2022年06月, 資源地質学会, Best Article Award 2021
Geochemical constraints on the mobilization of Ni and critical metals in laterite deposits, Sulawesi, Indonesia: A mass-balance approach
Ito, A;Otake, T;Maulana, A;Sanematsu, K;Sufriadin;Sato, T, 11763384

2017年, 日本粘土学会, 粘土学会論文賞　　　　　　　　　　　　　　　
高アルカリ環境における圧縮ベントナイト中のシリカ鉱物の溶解: X線CT観察および地球化学モデリングによる定量的評価
中林亮;木嶋達也;塚田康元;佐藤努;大竹翼;金子勝比古;米田哲郎

2011年, International Society for the Study of the Origin of Life, Best Poster award, Origins 2011 International Conference　　　　　　　　　　　　　　　
Tsubasa Otake

2008年, Astrobiology Science Conference 2008, Frank Drake Award　　　　　　　　　　　　　　　
Tsubasa Otake

Primary Fe isotope signatures record oxidative precipitation in 3.2 Ga ferruginous siliciclastic sedimentary rocks deposited in a shallow ocean environment
Ryohei Suzumeji, Tsubasa Otake, Daizo Yamauchi, Yoko Ohtomo, Takeshi Kakegawa, Christoph Heubeck, Shin ichi Yamasaki, Tsutomu Sato
Precambrian Research, 413, 107574, 2024年10月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, Iron (Fe) isotopic compositions of Iron formations (IFs) have the potential to constrain the oceanic redox environment and marine biosphere on the early Earth. However, the interpretation of Fe isotope ratios in IFs is controversial and related to various factors, such as Fe sources, mode of primary precipitation, and subsequent mineral transformations. This paper presents whole-rock Fe isotope data for ca. 3.2 Ga unweathered ferruginous siliciclastic sedimentary rocks deposited in a shallow ocean in the lower part (unit MdI1) of the Moodies Group, Barberton Greenstone Belt, South Africa. We also experimentally examined Fe isotope effects during the precipitation of Fe2+-silicates (e.g., greenalite), proposed as primary Fe minerals in IFs. The Fe isotope data show significant variation (δ56Fe = −0.58 ‰ to +0.60 ‰) for different lithologies (i.e., magnetite-rich siltstone, carbonate-rich siltstone, sandy siltstone, and jaspilite). The δ56Fe values (δ56Fe = −0.54 ‰ to +0.60 ‰) of the magnetite-rich siltstones tend to decrease with decreasing Fe2O3(T)/Al2O3 ratios and matrix ratios (the percentage of detrital grains with a size of <30 μm). Carbonate-rich siltstones also fall on the same Fe2O3(T)/Al2O3 – δ56Fe and matrix ratio – δ56Fe trends as magnetite-rich siltstone. The synthetic experiment showed that isotope fractionation during anoxygenic Fe2+-silicate precipitation from dissolved ferrous Fe (Fe2+(aq)) was much smaller (Δ56FeFe2+-silicate–Fe2+(aq) < +0.3 ‰) than that of oxidative precipitation. These results indicate that Fe isotopic variations in Fe-rich siltstones (magnetite- and carbonate-rich siltstones) are only explained by the oxidative precipitation of Fe2+(aq) supplied from the deep ocean following Rayleigh-type fractionation. Low carbonate-C isotope ratios (δ13Ccarb = −5.8 ‰ to −3.7 ‰) of the Fe-rich siltstones show that magnetite and ankerite or Mg-siderite formed from a primary Fe3+-bearing mineral by oxidation of organic C after Fe burial. The consistent Fe2O3(T)/Al2O3 – δ56Fe trends between the magnetite- and carbonate-rich siltstones suggest that Fe reduction during diagenetic and/or metamorphic transformation processes of Fe-bearing minerals caused negligible changes in the whole-rock Fe isotope composition, possibly because of limited mobility of Fe2+ in the sediment. Consequently, the Fe isotope compositions predominantly record the primary precipitation process that occurred in the water column of a 3.2 Ga shallow ocean environment., 46553825

Atmospheric hydrochloric and nitric acid leaching of a limonite ore from the Wolo mine area, Southeast Sulawesi, Indonesia
Sufriadin, Malyanus YEPTA, Irzal NUR, Purwanto, Rizky AMALIA, Ulva Ria IRFAN, Djabal Nur BASIR, Tsubasa OTAKE
Journal of Metals, Materials and Minerals, 34, 1, 1875, 1875, Metallurgy and Materials Science Research Institute, Chulalongkorn University, 2024年03月19日, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, The atmospheric acid leaching studies of a limonite ore sample from the Wolo mine area, Southeast Sulawesi, Indonesia, have been performed using hydrochloric acid (HCl) and nitric acid (HNO3). The objectives of these studies were to compare the leaching degree of metals (Ni, Co, Fe, and Al) and to analyze the dissolution behavior of minerals under different acid concentrations. Mineralogical characterization of the ore sample was conducted using optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction, whereas chemical composition was determined by X-ray fluorescence (XRF) spectrometry and atomic absorption spectroscopy (AAS), respectively. An atmospheric leaching test was done with the variables of acid concentration, leaching duration of 90 min, and leaching temperature of 100℃. Limonite ore samples contain goethite, gibbsite, talc, quartz, and lizardite. It was revealed that as much as 92.22% of Ni and 90.14% of Fe could be leached using 3 M HCl, whereas only 63.14% of Ni and 38.74% of Fe could be extracted from limonite ore using 3 M HNO3. The higher leaching degree of Fe in HCl indicates low selectivity with Ni, which might contaminate pregnant leach solution (PLS), leading to further complications in the purification process. Results of the leaching experiment show that goethite was more easily dissolved in HCl than in HNO3.

Immobilization Forms of Cadmium and Mercury in a Potassium-Activated Metakaolin-Based Geopolymer
Pramesti Prihutami, Raudhatul Islam Chaerun, Yusuke Ohya, Tsubasa Otake, Ryosuke Kikuchi, Tsutomu Sato
Minerals, 14, 3, 311, 311, 2024年03月15日, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, Previous studies of cadmium and mercury immobilization in geopolymers have produced inconsistent results due to their different pozzolans, metal concentrations, and mixing procedures. Understanding the effects of these parameters on heavy metal immobilization is key to predicting their long-term stability. In this study, cadmium and mercury were incorporated into a metakaolin-based K-activated geopolymer by three mixing procedures and concentrations of 0.02–1.00 wt.%. The samples were then immersed in water for 90 d to determine their stability. The results show that mercury is readily leached from the geopolymer, but cadmium is retained. Adding the heavy metals in salt form converts the metals into cadmium hydroxide and mercury oxide that reside at the bottom of the geopolymer. Mixing the salts with water forms soluble heavy metals prior to geopolymerization. This procedure produces more-homogeneous geopolymers. Cadmium is associated with silicate and aluminate, giving a better stability, whereas mercury forms mercury oxide. Different cadmium and mercury concentrations do not change the metal speciation as mercury is affected by relativistic contribution.

The formation of schwertmannite colloids and natural remediation of toxic elements from Shojin River, Hokkaido, Japan
Frances Chikanda, Sereyroith Tum, Tatsuya Matsui, Susumu Norota, Tsubasa Otake, Tsutomu Sato
Resource Geology, 73, 1, Wiley, 2023年06月, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, 27289727

Formation of magnesium silicate hydrate (M-S-H) at pH 10 and 50°C in open-flow systems
Yuto Nishiki, Jordi Cama, Tsubasa Otake, Ryosuke Kikuchi, Misato Shimbashi, Tsutomu Sato
Applied Geochemistry, 148, 105544, 105544, Elsevier BV, 2023年01月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）

Difference in expansion and dehydration behaviors between NH4- and K-montmorillonite
Ryohei Kawakita, Akito Saito, Hiroshi Sakuma, Sohtaro Anraku, Ryosuke Kikuchi, Tsubasa Otake, Tsutomu Sato
Applied Clay Science, 231, 106722, 106722, Elsevier BV, 2023年01月, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, Montmorillonite (Mt) expansion and swelling are key factors determining the barrier performance of bentonite in trans-uranic (TRU) and high-level radioactive waste disposal. In the case of co-located geological disposal of TRU and high-level waste, NH4+ ions formed from NO3− ions leached from TRU waste may contact bentonite, exchanging with interlayer cations of Mt. to form NH4-Mt, with a reduction in barrier performance. Because of the similar hydration energies of NH4+ and K+, NH4-Mt may have less expandability or even change to a non-expandable mineral such as K-Mt. An understanding of the expansion and alteration behavior of NH4-Mt, especially in comparison with K-Mt, is thus necessary in waste-disposal safety assessment. Here, the hydration behavior of NH4-Mt was investigated by X-ray diffraction (XRD) analysis and molecular dynamics (MD) simulation and compared with that of K-Mt. XRD profiles under relative humidity (RH) control indicate that expansion of NH4-Mt is similar to that of K-Mt at >40% RH with slightly different d-values. However, NH4-Mt expansion is kept at ∼20% RH, while K-Mt tends to dehydrate. MD simulations indicate that hydrogen bonding with NH4+ ions causes the differences in hydration behaviors of NH4- and K-Mt, increasing basal spacing in dehydrated states and promoting hydration. This “hydration gap” may be attributed to differences in alteration to non-expandable minerals by dehydration, with NH4+ having less tendency for alternation and less of an effect on the barrier performance of bentonite than K+.

Retention mechanism of cesium in chabazite embedded into metakaolin-based alkali activated materials
Raudhatul Islam Chaerun, Natatsawas Soonthornwiphat, Kanako Toda, Kazuma Kuroda, Xiaobo Niu, Ryosuke Kikuchi, Tsubasa Otake, Yogarajah Elakneswaran, John L. Provis, Tsutomu Sato
Journal of Hazardous Materials, 440, 129732, 129732, Elsevier BV, 2022年10月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）

Effects of lignosulfonate on synthesis products of the pozzolanic reaction
Kanako Toda, Daisuke Minato, Takumi Saito, Ryosuke Kikuchi, Tsubasa Otake, Tsutomu Sato
Cement, 9, 100042, 100042, Elsevier BV, 2022年09月, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）

Low-Temperature Hydrothermal Synthesis of Chromian Spinel from Fe-Cr Hydroxides Using a Flow-Through Reactor
Yoko Ohtomo, Jeehyun Yang, Miu Nishikata, Daisuke Kawamoto, Yuki Kimura, Tsubasa Otake, Tsutomu Sato
Minerals, 12, 9, 1110, 1110, MDPI AG, 2022年08月30日, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, Recent studies have suggested that a chromian spinel can be formed under natural hydrothermal conditions; however, the required conditions, process, and associated redistribution of Cr are still poorly understood. Here, chromian spinel formation was performed by Fe-Cr hydroxides alteration with an Fe2+(aq) supply at 150, 170, and 200 °C and 5 MPa simulating the diagenetic process. The flow-through system enabled the Fe2+(aq) supply to be leached from the magnetite by an acidic solution to synthesize Fe-Cr hydroxides as the starting material with two reaction cells, flow lines, heaters, and a high-performance liquid chromatography (HPLC) pump. The accuracy of the temperature measurement was confirmed based on the amorphous silica solubility. Mineralogical analysis of solid samples recovered from the reaction cell indicated that the chromian spinel was formed between 150 and 170 °C from Fe-Cr hydroxides through goethite with a simultaneous hematite formation, while Mössbauer spectra showed that a large quantity of Fe-Cr ferrihydrites still remained after the experiments probably because of the Cr addition to the stability of ferrihydrites. The Cr/Fe ratio of the chromian spinel was smaller than that of the bulk of the Fe-Cr ferrihydrites and equivalent to Cr-rich magnetite, suggesting a redistribution of Cr during the transformation from goethite to synthesized spinel under the hydrothermal conditions., 10843041

Characteristics and Formation Pathways of Iron- and Magnesium-Silicate-Hydrates and Smectites Under Natural Alkaline Conditions
Misato Shimbashi, Shingo Yokoyama, Ryosuke Kikuchi, Tsubasa Otake, Tsutomu Sato
Clays and Clay Minerals, Springer Science and Business Media LLC, 2022年08月23日, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）

Water quality in the Lisungwi and Kaphamtengo Rivers in Manondo, Central Malawi: Assessment of the impact of artisanal small scale gold mining
Frances Chikanda, Tsubasa Otake, Jones Mwatseteza, Tsutomu Sato
Malawi Journal of Science and Technology, 14, 1, 29, 43, 2022年07月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, 27289727

Seasonal effects of natural attenuation on drainage contamination from artisanal gold mining, Cambodia: Implication for passive treatment
Sereyroith Tum, Kanako Toda, Tatsuya Matsui, Ryosuke Kikuchi, Sitha Kong, Panha Meas, Unsovath Ear, Yoko Ohtomo, Tsubasa Otake, Tsutomu Sato
Science of The Total Environment, 806, 150398, 150398, Elsevier BV, 2022年02月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）

Mineralogical evolution of a weathering profile in the Tagaung Taung Ni laterite deposit: significance of smectite in the formation of high-grade Ni ore in Myanmar
Ayaka Murofushi, Tsubasa Otake, Kenzo Sanematsu, Kyaw Zay Ya, Akane Ito, Ryosuke Kikuchi, Tsutomu Sato
Mineralium Deposita, 57, 1107, 1122, Springer Science and Business Media LLC, 2022年01月12日, ［査読有り］, ［責任著者］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, 27289727

地球表層環境における鉄の濃集と鉄鉱床の形成
大竹 翼, 大友 陽子
資源地質, 71, 2, 57, 73, 2021年12月, ［査読有り］, ［筆頭著者, 責任著者］, ［国内誌］
日本語, 研究論文（学術雑誌）, 27289727

Geochemical constraints on the mobilization of Ni and critical metals in laterite deposits, Sulawesi, Indonesia: A mass‐balance approach
Akane Ito, Tsubasa Otake, Adi Maulana, Kenzo Sanematsu, Sufriadin, Tsutomu Sato
Resource Geology, 71, 3, 255, 282, Wiley, 2021年07月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, 27289727

