Updated on 2025/08/02

写真a

 
YAMASHITA Katsuyuki
 
Organization
Faculty of Environmental, Life, Natural Science and Technology Associate Professor
Position
Associate Professor
External link

Degree

  • Ph.D. ( University of Alberta )

Research Interests

  • 隕石

  • 同位体年代学

  • 質量分析

  • 同位体

  • 地球化学

  • 太陽系

Research Areas

  • Natural Science / Space and planetary sciences

Education

  • University of Alberta    

    1993.9 - 1998.3

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  • Kyushu University   大学院理学研究科   地質学専攻

    1991.4 - 1993.3

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  • Kyushu University   理学部   地質学科

    1987.4 - 1991.3

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Research History

  • 海洋研究開発機構(JAMSTEC), 外来研究員

    2025.4

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  • 海洋研究開発機構(JAMSTEC)   招聘上席研究員

    2023.2 - 2025.3

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  • Okayama University   理学部地球科学科   Associate Professor

    2011.2

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  • Okayama University   地球物質科学研究センター   Associate Professor

    2007.4 - 2011.1

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  • Okayama University   地球物質科学研究センター   Associate Professor (as old post name)

    2006.5 - 2007.3

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  • Kobe University   理学部地球惑星科学科   Research Assistant

    1999.10 - 2006.4

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  • ハーバード大学   研究員

    1998.4 - 2000.1

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Professional Memberships

  • The Meteoritical Society

    2006.6

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  • 日本地球惑星科学連合

    2003.11

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  • Geochemical Society

    2001.5

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  • American Geophysical Union

    1997.12

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  • Geological Society of America

    1997.9

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  • 日本地球化学会

    1992.9

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  • The Geochemical Society of Japan

    1991

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Committee Memberships

  • 日本地球惑星科学連合   ダイバーシティ推進委員会委員  

    2016   

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    Committee type：Academic society

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Papers

  • Zirconium isotope composition indicates s-process depletion in samples returned from asteroid Ryugu Reviewed

    Maria Schönbächler, Manuela A. Fehr, Tetsuya Yokoyama, Ikshu Gautam, Nao Nakanishi, Yoshinari Abe, Jérôme Aléon, Conel Alexander, Sachiko Amari, Yuri Amelin, Ken‐ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon‐Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Koki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming‐Chang Liu, Yuki Masuda, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Kazuhide Nagashima, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara Russell, Naoya Sakamoto, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing‐Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai‐Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei‐ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto

    Meteoritics & Planetary Science   2024.11

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

    Abstract

    Nucleosynthetic isotope variations are powerful tracers to determine genetic relationships between meteorites and planetary bodies. They can help to link material collected by space missions to known meteorite groups. The Hayabusa 2 mission returned samples from the Cb‐type asteroid (162173) Ryugu. The mineralogical, chemical, and isotopic characteristics of these samples show strong similarities to carbonaceous chondrites and in particular CI chondrites. The nucleosynthetic isotope compositions of Ryugu overlap with CI chondrites for several elements (e.g., Cr, Ti, Fe, and Zn). In contrast to these isotopes, which are of predominately supernovae origin, s‐process variations in Mo isotope data are similar to those of carbonaceous chondrites, but even more s‐process depleted. To further constrain the origin of this depletion and test whether this signature is also present for other s‐process elements, we report Zr isotope compositions for three bulk Ryugu samples (A0106, A0106‐A0107, C0108) collected from the Hayabusa 2 mission. The data are complemented with that of terrestrial rock reference materials, eucrites, and carbonaceous chondrites. The Ryugu samples are characterized by distinct 96Zr enrichment relative to Earth, indicative of a s‐process depletion. Such depletion is also observed for carbonaceous chondrites and eucrites, in line with previous Zr isotope work, but it is more extreme in Ryugu, as observed for Mo isotopes. Since s‐process Zr and Mo are coupled in mainstream SiC grains, these distinct s‐process variations might be due to SiC grain depletion in the analyzed materials, potentially caused by incomplete sample digestion, because the Ryugu samples were dissolved on a hotplate only to avoid high blank levels for other elements (e.g., Cr). However, local depletion of SiC grains cannot be excluded. An alternative, equally possible scenario is that aqueous alteration redistributed anomalous, s‐process‐depleted, Zr on a local scale, for example, into Ca‐phosphates or phyllosilicates.

    DOI： 10.1111/maps.14279

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  • Radial transport and nebular thermal processing of millimeter‐sized solids in the Solar protoplanetary disk inferred from Cr‐Ti‐O isotope systematics of chondrules Reviewed

    Kohei Fukuda, Yuki Hibiya, Craig R. Kastelle, Katsuhiko Suzuki, Tsuyoshi Iizuka, Katsuyuki Yamashita, Thomas E. Helser, Noriko T. Kita

