0.5% (5 parts per thousand). Within these error values, we can distinguish biogenic CO2 from abiogenic CO2.
  • 山本 順司
    地球化学 41 2 63 - 75 日本地球化学会 2007年05月25日 [査読無し][通常論文]
     
    An active convergent plate boundary comprises dynamic material circulation system where materials risen up from descending oceanic plate partly go back to the Earth's surface. An evaluation of the material flux in this system is important to assess future view of the planet Earth. In the mantle wedge, fluids circulate in various forms; i.e., aqueous fluids released from the descending oceanic lithosphere trigger partial melting of the mantle wedge, and the melt ascends through the mantle wedge leading arc volcanism. Investigations of mantle-derived xenoliths sampled from the active margin o...
  • Junji Yamamoto, Hiroyuki Kagi, Yoko Kawakami, Naoto Hirano, Masaki Nakamura
    EARTH AND PLANETARY SCIENCE LETTERS 253 3-4 369 - 377 2007年01月 [査読有り][通常論文]
     
    The density, and therefore the pressure, Of CO2 fluid inclusions in minerals can be estimated from the Fermi diad splitting of Raman spectra Of CO2. An accurate determination of the pressure Of CO2 fluid inclusions enables the estimation of the depth origin of rocks from the deep Earth. A micro-Raman densimeter was applied to ultramafic-mafic xenoliths sampled along the Ohku coast of Oki-Dogo Island in the Sea of Japan (East Sea). The density Of CO2 fluid inclusions in the mafic granulite was 1.02-1.05 g/cm(3), while those of Iherzolites were 0.98-1.02 g/cm. In contrast, the density Of CO2 fluid inclusions measured in olivine gabbro, clinopyroxenite, and harzburgite were lower ranging from 0.86- to 0.99 g/cm(3). Taking into account the temperature condition estimated using a pyroxene thermometer, the mafic granulite originated from a depth of 27-30 km and the lherzolites from 2529 km. The overlapping depth of 27-29 km can be interpreted as the depth including the Moho discontinuity under Oki-Dogo Island 3.3 Ma. This estimation is consistent with geophysical observations. (c) 2006 Elsevier B.X. All rights reserved.
  • Naoto Hirano, Eiichi Takahashi, Junji Yamamoto, Natsue Abe, Stephanie P. Ingle, Ichiro Kaneoka, Takafumi Hirata, Jun-Ichi Kimura, Teruaki Ishii, Yujiro Ogawa, Shiki Machida, Kiyoshi Suyehiro
    SCIENCE 313 5792 1426 - 1428 2006年09月 [査読有り][通常論文]
     
    Volcanism on Earth is known to occur in three tectonic settings: divergent plate boundaries ( such as mid-ocean ridges), convergent plate boundaries ( such as island arcs), and hot spots. We report volcanism on the 135 million-year-old Pacific Plate not belonging to any of these categories. Small alkalic volcanoes form from small percent melts and originate in the asthenosphere, as implied by their trace element geochemistry and noble gas isotopic compositions. We propose that these small volcanoes erupt along lithospheric fractures in response to plate flexure during subduction. Minor extents of asthenospheric melting and the volcanoes' tectonic alignment and age progression in the direction opposite to that of plate motion provide evidence for the presence of a small percent melt in the asthenosphere.
  • Junji Yamamoto, Hiroyuki Kagi
    CHEMISTRY LETTERS 35 6 610 - 611 2006年06月 [査読有り][通常論文]
     
    Micro-Raman spectroscopy enables nondestructive analyses Of CO2 fluid density in a very small volume. For application of the method to CO2 fluid inclusions in minerals originated from the deep Earth having widely various densities, we extended the relational expression between the density and Raman spectra Of CO2 up to the density corresponding to the boundary between liquid and solid.
  • Evidence for partial melt in Earth's asthenosphere: volcanism in response to plate flexure during subduction of the Cretaceous Pacific Plate
    Hirano N, Takahashi E, Yamamoto J, Machida S, Abe N, Ingle S, Kaneoka I, Hirata T, Kimura J, Ishii T, Ogawa Y, Suyehiro K
    Science 313 1426 - 1428 2006年 [査読有り][通常論文]
  • 山本 順司, 鍵 裕之
    現代化学 0 409 44 - 49 東京化学同人 2005年04月 [査読無し][通常論文]
  • J Yamamoto, PG Burnard
    GEOCHIMICA ET COSMOCHIMICA ACTA 69 3 727 - 734 2005年02月 [査読有り][通常論文]
     
    Noble gas abundances in basaltic glasses from ocean islands (OIBs) are generally lower than those of mid-oceanic ridge basalts (MORBs), contrary to most geodynamic models which usually require that the source of OIBs is less degassed (resulting in higher primordial noble gas abundances) and more trace element enriched (resulting in higher radiogenic noble gas abundances) than the MORB source. Therefore, noble gas abundances in OIBs are often thought to have been reduced by extensive gas loss from the magma before eruption. The extent of magmatic degassing can be tested as it will cause characteristic changes in the composition of the volatiles; notably the He-4/Ar-40* ratio (where Ar-40* is Ar-40 corrected for atmospheric contamination) will increase in residual volatiles due to the higher solubility of He relative to Ar. The degree of He-As fractionation for a given fraction of gas loss depends on the ratio of the solubilities, S-He/S-Ar, which is sensitive to (among other things) the CO2 and H2O content of the basalt at the time of degassing. From a global database of OIB and MORB glasses, we show that He-4/Ar-40* ratios of MORB glasses are broadly consistent with degassing of a magma with an initial Ar-40 of approximate to1.5 x 10(-5) ccSTP/g, i.e., similar to that of the "popping rock." However, OIB glasses generally have lower Ar-40* concentration for a given He-4/Ar-40*. While this would appear to require lower Ar-40* abundances in the undegassed OIB magmas, the higher volatile contents of OIBs will reduce S-He/S-Ar (relative to MORBs) during degassing. By modeling S-He/S-Ar in OIBs, it is possible to show that extensive degassing of OIBs can occur without dramatically increasing the He-4/Ar-40* ratio. We show that undegassed Ar-40 concentrations of OEB magmas were probahl. similar to those of MORBs. Copyright (C) 2005 Elsevier Ltd.
  • 角野 浩史, 山本 順司, 熊谷 英憲
    岩石鉱物科学 34 4 173 - 185 日本鉱物科学会 2005年 [査読無し][通常論文]
     
    Because of chemical inertness of noble gases, their isotopic compositions trapped in mantle-derived xenoliths provide valuable information about mantle processes. Here we present a review of noble gas studies of mantle xenoliths from several tectonic settings with specific attention to mantle metasomatism. Numerous metasomatic traces have been identified as noble gas isotopic anomalies found in fluid or melt inclusions or in minerals of metasomatic origin in the suboceanic and subcontinental lithosphere. The noble gas isotopic ratio of MORB source, which is generally regarded as representin...
  • 山本順司, 石橋秀巳, 川上曜子, 鍵裕之
    岩石鉱物科学 34 4 159 - 172 2005年 [査読有り][通常論文]
     