The Latowu Ultramafic Rock-Hosted Iron Mineralization in the Southeastern Arm Sulawesi, Indonesia: Characteristics, Origin, and Implication for Beneficiation　　　　　　　　　　　　　　　
Sufriadin, Sri Widodo, Meinarni Thamrin, Akane Ito, Tsubasa Otake
International Journal on Advanced Science Engineering and Information Technology, 11, 3, 987, 993, 2021年06月, ［査読有り］, ［最終著者］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）

The formation of Fe colloids and layered double hydroxides as sequestration agents in the natural remediation of mine drainage
Frances Chikanda, Tsubasa Otake, Aoi Koide, Akane Ito, Tsutomu Sato
Science of The Total Environment, 774, 145183, 145183, Elsevier BV, 2021年06月, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, The increasing need to treat wastewater from mine effluents has drawn attention to passive treatment systems. Colloids are common in mine waters and are highly reactive, so their formation, characteristics, behavior, and the critical factors that affect them need to be understood for designing efficient treatment systems. An investigation was conducted at the abandoned Ainai mine drainage, Japan, where aeration is utilized to remove Fe, As, and Zn from circumneutral wastewater drainage, during rainy and dry seasons of 2016 and 2018 respectively, based on observations of physiochemical characteristics, elemental concentrations in dissolved and colloidal fractions, transmission electron microscopy, and synthetic experiments. In this circumneutral Fe-rich mine drainage, Fe2+ is oxidized to Fe3+, resulting in the formation of Fe colloids that incorporate As during their formation. Colloid formation increases turbidity, and, in the rainy season, increased colloidal interaction enhances their aggregation and higher flow rates lead to greater mobilization of the colloids. Zn-bearing colloids are rare in Ainai mine drain-age because the Zn concentrations are low. However, Zn-Fe layered double hydroxide (LDH) was identified and confirmed by geochemical modelling and experiments. The Zn-Fe LDH was formed by isomorphous substitution of Zn into an Fe2+-Fe3+-CO32-LDH, at pH greater than 7.5, thereby achieving efficient natural remediation of Zn and As in the drainage. (c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)., 11763384

Geochemical behaviour of heavy metals in sludge effluents and solid deposits on the Zambian Copperbelt: Implication for effluent treatment and sludge reuse
Cryton Phiri, Daiki Shimazui, Tsubasa Otake, Ryosuke Kikuchi, Isaac Chintu, Meki Chirwa, Lawrence Kalaba, Imasiku Nyambe, Tsutomu Sato
Science of The Total Environment, 769, 144342, 144342, Elsevier BV, 2021年05月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）

Subseafloor sulphide deposit formed by pumice replacement mineralisation
Tatsuo Nozaki, Toshiro Nagase, Yutaro Takaya, Toru Yamasaki, Tsubasa Otake, Kotaro Yonezu, Kei Ikehata, Shuhei Totsuka, Kazuya Kitada, Yoshinori Sanada, Yasuhiro Yamada, Jun-ichiro Ishibashi, Hidenori Kumagai, Lena Maeda, the D, Chikyu Expeditio, Scientists
Scientific Reports, 11, 1, 8809, Springer Science and Business Media LLC, 2021年04月, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, Seafloor massive sulphide (SMS) deposits, modern analogues of volcanogenic massive sulphide (VMS) deposits on land, represent future resources of base and precious metals. Studies of VMS deposits have proposed two emplacement mechanisms for SMS deposits: exhalative deposition on the seafloor and mineral and void space replacement beneath the seafloor. The details of the latter mechanism are poorly characterised in detail, despite its potentially significant role in global metal cycling throughout Earth’s history, because in-situ studies require costly drilling campaigns to sample SMS deposits. Here, we interpret petrographic, geochemical and geophysical data from drill holes in a modern SMS deposit and demonstrate that it formed via subseafloor replacement of pumice. Samples from the sulphide body and overlying sediment at the Hakurei Site, Izena Hole, middle Okinawa Trough indicate that sulphides initially formed as aggregates of framboidal pyrite and matured into colloform and euhedral pyrite, which were replaced by chalcopyrite, sphalerite and galena. The initial framboidal pyrite is closely associated with altered material derived from pumice, and alternating layers of pumiceous and hemipelagic sediments functioned as a factory of sulphide mineralisation. We infer that anhydrite-rich layers within the hemipelagic sediment forced hydrothermal fluids to flow laterally, controlling precipitation of a sulphide body extending hundreds of meters., 11549321

Large Fe isotope fractionations in sulfide ores and ferruginous sedimentary rocks from the Kuroko volcanogenic massive sulfide deposits in the Hokuroku district, northeast Japan
Tsubasa Otake, Ryoichi Yamada, Ryohei Suzuki, Shunsuke Nakamura, Akane Ito, Ki-Cheol Shin, Tsutomu Sato
Geochimica et Cosmochimica Acta, 295, 49, 64, Elsevier BV, 2021年02月, ［査読有り］, ［筆頭著者, 責任著者］, ［国際誌］
英語, 研究論文（学術雑誌）, Anoxic seawater may have played an important role in the preservation of volcanogenic massive sulfide (VMS) deposits in the Hokuroku district, northeast Japan, which is the type locality for Kuroko-type VMS deposits. In this study, we investigated the Fe isotopic compositions of sulfide ores and overlying ferruginous sedimentary rocks in these deposits. These data, coupled with petrographic and geochemical data, enable us to investigate the key formation processes and conditions during the formation of large Kuroko-type VMS deposits. Large Fe isotope variations of ca. 4 parts per thousand (delta Fe-56) associated with negative or positive Ce anomalies characterize the ferruginous sedimentary rocks formed in the Kuroko VMS deposits and post-Kuroko hydrothermal activity. This suggests that iron (hydr)oxides were precipitated by the partial oxidation of dissolved Fe2+ derived from hydrothermal fluids in anoxic or suboxic pools in the Hokuroku Basin. Positive Eu anomalies in the ferruginous cherts closely associated with the Kuroko VMS deposits indicate formation from high-temperature hydrothermal fluids. Zincrich black ores in both the Matsumine and Fukazawa deposits have lower delta Fe-56 values, due to rapid precipitation of pyrite triggered by the mixing of hydrothermal fluids with seawater. Positive shifts in delta Fe-56 values in the ferruginous cherts from the Ezuri and Fukazawa deposits may be explained by simultaneous precipitation of ferruginous sedimentary rocks with black ores, which modified the delta Fe-56 values of the hydrothermal fluids to positive values. However, Cu-rich yellow ores show no significant Fe isotope fractionation as compared with the dissolved Fe in the hydrothermal fluids, and were likely formed by slow growth of pyrite that replaced the black ores. The difference in the abundance of sulfide ores between the Matsumine and Fukazawa deposits may reflect the duration of hydrothermal circulation. (C) 2020 Elsevier Ltd. All rights reserved., 27289727

Chromium occurrence in a nickel laterite profile and its implications to surrounding surface waters
Ruth Esther Delina, Carlo Arcilla, Tsubasa Otake, Jhonard John Garcia, Mark Tan, Akane Ito
Chemical Geology, 558, 119863, 119863, Elsevier BV, 2020年12月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）

Effect of Soil Organic Matters in Dredged Soils to Utilization of their Mixtures Made with a Steel Slag
Kanako Toda, Ryosuke Kikuchi, Tsubasa Otake, Satoshi Nishimura, Yuzoh Akashi, Michihiro Aimoto, Takeshi Kokado, Tsutomu Sato
Materials, 13, 23, 5450, 5450, MDPI AG, 2020年11月30日, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, Dredged soils have been used as construction materials by alkaline activation with steel slag (steel slag-dredged soil mixtures) at harbors. Such mixtures develop strength chiefly by calcium silicate hydrate (C-S-H) formation by the pozzolanic reaction. However, the strength of such mixtures is unpredictable, and in some cases, mixtures have been too soft for the intended engineering application. An identification of strength development indicators would accelerate evaluation processes for strength development to facilitate and promote the utilization of such materials. This paper focuses on the relationship between the characteristics of soil organic matters in dredged soils and the strength development of the mixtures by a comparison of eight dredged soils collected from eight different Japanese harbors. The characteristics of the soil organic matters were identified to determine as indicators of mixtures with weak strength development, i.e., enriched sulfur content in extracted soil organic matter (humic acid) fraction, and the N/C ratio of humic acid similar to land humic acid standards. Increases in the validated fraction of dredged soils and steel slag by replacing fractions disadvantageous to construction resources would contribute to reduce waste production, which would lower the environmental impact of the use, aiming to achieve sustainable utilization of such materials.

Formation of Natural Silicate Hydrates by the Interaction of Alkaline Seepage and Sediments Derived from Serpentinized Ultramafic Rocks at Narra, Palawan, the Philippines
Misato Shimbashi, Shingo Yokoyama, Yasutaka Watanabe, Tsutomu Sato, Tsubasa Otake, Ryosuke Kikuchi, Minoru Yamakawa, Naoki Fujii
Minerals, 10, 8, 719, 719, MDPI AG, 2020年08月17日, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, In radioactive waste disposal facilities, low-permeability engineered barrier materials are important for inhibiting radionuclide migration. However, dissolution–precipitation reactions under alkaline conditions change the permeability of engineered barriers. To understand long-term dissolution–precipitation reactions under alkaline conditions in chemically complex systems, trenches and drill holes were excavated at Narra in Palawan, where alkaline fluids (pH > 11) have been naturally produced, seeping into clastic sediments derived from serpentinized ultramafic rocks and gabbro of Palawan ophiolite. Interaction between the alkaline seepage and clastic sediments, which have been deposited since 15,000 radiocarbon years before present (14C yr BP), led to dissolution of minerals and the precipitation of Si-bearing phases which were divided into two main categories: Fe-Mg-Si infillings and Ca-Si infillings. The former category was composed of iron-magnesium-silicate-hydrate (F-M-S-H) and a nontronite-like mineral and was widely recognized in the clastic sediments. The nontronite-like mineral likely formed by interaction between silicates and alkaline seepage mixed with infiltrated seawater, whereas F-M-S-H formed by the reaction of silicates with alkaline seepage in the absence of seawater infiltration. Ca-Si infillings included 14 Å tobermorite and were precipitated from alkaline seepage combined with the Ca and Si supplied by the dissolution of calcite and silicates in the clastic sediments.

Encapsulation of Sr-loaded titanate spent adsorbents in potassium aluminosilicate geopolymer
Natatsawas Soonthornwiphat, Yutaro Kobayashi, Kanako Toda, Kazuma Kuroda, Chaerun Raudhatul Islam, Tsubasa Otake, Yogarajah Elakneswaran, John L. Provis, Tsutomu Sato
Journal of Nuclear Science and Technology, 57, 10, 1, 8, Informa UK Limited, 2020年06月05日, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）

Precipitation of magnesium silicate hydrate in natural alkaline surface environments　　　　　　　　　　　　　　　
Y. Nishiki, T. Sato, T. Katoh, T. Otake, R. Kikuchi
Clay Science, 24, 1, 1, 13, 2020年06月, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）

Geochemical characteristics of ores and surface waters for environmental risk assessment in the Pinpet iron deposit, southern Shan State, Myanmar
K. Zay Ya, T. Otake, A. Koide, K. Sanematsu, T. Sato
Resource Geology, 70, 296, 308, 2020年02月, ［査読有り］, ［責任著者］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, 11763384

Magmatic-hydrothermal processes associated with Rare Earth Element enrichment in the Kangankunde carbonatite complex, Malawi
F. Chikanda, T. Otake, Y. Ohtomo, A. Ito, T. D. Yokoyama, T. Sato
Minerals, 9, 7, 442, 442, MDPI AG, 2019年07月, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, Carbonatites undergo various magmatic-hydrothermal processes during their evolution that are important for the enrichment of rare earth elements (REE). This geochemical, petrographic, and multi-isotope study on the Kangankunde carbonatite, the largest light REE resource in the Chilwa Alkaline Province in Malawi, clarifies the critical stages of REE mineralization in this deposit. The δ56Fe values of most of the carbonatite lies within the magmatic field despite variations in the proportions of monazite, ankerite, and ferroan dolomite. Exsolution of a hydrothermal fluid from the carbonatite melts is evident based on the higher δ56Fe of the fenites, as well as the textural and compositional zoning in monazite. Field and petrographic observations, combined with geochemical data (REE patterns, and Fe, C, and O isotopes), suggest that the key stage of REE mineralization in the Kangankunde carbonatite was the late magmatic stage with an influence of carbothermal fluids i.e. magmatic–hydrothermal stage, when large (~200 µm), well-developed monazite crystals grew. The C and O isotope compositions of the carbonatite suggest a post-magmatic alteration by hydrothermal fluids, probably after the main REE mineralization stage, as the alteration occurs throughout the carbonatite but particularly in the dark carbonatites.

Correction: Toda, k., et al. Key factors affecting strength development of steel slag-dredged soil mixtures. (Minerals (2018), 8(5), 174)
Kanako Toda, Haruna Sato, Nilan Weerakoon, Tsubasa Otake, Satoshi Nishimura, Tsutomu Sato
Minerals, 8, 10, MDPI AG, 2018年10月22日
英語, 研究論文（学術雑誌）, The authors wish to make the following corrections to this paper [1]: Toda, K.
Sato, H.
Weerakoon, N.
Otake, T.
Nishimura, S.
Sato, T. Key Factors Affecting Strength Development of Steel Slag-Dredged Soil Mixtures. Minerals 2018, 8, 174. 1. Change in Main Body Paragraphs On page 2 of 16, lines 90–91, the sentence “Purified humic acid content was highest in soil D (2.04%) followed by C (1.23%), A (1.02%) and B (0.74%)” should be “Purified humic acid content was highest in soil D (0.30%) followed by B (0.20%), C (0.14%) and A (0.09%)”. Consequently, on page 11 of 16, lines 320–322, the sentence “This suggests that the content of humic acids in soils A, B, C and D (0.74–2.04%) is not sufficient to act as a pH buffer” should be “This suggests that the content of humic acids in soils A, B, C and D (0.09–0.30%) is not sufficient to act as a pH buffer”. These changes have no material impact on the conclusions of our paper. We apologize to our readers. 2. Change in Table Due to mislabeling, replace Table 2: Table 2. Mineral dissolution rates and surface areas of silica-bearing phases loaded in the geochemical modeling as reactants. (Table presented). Table 2. Mineral dissolution rates and surface areas of silica-bearing phases loaded in the geochemical modeling as reactants. (Table presented).