    Meteoritics & Planetary Science   2024.10

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

    Abstract

    Understanding the material transport and mixing processes in the Solar protoplanetary disk provides important constraints on the origin of chemical and isotopic diversities of our planets. The limited extent of radial transport and mixing between the inner and outer Solar System has been suggested based on a fundamental isotopic dichotomy between non‐carbonaceous (NC) and carbonaceous (CC) meteorite groups. The limited transport and mixing could be further tested by tracing the formation regions of individual meteoritic components, such as Ca‐Al‐rich inclusions (CAIs) and chondrules. Here, we show further evidence for the outward transport of CAIs and chondrules from the inner and subsequent thermal processing in the outer region of the protoplanetary disk based on the petrography and combined Cr‐Ti‐O isotope systematics of chondrules from the Vigarano‐like (CV) carbonaceous chondrite Allende. One chondrule studied consists of an olivine core that exhibits NC‐like Ti and O, but CC‐like Cr isotopic signatures, which is enclosed by a pyroxene igneous rim with CC‐like O isotope ratios. These observations indicate that the olivine core formed in the inner Solar System. The olivine core then migrated into the outer Solar System and experienced nebular thermal processing that generated the pyroxene igneous rim. The nebular thermal processing would result in Cr isotope exchange between the olivine core and CC‐like materials, but secondary alteration effects on the parent body are also responsible for the CC‐like Cr isotope signature. By combining previously reported Cr‐Ti‐O isotope systematics of CV chondrules, we show that some CV chondrules larger than ~1 mm would have formed in the inner Solar System. The accretion of the millimeter‐sized, inner Solar System solids onto the CV carbonaceous chondrite parent body would require their very early migration into the outer Solar System within the first 1 million years after the Solar System formation.

    DOI： 10.1111/maps.14276

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  • The Ni isotopic composition of Ryugu reveals a common accretion region for carbonaceous chondrites Reviewed

    Fridolin Spitzer, Thorsten Kleine, Christoph Burkhardt, Timo Hopp, Tetsuya Yokoyama, Yoshinari Abe, Jérôme Aléon, Conel M. O’D Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Mayu Morita, Fréderic Moynier, Kazuko Motomura, Izumi Nakai, Kazuhide Nagashima, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto

    Science Advances   10 ( 39 )   2024.9

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Association for the Advancement of Science (AAAS)  

    The isotopic compositions of samples returned from Cb-type asteroid Ryugu and Ivuna-type (CI) chondrites are distinct from other carbonaceous chondrites, which has led to the suggestion that Ryugu/CI chondrites formed in a different region of the accretion disk, possibly around the orbits of Uranus and Neptune. We show that, like for Fe, Ryugu and CI chondrites also have indistinguishable Ni isotope anomalies, which differ from those of other carbonaceous chondrites. We propose that this unique Fe and Ni isotopic composition reflects different accretion efficiencies of small FeNi metal grains among the carbonaceous chondrite parent bodies. The CI chondrites incorporated these grains more efficiently, possibly because they formed at the end of the disk’s lifetime, when planetesimal formation was also triggered by photoevaporation of the disk. Isotopic variations among carbonaceous chondrites may thus reflect fractionation of distinct dust components from a common reservoir, implying CI chondrites/Ryugu may have formed in the same region of the accretion disk as other carbonaceous chondrites.

    DOI： 10.1126/sciadv.adp2426

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  • Pyrrhotites in asteroid 162173 Ryugu: Records of the initial changes on their surfaces with aqueous alteration Reviewed

    Hiroharu Yui, Shu-hei Urashima, Morihiko Onose, Mayu Morita, Shintaro Komatani, Izumi Nakai, Yoshinari Abe, Yasuko Terada, Hisashi Homma, Kazuko Motomura, Kiyohiro Ichida, Tetsuya Yokoyama, Kazuhide Nagashima, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Peter Hoppe, Gary R. Huss, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Sasha Krot, Ming-Chang Liu, Yuki Masuda, Frédéric Moynier, Ann Nguyen, Larry Nittler, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Tommaso Di Rocco, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto

    Geochimica et Cosmochimica Acta   379   172 - 183   2024.8

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

    DOI： 10.1016/j.gca.2024.06.016

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  • Disequilibrium oxygen isotope distribution among aqueously altered minerals in Ryugu asteroid returned samples Reviewed

    Noriko T. Kita, Kouki Kitajima, Kazuhide Nagashima, Noriyuki Kawasaki, Naoya Sakamoto, Wataru Fujiya, Yoshinari Abe, Jérôme Aléon, Conel M. O'D. Alexander, Sachiko Amari, Yuri Amelin, Ken‐ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon‐Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming‐Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing‐Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai‐Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei‐ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto

    Meteoritics & Planetary Science   2024.4

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

    Abstract

    Oxygen 3‐isotope ratios of magnetite and carbonates in aqueously altered carbonaceous chondrites provide important clues to understanding the evolution of the fluid in the asteroidal parent bodies. We conducted oxygen 3‐isotope analyses of magnetite, dolomite, and breunnerite in two sections of asteroid Ryugu returned samples, A0058 and C0002, using a secondary ion mass spectrometer (SIMS). Magnetite was analyzed by using a lower primary ion energy that reduced instrumental biases due to the crystal orientation effect. We found two groups of magnetite data identified from the SIMS pit morphologies: (1) higher δ18O (from 3‰ to 7‰) and ∆17O (~2‰) with porous SIMS pits mostly from spherulitic magnetite, and (2) lower δ18O (~ −3‰) and variable ∆17O (0‰–2‰) mostly from euhedral magnetite. Dolomite and breunnerite analyses were conducted using multi‐collection Faraday cup detectors with precisions ≤0.3‰. The instrumental bias correction was applied based on carbonate compositions in two ways, using Fe and (Fe + Mn) contents, respectively, because Ryugu dolomite contains higher amounts of Mn than the terrestrial standard. Results of dolomite and breunnerite analyses show a narrow range of ∆17O; 0.0‰–0.3‰ for dolomite in A0058 and 0.2‰–0.8‰ for dolomite and breunnerite in C0002. The majority of breunnerite, including large ≥100 μm grains, show systematically lower δ18O (~21‰) than dolomite (25‰–30‰ and 23‰–27‰ depending on the instrumental bias corrections). The equilibrium temperatures between magnetite and dolomite from the coarse‐grained lithology in A0058 are calculated to be 51 ± 11°C and 78 ± 14°C, depending on the instrumental bias correction scheme for dolomite; a reliable temperature estimate would require a Mn‐bearing dolomite standard to evaluate the instrumental bias corrections, which is not currently available. These results indicate that the oxygen isotope ratios of aqueous fluids in the Ryugu parent asteroid were isotopically heterogeneous, either spatially, or temporary. Initial water ice accreted to the Ryugu parent body might have ∆17O > 2‰ that was melted and interacted with anhydrous solids with the initial ∆17O < 0‰. In the early stage of aqueous alteration, spherulitic magnetite and calcite formed from aqueous fluid with ∆17O ~ 2‰ that was produced by isotope exchange between water (∆17O > 2‰) and anhydrous solids (∆17O < 0‰). Dolomite and breunnerite, along with some magnetite, formed at the later stage of aqueous alteration under higher water‐to‐rock ratios where the oxygen isotope ratios were nearly at equilibrium between fluid and solid phases. Including literature data, δ18O of carbonates decreased in the order calcite, dolomite, and breunnerite, suggesting that the temperature of alteration might have increased with the degree of aqueous alteration.

    DOI： 10.1111/maps.14163

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  • Pervasive aqueous alteration in the early Solar System revealed by potassium isotopic variations in Ryugu samples and carbonaceous chondrites Reviewed

    Yan Hu, Frédéric Moynier, Wei Dai, Marine Paquet, Tetsuya Yokoyama, Yoshinari Abe, Jérôme Aléon, Conel M. O'D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Koki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Mayu Morita, Kazuko Motomura, Izumi Nakai, Kazuhide Nagashima, David Nesvorný, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto

    Icarus   409   115884 - 115884   2024.2

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

    DOI： 10.1016/j.icarus.2023.115884

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  • Hydrogen in magnetite from asteroid Ryugu Reviewed

    J. Aléon, S. Mostefaoui, H. Bureau, D. Vangu, H. Khodja, K. Nagashima, N. Kawasaki, Y. Abe, C. M. O'D. Alexander, S. Amari, Y. Amelin, K. Bajo, M. Bizzarro, A. Bouvier, R. W. Carlson, M. Chaussidon, B.‐G. Choi, N. Dauphas, A. M. Davis, T. Di Rocco, W. Fujiya, R. Fukai, I. Gautam, M. K. Haba, Y. Hibiya, H. Hidaka, H. Homma, P. Hoppe, G. R. Huss, K. Ichida, T. Iizuka, T. R. Ireland, A. Ishikawa, S. Itoh, N. T. Kita, K. Kitajima, T. Kleine, S. Komatani, A. N. Krot, M.‐C. Liu, Y. Masuda, M. Morita, K. Motomura, F. Moynier, I. Nakai, A. Nguyen, L. R. Nittler, M. Onose, A. Pack, C. Park, L. Piani, L. Qin, S. S. Russell, N. Sakamoto, M. Schönbächler, L. Tafla, H. Tang, K. Terada, Y. Terada, T. Usui, S. Wada, M. Wadhwa, R. J. Walker, K. Yamashita, Q.‐Z. Yin, T. Yokoyama, S. Yoneda, E. D. Young, H. Yui, A.‐C. Zhang, T. Nakamura, H. Naraoka, T. Noguchi, R. Okazaki, K. Sakamoto, H. Yabuta, M. Abe, A. Miyazaki, A. Nakato, M. Nishimura, T. Okada, T. Yada, K. Yogata, S. Nakazawa, T. Saiki, S. Tanaka, F. Terui, Y. Tsuda, S. Watanabe, M. Yoshikawa, S. Tachibana, H. Yurimoto

    Meteoritics and Planetary Science   2024.1

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    Publishing type：Research paper (scientific journal)   Publisher：Wiley  

    Abstract

    In order to gain insights on the conditions of aqueous alteration on asteroid Ryugu and the origin of water in the outer solar system, we developed the measurement of water content in magnetite at the micrometer scale by secondary ion mass spectrometry (NanoSIMS) and determined the H and Si content of coarse‐grained euhedral magnetite grains (polyhedral magnetite) and coarse‐grained fibrous (spherulitic) magnetite from the Ryugu polished section A0058‐C1001. The hydrogen content in magnetite ranges between ~900 and ~3300 wt ppm equivalent water and is correlated with the Si content. Polyhedral magnetite has low and homogenous silicon and water content, whereas fibrous magnetite shows correlated Si and water excesses. These excesses can be explained by the presence of hydrous Si‐rich amorphous nanoinclusions trapped during the precipitation of fibrous magnetite away from equilibrium and testify that fibrous magnetite formed from a hydrous gel with possibly more than 20 wt% water. An attempt to determine the water content in sub‐μm framboids indicates that additional calibration and contamination issues must be addressed before a safe conclusion can be drawn, but hints at elevated water content as well. The high water content in fibrous magnetite, expected to be among the first minerals to crystallize at low water–rock ratio, points to the control of water content by local conditions of magnetite precipitation rather than large‐scale alteration conditions. Systematic lithological variations associated with water‐rich and water‐poor magnetite suggest that the global context of alteration may be better understood if local water concentrations are compared with millimeter‐scale distribution of the various morphologies of magnetite. Finally, the high water content in the magnetite precursor gel indicates that the initial O isotopic composition in alteration water must not have been very different from that of the earliest magnetite crystals.