    Fluid inclusions in mantle-derived minerals can serve as a messenger from the deep Earth. If CO2 is a dominant phase of the fluid, the relationship between intensity ratio and frequency separation of the Fermi diad bands in the Raman spectra of CO2 can be used for determination of density of the inclusions. The intensity ratio and the frequency separation between the peaks thereby increase with density of CO2. Kawakami et al. (2003) have established the relationship between density of CO2 and the frequency separation of the Fermi diad bands using the Raman data on CO2 fluid with densities from 0.1 to 1.21 g/cm3, including super critical fluids at 58–59°C. Thus, micro-Raman spectroscopic analysis allows us to reveal multiple densities of the small fluid inclusions by one-by-one density analysis. Generally, inclusions show CO2 densities (pressure) specific to the individual host minerals in the order of spinel > orthopyroxene ~ clinopyroxene ≫ olivine. The density of CO2 reflects how strong host minerals are to withstand the pressure differential between the inclusion’s internal pressure and the external environmental pressure during transport of xenoliths to near the Earth’s surface. Olivine underwent considerable plastic deformation resulting in the density reduction of CO2 fluid inclusions. On the other hand, the slightly higher density of CO2 in spinel can be explained by elastic deformation of the minerals during ascent and cooling of the xenoliths. Conversely, the density of CO2 inclusions in pyroxene will work as a useful geobarometer requisite for discussions on the origin of mantle-derived minerals. © 2005, Japan Association of Mineralogical Sciences. All rights reserved.
  • K Notsu, K Sugiyama, M Hosoe, A Uemura, Y Shimoike, F Tsunomori, H Sumino, J Yamamoto, T Mori, PA Hernandez
    JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH 139 3-4 147 - 161 2005年01月 [査読有り][通常論文]
     
    lwojima volcano, located on the southernmost part of the Izu-Ogasawara arc, is characterized by the extrusion of trachyte or trachy andesite lavas and pyroclastic rocks of Holocene and surface thermal manifestations. Small phreatic explosions have been recorded frequently during the last 100 years with the most recent in 1999 and 2001. In order to elucidate the behavior of volcanic volatiles and to assess the potential activity of this volcano, diffuse CO2 efflux, CO2 content and delta(13) C-CO2 in soil gas, and soil temperature at 30 cm depth were measured at 272 sites in March 2000, 112 sites in December 2000 and 40 sites in December 2001. We found that high CO2 efflux values, of more than 100 g M-2 day(-1), occurred at several locations on Motoyama volcano corresponding with high soil temperatures (more than 60 degreesC at 30 cm depth) region and with areas where CO2 with magmatic delta(13)C was observed. Here, the magmatic delta(13)C determined for fumarolic CO2 data ranged from -2%o to +3%o, which is clearly higher than magmatic gas values (-8%o to -2%o) typically found in island are settings around the world. However, this can be explained in terms of carbon-isotope fractionation between calcite and CO2 under subsurface temperature and pressure conditions at lwojima. A total efflux Of CO2 for lwojima. volcano is estimated to be 760 t day(-1), with a magmatic contribution of about 450 t day. This value is rather high compared with other volcanoes in island arc settings. Since Iwojima has no visible plume, almost all volcanic CO2 is released as diffuse efflux through the volcanic edifice. (C) 2004 Elsevier B.V All rights reserved.
  • N Hirano, J Yamamoto, H Kagi, T Ishii
    CONTRIBUTIONS TO MINERALOGY AND PETROLOGY 148 1 47 - 54 2004年09月 [査読有り][通常論文]
     
    Young (6 Ma) alkali-basalts were collected from the toe of the oceanward slope of the northern Japan Trench. Two types of olivine are present in these lavas, xenocrysts with reaction rims and magmatic. The forsterite (Fo) (no. 91-92) values and NiO contents (0.3-0.5 wt%) of the xenocrysts are similar in composition to those of the depleted mantle peridotite. The groundmass olivines have relatively lower Fo values (no. 81-88) and NiO contents (0.1-0.5 wt%). Reaction rims and the vicinity of the silicate inclusion in xenocrysts show the intermediate compositions between the xenocryst and magmatic olivines. Chromian spinel inclusions in the xenocrysts also show the depleted composition in the range of abyssal peridotite. CO2 fluid inclusions in the xenocryst records pressures before entrainment into the host magma up to 0.4 GPa, which corresponds to a depth of up to 14 km of lithospheric mantle. These data indicate that the xenocrysts originate from MORB-depleted mantle.
  • J Yamamoto, Kaneoka, I, S Nakai, H Kagi, VS Prikhod'ko, S Arai
    CHEMICAL GEOLOGY 207 3-4 237 - 259 2004年07月 [査読有り][通常論文]
     
    By applying both vacuum crushing and stepwise heating methods for the extraction of the noble gases, we have discovered He-3/He-4 ratios much lower than the atmospheric ratio (similar to 0.3 R-A; R-A is the atmospheric He-3/He-4 ratio of 1.4 x 10(-6)) and relatively low Ar-40/Ar-36 ratios (<1 000) in olivine separates from some subcontinental mantle-derived xenoliths from Far Eastern Russia. The low He-3/He-4 ratios cannot be explained by the addition of radiogenic He-4 generated in-situ after the eruption of magma entraining the xenoliths. Furthermore, petrographic evidence suggests that incorporation of crustal fluids is not likely. Hence, it must reflect a feature of the Far Eastern Russian upper mantle. Spectroscopic and petrographic observations confirm that there are at least two compositionally distinct fluids in these xenoliths; liquid CO2 inclusions and melt inclusions with shrinkage bubbles. Based on the crushing experiments, it is inferred that the inclusions of liquid CO2 have a He-3/He-4 ratio similar to that of MORB, and the component with the low He-3/He-4 ratio is derived from the shrinkage bubbles in the melt inclusions. For the present samples, the Ar-40/Ar-36 ratios obtained by crushing were less than 1060, suggesting incorporation of atmospheric components in the source materials. Since low Ar-40/Ar-36 ratios were observed irrespective of the occurrence of the liquid CO, inclusions, the atmospheric component exists in the melt inclusions. Ne and Xe isotopes are also consistent with incorporation of atmospheric components. Since the Far Eastern Russia area was located at a subduction zone in the Jurassic-early Cretaceous Period, it is most likely that the melt inclusions displaying atmospheric noble gas characteristics together with low He-3/He-4 ratios have been derived from the Jurassic-Cretaceous subducted slab. Although we cannot exclude the possibility that low He-3/He-4 ratios are due to the existence of minor U-bearing minerals in the lithospheric continental mantle caused by metasomatism, we have no petrographical evidence for such minerals in this area. On the other hand, He-3/He-4 ratios observed in the liquid CO2 inclusions, which are similar to the MORB-like value, might reflect the general character of the upper mantle. The Far Eastern Russian mantle may therefore be a MORB-like source that has been partly infiltrated by subduction-related fluids. (C) 2004 Elsevier B.V. All rights reserved.
  • Y Nishio, N Shun'ichi, J Yamamoto, H Sumino, T Matsumoto, VS Prikhod'ko, S Arai
    EARTH AND PLANETARY SCIENCE LETTERS 217 3-4 245 - 261 2004年01月 [査読有り][通常論文]
     