Geochemical study of ultramafic rocks from Latowu area of North Kolaka, Southeast Sulawesi and its implication for CO2 sequestration
Sufriadin, S. Widodo, A. Ito, T. Otake, K. Sanematsu
Journal of Degraded and Mining Lands Management, 5, 4, 1403, 1408, International Research Centre for the Management of Degraded and Mining Lands, 2018年07月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）

Key factors affecting strength development of steel slag-dredged soil mixtures
Kanako Toda, Haruna Sato, Nilan Weerakoon, Tsubasa Otake, Satoshi Nishimura, Tsutomu Sato
Minerals, 8, 5, 174, MDPI AG, 2018年05月01日, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, Some of the steel slag from ironworks and dredged soils from marine and waterfront engineering work are partially treated as waste. However, a mixture of these two kinds of waste has the potential to be used as construction materials when mixed, due to chemical reactions forming secondary phases. Utilizing waste of such kind as a resource will help to improve sustainability in society by reducing waste and replacing virgin resources such as cement. Recently, it was reported that mixtures of steel slag and dredged soil hardens under specific conditions. The phase compositions of dredged soils and steel slags vary depending on the quantity of each component, which results in unpredictable strength development of mixtures. The effect of the variations in the components of steel slags and dredged soils on strength development of the mixtures is not yet clear, limiting the utilization of both materials. Understanding the hardening mechanisms of the mixtures will enable the prediction of strength development. Focusing on the variations in the components in steel slags and, especially of dredged soils, this study aims to identify the components in both materials that affect the secondary phase formation that are responsible for strength development. We found support for suggestions that calcium silicate hydrate, C-S-H, is one of the secondary phases responsible for the strength development of the mixtures. From a comparison of two kinds of steel slags and various dredged soils, the amount of portlandite in the steel slags and the amount of amorphous silica in the dredged soils are suggested as a couple of the key components of starting materials involved in the C-S-H formation.

Formation of Fe-and Mg-rich smectite under hyperalkaline conditions at narra in Palawan, the Philippines
Misato Shimbashi, Tsutomu Sato, Minoru Yamakawa, Naoki Fujii, Tsubasa Otake
Minerals, 8, 4, 155, MDPI AG, 2018年04月01日, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, The formation of Fe-and Mg-rich smectite and zeolite under alkaline conditions, as secondary minerals after the alkaline alteration of bentonite in repositories for radioactive waste, is of major concern. It is crucial for safety assessments to know whether smectite is formed as a secondary mineral after the alkaline alteration of bentonite. In the present paper, Fe-and Mg-rich smectite, which interacted with the hyperalkaline groundwater at Narra in Palawan, Philippines, was used. Mineralogical and geochemical investigation was conducted to understand the formation process of the smectite and the factors determining the formation of secondary mineral species. The results suggest that a certain amount of smectite may be generated under hyperalkaline conditions, by alteration from amorphous or poorly crystalline components such as M-S-H and F-S-H. Therefore, the controlling factor determining whether smectite or zeolite will be generated as secondary minerals after alkaline alteration of bentonite could be whether nuclei of M-S-H and/or F-S-H are formed. Whether such formation takes place may be determined by the presence of dissolved Mg2+ and Fe2+ in the environment. The formation process of smectite under alkaline conditions, suggested by the results here, is analogous to the generally accepted model of smectite formation as it may have occurred on early Mars.

Dissolved silica effects on adsorption and Co-precipitation of Sb(III) and Sb(V) with ferrihydrite
Shuang Zhou, Tsutomu Sato, Tsubasa Otake
Minerals, 8, 3, 101, MDPI AG, 2018年03月05日, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, Elevated antimony concentrations in aqueous environments from anthropogenic sources are becoming of global concern. In this respect iron oxides are known to strongly adsorb aqueous antimony species with different oxidation states, but the effect of silica on the removal characteristics is not well understood despite being a common component in the environment. In this study, ferrihydrite was synthesized at various Si/Fe molar ratios to investigate its adsorption and co-precipitation behaviors with aqueous antimony anionic species, Sb(III) and Sb(V). The X-ray diffraction analyses of the precipitates showed two broad diffraction features at approximately 35° and 62° 2θ, which are characteristics of 2-line ferrihydrite, but no significant shifts in peak positions in the ferrihydrite regardless of the Si/Fe ratios. The infrared spectra showed a sharp band at ~930 cm−1, corresponding to asymmetric stretching vibrations of Si–O–Fe bonds which increased in intensity with increasing Si/Fe molar ratios. Further, the surface charge on the precipitates became more negative with increasing Si/Fe molar ratios. The adsorption experiments indicated that Sb(V) was preferentially adsorbed under acidic conditions which decreased dramatically with increasing pH while the adsorption rate of Sb(III) ions was independent of pH. However, the presence of silica suppressed the adsorption of both Sb(III) and Sb(V) ions. The results showed that Sb(III) and Sb(V) ions were significantly inhibited by co-precipitation with ferrihydrite even in the presence of silica by isomorphous substitution in the ferrihydrite crystal structure.

Mechanisms of Se(IV) co-precipitation with ferrihydrite at acidic and alkaline conditions, and its behavior during aging　　　　　　　　　　　　　　　
P. C. M. Francisco, T. Sato, T. Otake, T. Kasama, S. Suzuki, H. Shiwaku, T. Yaita
Environmental Science and Technology, 52, 4817, 4826, 2018年03月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）

Effect of dissolved silica on immobilization of boron by magnesium oxide
Shoko Nozawa, Tsutomu Sato, Tsubasa Otake
Minerals, 8, 2, 76, MDPI AG, 2018年02月24日, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, The effect of silica on the immobilization reaction of boron by magnesium oxide was investigated by laboratory experiments. In the absence of silica, due to dissolution of the magnesium oxide, boron was removed from solutions by the precipitation of multiple magnesium borates. In the presence of silica, magnesium silica hydrate (M-S-H) was formed as a secondary mineral, which takes up boron. Here11 B magic-angle spinning nuclear magnetic resonance (MAS-NMR) and Fourier transform infrared spectrometer (FT-IR) data show that a part of the boron would be incorporated into M-S-H structures by isomorphic substitution of silicon. Another experiment where magnesium oxide and amorphous silica were reacted beforehand and boron was added later showed that the shorter the reaction time of the preceding reaction, the higher the sorption ratio of boron. That is, boron was incorporated into the M-S-H mainly by coprecipitation. The experiments in the study here show that the sorption of boron in the presence of silica is mainly due to the incorporation of boron during the formation of the M-S-H structure, which suggests that boron would not readily leach out, and that stable immobilization of boron can be expected.

Geochemical signatures and processes in a stream contaminated by heavy mineral processing near Ipoh city, Malaysia
Akane Ito, Tsubasa Otake, Ki-Cheol Shin, Kamar Shah Ariffin, Fei-Yee Yeoh, Tsutomu Sato
APPLIED GEOCHEMISTRY, 82, 89, 101, PERGAMON-ELSEVIER SCIENCE LTD, 2017年07月, ［査読有り］, ［責任著者］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, The environmental impacts of a heavy mineral processing involving rare earth elements (REEs) in the Kinta River and its tributaries near Ipoh city in Malaysia is investigated using geochemical and isotopic signatures and geochemical modeling. Analysis of water, sediment, suspended particulate matter, and rock samples reveals that stream waters close to the heavy mineral processing plant site are anthropogenically influenced, as indicated by slightly low pH (4.98-6.24) and elevated concentrations of Fe (up to 129 mg/L), Cl- (1540 mg/L), total REEs (1580 mu g/L), U (17.2 mu g/L), and Th (0.33 mu g/L). REE patterns and Pb isotope ratios of waters and sediments from a tributary are similar to those of tailings pond seepage and sediments, suggesting that not only these elements but also U and Th are derived from heavy mineral processing. The delta Fe-56 values of water in the tributary decrease downstream, accompanied by a decrease in Fe concentration, which is likely due to isotope fractionation via oxidative precipitation of Fe hydroxides. The concentrations of REEs, U, and Th decrease downstream, accompanied by an increase in pH, with different removal factors (Th > U > REEs). The influence of contamination is confined to within similar to 1.5 km downstream of the source. Tamm's acid oxalate extraction (to dissolve only low crystalline phases) showed that Th and Al concentrations were lower while U and Fe concentrations were higher in downstream suspended particulate samples, suggesting that Th and U may be removed by different mechanisms from stream water. The results of geochemical modeling suggest that Th precipitated as a solid phase, such as an intermediate between ThO2 and Th(OH)(4), with increasing stream water pH. In contrast, U may have been removed by adsorption onto Fe hydroxides, as supported by surface complexation modeling. The geochemical signatures and processes discussed in this study may be applicable for environmental assessment of REE processing. (C) 2017 Elsevier Ltd. All rights reserved.

Microstructural properties of hardened cement paste blended with coal fly ash, sugar mill lime sludge and rice hull ash
Einstine M. Opiso, Tsutomu Sato, Tsubasa Otake
Advances in Concrete Construction, 5, 3, 289, 301, Techno Press, 2017年06月01日, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, The synergistic interactions of supplementary cementitious materials (SCMs) with ordinary portland cement (OPC) in multi-blended systems could enhance the mechanical and durability properties of concrete and increase the amount of cement that can be replaced. In this study, the characteristics of the hydration products as well as paste microstructure of blended cement containing 20% coal fly ash, 10% rice hull ash and 10% sugar mill lime sludge in quaternary blended system was investigated. Portlandite content, hydration products, compressive strength, pore size distribution and microstructural architecture of hydrated blended cement pastes were examined. The quaternary blended cement paste showed lower compressive strength, reduced amount of Portlandite phases, and higher porosity compared to plain hardened cement paste. The interaction of SCMs with OPC influenced the hydration products, resulting to the formation of ettringite and monocarboaluminate phases. The blended cement paste also showed extensive calcium silicate hydrates and calcium aluminate silicate hydrates but unrefined compared to plain cement paste. In overall, the expected synergistic reaction was significantly hindered due to the low quality of supplementary cementitious materials used. Hence, pre-treatments of SCMs must be considered to enhance their reactivity as good quality SCMs can become limited in the future.

Effects of Glycine, Water, Ammonia, and Ammonium Bicarbonate on the Oligomerization of Methionine
Rui Huang, Yoshihiro Furukawa, Tsubasa Otake, Takeshi Kakegawa
ORIGINS OF LIFE AND EVOLUTION OF BIOSPHERES, 47, 2, 145, 160, SPRINGER, 2017年06月, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, The abiotic oligomerization of amino acids may have created primordial, protein-like biological catalysts on the early Earth. Previous studies have proposed and evaluated the potential of diagenesis for the amino acid oligomerization, simulating the formation of peptides that include glycine, alanine, and valine, separately. However, whether such conditions can promote the formation of peptides composed of multiple amino acids remains unclear. Furthermore, the chemistry of pore water in sediments should affect the oligomerization and degradation of amino acids and oligomers, but these effects have not been studied extensively. In this study, we investigated the effects of water, ammonia, ammonium bicarbonate, pH, and glycine on the oligomerization and degradation of methionine under high pressure (150 MPa) and high temperature conditions (175 A degrees C) for 96 h. Methionine is more difficult to oligomerize than glycine and methionine dimer was formed in the incubation of dry powder of methionine. Methionine oligomers as long as trimers, as well as methionylglycine and glycylmethionine, were formed under every condition with these additional compounds. Among the compounds tested, the oligomerization reaction rate was accelerated by the presence of water and by an increase in pH. Ammonia also increased the oligomerization rate but consumed methionine by side reactions and resulted in the rapid degradation of methionine and its peptides. Similarly, glycine accelerated the oligomerization rate of methionine and the degradation of methionine, producing water, ammonia, and bicarbonate through its decomposition. With Gly, heterogeneous dimers (methionylglycine and glycylmethionine) were formed in greater amounts than with other additional compounds although smaller amount of these heterogeneous dimers were formed with other additional compounds. These results suggest that accelerated reaction rates induced by water and co-existing reactive compounds promote the oligomerization of less reactive amino acids during diagenesis and enhance the formation of peptides composed of multiple amino acids.

A novel method for remediation of nickel containing wastewater at neutral conditions
Haruko Hase, Toru Nishiuchi, Tsutomu Sato, Tsubasa Otake, Tsuyoshi Yaita, Tohru Kobayashi, Tetsuro Yoneda
JOURNAL OF HAZARDOUS MATERIALS, 329, 49, 56, ELSEVIER SCIENCE BV, 2017年05月, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, Heavy metals contained in wastewater are generally removed by adding antalkaline to increase the pH, and Ni is commonly precipitated as Ni-hydroxides at pH 10. However, a more sustainable remediation method of treatment at neutral conditions would be attractive due to the high cost of chemical reagents and inefficient treatment at present. Based on natural attenuation, the method of adding Al ions has been used in wastewater treatment to precipitate layered double hydroxides (LDH). Here, we investigated the use of Al ion addition in the Ni containing wastewater treatment, experimentally and thermodynamically. By co-precipitation experiments adding Al ions to Ni-containing water, Ni was selectively incorporated into the structure of LDH, and the removal efficiency of Ni was close to 100% even in pH 7 and 8 samples (lower pH than conventional methods) with initial Ni concentrations of 200-10,000 mg/L. Geochemical modeling results replicate the experimental results well when the Al/Ni ratio of LDH is assumed to be 0.33. This model makes it possible to estimate the amount of Al ions and additive agents necessary for use in treatment of wastewater containing different Ni concentrations. (C) 2017 Elsevier B.V. All rights reserved.