    DOI： 10.1111/maps.14139

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  • Petrography and Rb-Sr mineral age of mafic dyke rock from Niban Iwa, Lützow-Holm Complex, East Antarctica Reviewed

    Tomoharu MIYAMOTO, Katsuyuki YAMASHITA, Daniel J. DUNKLEY, Toshiaki TSUNOGAE, Mutsumi KATO

    Journal of Mineralogical and Petrological Sciences   119 ( 1 )   n/a - n/a   2024

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    Publishing type：Research paper (scientific journal)   Publisher：Japan Association of Mineralogical Sciences  

    DOI： 10.2465/jmps.231207

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  • Analysis of Cation Composition in Dolomites on the Intact Particles Sampled from Asteroid Ryugu Reviewed

    Mayu Morita, Hiroharu Yui, Shu-hei Urashima, Morihiko Onose, Shintaro Komatani, Izumi Nakai, Yoshinari Abe, Yasuko Terada, Hisashi Homma, Kazuko Motomura, Kiyohiro Ichida, Tetsuya Yokoyama, Kazuhide Nagashima, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Peter Hoppe, Gary R. Huss, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Sasha Krot, Ming-Chang Liu, Yuki Masuda, Frédéric Moynier, Ann Nguyen, Larry Nittler, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Tommaso Di Rocco, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto

    Analytical Chemistry   2023.12

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

    DOI： 10.1021/acs.analchem.3c03463

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  • Neodymium‐142 deficits and samarium neutron stratigraphy of C‐type asteroid (162173) Ryugu Reviewed

    Zachary A. Torrano, Michelle K. Jordan, Timothy D. Mock, Richard W. Carlson, Ikshu Gautam, Makiko K. Haba, Tetsuya Yokoyama, Yoshinari Abe, Jérôme Aléon, Conel Alexander, Sachiko Amari, Yuri Amelin, Ken‐ichi Bajo, Martin Bizzarro, Audrey Bouvier, Marc Chaussidon, Byeon‐Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Koki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming‐Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Kazuhide Nagashima, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing‐Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai‐Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei‐ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto

    Meteoritics and Planetary Science   2023.12

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

    Abstract

    We report Nd and Sm isotopic compositions of four samples of Ryugu returned by the Hayabusa2 mission, including “A” (first touchdown) and “C” (second touchdown) samples, and several carbonaceous chondrites to evaluate potential genetic relationships between Ryugu and known chondrite groups and track the cosmic ray exposure history of Ryugu. We resolved Nd and Sm isotopic anomalies in small (<20 ng Nd and Sm) sample sizes via thermal ionization mass spectrometer using 1013 Ω amplifiers. Ryugu samples exhibit resolvable negative μ142Nd values consistent with carbonaceous chondrite values, suggesting that Ryugu is related to the parent bodies of carbonaceous chondrites. Ryugu's negative μ149Sm values are the result of exposure to galactic cosmic rays, as demonstrated by the correlation between 150Sm/152Sm and 149Sm/152Sm ratios that fall along the expected neutron capture correlation line. The neutron fluence calculated in the “A” samples (2.75 ± 1.94 × 1015 n cm−2) is slightly higher compared to the “C” samples (0.95 ± 2.04 × 1015 n cm−2), though overlapping within measurement uncertainty. The Sm results for Ryugu, at this level of precision, thus are consistent with a well‐mixed surface layer at least to the depths from which the “A” and “C” samples derive.

    DOI： 10.1111/maps.14109

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  • Nucleosynthetic s-Process Depletion in Mo from Ryugu samples returned by Hayabusa2 Reviewed

    N. Nakanishi, T. Yokoyama, A. Ishikawa, R.J. Walker, Y. Abe, J. Aléon, C.M.O'D. Alexander, S. Amari, Y. Amelin, K.-I. Bajo, M. Bizzarro, A. Bouvier, R.W. Carlson, M. Chaussidon, B.-G. Choi, N. Dauphas, A.M. Davis, T. Di Rocco, W. Fujiya, R. Fukai, I. Gautam, M.K. Haba, Y. Hibiya, H. Hidaka, H. Homma, P. Hoppe, G.R. Huss, K. Ichida, T. Iizuka, T.R. Ireland, S. Itoh, N. Kawasaki, N.T. Kita, K. Kitajima, T. Kleine, S. Komatani, A.N. Krot, M.-C. Liu, Y. Masuda, M. Morita, K. Motomura, F. Moynier, I. Nakai, K. Nagashima, A. Nguyen, L. Nittler, M. Onose, A. Pack, C. Park, L. Piani, L. Qin, S.S. Russell, N. Sakamoto, M. Schönbächler, L. Tafla, H. Tang, K. Terada, Y. Terada, T. Usui, S. Wada, M. Wadhwa, K. Yamashita, Q.-Z. Yin, S. Yoneda, E.D. Young, H. Yui, A.-C. Zhang, T. Nakamura, H. Naraoka, T. Noguchi, R. Okazaki, K. Sakamoto, H. Yabuta, M. Abe, A. Miyazaki, A. Nakato, M. Nishimura, T. Okada, T. Yada, K. Yogata, S. Nakazawa, T. Saiki, S. Tanaka, F. Terui, Y. Tsuda, S.-I. Watanabe, M. Yoshikawa, S. Tachibana, H. Yurimoto