    Isotopic signatures of mantle-derived xenoliths have provided much information on the evolution of their mantle source regions. A recently developed multiple-collector inductively coupled plasma mass spectrometry method allows precise and accurate lithium isotopic determinations of Li-poor samples such as peridotites. We present Li-Sr-Nd isotopic systematics of clinopyroxenes (CPXs) in mantle-derived ultramafic xenoliths. The results show that Ichino-megata (Northeastern Japan) and Bullenmerri (Southeastern Australia) samples have positive delta(7)Li values (delta(7)Li similar to +4 to +7 parts per thousand, delta(7)Li = [[Li-7/Li-6]sample/[Li-7/Li-6](L-SVEC) (standard) - 1] x 1000) common to values previously reported for terrestrial volcanic rocks. By contrast, unusually low delta(7)Li values (delta(7)Li similar to - 17 parts per thousand) are observed in many samples from the Far East region of Russia (Sveyagin, Ennokentiev, and Fevralsky) and southwestern Japan (Kurose and Takashima). The delta(7)Li values of Sikhote-Alin (Sveyagin and Ennokentiev) samples vary widely from -17.1 parts per thousand to -3.1 parts per thousand, while the delta(7)Li values are positively correlated with Nd-143/Nd-144, and negatively correlated with Sr-87/Sr-86. On the other hand, the delta(7)Li values of the Bullenmerri samples are essentially constant (delta(7)Li = +5.0 to + 6.0 parts per thousand), while the Sr-87/Sr-86 (0.7027similar to0.7098) and Nd-143/Nd-144 ratios (0.51224similar to0.51297) vary widely. These features can be explained by the results of a binary mixing between a depleted component (low-Sr-87/Sr-86, and high-Nd-143/Nd-144) and an enriched component (high-Sr-87/Sr-86, and low-Nd-143/Nd-144). The enriched component (metasomatic agent) in the mantle beneath the Sikhotc-Alin area has extraordinarily low delta(7)Li value ( < - 17 parts per thousand), whereas the metasomatic agent in the mantle beneath the Bullenmerri area has positive delta(7)Li value (+6 parts per thousand). Based on the Sr-Nd isotopic systematics and coexistent hydrous mineral, metasomatic agents of the Sikhote-Alin and Bullenmerri samples are classified into anhydrous EM1-type and hydrous EM2-type, respectively. From these features, we infer that anhydrous EM1-like metasomatic agent may have an extremely low delta(7)Li value, whereas hydrous EM2-like metasomatic agent may have a positive delta(7)Li value. It has been predicted that the delta(7)Li value of subducted highly altered mid-ocean ridge basalt (MORB) would be extremely low compared to that of fresh MORB due to the preferential loss of heavier Li (delta(7) Li > altered MORB) from the subducted slab during dehydration at low temperature. Consequently, it is deduced that Li of metasomatic agent with an extremely low delta(7)Li value is derived from subducted highly altered basalt. The enrichment of isotopically light Li (low delta(7)Li) may be a general property of EM1 mantle reservoir. The Li isotopic data suggest further that the EM1 and HIMU sources originate from different parts of a recycling oceanic crust. This is essentially the same as the models proposed previously based on the radiogenic isotopic data, but with the Li isotopic data requiring uppermost, highly altered basaltic crust as pelagic sediment in the EM1 source, but not so in the HIMU end-member. Because of the apparent sensitivity of Li isotopic composition to the alteration profile of subducted MORB, it may provide complementary information to Sr, Nd, and Pb isotopic compositions regarding the mantle source. (C) 2003 Elsevier B.V. All rights reserved.
  • T Mizukami, Wallis, SR, J Yamamoto
    NATURE 427 6973 432 - 436 2004年01月 [査読有り][通常論文]
     
    Tectonic plate motion is thought to cause solid-state plastic flow within the underlying upper mantle and accordingly lead to the development of a lattice preferred orientation of the constituent olivine crystals(1-3). The mechanical anisotropy that results from such preferred orientation typically produces a direction of maximum seismic wave velocity parallel to the plate motion direction(4,5). This has been explained by the existence of an olivine preferred orientation with an 'a-axis' maximum parallel to the induced mantle flow direction(3,5,6-8). In subduction zones, however, the olivine a axes have been inferred to be arranged roughly perpendicular to plate motion(9-13), which has usually been ascribed to localized complex mantle flow patterns(10-13). Recent experimental work(14) suggests an alternative explanation: under conditions of high water activity, a 'B-type' olivine preferred orientation may form, with the a-axis maximum perpendicular to the flow direction. Natural examples of such B-type preferred orientation are, however, almost entirely unknown. Here we document widespread B-type olivine preferred orientation patterns from a subduction-type metamorphic belt in southwest Japan and show that these patterns developed in the presence of water. Our discovery implies that mantle flow above subduction zones may be much simpler than has generally been thought.
  • GP Glasby, T Yamanaka, J Yamamoto, H Sato, K Notsu
    RESOURCE GEOLOGY 54 4 413 - 424 2004年 [査読有り][通常論文]
     
    Northern Honshu is the most important area for mineral and oil resources in Japan. Many kuroko deposits and oil aryl gas fields are distributed in two belts along the northeast Japan arc. the kuroko metal-belt on the Pacific side and the oil-belt on the Sea of Japan side. The kuroko deposits are located mainly in the Green Tuff strata which formed as a result of submarine volcanisin during the late Miocene and Pliocene. Most of the source rocks of the oil and gas deposits formed at the same time as the kuroko deposits and some of them are located in reservoirs of hydrothermally-altered volcanic rocks in the Green Tuff region. There is general agreement that the kuroko deposits formed as a result of submarine hydrothermal and magmatic activity whereas almost all petroleum geologists and geochemists consider that hydrocarbon deposits were generated independently of such activity. Since the discovery of hydrothermally-generated petroleum in the Guaymas Basin. Gulf of California, however. it is clear that petroleum can be formed almost instantaneously in terrestrial and submarine hydrothermal areas. The paleo-northeastern Sea of Japan is therefore considered to be a potential area for hydrothermal petroleum generation because thick organic-rich sediments overlie an active submarine volcanic area. Several lines of geological and geochemical evidence suggest the possibility of hydrothermally-enhanced maturation of organic matter and the contribution of magmatic activity to the formation of these deposits. Although most of the oil and gas in northern Honshu has been generated conventionally as a consequence of the high geothermal gradients there. it appears that some of the oil and gas fields may have formed as a result of extensive hydrothermal and magmatic activity during the late Miocene to Pliocene. Because of the much steeper angle of the faults in the vicinity of the Hokuroku basin than in the Akita basin, the magmatic contribution to the kuroko mineralization would have been far greater than to the oil and gas deposits of the Niigata and Akita basins. We therefore propose a strong relationship between metal and oil and gas generation in northern Honshu based on the structure and tectonics of the northern Honshu arc-back-arc system.
  • Y Kawakami, J Yamamoto, H Kagi
    APPLIED SPECTROSCOPY 57 11 1333 - 1339 2003年11月 [査読有り][通常論文]
     