5-year chemico-physical evolution of concrete-claystone interfaces, Mont Terri rock laboratory (Switzerland)
Urs Mader, Andreas Jenni, Catherine Lerouge, Stephane Gaboreau, Satoru Miyoshi, Yukinobu Kimura, Veerle Cloet, Masaaki Fukaya, Francis Claret, Tsubasa Otake, Masahito Shibata, Babara Lothenbach
SWISS JOURNAL OF GEOSCIENCES, 110, 1, 307, 327, SPRINGER BASEL AG, 2017年04月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, The Cement-Opalinus Clay Interaction (CI) Experiment at the Mont Terri rock laboratory is a long-term passive diffusion-reaction experiment between contrasting materials of relevance to engineered barrier systems/near-field for deep disposal of radioactive waste in claystone (Opalinus Clay). Reaction zones at interfaces of Opalinus Clay with two different types of concrete (OPC and "low-pH"/ESDRED) were examined by sampling after 2.2 and 4.9 years. Analytical methods included element mapping (SEM, EPMA), select spot analysis (EDAX), C-14-MMA impregnation for radiography, and powder methods (IR, XRD, clay-exchanger characterisation) on carefully extracted miniature samples (mm). The presence of aggregate grains in concrete made the application of all methods difficult. Common features are a very limited extent of reaction within claystone, and a distinct and regularly zoned reaction zone within the cement matrix that is more extensive in the low-alkali cement (ESDRED). Both interfaces feature a de-calcification zone and overprinted a carbonate alteration zone thought to be mainly responsible for the observed porosity reduction. While OPC shows a distinct sulphate enrichment zone (indicative of ingress from Opalinus Clay), ESDRED displays a wide Mg-enriched zone, also with claystone pore-water as a source. A conclusion is that substitution of OPC by low-alkali cementitious products is not advantageous or necessary solely for the purpose of minimizing the extent of reaction between claystone and cementitious materials. Implications for reactive transport modelling are discussed.

低温熱水環境下でのクロムスピネルの合成実験と電子顕微鏡による観察
西方 美羽, 大友 陽子, 大竹 翼, 木村 勇気, 川本 大祐, 佐藤 努
日本地球化学会年会要旨集, 64, 310, 310, 一般社団法人日本地球化学会, 2017年
日本語,

縞状鉄鉱層中のクロムのホスト鉱物はクロムスピネルであるがその起源は明らかになっていない。本研究では縞状鉄鉱層の初期沈殿物を模した鉄、クロム水酸化物を合成しフロースルー型実験装置を用いて二価鉄を含む150℃の熱水と1週間反応させた。生成物の固体分析の結果から主生成物がゲーサイトでありさらにスピネル鉱物が生成していることがわかった。さらにSEM分析ではスピネル様の結晶が観察でき、TEM分析からスピネル鉱物と同様の面間隔の値を持つクロムを含むスピネル様の粒子の凝集体が観察されたことからクロムスピネルが熱水実験により合成されたことが明らかになった。

Adsorption and Post Adsorption Behavior of Schwertmannite with Various Oxyanions　　　　　　　　　　　　　　　
K. Khamphila, R. Kodama, T. Sato, T. Otake
Journal of Minerals and Materials Characterization and Engineering, 5, 90, 106, 2017年, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）

Cerium removal by activated carbon derived from palm kernel shell　　　　　　　　　　　　　　　
C.-H. Ooi, A. Ito, T. Otake, F.-Y. Yeoh
Advanced Materials Letters, 8, 2, 145, 149, 2017年, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）

Kinetics of Fe3+ mineral crystallization from ferrihydrite in the presence of Si at alkaline conditions and implications for nuclear waste disposal
Paul Clarence M. Francisco, Tsutomu Sato, Tsubasa Otake, Takeshi Kasama
AMERICAN MINERALOGIST, 101, 9-10, 2057, 2069, MINERALOGICAL SOC AMER, 2016年09月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, Fe3+ minerals are ubiquitous in diverse near-surface environments, where they exert important controls on trace species transport. In alkaline environments such as the glass-steel interface in geological high-level radioactive waste disposal sites that use cement for plugging and grouting, Fe minerals are closely associated with Si that may affect their crystallization behavior as well as their capacities to regulate hazardous element cycling. While it is well known that Si retards Fe mineral crystallization, there is currently an overall lack of quantitative information on the rates of crystallization of stable Fe minerals in the presence of Si at alkaline conditions. Crystallization of Fe3+ minerals goethite and hematite from ferrihydrite co-precipitated with different amounts of Si was studied at pH 10 and at temperatures ranging from 50 to 80 degrees C using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Mineral abundances evaluated from Rietveld refinement of XRD data show that the proportion of goethite in the final assemblage decreases relative to hematite with increasing Si. TEM observation of goethite and hematite crystals formed in the presence of Si show significant morphological differences compared to those formed in the absence of Si. Rate constants for crystallization derived from fitting of time-dependent changes in mineral abundances with the Avrami equation show a decreasing trend with increasing Si for both goethite and hematite. Apparent activation energies for crystallization for both minerals increase with increasing Si, with that of goethite increasing more drastically compared to hematite, indicating the inhibitive effect of Si on the crystallization of both minerals. The overall inhibition of crystallization may be explained in terms of the effects of Si on the surface properties of the ferrihydrite precursor. The rate constants and apparent activation energies reported in this study may be useful in estimating the crystallization behavior and timescales of Fe minerals in both natural and engineered environments. This information may eventually be helpful in predicting the fate of hazardous elements in such environments.

Effect of octahedrally coordinated aluminum ions on the uptake of Au(III) chloro-hydroxy complexes in Al–Si systems
Otake, T, Yokoyama, T, Francisco, P. C. M, Watanabe, K
Geochemical Journal, 49, 4, 343, 350, GEOCHEMICAL SOC JAPAN, 2015年, ［査読有り］, ［筆頭著者, 責任著者］, ［国際誌］
英語, 研究論文（学術雑誌）, The uptake of Au(III) complexes (initial [Au] = 25 mu mol.dm(-3)) by Al-Si-bearing precipitates formed by the hydrolysis of aluminum ions (initial [Al] = 0.04 mol.din(-3)) in the presence of either solid silica or aqueous silicic acid was investigated at pH 6.0, [Cl-] = 0.24 mol.dm(-3), and ambient temperature. A maximum of 40% of the total quantity of Au(III) complexes present in solution was sorbed onto the precipitate after 24 h in the absence of silica. Both solid silica and silicic acid inhibited the gold uptake, and silicic acid was a more effective inhibitor. Analyses of the solids showed that the fraction of octahedrally coordinated aluminum decreased as the bulk atomic Si/Al ratio in the solid increased. This decrease was more rapid in the presence of silicic acid than solid silica owing to the more efficient incorporation of aluminum into the silica structure. The zeta potential of the precipitates decreased as the fraction of octahedrally coordinated aluminum decreased and the atomic Si/Al ratio increased. The gold uptake decreased as the zeta potential of the precipitates decreased, suggesting that negatively charged Au(III) complexes were sorbed on the precipitates via electrostatic interactions. Our findings suggest that the octahedrally coordinated aluminum determined the quantity of the gold uptake by governing the positive charge on the precipitate surface. In addition, desorption was promoted by the presence of solid silica after 5 h, suggesting that silica may promote the release of Au(III) chloro-hydroxy complexes as well as other negatively charged metal complexes from aluminum oxides or iron oxides in soil or sediment.

南アフリカ・バーバトン地域ムーディーズ層群中の縞状鉄鉱層中におけるクロム濃集の空間的広がり
石川 宏, 大竹 翼, 川井 洋二, 佐藤 努, 掛川 武
日本地球化学会年会要旨集, 61, 127, 127, 日本地球化学会, 2014年
日本語, 地球表層の酸化は酸素発生型光合成細菌の出現が原因であると考えられているが、その進化時期と初期地球表層環境の変遷については明らかになっていない。主に先カンブリア時代に産出する縞状鉄鉱層の微量元素や同位体組成は、形成当時の海洋溶存成分を反映していると考えられ、初期地球表層環境の推定に用いられてきた。本研究の目的は，南アフリカ・バーバトン地域において主に浅海性堆積岩から構成されるムーディーズ層群中の約32億年前に形成した縞状鉄鉱層中で発見されたクロム濃集の空間的広がりを明らかにすることである。そのため、バーバトンから南西に10kmほどに位置する、先行研究においてクロム濃集がみられたMoodise Hills (MH)および北東に10kmほどに位置するEureka synclineにあるGate of Paradise (GP)において調査を行った。

鉄・マンガン堆積岩中のレアアースパターンと鉄同位体比から推定される黒鉱鉱床形成後の堆積環境の変遷
大竹 翼, 鈴木 陵平, 山田 亮一, 申 基澈, 昆 慶明, 佐藤 努
日本地球化学会年会要旨集, 61, 8, 8, 日本地球化学会, 2014年
日本語, 本研究では，黒鉱鉱床のような大規模塊状硫化物鉱床の形成要因と当時の海洋環境の関係性をレアアースパターンと鉄安定同位体比を用いて調べた。黒鉱形成後に堆積した鉄に富む化学堆積岩には、レアアースパターンがCeの負異常を示し，また大きな鉄の同位体分別を示すものが存在することから，当時の海洋は酸化還元環境に関して成層化していたと考えられる。このことは，大規模塊状硫化物鉱床の形成において還元的な海洋環境が重要な要因の一つであることを示唆している。

Mineral Synthesis in Si–Al–Ca Systems and Their Iodide Sorption Capacity under Alkaline Conditions
X. Liu, A. Asai, T. Sato, E. Opiso, T. Otake, T. Yoneda
Water, Air, & Soil Pollution, 224, 3, 1442, SPRINGER, 2013年03月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, The release of anionic nuclides such as I-129 from underground nuclear waste disposals is of great environmental concern due to its long half-life and high mobility in alkaline environments. The leachability of iodide is largely dependent on the sorption capacity of various Ca-bearing minerals such as ettringite, hydrocalumite, and calcium silicate hydrate (C-S-H) which are common hydration products of cement materials. Moreover, the pore water chemistry of cement materials is dominated by Si, Al, and Ca during the initial stage of weathering, and the ratios of the ions present vary much depending on the source materials. Examining the mineral phases generated in Si-Al-Ca systems with respect to different ratios of Si, Al, and Ca and their interaction with iodide is important to better understand the sorption behavior of iodide in nuclear waste disposal facilities. In this study, the mineral synthesis in Si-Al-Ca systems was conducted under alkaline conditions at ambient temperature, and the sorption behavior of iodide with the mineral phases was investigated during and after the mineral formation. The results showed that portlandite, C-S-H, stratlingite (CASH), hydrocalumite, gibbsite, and amorphous compounds were precipitated from the systems, depending on the Si, Al, and Ca ratios. The K-d values of iodide were greatly affected by the Ca content and relatively high Ca-containing phases such as hydrocalumite, C-S-H, CASH, and portlandite showed high iodide retention capacity. Hence, ensuring the formation of these secondary minerals by modification of the chemical composition of cement materials could assist in safety design of nuclear waste disposals.

高アルカリ環境における圧縮ベントナイト中のシリカ鉱物の溶解 : X線CT観察および地球化学モデリングによる定量的評価
中林亮, 木嶋達也, 塚田康元, 佐藤努, 大竹翼, 金子勝比古, 米田哲郎
粘土科学, 52, 1, 9, 22, 一般社団法人 日本粘土学会, 2013年, ［査読有り］, ［国内誌］
日本語, 研究論文（学術雑誌）, Dissolution rates of montmorillonite in bentonite under hyperalkaline conditions have been obtained to evaluate the long-term performance of engineered barriers for radioactive waste disposal. The saturation state of pore water with respect to montmorillonite in bentonite has been demonstrated as an important factor controlling montmorillonite dissolution rate. Pore water chemistry including the saturation state may be significantly affected by the dissolution of accessory minerals in bentonite. The bentonite "Kunigel V1", which is being considered for use in radioactive disposal barriers in Japan, actually contains a large amount (〜50 %) of accessory silica minerals, such as chalcedony and quartz. Dissolution of the silica minerals may inhibit the dissolution of montmorillonite in the bentonite by increasing the silica concentration and hence the saturation state with respect to montmorillonite in the pore water. Therefore, the objectives of this study are to examine the dissolution kinetics of the silica minerals and the effect of dissolved silica on the dissolution of montmorillonite in a compacted bentonite using X-ray computed tomography (CT) and geochemical modeling. Advective alteration experiments of a compacted bentonite (Kunigel V1) with a dry density of 0.3 Mg/m^3 was conducted with 0.3M NaOH solution at 70℃ for 360 days. X-ray CT images, which were taken every 10 days, showed that the volume of a light colored material decreased as the interaction between the bentonite and hyperalkaline-fluid progressed during the experiments. This is attributed to the dissolution of accessory silica minerals in the bentonite. XRD analyses of altered bentonite after the experiments identified that the accessory mineral was mainly chalcedony. The kinetic data for dissolution of chalcedony was obtained by developing the methodology to quantify the volume of accessory minerals in the CT images. These results showed that chalcedony was almost completely dissolved in the area close to the fluid input within 80 days. The geochemical transport model consistent with the experimental results indicates that the pore water in the bentonite became near saturation with respect to montmorillonite due to the dissolution of silica minerals in bentonite, inhibiting the dissolution of montmorillonite in bentonite. The model also indicates that the inhibition of montmorillonite dissolution will not be sustained beyond the experimental duration under the same experimental conditions. However, a compacted bentonite with higher dry density such as 1.6 Mg/m^3, where diffusion is the dominant mass transport mechanism, has been considered for use in actual radioactive disposal barriers in Japan. In the much more compacted bentonite system, dissolution of montmorillonite will be inhibited for a much longer term. Therefore, it is important to consider the dissolution behavior of silica minerals to sufficiently evaluate the long-term performance of bentonite as a component of engineered barriers for radioactive waste disposal.