    Geochemical Perspectives Letters   28   31 - 36   2023.12

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：European Association of Geochemistry  

    DOI： 10.7185/geochemlet.2341

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  • The Magnesium Isotope Composition of Samples Returned from Asteroid Ryugu Reviewed

    Martin Bizzarro, Martin Schiller, Tetsuya Yokoyama, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Mayu Morita, Fréderic Moynier, Kazuko Motomura, Izumi Nakai, Kazuhide Nagashima, David Nesvorný, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto

    The Astrophysical Journal Letters   958 ( 2 )   L25 - L25   2023.11

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

    Abstract

    The nucleosynthetic isotope composition of planetary materials provides a record of the heterogeneous distribution of stardust within the early solar system. In 2020 December, the Japan Aerospace Exploration Agency Hayabusa2 spacecraft returned to Earth the first samples of a primitive asteroid, namely, the Cb-type asteroid Ryugu. This provides a unique opportunity to explore the kinship between primitive asteroids and carbonaceous chondrites. We report high-precision μ26Mg* and μ25Mg values of Ryugu samples together with those of CI, CM, CV, and ungrouped carbonaceous chondrites. The stable Mg isotope composition of Ryugu aliquots defines μ25Mg values ranging from –160 ± 20 ppm to –272 ± 30 ppm, which extends to lighter compositions relative to Ivuna-type (CI) and other carbonaceous chondrite groups. We interpret the μ25Mg variability as reflecting heterogeneous sampling of a carbonate phase hosting isotopically light Mg (μ25Mg ∼ –1400 ppm) formed by low temperature equilibrium processes. After correcting for this effect, Ryugu samples return homogeneous μ26Mg* values corresponding to a weighted mean of 7.1 ± 0.8 ppm. Thus, Ryugu defines a μ26Mg* excess relative to the CI and CR chondrite reservoirs corresponding to 3.8 ± 1.1 and 11.9 ± 0.8 ppm, respectively. These variations cannot be accounted for by in situ decay of 26Al given their respective 27Al/24Mg ratios. Instead, it requires that Ryugu and the CI and CR parent bodies formed from material with a different initial 26Al/27Al ratio or that they are sourced from material with distinct Mg isotope compositions. Thus, our new Mg isotope data challenge the notion that Ryugu and CI chondrites share a common nucleosynthetic heritage.

    DOI： 10.3847/2041-8213/ad09d9

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  • Water circulation in Ryugu asteroid affected the distribution of nucleosynthetic isotope anomalies in returned sample Reviewed

    Tetsuya Yokoyama, Meenakshi Wadhwa, Tsuyoshi Iizuka, Vinai Rai, Ikshu Gautam, Yuki Hibiya, Yuki Masuda, Makiko K. Haba, Ryota Fukai, Rebekah Hines, Nicole Phelan, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Trevor Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Koki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Kazuhide Nagashima, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto

    Science Advances   9 ( 45 )   2023.11

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Association for the Advancement of Science (AAAS)  

    Studies of material returned from Cb asteroid Ryugu have revealed considerable mineralogical and chemical heterogeneity, stemming primarily from brecciation and aqueous alteration. Isotopic anomalies could have also been affected by delivery of exogenous clasts and aqueous mobilization of soluble elements. Here, we show that isotopic anomalies for mildly soluble Cr are highly variable in Ryugu and CI chondrites, whereas those of Ti are relatively uniform. This variation in Cr isotope ratios is most likely due to physicochemical fractionation between 54 Cr-rich presolar nanoparticles and Cr-bearing secondary minerals at the millimeter-scale in the bulk samples, likely due to extensive aqueous alteration in their parent bodies that occurred after Solar System birth. In contrast, Ti isotopes were marginally affected by this process. Our results show that isotopic heterogeneities in asteroids are not all nebular or accretionary in nature but can also reflect element redistribution by water.

    DOI： 10.1126/sciadv.adi7048

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  • The Oxygen Isotopic Composition of Samples Returned from Asteroid Ryugu with Implications for the Nature of the Parent Planetesimal Reviewed

    Haolan Tang, Edward D. Young, Lauren Tafla, Andreas Pack, Tommaso Di Rocco, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Kazuhide Nagashima, Izumi Nakai, Ann Nguyen, Larry Nittler, Morihiko Onose, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto

    The Planetary Science Journal   4 ( 8 )   144 - 144   2023.8

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

    Abstract

    We present oxygen isotopic analyses of fragments of the near-Earth Cb-type asteroid Ryugu returned by the Hayabusa2 spacecraft that reinforce the close correspondence between Ryugu and CI chondrites. Small differences between Ryugu samples and CI chondrites in ${ { \rm{\Delta } } }^{ { \prime} 17}{\rm{O } }$ can be explained at least in part by contamination of the latter by terrestrial water. The discovery that a randomly sampled C-complex asteroid is composed of CI-chondrite-like rock, combined with thermal models for formation prior to significant decay of the short-lived radioisotope 26Al, suggests that if lithified at the time of alteration, the parent body was small (≪50 km radius). If the parent planetesimal was large (>50 km in radius), it was likely composed of high-permeability, poorly lithified sediment rather than consolidated rock.