    We investigated the applicability of Raman microprobe spectroscopy for determining the density of CO2 in fluid inclusions in minerals of mantle-derived xenolith samples. A separation (Delta) between two Raman bands of CO2 due to Fermi resonance can be a reliable densimeter for CO2 fluid. The relationship between the density of CO2 (g/cm(3)) and Delta(cm(-1)) can be expressed as: d = -0.03238697Delta(3) + 10.08428Delta(2) - 1046.189Delta + 36163.67. This equation was obtained from the Raman data on CO2 fluid with densities from 0.1 to 1.21 g/cm(3), including super critical fluids at 58-59 degreesC. The Delta value was constant with increasing temperature from room temperature to 200 degreesC. This indicates that the Raman densimeter is not affected by a possible rise in temperature, an artifact induced by the high flux of the incident laser. The minimum size of measurable inclusions is 1 mum, and the precision in the determination of Delta is 0.1 cm(-1), corresponding to 0.02 g/cm(3) for inclusions of 1 mum in size. The precision can be better for larger inclusions. The micro-Raman densimeter can determine the density of CO2 fluid inclusions over a wide range. In particular, densities of gas and mixtures of gas and liquid phases, which cannot be measured by microthermometry, can be determined.
  • Noble gases in mantle-derived xenocrysts in an alkali basalt from Japan Trench oceanward slope
    Yamamoto J, Hirano N, Hanyu T, Kagi H, Kaneoka I
    Plume and problems of deep sources of alkaline magmatism (edited by N.V. Vladykin) 39 - 50 2003年 [査読有り][通常論文]
  • J Yamamoto, H Kagi, Kaneoka, I, Y Lai, VS Prikhod'ko, S Arai
    EARTH AND PLANETARY SCIENCE LETTERS 198 3-4 511 - 519 2002年05月 [査読有り][通常論文]
     
    Micro-Raman spectroscopic analysis allows us to estimate the internal pressure of small fluid inclusions. We applied this method to CO2-dominated fluid inclusions in mantle-derived xenoliths. The pressures estimated from the equilibration temperature and density of the fluid range from 0.96 to 1.04 GPa corresponding to depths of up to 30 km, which confirms that these rocks and fluids are of uppermost mantle origin. Furthermore, the inclusions show pressures specific to the individual host minerals (spinel greater than or equal to orthopyroxene approximate to clinopyroxene much greater than olivine). In particular. the densities of CO2 in pyroxenes are 10% higher than in olivine. Such an enormous difference cannot be explained by elastic deformation of the minerals during ascent of the xenoliths, although the process may explain the slightly higher density of CO2 in spinel. During the ascent. the strain rate of orthopyroxene calculated using the 'constitutive equation' is several orders of magnitude lower than that of olivine. The difference in densities of CO2 among the host mineral species is therefore attributable to the rheological properties of the minerals. Present internal pressures of fluid inclusions can be a sensitive strength marker of mantle minerals. Conversely, the density of CO2 inclusions in pyroxene (and spinel) may be a useful geobarometer. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Ichiro Kaneoka, Takeshi Hanyu, Junji Yamamoto, Yayoi N. Miura
    Geophysical Monograph Series 128 373 - 389 2002年 [査読有り][通常論文]
     
    Noble gas isotopes were analyzed for glass and olivine phenocrysts of Hawaiian submarine volcanic rocks collected at depths of 2300-5700 m using submersibles "Shinkai 6500" and "Kaiko". Both crushing and heating methods were used for extracting noble gases. Loihi samples had 3He/4He of 21-32 Ra, 20Ne/22Ne of 10-12 and 40Ar/36Ar of 300-2700, while Kilauea samples had 3He/4He of 13-15 Ra, 20Ne/22Ne of 10.6-11.1, and 40Ar/36Ar of 800-3600. For all samples analyzed, the 129Xe/130Xe cannot be distinguished from the atmospheric value within analytical uncertainty. Olivine separates from two Koolau basaltic rocks collected at depths of about 3600 m and 3100 m have 3He/4He of about 19 Ra, whereas other Koolau samples collected at depths of less than 3000 m have 3He/4He of 14-15 Ra like subaerial Koolau rocks. The samples collected from Loihi, in the pre-shield stage, contain both higher and more variable values of 3He/He compared to the shield-building stage of other volcanoes in the Hawaiian chain. The post-shield and rejuvenated stages show the lowest 3He/4He, overlapping values obtained for MORB. We interpret this age trend to reflect an increasing degree of interaction between the rising plume magma and the uppermost part of asthenosphere. The extreme He isotope variation shown at Loihi may represent additional interaction of the plume magma with the old, altered oceanic crust. The variation of heavier noble gases may indicate incorporation of seawater into the magma before eruption.
  • J Matsuda, T Matsumoto, H Sumino, K Nagao, J Yamamoto, Y Miura, Kaneoka, I, N Takahata, Y Sano
    GEOCHEMICAL JOURNAL 36 2 191 - 195 2002年 [査読有り][通常論文]
     
    We have prepared an artificial mixture of 3 He and 4 fie to be used as an internal standard for precise He-3/He-4 measurements of terrestrial mantle-derived samples. The mixture is named HESJ (He Standard of Japan). The He-3/He-4 ratio of HESJ was determined by obtaining the weighted average of repeated analyses from five machines in four laboratories in Japan. The recommended value of the He-3/He-4 ratio of HESJ relative to the air value (R/Ra) is 20.63 +/- 0.10. HESJ is available to all researchers.
  • J Yamamoto, M Watanabe, Y Nozaki, Y Sano
    JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH 107 1-3 19 - 26 2001年06月 [査読有り][通常論文]
     
    The concentrations of helium and carbon in fluorite associated with Cretaceous to Neogene (90-13 Ma) granitic magmatism in the Japanese are have been measured. Concentrations of Li, U, Th and Gd were measured to correct for secondary generated He-3. The CO2/He-3 of fluorites are almost uniform (1.5 x 10(10)-4 x 10(10)) and in fair agreement with the range of present island are volcanic gases. The calculated mantle C contribution in the Mesozoic subduction zone appear to have been identical to the present one (7-19%) indicating that the C flux from the mantle in supra-subduction zone environments has remained fairly constant during the past 70 million years. (C) 2001 Elsevier Science B.V. All rights reserved.