Abiotic Formation of Valine Peptides Under Conditions of High Temperature and High Pressure
Yoshihiro Furukawa, Tsubasa Otake, Takato Ishiguro, Hiromoto Nakazawa, Takeshi Kakegawa
ORIGINS OF LIFE AND EVOLUTION OF BIOSPHERES, 42, 6, 519, 531, SPRINGER, 2012年12月, ［査読有り］, ［国際誌］
英語, 研究論文（学術雑誌）, We investigated the oligomerization of solid valine and the stabilities of valine and valine peptides under conditions of high temperature (150-200 A degrees C) and high pressure (50-150 MPa). Experiments were performed under non-aqueous condition in order to promote dehydration reaction. After prolonged exposure of monomeric valine to elevated temperatures and pressures, the products were analyzed by liquid chromatography mass spectrometry comparing their retention times and masses. We identified linear peptides that ranged in size from dimer to hexamer, as well as a cyclic dimer. Previous studies that attempted abiotic oligomerization of valine in the absence of a catalyst have never reported valine peptides larger than a dimer. Increased reaction temperature increased the dissociative decomposition of valine and valine peptides to products such as glycine, beta-alanine, ammonia, and amines by processes such as deamination, decarboxylation, and cracking. The amount of residual valine and peptide yields was greater at higher pressures at a given temperature, pressure, and reaction time. This suggests that dissociative decomposition of valine and valine peptides is reduced by pressure. Our findings are relevant to the investigation of diagenetic processes in prebiotic marine sediments where similar pressures occur under water-poor conditions. These findings also suggest that amino acids, such as valine, could have been polymerized to peptides in deep prebiotic marine sediments within a few hundred million years.

2011年度 資源地質学会若手会秋季巡検ー秋田圏北鹿地域の黒鉱鉱床と火山岩ー
長谷川樹, 山田亮一, 大竹翼, 野崎達夫
資源地質, 62, 3, 249, 257, The Society of Resource Geology, 2012年, ［招待有り］, ［国内誌］
日本語, 研究論文（学術雑誌）

Stability of Amino Acids and Their Oligomerization Under High-Pressure Conditions: Implications for Prebiotic Chemistry
Tsubasa Otake, Takashi Taniguchi, Yoshihiro Furukawa, Fumio Kawamura, Hiromoto Nakazawa, Takeshi Kakegawa
ASTROBIOLOGY, 11, 8, 799, 813, MARY ANN LIEBERT INC, 2011年10月, ［査読有り］, ［筆頭著者, 責任著者］, ［国際誌］
英語, 研究論文（学術雑誌）, The polymerization of amino acids leading to the formation of peptides and proteins is a significant problem for the origin of life. This problem stems from the instability of amino acids and the difficulty of their oligomerization in aqueous environments, such as seafloor hydrothermal systems. We investigated the stability of amino acids and their oligomerization reactions under high-temperature (180-400 degrees C) and high-pressure (1.0-5.5 GPa) conditions, based on the hypothesis that the polymerization of amino acids occurred in marine sediments during diagenesis and metamorphism, at convergent margins on early Earth. Our results show that the amino acids glycine and alanine are stabilized by high pressure. Oligomers up to pentamers were formed, which has never been reported for alanine in the absence of a catalyst. The yields of peptides at a given temperature and reaction time were higher under higher-pressure conditions. Elemental, infrared, and isotopic analyses of the reaction products indicated that deamination is a key degradation process for amino acids and peptides under high-pressure conditions. A possible NH(3)-rich environment in marine sediments on early Earth may have further stabilized amino acids and peptides by inhibiting their deamination.

硫黄同位体から読み取る太古代地球の表層環境：現状とその問題点
大竹翼, 渡辺由美子
地球化学, 45, 4, 251, 264, 日本地球化学会, 2011年, ［査読有り］, ［招待有り］, ［筆頭著者, 責任著者］, ［国内誌］
日本語, 研究論文（学術雑誌）, Since the discovery of Anomalous Isotope Fractionation (AIF) of sulfur, or more commonly termed Mass-Independent Fractionation (MIF) of sulfur, in many sedimentary rocks older than 2.45Ga, and its virtual absence in younger rocks, the AIF record has been cited by many researchers as unequivocal evidence for a dramatic change from an anoxic to oxic atmosphere around 2.45Ga. However, multiple sulfur isotope data from these natural samples have been interpreted based on the assumption that sulfur chemistry in gas phase is only responsible for AIF of sulfur in nature. The objective of this review is to evaluate this assumption. First, results of ab initio calculations for equilibrium isotope exchange between S-bearing species show that deviations from the mass-dependent relationships during equilibrium processes are much smaller than those found in Archean sedimentary rocks. Consequently, AIF requires a property that is a discontinuous function of mass (e.g., nuclear volume, magnetic moment, asymmetry of molecules, isotopic abundance). The number of bound states may be another discontinuous function of mass, which fractionates S isotopes anomalously during chemisorption at a high temperature (e.g., >100℃). A recent experimental study also showed that thermochemical sulfate reduction by simple amino acids produces AIF of sulfur. These results suggest that an alternative process, such as reactions between organic matter in sediments and sulfate-rich hydrothermal solutions, may have caused AIF signatures of sulfur in Archean sedimentary rocks.

バリン重合反応に対する圧力の影響
古川 善博, 大竹 翼, 中沢 弘基, 掛川 武
日本地球化学会年会要旨集, 58, 55, 55, 日本地球化学会, 2011年
初期地球におけるアミノ酸の重合反応は、生命誕生に至る重要な一段階と考えられている。これまでの研究の多くは、初期地球のアミノ酸の重合反応は干潟や海底熱水噴出孔付近で起こるという提案に基づき、研究が行われてきた。これらの環境を模擬した実験ではアミノ酸の重合が確認されているが、その重合度は低く、さらに、これらの環境では場合によってアミノ酸の光化学分解または熱分解が卓越することが問題視されている。近年、このような問題に対して、アミノ酸の重合が初期地球の海洋堆積物内の高温高圧低含水率環境で起こるという提案がなされ、研究が行われている。本研究はこのような仮説に基づき、特に、アミノ酸重合反応に対する圧力の影響を明らかにする。海洋堆積物内の高温高圧低含水率環境を模擬し、アミノ酸の重合反応を研究するため、アミノ酸（バリン）を金カプセルに封入し、高温高圧環境（150-200°C、50-150 MPa）で長時間反応させた（0-192時間）。回収試料中のペプチドは液体クロマトグラフィー質量分析（LC/MS）を用いて、残存アミノ酸と副生成物は液体クロマトグラフィー（HPLC; OPA誘導体化）を用いて分析を行った。実験試料から検出されたペプチドは2-6量体の直鎖ペプチドと環状2量体であった。この他に、バリンの分解に伴ってグリシン、β-アラニン、アンモニア、メチルアミン、エチルアミンも検出された。バリンの分解率は反応時間、反応温度とおともに上昇した。一定の温度(200°C)、24時間反応条件では、バリンの残存率は高く(~80%)、圧力に影響されない、また、バリンペプチドの収率は圧力とともに減少することが明らかになった。一方、一定の温度(200°C)、192時間反応条件では、バリンの残存率は低く(0.2–2%)、バリン残存率およびバリンペプチド収率は圧力とともに上昇することが明らかになった。副生成物であるグリシン、β-アラニン、アンモニア、メチルアミン、エチルアミンの生成はバリンの分解反応が脱ガス反応であることを示唆している。このことは、バリンの分解率が高い反応時間において圧力がバリンの分解を抑制したことと整合的である。このことから、圧力が脱ガス反応を抑制し、バリンとバリンペプチドの安定性を向上させたことによりバリンペプチドを生成する脱水重合反応（非脱ガス反応）、が促進され高収率のペプチド生成に至ったと考えられる。これらの結果は、初期地球の海洋堆積物深部環境において、脱水反応を促進する低含水率だけでなく、圧力もペプチド生成に貢献することを示唆する。また、これらの結果はグリシンやアラニンの先行研究とも整合的である。

高温高圧条件下における固体アミノ酸の安定性と重合反応
大竹 翼, 谷口 尚, 古川 善博, 中沢 弘基, 掛川 武
日本地球化学会年会要旨集, 58, 120, 120, 日本地球化学会, 2011年
本研究では，幅広い温度 (180-400度)・圧力 (1-5.5 GPa) 条件下でアミノ酸の重合実験を行い，生命の起源に必要なアミノ酸の安定性及び重合反応に対する温度・圧力の影響を実験的に調べることを目的とした．その結果，同じ温度条件下では，アミノ酸はより高圧下では長時間存在できていた．また，生成したペプチドの量もより高圧下で多くなることが明らかになった．アラニンが触媒を用いずに単量体から５量体まで重合した例は，本研究が初めてである．本研究によって，高圧下ではアミノ基の安定性がアミノ酸の安定性に大きく関わっている事が明らかとなり，冥王代の海洋堆積物中において，周囲のアンモニア濃度がアミノ酸の安定性に関係することが示唆された．

秋田県北鹿地域に産する泥岩(15-10Ma)中の 黄鉄鉱の産状から推定される古日本海低層環境変動
遠藤 美里, 山田 亮一, 大竹 翼, 掛川 武
日本地球化学会年会要旨集, 58, 95, 95, 日本地球化学会, 2011年
黒鉱鉱床を多く胚胎する秋田県北鹿地域は、鉱床形成時に海底近傍が無酸素状態であったという報告がある。本研究では、北鹿地域の黒鉱形成前後（15から10Ma）の連続した時間軸の中で古日本海に堆積した泥岩を研究対象とし、北鹿海盆低層の環境変動と微生物活動の関係を考察することを目的とした。黒鉱形成とほぼ同時期に堆積した泥岩中のフランボイダル黄鉄鉱は、その平均直径及び標準偏差が小さかった。フランボイダル黄鉄鉱は堆積物直上の海洋環境によってサイズ分布が異なると知られていることから、黒鉱形成時には北鹿海盆低層がeuxinicな海洋であり、広域的に硫化水素に富んだ低層水が分布していたと考えられる。また、黒鉱形成とほぼ同時期に堆積した泥岩中の黄鉄鉱の硫黄安定同位体比は非常に軽い値を示したことから、硫化水素生成は、黒鉱形成時であっても無酸素海洋中で活動していた硫酸還元菌によるものであり、海底熱水からの寄与は少ないことが見いだされた。

Mechanisms of iron oxide transformations in hydrothermal systems
Tsubasa Otake, David J. Wesolowski, Lawrence M. Anovitz, Lawrence F. Allard, Hiroshi Ohmoto
GEOCHIMICA ET COSMOCHIMICA ACTA, 74, 21, 6141, 6156, PERGAMON-ELSEVIER SCIENCE LTD, 2010年11月, ［査読有り］, ［筆頭著者, 責任著者］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, Coexistence of magnetite and hematite in hydrothermal systems has often been used to constrain the redox potential of fluids, assuming that the redox equilibrium is attained among all minerals and aqueous species. However, as temperature decreases, disequilibrium mineral assemblages may occur due to the slow kinetics of reaction involving the minerals and fluids. In this study, we conducted a series of experiments in which hematite or magnetite was reacted with an acidic solution under H(2)-rich hydrothermal conditions (T = 100-250 degrees C, P(H2) = 0.05-5 MPa) to investigate the kinetics of redox and non-redox transformations between hematite and magnetite, and the mechanisms of iron oxide transformation under hydrothermal conditions. The formation of euhedral crystals of hematite in 150 and 200 degrees C experiments, in which magnetite was used as the starting material, indicates that non-redox transformation of magnetite to hematite occurred within 24 h. The chemical composition of the experimental solutions was controlled by the non-redox transformation between magnetite and hematite throughout the experiments. While solution compositions were controlled by the non-redox transformation in the first 3 days in a 250 degrees C experiment, reductive dissolution of magnetite became important after 5 days and affected the solution chemistry. At 100 degrees C, the presence of maghemite was indicated in the first 7 days. Based on these results, equilibrium constants of non-redox transformation between magnetite and hematite and those of non-redox transformation between magnetite and maghemite were calculated. Our results suggest that the redox transformation of hematite to magnetite occurs in the following steps: (1) reductive dissolution of hematite to Fe((aq))(2+) and (2) non-redox transformation of hematite and Fe((aq))(2+) to magnetite. (C) 2010 Elsevier Ltd. All rights reserved.

Primary haematite formation in an oxygenated sea 3.46 billion years ago
Masamichi Hoashi, David C. Bevacqua, Tsubasa Otake, Yumiko Watanabe, Arthur H. Hickman, Satoshi Utsunomiya, Hiroshi Ohmoto
NATURE GEOSCIENCE, 2, 4, 301, 306, NATURE PUBLISHING GROUP, 2009年04月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, The timing of the origin of photosynthesis on the early Earth is greatly debated. It is generally agreed, on the basis of the presence of biological molecules found in shales from the Hamersley Basin, Australia, that oxygenic photosynthesis had evolved 2.7 billion years (Gyr) ago. However, whether photosynthesis occurred before this time remains controversial. Here we report primary haematite crystals and associated minerals within the marine sedimentary rocks preserved in a jasper formation of the Pilbara Craton, Australia, which we interpret as evidence for the formation of these rocks in an oxygenated water body 3.46 Gyr ago. We suggest that these haematite crystals formed at temperatures greater than 60 degrees C from locally discharged hydrothermal fluids rich in ferrous iron. The crystals precipitated when the fluids rapidly mixed with overlying oxygenated sea water, at depths greater than 200m. As our findings imply the existence of noticeable quantities of molecular oxygen, we propose that organisms capable of oxygenic photosynthesis evolved more than 700 million years earlier than previously recognized, resulting in the oxygenation of at least some intermediate and deep ocean regions.