    DOI： 10.3847/psj/acea62

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    Other Link： https://iopscience.iop.org/article/10.3847/PSJ/acea62/pdf

  • Abundant presolar grains and primordial organics preserved in carbon-rich exogenous clasts in asteroid Ryugu Reviewed

    Ann N. Nguyen, Prajkta Mane, Lindsay P. Keller, Laurette Piani, Yoshinari Abe, Jérôme Aléon, Conel M. O'D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Kazuhide Nagashima, David Nesvorný, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto

    Science Advances   9 ( 28 )   2023.7

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Association for the Advancement of Science (AAAS)  

    Preliminary analyses of asteroid Ryugu samples show kinship to aqueously altered CI (Ivuna-type) chondrites, suggesting similar origins. We report identification of C-rich, particularly primitive clasts in Ryugu samples that contain preserved presolar silicate grains and exceptional abundances of presolar SiC and isotopically anomalous organic matter. The high presolar silicate abundance (104 ppm) indicates that the clast escaped extensive alteration. The 5 to 10 times higher abundances of presolar SiC (~235 ppm), N-rich organic matter, organics with N isotopic anomalies (1.2%), and organics with C isotopic anomalies (0.2%) in the primitive clasts compared to bulk Ryugu suggest that the clasts formed in a unique part of the protoplanetary disk enriched in presolar materials. These clasts likely represent previously unsampled outer solar system material that accreted onto Ryugu after aqueous alteration ceased, consistent with Ryugu’s rubble pile origin.

    DOI： 10.1126/sciadv.adh1003

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  • Carbonate record of temporal change in oxygen fugacity and gaseous species in asteroid Ryugu Reviewed

    Wataru Fujiya, Noriyuki Kawasaki, Kazuhide Nagashima, Naoya Sakamoto, Conel M. O’D. Alexander, Noriko T. Kita, Kouki Kitajima, Yoshinari Abe, Jérôme Aléon, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto

    Nature Geoscience   16 ( 8 )   675 - 682   2023.7

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

    DOI： 10.1038/s41561-023-01226-y

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  • Hydrogen Isotopic Composition of Hydrous Minerals in Asteroid Ryugu Reviewed

    Laurette Piani, Kazuhide Nagashima, Noriyuki Kawasaki, Naoya Sakamoto, Ken-ichi Bajo, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Shoichi Itoh, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Liping Qin, Sara S. Russell, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto

    The Astrophysical Journal Letters   946 ( 2 )   L43 - L43   2023.4

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    Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

    Abstract

    Rock fragments of the Cb-type asteroid Ryugu returned to Earth by the JAXA Hayabusa2 mission share mineralogical, chemical, and isotopic properties with the Ivuna-type (CI) carbonaceous chondrites. Similar to CI chondrites, these fragments underwent extensive aqueous alteration and consist predominantly of hydrous minerals likely formed in the presence of liquid water on the Ryugu parent asteroid. Here we present an in situ analytical survey performed by secondary ion mass spectrometry from which we have estimated the D/H ratio of Ryugu’s hydrous minerals, D/HRyugu, to be [165 ± 19] × 10−6, which corresponds to δDRyugu = +59 ± 121‰ (2σ). The hydrous mineral D/HRyugu’s values for the two sampling sites on Ryugu are similar; they are also similar to the estimated D/H ratio of hydrous minerals in the CI chondrites Orgueil and Alais. This result reinforces a link between Ryugu and CI chondrites and an inference that Ryugu’s samples, which avoided terrestrial contamination, are our best proxy to estimate the composition of water at the origin of hydrous minerals in CI-like material. Based on this data and recent literature studies, the contribution of CI chondrites to the hydrogen of Earth’s surficial reservoirs is evaluated to be ∼3%. We conclude that the water responsible for the alteration of Ryugu’s rocks was derived from water ice precursors inherited from the interstellar medium; the ice partially re-equilibrated its hydrogen with the nebular H2 before being accreted on the Ryugu’s parent asteroid.