書籍

その他活動・業績

特許

  • 特許6667757:地球の比重層構造モデル  
    山本順司, 徳永彩未  徳永彩未, 山本順司
  • 意匠登録第1601813号:地球層構造模型  
    山本順司, 徳永彩未
  • 特許6806959:ダイオキシン類の毒性予防および阻止剤  
    徳永彩未  徳永彩未

受賞

  • 2013年08月 日本地学教育学会 教育実践優秀賞
     海浜砂の多種選別分析法による後背地地質推定プログラム 
    受賞者: 下岡順直;三好雅也;山本順司;三好まどか;竹村恵二
  • 2012年08月 日本地学教育学会 優秀論文賞
     七輪でマグマをつくる 
    受賞者: 下岡順直;三好雅也;馬渡秀夫;吉川慎;山本順司;渡辺克裕;齋藤武士;杉本健;山田誠;三好まどか;竹村恵二
  • 2006年09月 日本地球化学会 日本地球化学会 奨励賞
     マントル起源鉱物中の流体包有物から探る沈み込み帯の物質循環系 
    受賞者: 山本順司

共同研究・競争的資金等の研究課題

  • 結晶内弾性変形のナノスケール可視化法の開発
    日本学術振興会:科学研究費助成事業 挑戦的研究(萌芽)
    研究期間 : 2020年07月 -2023年03月 
    代表者 : 山本 順司, 鍵 裕之, 石橋 秀巳
  • マントルウェッジにおける沈み込み由来炭素の探索
    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 : 山本 順司, 馬上 謙一, 吉村 俊平
  • マグマ生成から噴火へーメルト包有物からの新展開
    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 : 羽生 毅, 清水 健二, 金子 克哉, 木元 克典, 山本 順司, 石塚 治
  • ルビジウムの分子地球化学:分子レベルの物理化学的普遍性が生む多様な地球惑星科学
    日本学術振興会:科学研究費助成事業 挑戦的研究(萌芽)
    研究期間 : 2019年06月 -2021年03月 
    代表者 : 高橋 嘉夫, 山本 順司, 板井 啓明
  • 揮発性元素のマントル大循環
    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 : 2017年04月 -2020年03月 
    代表者 : 羽生 毅, 清水 健二, 山本 順司
     
    火山岩及びそのマグマ源であるマントルの持つ揮発性成分組成を決定することを目的として、火山岩の斑晶鉱物が内包するメルト包有物の化学分析を行った。 本年度は、マントル由来の火山岩として南太平洋のライババエ島に産する海洋島玄武岩を対象とした。玄武岩に含まれるオリビン鉱物斑晶に対して、前年度までに立ち上げたメルト包有物加熱装置を用いて、組成的に均質なガラス質のメルト包有物を作成した。このメルト包有物に含まれる気泡中の二酸化炭素密度測定を、顕微ラマン分光分析技術を用いて測定した。次にメルト包有物のガラス質部分と気泡の体積を、マイクロX線CTスキャンを用いて分析した。さらに、ガラス質部分の揮発性成分、主成分、微量成分、鉛同位体比を、二次イオン質量分析計、電子線プローブ、レーザーアブレーション誘導プラズマ質量分析計を用いて測定した。 その結果、塩素に関して重要な発見をした。ライババエ島の海洋島玄武岩には、鉛同位体比で区別される2種類のマグマが存在し、その違いはマグマ源に含まれるマントルを循環する太古代の海洋地殻の寄与量を反映することがこれまでの研究から分かっていたが、その寄与量と塩素量の間に相関があることを見出した。このことは、過去の海洋地殻物質がマントルに沈み込む際に海水の塩素を運搬し、地球表層とマントルの間で大規模な塩素循環を起こしていたことを意味する。海水からマントルへ塩素を運搬する働きは、地球表層の塩素量を調節し、生命の進化にも多大な影響を及ぼしていたことを考察し、学術論文として公表した。 また、上記の塩素以外の元素・成分に関する論文と、ラマン分光、マイクロX線CT、二次イオン質量分析計を組み合わせてメルト包有物中の二酸化炭素総量を測定する技術に関する論文を準備した。また、同様の研究を他のテクトニックセッティングに産する玄武岩の研究に応用するために、試料の準備を行った。
  • 日本学術振興会:科学研究費助成事業 挑戦的研究(萌芽)
    研究期間 : 2017年06月 -2019年03月 
    代表者 : 山本 順司, 吉村 俊平
     
    本研究では,炭素同位体比から読み取れる事象の空間分解能を飛躍的に高めることをめざし,ピコモルレベルの極微量炭素に適用できる革新的な炭素同位体比分析法の開拓をめざした.炭素は物質の起源を探る上で重要な指標となっている.この分析に必要とする炭素量を少なくできれば読み取る領域の空間分解能を向上させることができる. 本研究ではまず,炭酸塩鉱物のリン酸分解によって二酸化炭素を生成させるガラスラインの作製を行った.次いで,冷却固化させた二酸化炭素(ドライアイス)のラマン分光分析から,炭素同位体比を測定することに成功した.これにより,極微量炭素の分光炭素同位体分析法を確立するに至った
  • 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 : 2016年04月 -2019年03月 
    代表者 : 山本 順司, 鍵 裕之, 石橋 秀巳
     
    本研究では,革新的な分光学的手法を導入することにより,マントルウェッジに存在する炭素の起源の特定をめざした.マントルウェッジは沈み込んだ海洋プレートからもたらされる流体の通り道として常に議論の舞台となっている.物理的観測によって流体の存在が間接的に推察されつつあるが,その流体の実体や分布,起源などを論じるにはマントルウェッジを直接かつ精細に調べることが有用であろう.そこで本研究では,2mの焦点距離を持つ分光器を導入し,マントルウェッジ由来の捕獲岩に見られる二酸化炭素を含む流体包有物にも適用できる,高い空間分解能と波数分解能を持つ顕微分光炭素同位体分析法を確立した.
  • 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 : 2014年04月 -2017年03月 
    代表者 : 山本 順司, 石橋 秀巳
     
    本研究では,流体包有物をゼロ次元の応力源として利用する鉱物の弾性特性測定法の開発に挑んだ. 地球内部を探る手法の中で地震波トモグラフィーは傑出した存在感を示しつつあり,その解釈に必要な鉱物の弾性特性の重要性も増しつつある.しかし,既存の弾性特性には問題がある.鉱物の弾性特性は化学組成に強く依存するにも関わらず,天然鉱物から得た値は少なく,しかも測定値の有効数字は2桁程度である.地震波速度構造の精密な解釈には鉱物の弾性特性の精度・確度を共に高める必要があろう.そこで本研究では,微小な天然鉱物でも精度良く鉱物の弾性特性を測定できる新たな手法の開発に挑んだ.
  • 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 : 2013年04月 -2016年03月 
    代表者 : 山本 順司, 鍵 裕之, 石橋 秀巳, 鈴木 敏弘
     