Ab initio calculations for equilibrium fractionations in multiple sulfur isotope systems
Tsubasa Otake, Antonio C. Lasaga, Hiroshi Ohmoto
CHEMICAL GEOLOGY, 249, 3-4, 357, 376, ELSEVIER SCIENCE BV, 2008年04月, ［査読有り］, ［筆頭著者, 責任著者］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, Ab initio calculations of vibrational frequencies (v), reduced partition function ratios (0) of various gaseous and aqueous sulfur-bearing compounds, and isotopic fractionation factors (a) between them were performed on the multiple isotope systems using the Hartree-Fock (HF) and the Becke three-parameter Lee-Yang-Parr (B3LYP) density functional methods. Based on the comparison of the geometry, vibrational frequencies, and fractionation factors with those determined experimentally, the HF/6-31G(d) was chosen as the optimal method for the sulfur isotope systems. The results of computation for multiple sulfur fractionation factors indicate that the mass-dependent relationships, i.e., ((33)alpha - 1)/((34)alpha - 1) and ((36)alpha - 1)/((34)alpha - 1) values, converge only at high temperature (e.g., T>500 degrees C) to 0.515 and 1.89, respectively, which are the values previously derived from the Bigeleisen-Mayer approximations. However, they significantly deviate from these values with decreasing temperature, and depending on the sulfur species pairs that are involved in equilibrium isotope exchange reactions. The ((33)alpha- 1)/((34)alpha - 1) values and the ((36)alpha - 1)/ ((34)alpha- 1) values range from 0.505 to 0.517 and from 1.88 to 1.96, respectively, at 0 degrees C.
An isotopic crossover relationship, in which the fractionation factor changes from > 1.0 to < 1.0 (or from < 1.0 to > 1.0) about a specific temperature (i.e., crossover temperature), was observed in several species couples (e.g., S-2-H2S, S-8-H2S, CS2-H2S, SO3-SO4(aq)2-). Since the crossover temperatures vary among different isotope molecules, large changes in the ((33)alpha -1)/((34)alpha - 1) and ((36)alpha - 1)/((34)alpha - 1) values (e.g., > 1 to <0) also occur near the crossover temperatures.
The effects of solvation on the fractionation factors were investigated using the PCM models. The dielectric constant (P) of solvent, which is the dominant solvent characteristic, affects the fractionation factors between gaseous and aqueous species (e.g., SO2(g) and SO2(aq)), but the effect levels out for epsilon > 20. Among the solvent models, the IEF-PCM model yields the greatest fractionation factors between gaseous and aqueous species.
Overall, temperature, harmonic frequency, and mass of atoms bonded to sulfur (M are the three important parameters affecting the reduced partition function ratios, fractionation factors, and mass-dependent relationships. By decreasing temperature and increasing frequency and mass, the 1000((34)beta - 1) values increase and the ((33)beta - 1)/((34)beta - 1) values decrease (i.e., deviate from "expected" 0.515). The ((33)beta - 1)/((34)beta - 1) values converge to 0.516 only at higher temperature (e.g., T>600 degrees C), lower frequency (omega(e) <500 cm(-1)), and smaller mass (M<7 amu) and become as low as 0.503 at T=50 degrees C, omega(e) = 2500 cm(-1), and M=56 amu. (C) 2008 Elsevier B.V All rights reserved.

Anomalous fractionation of sulfur isotopes during heterogeneous reactions
Antonio C. Lasaga, Tsubasa Otake, Yumiko Watanabe, Hiroshi Ohmoto
EARTH AND PLANETARY SCIENCE LETTERS, 268, 1-2, 225, 238, ELSEVIER SCIENCE BV, 2008年04月, ［査読有り］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, Applying square adsorption-well and Morse potential models for the adsorption of a sulfur specie on a solid surface, we have evaluated the fractionation of four sulfur isotopes (S-32, S-33, S-34 and S-36) during chemisorption reactions. Heterogeneous reactions between solid and aqueous (or gaseous) species are found to produce anomalous fractionations of sulfur isotopes when the adsorption energy is small (<0.3 eV; 30 kJ/mol) and a discontinuity occurs in the number of bound energy levels of different sulfur isotopes. We refer to "anomalous sulfur isotope fractionation" when the Delta S-33 and (33)theta' (approximate to delta S-33/delta S-34) values of a sample fall outside of 0 +/- 0.2 parts per thousand and 0.51 +/- 0.01 parts per thousand, respectively, and/or when the Delta S-36 and (33)theta' (approximate to delta S-36/delta S-34) values of a sample fall outside of 0 +/- 0.4 parts per thousand and 1.9 +/- 0.1 parts per thousand, respectively. The magnitude of anomalous sulfur isotope effects during a heterogeneous reaction increases with increasing temperature. Depending on the values of chernisorption energy and bond strength, the delta S-33, delta S-34, delta S-36, Delta S-33 and Delta S-36 values of chernisorption products may be as variable as those observed in Archean sedimentary rocks.
Ab initio calculations for SO2 adsorption on a kerogen surface indicate the possibility of creating anomalous isotope signatures for the adsorbed species, such as: delta S-33/delta S-34 approximate to 1.08, delta S-36/delta S-34 approximate to 0.84, Delta S-33 = 7.0 to 13.parts per thousand, and Delta S-36= -13.0 to -25.2 parts per thousand in a temperature range of 0 to 200 degrees C) the magnitude of Delta S-33 and Delta S-36 increase with increasing temperature. These data, together with various geochemical data (e.g., organic C and sulfide S contents; hydrothermal alteration effects) on Archean sedimentary rocks with anomalous sulfur isotope fractionations, suggest that the anomalous sulfur isotope signatures in such rocks may have been created by heterogeneous reactions between organic matter (+ minerals) and sulfur-bearing aqueous solutions under hydrothermal conditions, rather than by UV photolysis of volcanic SO2 in an O-2-poor atmosphere. (C) 2008 Elsevier B.V. All rights reserved.

Experimental evidence for non-redox transformations between magnetite and hematite under H-2-rich hydrothermal conditions
Tsubasa Otake, David J. Wesolowski, Lawrence M. Anovitz, Lawrence F. Allard, Hiroshi Ohmoto
EARTH AND PLANETARY SCIENCE LETTERS, 257, 1-2, 60, 70, ELSEVIER SCIENCE BV, 2007年05月, ［査読有り］, ［筆頭著者, 責任著者］, ［国際共著］, ［国際誌］
英語, 研究論文（学術雑誌）, Transformations of magnetite ((FeFe2O4)-Fe-II-O-III) to hematite ((Fe2O3)-O-III) (and vice versa) have been thought by many scientists and engineers to require molecular O-2 and/or H-2. Thus, the presence of magnetite and/or hematite in rocks has been linked to a specific oxidation environment. However, the availability of reductants or oxidants in many geologic and industrial environments appears to have been too low to account for the transformations of iron oxides through redox reactions. Here, we report the results of hydrothermal experiments in mildly acidic and H-2-rich aqueous solutions at 150 degrees C, which demonstrate that transformations of magnetite to hematite, and hematite to magnetite, occur rapidly without involving molecular O-2 or H-2:
Fe3O4(Mt) + 2H((aq))(+) <-> Fe2O3 (Hm) + Fe-(aq)(2+) + H2O
The transformation products are chemically and structurally homogeneous, and typically occur as euhedral single crystals much larger than the precursor minerals. This suggests that, in addition to the expected release of aqueous ferrous species to solution, the transformations involve release of aqueous ferric species from the precursor oxides to the solution, which reprecipitate without being reduced by H-2. These redox-independent transformations may have been responsible for the formation of some iron oxides in natural systems, such as high-grade hematite ores that developed from Banded Iron Formations (BIFs), hematite-rich deposits formed on Mars, corrosion products in power plants and other industrial systems. (c) 2007 Elsevier B.V. All rights reserved.

Gold deposition in epithermal quartz-adularia veins: Experimental study on adsorption of gold on Al-Si systems　　　　　　　　　　　　　　　
Ohtake, T, Yokoyama, T, Uchida, A, Watanabe, K, Izawa, E
Proceedings of 11th International Association on the Genesis of Ore Deposits Symposium, 2002年, ［国際誌］
英語, 研究論文（国際会議プロシーディングス）

資源開発における環境負荷低減のための同位体研究　　　　　　　　　　　　　　　
大竹 翼, 同位体環境学がえがく世界：2020 年版, 2020年04月, ［筆頭著者］
日本語, 記事・総説・解説・論説等（その他）

岩石の風化と資源
大竹 翼, 季刊 資源と素材, 3, 3, 22, 23, 2018年09月, ［筆頭著者］
日本語, 記事・総説・解説・論説等（学術雑誌）, 11763384

可溶性シリカ共存下におけるMgO不溶化材によるホウ素の不溶化
野澤 笑子, 大竹 翼, 佐藤 努, 地下水・土壌汚染とその防止対策に関する研究集会講演集, 23, 314, 317, 2017年11月09日
[地盤工学会], 日本語

鉄鉱床は微生物が作った?　　　　　　　　　　　　　　　
大竹 翼, 季刊 資源と素材, 1, 2, 24, 25, 2016年06月, ［筆頭著者］
日本語

The Relationship Between Smectite/ Illite Ratios and Diagenetic History of Sandstone Reservoir, Batu Ayau Formation, Upper Kutai Basin, East Kalimantan, Indonesia　　　　　　　　　　　　　　　
T. Puji Astuti, S. Surjono, I. Warmada, D.P. Kusuma, Y. Tsukada, T. Otake, T. Sato, International Petroleum Technology Conference 2014, Kuala Lumpur Convention Center, Kuala Lumpur, Malaysia, 17895, 2014年12月
英語, 研究発表ペーパー・要旨（国際会議）

12 高温高圧環境下におけるアミノ酸の安定性と重合反応(一般講演,第36回学術講演会講演要旨集)
大竹 翼, 谷口 尚, 古川 善博, 中沢 弘基, 掛川 武, Viva origino, 39, 12, 12, 2011年
文部省科学研究費総合研究(B)「原始地球上における生命の起源に関する研究」班, 日本語

Stability of amino acids and peptides during diagenesis on the early Earth
T. Otake, T. Taniguchi, Y. Furukawa, H. Nakazawa, T. Kakegawa, GEOCHIMICA ET COSMOCHIMICA ACTA, 74, 12, A782, A782, 2010年06月
PERGAMON-ELSEVIER SCIENCE LTD, 英語, 研究発表ペーパー・要旨（国際会議）

Significance and challenges of the sustainable mining of Ni mineral resources
Tsubasa Otake
International Symposium on Chemical and Biological Hazards on One Health: Toward Sustainable Mineral Development and Pollution Monitoring, 2024年10月08日, 英語, 口頭発表（一般）
2024年10月08日 - 2024年10月09日, University of Botswana, Gaborone, ボツワナ共和国, 38572915, ［国際会議］

鉱山水処理施設におけるマンガン酸化物の沈殿メカニズム　　　　　　　　　　　　　　　
大竹 翼
グリーンレメディエーション研究会シンポジウム「休廃止鉱山のグリーン・レメディエーションと関連分野の最前線」, 2024年09月26日, 日本語, 口頭発表（招待・特別）
2024年09月26日 - 2024年09月26日, オンライン, 日本国, ［招待講演］, ［国内会議］

ニッケルラテライト鉱床における低結晶質ニッケルホスト鉱物の同定
大竹 翼, 大門 嵩泰, 菊池 亮佑, 佐藤 努
JpGU 2024, 2024年05月27日, 日本語, ポスター発表
2024年05月26日 - 2024年05月31日, 幕張メッセ, 日本国, 38572915, ［国内会議］

32億年前の浅海性縞状鉄鉱層における化学沈殿と初期続成作用によるFeとMg同位体分別
大竹 翼, 杉浦 遼平, 申基澈, 大友 陽子, 掛川 武, 佐藤 努
日本地球化学会第70回年会, 2023年09月21日, 日本語, 口頭発表（一般）
2023年09月21日 - 2023年09月23日, 27289727

Alteration patterns of host rocks in massive sulfide deposits that were possibly formed by subseafloor hydrothermal processes
T. Otake, A. Hoshi, K. Nakayama, T. Nozaki, R. Kikuchi, T. Sato
17th International Symposium on Water-Rock Interaction/14h Symposium on Applied Isotope Geochemistry, 2023年08月21日, 英語, ポスター発表
2023年08月18日 - 2023年08月22日, 仙台, 日本国, 44296638, ［国際会議］

Fe and Mg isotope fractionations in ferruginous sedimentary rocks from the ~3.2 Ga Moodies Group, Barberton Greenstone Belt, South Africa
T. Otake, R. Sugiura, K. Shin, Y. Ohtomo, T. Kakegawa, T. Sato
Goldschmidt 2023, 2023年07月13日, 英語, 口頭発表（一般）
2023年07月10日 - 2023年07月14日, Lyon, Frances, 27289727, ［国際会議］

低温蛇紋岩化反応における水素生成促進
大竹 翼, 菅原 あすか, 東野 駿太, 大友 陽子, 菊池 亮佑, 佐藤 努
JpGU 2023, 2023年05月23日, 日本語, ポスター発表
38572915, ［国内会議］

鉱床形成や環境影響理解のための安定同位体や微量元素の応用
大竹 翼
第4回『休廃止鉱山のグリーンレメディエーションと関連分野の最前線』, 2023年03月07日, 日本語, 口頭発表（招待・特別）
27289727, ［招待講演］, ［国内会議］

Formation of Ni-rich smectite in the Tagaung Taung Ni laterite deposit, Myanmar
Tsubasa Otake, Ayaka Murofushi, Takahiro Daimon, Ryosuke Kikuchi, Tsutomu Sato
Goldschmidt 2022, 2022年07月15日, 英語, 口頭発表（一般）
2022年07月11日 - 2022年07月15日, 11763384

Sustainable development of mineral resources in Indonesia
Tsubasa Otake
The 17th Hokkaido Indonesian Student Association Scientific Meeting 2022, 2022年07月11日, 英語, 口頭発表（招待・特別）
2022年07月11日 - 2022年07月11日, 27289727, ［招待講演］