    DOI： 10.3847/2041-8213/acc393

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  • Occurrences and chemical compositions of ultrapotassic mafic dyke rocks from Skallevikshalsen and Rundvågshetta, Lützow-Holm Complex, East Antarctica Reviewed

    Tomoharu MIYAMOTO, Katsuyuki YAMASHITA, Daniel J. DUNKLEY, Kazuhiko SHIMADA, Toshiaki TSUNOGAE, Mutsumi KATO

    Journal of Mineralogical and Petrological Sciences   118 ( ANTARCTICA )   n/a - n/a   2023

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Association of Mineralogical Sciences  

    DOI： 10.2465/jmps.221201

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  • Oxygen isotopes of anhydrous primary minerals show kinship between asteroid Ryugu and comet 81P/Wild2 Reviewed

    Noriyuki Kawasaki, Kazuhide Nagashima, Naoya Sakamoto, Toru Matsumoto, Ken-ichi Bajo, Sohei Wada, Yohei Igami, Akira Miyake, Takaaki Noguchi, Daiki Yamamoto, Sara S. Russell, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto

    Science Advances   8 ( 50 )   2022.12

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    Publishing type：Research paper (scientific journal)   Publisher：American Association for the Advancement of Science (AAAS)  

    DOI： 10.1126/sciadv.ade2067

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  • Contribution of Ryugu-like material to Earth’s volatile inventory by Cu and Zn isotopic analysis Reviewed

    Marine Paquet, Frederic Moynier, Tetsuya Yokoyama, Wei Dai, Yan Hu, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Izumi Nakai, Kazuhide Nagashima, David Nesvorný, Ann N. Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto

    Nature Astronomy   7 ( 2 )   182 - 189   2022.12

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    DOI： 10.1038/s41550-022-01846-1

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  • Ryugu’s nucleosynthetic heritage from the outskirts of the Solar System Reviewed

    Timo Hopp, Nicolas Dauphas, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Kazuhide Nagashima, David Nesvorný, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Tatsuaki Okada, Toru Yada, Kasumi Yogata, Satoru Nakazawa, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Makoto Yoshikawa, Shogo Tachibana, Hisayoshi Yurimoto

    Science Advances   8 ( 46 )   2022.11

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    Little is known about the origin of the spectral diversity of asteroids and what it says about conditions in the protoplanetary disk. Here, we show that samples returned from Cb-type asteroid Ryugu have Fe isotopic anomalies indistinguishable from Ivuna-type (CI) chondrites, which are distinct from all other carbonaceous chondrites. Iron isotopes, therefore, demonstrate that Ryugu and CI chondrites formed in a reservoir that was different from the source regions of other carbonaceous asteroids. Growth and migration of the giant planets destabilized nearby planetesimals and ejected some inward to be implanted into the Main Belt. In this framework, most carbonaceous chondrites may have originated from regions around the birthplaces of Jupiter and Saturn, while the distinct isotopic composition of CI chondrites and Ryugu may reflect their formation further away in the disk, owing their presence in the inner Solar System to excitation by Uranus and Neptune.

    DOI： 10.1126/sciadv.add8141

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  • The Solar System calcium isotopic composition inferred from Ryugu samples Reviewed

    F. Moynier, W. Dai, T. Yokoyama, Y. Hu, M. Paquet, Y. Abe, J. Aléon, C.M.O'D Alexander, S. Amari, Y. Amelin, K.-I. Bajo, M. Bizzarro, A. Bouvier, R.W. Carlson, M. Chaussidon, B.-G. Choi, N. Dauphas, A.M. Davis, T. Di Rocco, W. Fujiya, R. Fukai, I. Gautam, M.K. Haba, Y. Hibiya, H. Hidaka, H. Homma, P. Hoppe, G.R. Huss, K. Ichida, T. Iizuka, T.R. Ireland, A. Ishikawa, M. Ito, S. Itoh, N. Kawasaki, N.T. Kita, K. Kitajima, T. Kleine, S. Komatani, A.N. Krot, M.-C. Liu, Y. Masuda, K.D. McKeegan, M. Morita, K. Motomura, I. Nakai, K. Nagashima, D. Nesvorný, A. Nguyen, L. Nittler, M. Onose, A. Pack, C. Park, L. Piani, L. Qin, S.S. Russell, N. Sakamoto, M. Schönbächler, L. Tafla, H. Tang, K. Terada, Y. Terada, T. Usui, S. Wada, M. Wadhwa, R.J. Walker, K. Yamashita, Q.-Z. Yin, S. Yoneda, E.D. Young, H. Yui, A.-C. Zhang, T. Nakamura, H. Naraoka, T. Noguchi, R. Okazaki, K. Sakamoto, H. Yabuta, M. Abe, A. Miyazaki, A. Nakato, M. Nishimura, T. Okada, T. Yada, K. Yogata, S. Nakazawa, T. Saiki, S. Tanaka, F. Terui, Y. Tsuda, S.-I. Watanabe, M. Yoshikawa, S. Tachibana, H. Yurimoto

    Geochemical Perspectives Letters   24   1 - 6   2022.10

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    DOI： 10.7185/geochemlet.2238

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  • Presolar Stardust in Asteroid Ryugu Reviewed