    本課題では,捕獲岩が由来した深度を100mオーダーの解像度で決定できる地質圧力計の開発を目指した. リソスフェアは地球深部からもたらされる温度や流体の通り道として常に議論の舞台となっている.物理的観測によってその物質構造や流体の存在が間接的に推察されつつあるが,その検証や流体の実体,分布などを論じるには岩石構造を直接かつ精細に調べることが有用であろう.そこで我々は,捕獲岩に見られる流体包有物の残留圧力を利用し,捕獲岩の由来深度を精密に読み取ることにより,100mオーダーの解像度でリソスフェアの岩石構造を描き出すことに成功した.
  • 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 : 2012年04月 -2016年03月 
    代表者 : 川本 竜彦, 三部 賢治, 山本 順司, 石丸 聡子
     
    1) 東北日本弧一ノ目潟火山のレルゾライト捕獲岩には、炭酸塩鉱物と塩水からなる流体包有物が存在し、塩水は3.7±0.8%の塩濃度を持つ。2) マグマと水流体の間の微量成分元素分配のその場観察実験を行った。火山弧の下で海洋プレートからマントルウェッジに加わる超臨界流体は塩素を含み、上昇過程で塩水とメルトに分離することで島弧玄武岩の化学的特徴を説明する仮説を提案した。3) マントルウェッジに塩水をどう運ぶかに制約条件を与えるために、スラブを構成する高圧変成岩中の流体包有物を研究対象とした。特に、蛇紋岩メランジュに含まれるヒスイ輝石岩に注目し、複数の変成帯の岩石中に塩水を含む流体包有物を発見した。
  • 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 : 2008年04月 -2014年03月 
    代表者 : 沖野 郷子, 島 伸和, 篠原 雅尚, 佐藤 暢, 海野 進, 野木 義史, 浅田 美穂, 阿部 なつ江, 佐藤 利典, 森下 知晃, 中村 謙太郎, 富士原 敏也, 望月 伸竜, 山本 順司, 辻 健, 吉河 秀郎
     
    海底熱水系を「海底下の大河」と捉え、熱水の化学組成や噴出孔の様式は、周囲の地質・地球物理学的環境に規制されていることを示すための観測研究を実施した。南部マリアナ熱水域(イオウの大河)では、表層から上部マントルまでの構造を明らかにし、熱水系の発達過程が主に熱源となるマグマ活動の盛衰によって規制されることを明らかにした。インド洋海嶺三重点のKairei熱水フィールド(水素の大河)では、構造探査と岩石分析から、熱水の組成や循環様式が、テクトニックな海底拡大に起因する地下浅部のガブロ・カンラン岩類と海嶺軸部の火成活動との双方に規制されることがわかった。
  • 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 : 2011年 -2013年 
    代表者 : 山本 順司, 鍵 裕之, 大藤 弘明, 石橋 秀巳
     
    転位はホスト鉱物の塑性変形特性を表す組織である.本研究では流体包有物周辺に見られる転位組織を様々な手法で観察した.マントルの主要構成鉱物であるオリビンと斜方輝石では,流体包有物周辺の転位組織の発達に明瞭な違いが確認できた.これは両鉱物の降伏応力の違いを反映しており,流体包有物の流体圧力の差も説明できそうである.つまり,流体包有物周辺の転位の観察は,鉱物の流動特性を探るプローブとして機能することを確認できた.
  • マントルウェッジを通過するリサイクル炭素の検出
    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 : 2010年 -2011年 
    代表者 : 山本 順司
     
    本研究では「地殻流体」の化学的側面を補強するため,マントルウェッジ由来の捕獲岩に見られる流体包有物の化学分析を行った. マントルウェッジを通過するリサイクル流体の存在は,電磁気観測や地震波トモグラフィー,ダイナミクス計算,高温高圧実験など間接的なアプローチによって活発に議論されているが,その起源を厳密に決めるには化学的情報との組み合わせが重要である.そこで本研究では,極東ロシアや島根県で採取したマントル捕獲岩中の二酸化炭素包有物の炭素同位体比の測定を行った. マントル捕獲岩中の二酸化炭素包有物は非常に小さな流体として存在しており,また,一つの鉱物内に異なる形成時期を持つ包有物列が見られる場合もあり,その炭素同位体比の分析と解釈には注意が必要である.本研究では顕微ラマン分光分析装置によって包有物一つひとつの炭素同位体比分析に挑んだ.しかし,分光法による炭素同位体比の分析精度は地球科学的な議論に耐えられるレベルではなかった.そこで,本研究では予定通り,流体包有物を還元環境で焼き鈍し,流体包有物の主成分である二酸化炭素をグラファイト化させる手法の開発も行った.様々な条件を試した結果,グラファイトの生成に成功した.この開発の先には二次イオン質量分析装置による高精度局所炭素同位体分析への道が開けている. 炭素は単体で「地殻流体」を構成しているわけではない.マントルウェッジの炭素循環系の解明は,付随して動く様々な元素の循環モデルを解く手がかりになるであろう.
  • 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 : 2009年 -2011年 
    代表者 : 川本 竜彦, 小木曽 哲, 山本 順司, 三宅 亮
     
    放射光X線を用いて、高温高圧条件でのマグマと水流体の問の元素分配を決定した。特に、微量成分元素の分配係数に与える圧力と塩濃度の効果を理解した。また、マントル捕獲岩に含まれる流体包有物に含まれる塩濃度を決定した。その結果(1)島弧マントルには海水に似た塩水が存在し、(2)炭酸ガスを含むことを示した。これらの研究により、沈み込むスラブから炭酸ガスを含んだ塩水流体がマントルに付加され、マグマ生成や元素循環においてを何らかの役割を果たしていることを示した。
  • 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 : 2007年 -2010年 
    代表者 : 山野 誠, 馬場 聖至, 瀬野 徹三, 木下 正高, 後藤 忠徳, 後藤 秀作, 山本 順司, 川村 喜一郎, 濱元 栄起, 瀬野 徹三, 木下 正高, 後藤 忠徳, 後藤 秀作
     
    日本海溝北半部の広い範囲において、海溝海側で観測される熱流量が海底年齢に対して異常に高いことを明らかにした。高熱流量は、太平洋プレートが沈み込みにより変形している範囲に限られ、正断層の発達、海洋地殻内の間隙水循環に関連すると考えられる。また、高熱流量を示す太平洋プレート上で、人工電流送信による海底下浅部の電磁気探査に成功し、自然電磁場変動を用いた深部の探査と合わせて、沈み込む海洋地殻内の流体分布に関する情報が得られた。
  • 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 : 2007年 -2009年 
    代表者 : 沖野 郷子, 島 伸和, 佐藤 利典, 海野 進, 野木 義史, 富士原 敏也, 中村 恭之, 山本 順司, 佐藤 暢, 熊谷 英憲, 鈴木 勝彦, 阿部 なつ江, 原田 靖, 浅田 美穂, 篠原 雅尚, 中村 謙太郎, 仙田 量子, 佐藤 太一, 北村 貴幸, 水野 真理子, 水間 恵子
     