高品位Niラテライト鉱石におけるホスト相同定のための逐次抽出法の改善
大竹 翼, 大門 嵩泰, 実松 健造, 高橋 嘉夫, 佐藤 努
JpGU 2022, 2022年06月02日, 日本語, ポスター発表
2022年05月23日 - 2022年06月03日, 27289727

Formation processes of Ni laterite deposits: Implications for exploration, processing, and environments
T. Otake
International Webinar 2021: Managing Mine and Metallurgical Wastes for a Sustainable Metal Industry: Volarization and Remediation, 2021年11月26日, Department of Metallurgical Engineering, Bandung Institute of Technology, 英語, 口頭発表（招待・特別）
2021年11月26日 - 2021年11月26日, 27289727, ［招待講演］, ［国際会議］

大型科学掘削計画で拓く新しい資源濃集プロセス
大竹 翼
第 7 回北大・部局横断シンポジウム, 2021年10月01日, 日本語, 口頭発表（一般）
27289727

Niラテライト鉱床の高品位鉱石形成に関わる地球化学的要因
大竹 翼
資源地質学会第70回年会, 2021年06月30日, 日本語, 口頭発表（招待・特別）
11763384, ［招待講演］

地球表層環境における鉄の濃集と鉄鉱床の形成：レビュー
大竹 翼
JpGU 2021 (オンライン), 2021年06月03日, 日本語, 口頭発表（一般）
27289727

Environmental study on the Pinpet Fe deposit in southern Shan State, Myanmar
Kyaw Zay Ya, 大竹 翼, 実松 健造, 佐藤 努
JpGU-AGU Joint Meeting 2020, 2020年07月12日, 日本語, ポスター発表
2020年07月12日 - 2020年07月16日, 11763384

インドネシアおよびミャンマーにおける超苦鉄質岩の化学風化とニッケル濃集に与える地球化学的要因
大竹 翼
JpGU-AGU Joint Meeting 2020, 2020年07月12日, 日本語, ポスター発表
2020年07月12日 - 2020年07月16日, 11763384

低温蛇紋岩化反応における水素生成量に与えるシリカの影響　　　　　　　　　　　　　　　
大竹翼, 東野 駿太, 川喜田 竜平, 佐藤 努
日本地球化学会第66回年会, 2019年09月19日, 日本語, 口頭発表（一般）
［国内会議］

Mineralogical and Fe isotope correlations between Kuroko-type VMS deposits and a seafloor hydrothermal deposit in Okinawa Trough　　　　　　　　　　　　　　　
T. Otake, T. Ikeshima, T. Sato, J.-I. Ishibashi, T. Nozaki, H. Kumagai, L. Maeda, onboard members
Goldschmidt 2019, 2019年08月22日, 英語, 口頭発表（一般）
［国際会議］

Comparison of ore formation processes between VHMS deposits and a submarine hydrothermal ore deposit in Okinawa Trough　　　　　　　　　　　　　　　
T. Otake, T. Ikeshima, T. Sato, J-I Ishibashi, T. Nozaki, H. Kumagai, L. Maeda, onboard members
Goldschmidt 2018, 2018年08月17日, 英語, 口頭発表（一般）
［国際会議］

The role of multi-stage processes on REE enrichment in Kangankunde carbonatites, Malawi　　　　　　　　　　　　　　　
F. Chikanda, T. Otake, Y. Ohtomo, T. Sato
Goldschmidt 2018, 2018年08月14日, 英語, 口頭発表（一般）
［国際会議］

沖縄トラフ伊是名海穴海底熱水鉱床における鉱石形成プロセス: 黒鉱鉱床との比較　　　　　　　　　　　　　　　
大竹 翼, 池島 拓郎, 佐藤 努, 石橋 純一郎, 野崎 達生, 熊谷 英憲, 前田 玲奈, 航海乗船者一同
日本地球惑星科学連合2018年大会, 2018年05月23日, 英語, ポスター発表
［国内会議］

Hydrothermal synthesis of chromian spinel from iron and chromium hydroxides using a flow-through apparatus　　　　　　　　　　　　　　　
T. Otake, M. Nishikata, Y. Ohtomo, Y. Kimura, D. Kawamoto, T. Sato
American Chemical Society National Meeting, 2018年03月18日, 英語, 口頭発表（一般）
［国際会議］

Large Fe isotope fractionations found in sulfide ores and ferruginous cherts in volcanogenic massive sulfide deposits　　　　　　　　　　　　　　　
T. Otake, S. Nakamura, R. Yamada, K. Shin, S. Ono, T. Sato
Goldschmidt Conference 2017, 2017年09月16日, 英語, ポスター発表
［国際会議］

火山性塊状硫化物鉱床における鉄同位体分別と鉱床形成プロセス　　　　　　　　　　　　　　　
大竹翼, 中村峻介, 山田亮一, 申基澈, 小野修司, 佐藤努
日本地球惑星科学連合2017年大会, 2017年05月25日, 日本語, 口頭発表（一般）
［国内会議］

Spatial and temporal distributions of metallic ore deposits　　　　　　　　　　　　　　　
Tsubasa Otake
2016 5th International Doctoral Symposium-Sustainable Management of Resources and Environment in the 21st Century, 2016年11月10日, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

フロースルー型装置を用いた低温熱水環境下におけるクロムスピネルの合成実験　　　　　　　　　　　　　　　
大竹翼, 梁智現, 大友陽子, 佐藤努
2016年度日本地球化学会年会, 2016年09月14日, 日本語, 口頭発表（一般）
［国内会議］

沖縄トラフ海底熱水鉱床における鉱石鉱物組成の多様性とその定量的評価　　　　　　　　　　　　　　　
後藤翔太, 大竹翼, 川本大祐, 横山拓史, 小野修司, 伊藤真由美, 佐藤努
2016年資源地質学会年会, 2016年06月23日, 日本語, 口頭発表（一般）
［国内会議］

鉄・マンガン堆積岩の鉄同位体比から推定する海洋環境と熱水活動の変遷　　　　　　　　　　　　　　　
大竹 翼, 申 基澈
第5回同位体環境学シンポジウム, 2015年12月25日, 日本語, ポスター発表
［国内会議］

秋田県北鹿地域にみられる鉄・マンガンに富む化学堆積岩の鉄同位体比の特徴と黒鉱鉱床との関係性　　　　　　　　　　　　　　　
大竹翼, 鈴木凌平, 山田亮一, 申基澈, 昆慶明, 佐藤努
2015年度日本地球化学会第62回年会, 2015年09月16日, 日本語, 口頭発表（一般）
［国内会議］

Environmental impacts associated with heavy mineral processing: Case study in Malaysia　　　　　　　　　　　　　　　
Tsubasa Otake
The World Forum Meeting and Conference “Resources and Sustainability”, 2015年09月15日, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

Fe isotope variations in ferruginous sedimentary rocks above Kuroko deposits in the Hokuroku district, Northeast Japan　　　　　　　　　　　　　　　
T. Otake, R. Suzuki, R. Yamada, K. Shin, Y. Kon, T. Sato
Goldschmidt Conference 2015, 2015年08月18日, 英語, ポスター発表
［国際会議］

黒鉱鉱床形成後に堆積した鉄・マンガン堆積岩に記録された鉄同位体分別　　　　　　　　　　　　　　　
大竹翼, 鈴木陵平, 山田亮一, 申基澈, 昆慶明, 佐藤努
資源地質学会第65回年会講演会, 2015年06月25日, 日本語, 口頭発表（一般）
［国内会議］

秋田県北鹿地域に産する鉄・マンガン堆積岩の鉄同位体比と海洋環境の変動　　　　　　　　　　　　　　　
大竹翼, 鈴木凌平, 申基澈
第4 回同位体環境学シンポジウム, 2014年12月22日, 日本語, ポスター発表
［国内会議］

Environmental impacts associated with REE resources: case study of the tin tailing processing industry in Malaysia　　　　　　　　　　　　　　　
T. Otake, A. Ito, S. Anraku, K.-S. Ariffin, F.-Y. Yeoh, T. Sato
4th Asia Africa Mineral Resources Conference, 2014年10月13日, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

鉄・マンガン堆積岩中のレアアースパターンと鉄同位体比から推定される黒鉱鉱床形成後の堆積環境の変遷　　　　　　　　　　　　　　　
大竹翼, 鈴木陵平, 山田亮一, 申基澈, 昆慶明, 佐藤努
2014年度日本地球化学会年会, 2014年09月16日, 日本語, 口頭発表（一般）
［国内会議］

研究者を志すきっかけとなった南アフリカの鉱床達　　　　　　　　　　　　　　　
大竹 翼
鉱物科学会若手の会夜間集会, 2014年05月01日, 日本語, 公開講演，セミナー，チュートリアル，講習，講義等
［招待講演］, ［国内会議］

海洋における酸化還元環境の変遷と元素濃集　　　　　　　　　　　　　　　
大竹 翼
日本地球惑星科学連合2014年大会, 2014年04月28日, 日本語, 口頭発表（招待・特別）
［招待講演］, ［国内会議］

Chromium Enrichment in sedimentary rocks deposited in shallow water in the 3.2 Ga Moodies Group, South Africa　　　　　　　　　　　　　　　
T. Otake, Y. Sakamoto, S. Itoh, H. Yurimoto, T. Kakegawa
Goldschmidt Conference 2013, 2013年08月29日, 英語, ポスター発表
Florence, Italy, ［国際会議］

南アフリカ･バーバトン地域に産出する 浅海性縞状鉄鉱層中のクロムの農集　　　　　　　　　　　　　　　
大竹翼, 坂本佑樹, 伊藤正一, 圦本尚義, 掛川武
2013年資源地質学会年会, 2013年06月27日, 日本語, 口頭発表（一般）
東京, ［国内会議］

縞状鉄鉱層の微量元素・同位体分析によって紐解く地球と生命の共進化　　　　　　　　　　　　　　　
大竹 翼
第73回分析化学討論会, 2013年05月18日, 日本語, 口頭発表（招待・特別）
函館, ［招待講演］, ［国内会議］

CONCENTRATION OF ELEMENTS IN CHEMICAL SEDIMENTARY ROCKS RELATED TO CHANGES IN EARTH’S SURFACE ENVIRONMENTS　　　　　　　　　　　　　　　
Tsubasa Otake
5th AUN/SEED-Net Regional Conference on Geological Engineering, 2013年, 英語, 口頭発表（基調）
［招待講演］, ［国際会議］

資源地質学で紐解く地球と生命の共進化　　　　　　　　　　　　　　　
大竹 翼
北海道大学工学部 講演会, 2012年, 日本語, 公開講演，セミナー，チュートリアル，講習，講義等
［招待講演］, ［国内会議］

縞状鉄鉱層：資源地質学からアストロバイオロジーへ　　　　　　　　　　　　　　　
大竹 翼
東京工業大学 地惑セミナー, 2012年, 日本語, 口頭発表（招待・特別）
［招待講演］, ［国内会議］

太古代に見られる鉄に富んだ堆積岩の成因と当時の地球表層環境　　　　　　　　　　　　　　　
大竹 翼
産業義技術総合研究所 GREENシーズセミナー, 2012年, 日本語, 公開講演，セミナー，チュートリアル，講習，講義等
［招待講演］, ［国内会議］

北鹿地域における珪質堆積岩中のレアアースパターンと堆積環境の変遷　　　　　　　　　　　　　　　
大竹翼, 山田亮一, 鈴木稜平, 掛川武
日本地球化学会2012年年会, 2012年, 日本語, 口頭発表（一般）
［国内会議］

３２億年前の浅海性化学堆積岩から推定される当時の地球表層環境　　　　　　　　　　　　　　　
大竹翼, 坂本祐樹, 伊藤正一, 圦本尚義, 掛川武
地球惑星科学連合2012年大会, 2012年, 日本語, 口頭発表（招待・特別）
［招待講演］, ［国内会議］

Origins of magnetite and chromite in sedimentary rocks in a shallow water environment in the 3.2 Ga Moodies Group, South Africa.　　　　　　　　　　　　　　　
T. Otake, Y. Sakamoto, S. Itoh, H. Yurimoto, T. Kakegawa
2012 AGU Fall Meeting, 2012年, 英語, ポスター発表
［国際会議］

Earth’s surface environments inferred from chemical sedimentary rocks deposited in a shallow ocean 3.2 billion years ago.　　　　　　　　　　　　　　　
T. Otake, Y. Sakamoto, S. Itoh, H. Yurimoto, T. Kakegawa
G-COE symposium 2012: Achievements of G-COE program for Earth and planetary dynamics and the future perspective, 2012年, 英語, 口頭発表（招待・特別）
［招待講演］, ［国際会議］

生命の起源および進化に関する研究における海洋堆積物の続成/変成作用の重要　　　　　　　　　　　　　　　
大竹 翼
東京大学地球惑星システム科学セミナー, 2011年, 日本語, 公開講演，セミナー，チュートリアル，講習，講義等
［招待講演］, ［国内会議］

高温高圧条件下における固体アミノ酸の安定性と重合反応　　　　　　　　　　　　　　　
大竹翼, 谷口尚, 古川善博, 中沢弘基, 掛川武
日本地球化学会第58回年会, 2011年, 日本語, ポスター発表
［国内会議］

Mechanisms of iron oxide transformations in hydrothermal systems　　　　　　　　　　　　　　　
Otake, T, Wesolowski, D.J, Anovitz, L. M, Allard, L. F, Ohmoto, H
地球惑星科学連合2011年大会, 2011年, 日本語, 口頭発表（一般）
［国内会議］

Origins of chromite found in chemical and clastic sedimentary rocks of the 3.2 Ga Moodies Group, South Africa.　　　　　　　　　　　　　　　
Otake, T, Sakamoto, Y, Kakegawa, T
Goldschmidt Conference 2011, 2011年, 英語, 口頭発表（一般）
［国際会議］

Stability of amino acids and their oligomerization under high-pressure conditions　　　　　　　　　　　　　　　
Otake, T, Taniguchi, T, Furukawa, Y, Nakazawa, H, Kakegawa, T
Origins 2011 International Conference, 2011年, 英語, ポスター発表
［国際会議］