    超低速拡大系である南西インド洋海嶺34-41°Eにおいて、研究船を用いた地球物理学・地球化学的探査を行った。地磁気・重力・地震波構造探査の結果から、当該海域でのメルト供給量の時空間変動が明らかになり、その変動に対応して拡大プロセス(地形の非対称、斜交拡大)の変化が認められた。また、取得された岩石の分析からも、マントルの組成や温度の不均質が小スケールで生じていることが示された。上部マントルの電気伝導度構造と微小地震分布もあわせて明らかになった。
  • 超高精度地質圧力計の開発とマントル流体の四次元精査
    日本学術振興会:科学研究費助成事業 若手研究(B)
    研究期間 : 2006年 -2008年 
    代表者 : 山本 順司
     
    本課題で目指した研究項目を大別すると下記三点になる. (1)超高精度地質圧力計の開発 (2)超高精度地質圧力計の確度検証 (3)マントル捕獲岩に見られる流体貯留部の局所分析 (1)の課題は平成18年度に完結しているため,平成19年度は(2)についての研究活動を重点的に行う計画を立て,予定以上の成果を上げることができた.また,平成20年度に行う予定であった(3)の課題もほぼ完結させることができ,成果を学術雑誌に投稿中である. (2)の課題は,マグマによって運び上げられたマントルの岩石(マントル捕獲岩)中に存在する流体包有物が,その岩石が由来した深度を探る指標になりうるかどうかを検証することに主眼がある.マントル捕獲岩が地球深部から運び上げられた際,岩石周辺の圧力は大幅に減少するが,内在する流体はまだ高い圧力を保っており,その巨大な差応力によって流体包有物周辺の結晶格子が塑性変形を起こす可能性が考えられる.そこで我々は実際にマントル鉱物の塑性変形強度を探る実験を行い,降伏強度の推定に成功した(Yamamoto, et. al., 2008).また,鉱物の弾性的振る舞いについても究明することができた(Yamamoto and Kagi, 2008).マントル鉱物の弾性的・塑性的振る舞いを組み合わせて考察すると,地球深部からもたらされた岩石中の流体の密度がどの程度変化しているのか定量的に推定することができる.つまりその流体の密度は岩石の由来深度をどの程度忠実に反映しているものなのか定量的に議論し,補正することが可能になった. (3)の課題は,顕微分光分析やLA-ICP-MS,鉱物の真空破砕分析法を利用した局所流体分析をマントル試料に適用させることを目指すものである.平成20年度に行う予定であったが予察的な分析に着手することができ,その一部の成果を公表することができた(山本,2007; Arakawa, et. al., 2007). (1),(2),(3)の成果を組み合わせることによってマントル流体の4次元的分布を議論することが原理的に可能となった.
  • ラマンCT顕微鏡の開発と地球深部起源天然試料の圧力履歴探索
    日本学術振興会:科学研究費助成事業 萌芽研究
    研究期間 : 2006年 -2007年 
    代表者 : 鍵 裕之, 山本 順司, 土山 明
     
    本研究では、point-to-pointの3次元ラマン顕微鏡により、地球深部起源の試料に蓄積された残留圧力を、ラマンスペクトルの微小な圧力シフトから可視化することを目指した。研究当初から技術的な問題となっていたことであるが、実験室の±0.5℃程度の微小な温度変化が、微小なラマンスペクトルの波数変動を観察する上では無視できない影響を及ぼす。この問題を解決するためには、実験室の温度を0.1℃以下の精度で制御する必要があるが、そのような高度な空調設備を整備することは現実的ではない。そこで、分光器に波長標準となるネオンランプの発行線を導入し、ラマンスペクトルとネオンの蛍光スペクトルを常に同時に観測し、分光器を逐次校正する機構を取り入れた。これまでラマン散乱光を取り入れていた光ファイバーを2分岐化し、一方にネオン光を導入し、両者の信号をCCDカメラ上に2本のアレイとして同時に検出するシステムを築きあげた。この機構により、ラマンスペクトルと同時にネオンランプの発行スペクトルを測定することが可能となった。本装置を用いることにより、ラマンスペクトルを波数安定度0.05cm-1で測定することが達成され、長時間に及ぶ3次元ラマンマッピングにおいても、高精度にラマンマッピングを測定することが可能となった。一連の技術的な開発により、ダイヤモンド中に含まれる異種鉱物の残留応力を独立に決定することができ、これらの鉱物の熱膨張率と圧縮率から、包有物がダイヤモンドに取り込まれた温度圧力条件を見積もることが原理的に可能となった。現実的に得られる値は、ダイヤモンド生成環境と比較して低い温度、圧力となっているが、今後より高い空間分解能で残留圧力を求めることで、より高精度な温度圧力環境の見積もりを今後展開されるであろう。
  • 1億3千万年前の白亜紀太平洋プレート上で活動する新しい海底火山の形成過程解明
    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 : 2005年 -2007年 
    代表者 : 阿部 なつ江, 富士原 敏也, 杉岡 裕子, 馬場 聖至, 山本 順司, 荒木 英一郎, 高橋 成実, 市來 雅啓
     
    本課題は、北西太平洋で発見された若い海底火山(プチスポット火山)の形成過程解明のために、平成17-19年までの3年間、地質学的・地球物理学的調査、陸上での試料分析・データ解析という総合研究を実施した。各年度の成果は以下の通り。 平成17年度:「しんかい6500」による潜航(首席:平野)によって、新たに2つの小海丘がプチスポット火山であることを発見し、同支援母船「よこすか」および「かいれい」単独航海(首席:阿部)によるシングルチャンネル(SCS)地震波構造探査、両航海におけるOBEM設置・回収、HF-PCによる地殻熱流量測定を実施した。 平成18年度:「かいれい」(首席:中西)による同海域地形・重磁力SCS地震波構造探査。 平成19年度:同火山周辺に発生している海洋プレート内地震の震源決定の為の海底地震計3台設置、さらに広域の上部マントル電気伝導度構造決定の為の海底電位磁力計3台を設置、前年度より引き続き海底地形・重磁力測定を行った。また地殻熱流量測定を実施し予察的データを得た。さらに10月「しんかい6500」潜航調査にてマントル捕獲岩採取に成功した。また別の海域にて新たなプチスポット火山を発見した。 この間、プレスリリース2回を含む、国内外の学術誌、学会での発表を行った(研究発表の項参照)。そのうち、Fujiwara et al.(2007)GRLに掲載。American Geophysical Union(AGU)のニュース誌(EOS)のhighlightに取り上げられた。さらに、堀IODP統合国際深海掘削計画へ、プレポーザルを提出(718-Pre:Hirano et al.)。引き続き調査を実施するために、平成19年度にも深海調査研究公募に応募し、「よこすか単独」航海(平成20年度7-8月)採択された。
  • 顕微ラマン分光法による流体包有物一粒からの炭素同位体比測定法の開発
    日本学術振興会:科学研究費助成事業 萌芽研究
    研究期間 : 2004年 -2005年 
    代表者 : 鍵 裕之, 山本 順司
     
    昨年度までに、ラマン分光法によって二酸化炭素を主成分とする流体包有物のラマンスペクトルを顕微分光法によって精度よく測定する手法を確立した。本研究では炭素同位体比の測定を二酸化炭素のラマンスペクトルの形状解析から行う。また、既知の炭素同位体組成を持つ高密度な二酸化炭素流体を合成するラインを製作した。 酸化銅を酸化剤として、^<13>Cに富んだアモルファス炭素から同位体を濃縮した二酸化炭素を生成し、ボンベの二酸化炭素と混合し、任意の同位体組成をもつ二酸化炭素を生成することができるようになった。このラインは加圧により二酸化炭素流体を生成することができる。今年度は^<13>Cに富む二酸化炭素をライン中で生成し、まずは^<13>Cに富む二酸化炭素二酸化炭素のラマンスペクトルを測定し、これまで^<13>CO_2として帰属されていたラマンスペクトルの帰属が正しいか否かを確認することができた。また、サファイヤ窓付きのセルを製作し、生成した流体に2000気圧程度の高圧力をかけることができる装置の開発も行った。この装置を使用することによって、同位体組成の異なる二酸化炭素流体のラマンスペクトルを測定することに成功した。^<13>Cに起因する微小なラマンピークを数値演算によって切り出し、その強度を見積もる手法を見いだした。その結果、約20パーミル程度の精度でラマンスペクトルから二酸化炭素の炭素同位体比を測定できることがわかった。この精度は決して満足のいくものではないが、炭素が生物起源であるか地球内部起源であるかを区別するには十分の値である。今後は天然試料への適用を図る予定である。
  • 島弧下マントルに含まれる流体から,沈み込み帯の物質循環系を探る
    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 : 2002年 -2004年 
    代表者 : 山本 順司
     
    沈み込み帯の三次元的な物質構造と物質循環系を解き明かすため,マントル起源物質に適用できる超高精度の地質圧力計の開発に挑んだ.現在までの研究成果により,マントル構成鉱物に含まれる流体の密度と相図,輝石温度計を組み合わせることによって,流体の平衡圧力を見積もられることが確認できた.しかし,マントル鉱物に含まれる流体の密度には鉱物種に依存した系統的な差違が確認でき,鉱物の二次的な変形が影響を及ぼしている可能性が考えられる.そこで流動学的な計算を行うため,高温・高圧下での天然マントル構成鉱物の弾性・塑性変形強度をSPring8で測定した.現在,データの解析中であるが,この結果を用いて鉱物変形の圧力計への影響を見積もり,当手法を上部マントル物質に適用できる超高精度の地質圧力計として確立することを目指している. 上述の地質圧力計を実際に天然の試料に適用させるため,中国各地でマントル起源の捕獲岩を採取した.試料採取は主に山東省と遼寧省で行った.若干風化を被った試料もあったが,概ね予定通り尖晶石を含むマントル捕獲岩(レルゾライト)を採取することに成功した.現在,薄片を作製し,流体包有物の同定を進めているところである. 他に,予定していたパルス型レーザー光発振装置を用いた局所ガス抽出システムの開発も行った.一般的に,マントル構成鉱物には複数種の流体包有物が存在し,且つそれぞれが異なった起源や来歴を有すると考えられるため,流体包有物中の希ガスの同位体組成を個々に分析する技術が要請される.そこで赤外レーザー光を赤外光対応高倍率対物レンズによって数ミクロン径まで絞り,真空中で流体包有物を個々に撃ち抜くことに挑んだ.実際に超高真空に封入したマントル起源鉱物を10ミクロンのスポット径で掘削することに成功し,流体包有物一つ一つからガスを抽出することを可能にした.
  • 破砕セルとGC-MSの併用によるマントル起源流体の炭素同位体組成の決定
    日本学術振興会:科学研究費助成事業 萌芽研究
    研究期間 : 2002年 -2003年 
    代表者 : 鍵 裕之, 森 俊哉, 野津 憲治, 山本 順司
     
    これまでのところマントルの炭素同位体組成は一定と考えられているが、それを確かめなくてはいけない。炭素は地球表層からおそらくコアまで普遍的に分布する元素であるが、全地球の同位体分布を改めて見直したい、というのが本研究のねらいである。そのためには微少量のマントル流体を対象に、技術的な試行錯誤を繰り返しながら研究を進めることが本研究の目的である。昨年度は測定に用いる予定のマントル捕獲岩の採集を中国大陸において行った。 試料採集後、直ちに行った顕微鏡による薄片観察、ならびに顕微ラマンスペクトルの測定によって、採集したスピネルレルゾライトには炭酸ガスを主成分とする流体包有物が含まれることが明らかになった 昨年度末から今年度にかけて、マントル捕獲岩の希ガス同位体測定にすでに実績のあるクラッシャー(破砕機)を製作した。本装置を研究室に既存のGC-C-MSに取り付け、破砕によって生じるガスの組成を求めたうえで、炭素同位体比を測定した。本装置はハンマーで衝撃を与え、試料を破砕する装置である。マントル捕獲岩を試料として、実験を行ったところ、1グラムほどの試料から二酸化炭素の同位体組成を測定することができた。また、同時にメタンも試料中から検出され、二酸化炭素とは異なる同位体組成を持つことが明らかになった。本研究の過程で、新しいアイディアに基づく二酸化炭素同位体比非破壊分析の着想を持つことができた。

教育活動情報

主要な担当授業

  • 大学院共通授業科目(教育プログラム):博物館学
    開講年度 : 2019年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : 学術標本・資料、博物館、学芸員、アドバンストコース
  • 博物館経営論
    開講年度 : 2019年
    課程区分 : 学士課程
    開講学部 : 文学部
    キーワード : ミュージアム、経営、評価、地域社会、コミュニケーション
  • 博物館展示論
    開講年度 : 2019年
    課程区分 : 学士課程
    開講学部 : 文学部
    キーワード : 博物館、展示、学芸員
  • 地球資源科学
    開講年度 : 2019年
    課程区分 : 学士課程
    開講学部 : 理学部
    キーワード : 地下資源,地球内部環境,地球化学

大学運営

委員歴

  • 2018年08月 - 現在   国立研究開発法人日本原子力研究開発機構   地質環境長期安定性評価技術高度化開発委員会委員
  • 2018年07月 - 現在   日本地学教育学会   編集委員
  • 2020年04月 - 2022年03月   日本地球惑星科学連合   代議員
  • 2016年01月 - 2017年12月   日本地球化学会   評議員


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