縞状鉄鉱層中の初生鉱物としての赤鉄鉱の沈殿と続成作用による磁鉄鉱へのトランスフォーメーション　　　　　　　　　　　　　　　
大竹 翼
九州大学大学院生企画シンポジウム, 2010年, 日本語, 公開講演，セミナー，チュートリアル，講習，講義等
［招待講演］, ［国内会議］

初期地球における海洋堆積物中でのアミノ酸の安定性と重合反応　　　　　　　　　　　　　　　
大竹翼, 谷口尚, 古川善博, 中沢弘基, 掛川武
第51回高圧討論会, 2010年, 日本語, 口頭発表（一般）
［国内会議］

The Stability of amino acids and peptides during on the early Earth　　　　　　　　　　　　　　　
Otake, T, Taniguchi, T, Furukawa, Y, Nakazawa, H, Kakegawa, T
Global-Network Symposium on Earth’s Dynamics, 2010年, 英語, 口頭発表（一般）
［国際会議］

The stability of amino acids and peptides during diagenesis on the early Earth　　　　　　　　　　　　　　　
Otake, T, Taniguchi, T, Furukawa, Y, Nakazawa, H, Kakegawa, T
地球惑星科学連合2010年大会（国際セッション）, 2010年, 英語, 口頭発表（一般）
［国際会議］

Stability of amino acids and peptides during diagenesis on the early Earth　　　　　　　　　　　　　　　
Otake, T, Taniguchi, T, Furukawa, Y, Nakazawa, H, Kakegawa, T
2010 Goldschmidt conference, 2010年, 英語, ポスター発表
［国際会議］

平衡及び非平衡反応における硫黄の同位体効果と質量依存性の理論的研究　　　　　　　　　　　　　　　
大竹 翼
日本地球化学会第57回大会, 2010年, 日本語, 口頭発表（招待・特別）
［招待講演］, ［国内会議］

海洋堆積物の続成環境模擬実験における混合アミノ酸の重合と安定性　　　　　　　　　　　　　　　
大竹翼, 谷口尚, 古川善博, 中沢弘基, 掛川武
日本地球化学会第57回大会, 2010年, 日本語, ポスター発表
［国内会議］

A New Surface Reaction Model for Anomalous Fractionation of Sulfur Isotopes　　　　　　　　　　　　　　　
地球惑星科学連合2009年大会, 2009年, 日本語, 口頭発表（一般）
［国内会議］

初期地球における有機物と硫黄化合物の表面反応による特異な同位体分別の可能性　　　　　　　　　　　　　　　
T. Otake, A. C. Lasaga, Y. Watanabe, H. Ohmoto
第２回アストロバイオロジーワークショップ, 2009年, 日本語, 口頭発表（一般）
［国内会議］

Theoretical investigations for anomalous fracionation of sulfur isotopes during a surface reaction　　　　　　　　　　　　　　　
T. Otake, A. C. Lasaga, Y. Watanabe, H. Ohmoto
AGU Fall Meeting, 2009年, 英語, ポスター発表
［国際会議］

A New Surface Reaction Model for Anomalous Fractionation of Sulfur Isotopes　　　　　　　　　　　　　　　
地球惑星科学連合2009年大会, 2009年

Theoretical investigations of equilibrium and surface adsorption effects on mass-dependent fractionation in multiple sulfur isotope systems　　　　　　　　　　　　　　　
T. Otake, A. C. Lasaga, Y. Watanabe, H. Ohmoto
Astrobiology Science Conference, 2008年, 英語, ポスター発表
［国際会議］

Anomalous S isotope fractionations during reactions with an organic surface: I. theoretical investigations　　　　　　　　　　　　　　　
T. Otake, A. C. Lasaga, Y. Watanabe, H. Ohmoto
18th Annual Goldschmidt Conference, 2008年, 英語, 口頭発表（一般）
［国際会議］

Experimental evidence for non-redox transformation of hematite from magnetite under reducing conditions　　　　　　　　　　　　　　　
Otake, T, Wesolowski, D.J, Anovitz, L. M, Allard, L. F, Ohmoto, H
Astrobiology Science Conference, 2006年, 英語, 口頭発表（一般）
［国際会議］

Non-redox transformation of magnetite - hematite under H2-rich hydrothermal conditions　　　　　　　　　　　　　　　
Otake, T, Wesolowski, D.J, Anovitz, L. M, Allard, L. F, Ohmoto, H
19th General Meeting of the International Mineralogical Association, 2006年, 英語, 口頭発表（一般）
［国際会議］

Experimental evidence of non-redox transformation between magnetite and hematite under H2-rich hydrothermal conditions　　　　　　　　　　　　　　　
Otake, T, Wesolowski, D.J, Anovitz, L. M, Allard, L. F, Ohmoto, H
Annual Meeting of the Geological Society of America, 2006年, 英語, 口頭発表（一般）
［国際会議］

Magnetite transformation to hematite under H2 pressure at 150ºC　　　　　　　　　　　　　　　
Otake, T, Wesolowski, D.J, Anovitz, L. M, Allard, L. F, Ohmoto, H
15th Annual Goldschmidt Conference, 2005年, 英語, 口頭発表（一般）
［国際会議］

“Detrital” pyrites in the Archean Witwatersrand Basin (South Africa) are not detrital　　　　　　　　　　　　　　　
T. Otake, Y. Watanabe, W. Altermann, H. Ohmoto
Astrobiology Science Conference, 2004年, 英語, ポスター発表
［国際会議］

Al－Si酸化物表面への金(III)イオンの吸着実験 石英脈への金の濃縮における6配位Alの重要性－　　　　　　　　　　　　　　　
大竹翼, 横山拓史, 内田明子, 渡邊公一郎, 井澤英二
資源地質学会, 2002年, 日本語, ポスター発表
［国内会議］

Gold deposition in epithermal quartz-adularia veins: Epithermal study on adsorption of gold on Al-Si systems　　　　　　　　　　　　　　　
Ohtake, T, Yokoyama, T, Uchida, A, Watanabe, K, Izawa, E
11th International Association on the Genesis of Ore Deposits Symposium, 2002年, 英語, ポスター発表
［国際会議］

地球の科学　　　　　　　　　　　　　　　
東北大学

自然科学総合実験　　　　　　　　　　　　　　　
東北大学

応用地質学　　　　　　　　　　　　　　　
北海道大学

資源化学I　　　　　　　　　　　　　　　
北海道大学

Technical English (in Japanese)　　　　　　　　　　　　　　　
Hokkaido Unviersity

Applied Geology (in Japanese)　　　　　　　　　　　　　　　
Hokkaido University

Environmental Geology II　　　　　　　　　　　　　　　
Hokkaido University

Seminar for PARE　　　　　　　　　　　　　　　
Hokkaido University

Field Work Training for PARE　　　　　　　　　　　　　　　
Hokkaido Unviersity

PARE演習Ⅱ－人口・活動・資源・環境の連環－　　　　　　　　　　　　　　　
北海道大学

PARE 実習Ⅱ－人口・活動・資源・環境の連環　　　　　　　　　　　　　　　
北海道大学

Environmental Geology II　　　　　　　　　　　　　　　
北海道大学大学院

環境地質学特論　　　　　　　　　　　　　　　
北海道大学大学院

資源循環システム実験II（岩石の肉眼鑑定、顕微鏡観察、地形図・地質図）　　　　　　　　　　　　　　　
北海道大学

技術英語　　　　　　　　　　　　　　　
北海道大学

科学掘削コア試料を用いた32億年前の金属元素循環と酸化還元環境の解明
科学研究費助成事業
2024年04月 - 2028年03月
大竹 翼
日本学術振興会, 基盤研究(A), 北海道大学, 研究代表者, 24H00436

鉱床成因における微生物―硫化鉱物―水反応プロセスの地球化学的解明
科学研究費助成事業
2023年04月 - 2026年03月
淵田 茂司, 大竹 翼, 吉田 健太
日本学術振興会, 学術変革領域研究(B), 東京海洋大学, 研究分担者, 23H03814

熱水鉱床形成における微生物活動の寄与を定量化する～生物鉱学の創成を目指して～
科学研究費助成事業
2023年04月 - 2026年03月
野崎 達生, 栗林 貴弘, 石田 章純, 牛久保 孝行, 大竹 翼
日本学術振興会, 基盤研究(B), 国立研究開発法人海洋研究開発機構, 研究分担者, 23H01914

低温蛇紋岩化反応による水素生成促進メカニズムの解明
科学研究費助成事業 挑戦的研究(開拓)
2022年06月 - 2025年03月
大竹 翼
日本学術振興会, 挑戦的研究(開拓), 北海道大学, 研究代表者, 22K18325

国際大陸掘削計画による32億年前の生物圏―水圏―大気圏―岩石圏相互作用の解明
科学研究費助成事業 基盤研究(A)
2020年04月 - 2024年03月
大竹 翼
R3年度はR2年度に現地での新型コロナ感染拡大のため遅れていた科学掘削が開始された。バーバトン地域の4サイト(site 2, 3, 4, 5)において合計7本のコアを掘削した。これらの掘削コアは、当時の海洋環境に関する情報を保持していると考えられる化学堆積岩（縞状鉄鉱層: BIF, ジャスパー）や沿岸域の生態系に関する情報を保存している可能性がある浅海性堆積岩を含んでいる。現地のコア記載も進んでいる。またすでに露頭や稼行中の鉱山で採取済みの岩石試料を使用して分析手法の確立に取り組んだ。鉄 (Fe) およびクロム (Cr) 安定同位体比の分析についてはBIF試料において良好に単離などの前処理を行うことができ、分析条件を確立することができた。Fe同位体比については十数試料の分析が完了しており、その値から海洋からの化学沈澱のシグナルを保持していることが明らかとなった。その同位体変動幅は鉄の酸化沈澱でのみ説明可能であり、32億年まえの浅海域で海洋中の溶存二価鉄が酸化されるプロセスがすでに存在していたと考えられる。また、有機物を抽出して微細構造分析を行ったところフィルム状の有機物を検出し、比較的未熟成であることも明らかとなった。さらにその有機物に含まれている窒素（N）の同位体比を測定したところ、誤差は大きかったが酸素発生光合成細菌の寄与を示唆する同位体的に重たい値を示した。ヨハネスブルグ大学におけるLA-ICP-MSによるジルコンの分析についても条件などを確立し、分析環境を整えた。
日本学術振興会, 基盤研究(A), 北海道大学, 研究代表者, 20H00184

湿地帯の文化的景観と食の安全保障に対 する工業化の影響　　　　　　　　　　　　　　　
二国間交流事業
2021年04月 - 2023年03月
松島 肇, Ariya Aruninta, 波多野 隆介, 五十嵐 敏文, 大竹 翼, 根岸 淳二郎, 小池 聡, John Bower, 武田 量
日本学術振興会, タイ（NRCT）との共同研究, 北海道大学;Chulalongkorn University, 研究分担者, ［国際共著］, JPJSBP120219201

マグネシウムシリケート水和物：その正体と生成の全容解明　　　　　　　　　　　　　　　
科学研究費補助金 基盤研究(A)
2019年04月 - 2022年03月
佐藤 努
日本学術振興会, 研究分担者, 競争的資金

自然に学ぶ新しい水素製造法の探究　　　　　　　　　　　　　　　
科学研究費補助金 挑戦的研究(萌芽)
2017年04月 - 2020年03月
大竹 翼
日本学術振興会, 研究代表者, 競争的資金

鉄コロイドによるレアメタル濃集探査のための新同位体指標
科学研究費補助金 基盤研究(B)
2017年04月 - 2020年03月
大竹 翼
日本学術振興会, 研究代表者, 競争的資金

塊状硫化物鉱床に伴う化学堆積岩の地球化学的特徴と探査指標としての可能性　　　　　　　　　　　　　　　
一般研究助成
2016年04月 - 2019年03月
大竹 翼
一般財団法人日本鉱業振興会, 研究代表者, 競争的資金

次世代海洋資源調査技術: 鉱床モデルの構築に向けた熱水化学反応の解明
戦略的イノベーション創造プログラム
2015年10月 - 2019年03月
石橋 純一郎
内閣府 総合科学技術・イノベーション会議, 研究分担者, 競争的資金

初期地球表層環境における化学的元素濃集プロセスの解明
科学研究費補助金 若手研究(A)
2014年04月 - 2017年03月
大竹 翼
日本学術振興会, 研究代表者, 競争的資金

レアアース資源開発における環境影響評価と精錬廃水からの放射性物質除去法の確立　　　　　　　　　　　　　　　
国内研究助成（萌芽的研究）
2013年10月 - 2014年09月
大竹 翼
クリタ水・環境化学振興財団, 研究代表者, 競争的資金

局所安定同位体比分析によって明らかにする鉄に富んだ堆積岩の成因と初期地球の表層環境　　　　　　　　　　　　　　　
北海道大学総長室事業推進経費
2012年04月 - 2013年03月
大竹 翼
北海道大学, 研究代表者, 競争的資金

非生物反応における硫黄安定同位体分別効果と質量依存性の実験的・理論的研究
科学研究費補助金
2010年04月 - 2012年03月
大竹 翼
第一原理計算の結果,核の大きさによる同位体効果では硫黄の特異な同位体分別は起こらない事が明らかになった一方,様々な表面反応では特異な同位体効果が起きうる事が明らかになった.非生物反応の非平衡反応では,平衡時の質量依存則に従う可能性がある事が示された.また,高温高圧実験の結果,有機物の無機的硫酸還元反応によって硫化鉄の生成に成功した.
日本学術振興会, 若手研究(B), 研究代表者, 競争的資金, 22740342

硫黄の未知同位体分別効果の理論的及び実験的解明　　　　　　　　　　　　　　　
若手研究者奨励研究基金
2009年04月 - 2010年03月
大竹 翼
東北大学大学院理学研究科, 研究代表者, 競争的資金

学士課程, 工学部

修士課程, 工学院

博士課程, 工学院