    Jens Barosch, Larry R. Nittler, Jianhua Wang, Conel M. O’D. Alexander, Bradley T. De Gregorio, Cécile Engrand, Yoko Kebukawa, Kazuhide Nagashima, Rhonda M. Stroud, Hikaru Yabuta, Yoshinari Abe, Jérôme Aléon, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Laure Bejach, Martin Bizzarro, Lydie Bonal, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, George D. Cody, Emmanuel Dartois, Nicolas Dauphas, Andrew M. Davis, Alexandre Dazzi, Ariane Deniset-Besseau, Tommaso Di Rocco, Jean Duprat, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Minako Hashiguchi, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Kanami Kamide, Noriyuki Kawasaki, A. L. David Kilcoyne, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Mutsumi Komatsu, Alexander N. Krot, Ming-Chang Liu, Zita Martins, Yuki Masuda, Jérémie Mathurin, Kevin D. McKeegan, Gilles Montagnac, Mayu Morita, Smail Mostefaoui, Kazuko Motomura, Frédéric Moynier, Izumi Nakai, Ann N. Nguyen, Takuji Ohigashi, Taiga Okumura, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Eric Quirico, Laurent Remusat, Sara S. Russell, Naoya Sakamoto, Scott A. Sandford, Maria Schönbächler, Miho Shigenaka, Hiroki Suga, Lauren Tafla, Yoshio Takahashi, Yasuo Takeichi, Yusuke Tamenori, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Maximilien Verdier-Paoletti, Sohei Wada, Meenakshi Wadhwa, Daisuke Wakabayashi, Richard J. Walker, Katsuyuki Yamashita, Shohei Yamashita, Qing-Zhu Yin, Tetsuya Yokoyama, Shigekazu Yoneda, Edward D. Young, Hiroharu Yui, Ai-Cheng Zhang, Masanao Abe, Akiko Miyazaki, Aiko Nakato, Satoru Nakazawa, Masahiro Nishimura, Tatsuaki Okada, Takanao Saiki, Satoshi Tanaka, Fuyuto Terui, Yuichi Tsuda, Sei-ichiro Watanabe, Toru Yada, Kasumi Yogata, Makoto Yoshikawa, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Shogo Tachibana, Hisayoshi Yurimoto

    The Astrophysical Journal Letters   935 ( 1 )   L3 - L3   2022.8

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    DOI： 10.3847/2041-8213/ac83bd

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  • Samples returned from the asteroid Ryugu are similar to Ivuna-type carbonaceous meteorites Reviewed International journal

    Tetsuya Yokoyama, Kazuhide Nagashima, Izumi Nakai, Edward D. Young, Yoshinari Abe, Jérôme Aléon, Conel M. O’D. Alexander, Sachiko Amari, Yuri Amelin, Ken-ichi Bajo, Martin Bizzarro, Audrey Bouvier, Richard W. Carlson, Marc Chaussidon, Byeon-Gak Choi, Nicolas Dauphas, Andrew M. Davis, Tommaso Di Rocco, Wataru Fujiya, Ryota Fukai, Ikshu Gautam, Makiko K. Haba, Yuki Hibiya, Hiroshi Hidaka, Hisashi Homma, Peter Hoppe, Gary R. Huss, Kiyohiro Ichida, Tsuyoshi Iizuka, Trevor R. Ireland, Akira Ishikawa, Motoo Ito, Shoichi Itoh, Noriyuki Kawasaki, Noriko T. Kita, Kouki Kitajima, Thorsten Kleine, Shintaro Komatani, Alexander N. Krot, Ming-Chang Liu, Yuki Masuda, Kevin D. McKeegan, Mayu Morita, Kazuko Motomura, Frédéric Moynier, Ann Nguyen, Larry Nittler, Morihiko Onose, Andreas Pack, Changkun Park, Laurette Piani, Liping Qin, Sara S. Russell, Naoya Sakamoto, Maria Schönbächler, Lauren Tafla, Haolan Tang, Kentaro Terada, Yasuko Terada, Tomohiro Usui, Sohei Wada, Meenakshi Wadhwa, Richard J. Walker, Katsuyuki Yamashita, Qing-Zhu Yin, Shigekazu Yoneda, Hiroharu Yui, Ai-Cheng Zhang, Harold C. Connolly, Dante S. Lauretta, Tomoki Nakamura, Hiroshi Naraoka, Takaaki Noguchi, Ryuji Okazaki, Kanako Sakamoto, Hikaru Yabuta, Masanao Abe, Masahiko Arakawa, Atsushi Fujii, Masahiko Hayakawa, Naoyuki Hirata, Naru Hirata, Rie Honda, Chikatoshi Honda, Satoshi Hosoda, Yu-ichi Iijima, Hitoshi Ikeda, Masateru Ishiguro, Yoshiaki Ishihara, Takahiro Iwata, Kosuke Kawahara, Shota Kikuchi, Kohei Kitazato, Koji Matsumoto, Moe Matsuoka, Tatsuhiro Michikami, Yuya Mimasu, Akira Miura, Tomokatsu Morota, Satoru Nakazawa, Noriyuki Namiki, Hirotomo Noda, Rina Noguchi, Naoko Ogawa, Kazunori Ogawa, Tatsuaki Okada, Chisato Okamoto, Go Ono, Masanobu Ozaki, Takanao Saiki, Naoya Sakatani, Hirotaka Sawada, Hiroki Senshu, Yuri Shimaki, Kei Shirai, Seiji Sugita, Yuto Takei, Hiroshi Takeuchi, Satoshi Tanaka, Eri Tatsumi, Fuyuto Terui, Yuichi Tsuda, Ryudo Tsukizaki, Koji Wada, Sei-ichiro Watanabe, Manabu Yamada, Tetsuya Yamada, Yukio Yamamoto, Hajime Yano, Yasuhiro Yokota, Keisuke Yoshihara, Makoto Yoshikawa, Kent Yoshikawa, Shizuho Furuya, Kentaro Hatakeda, Tasuku Hayashi, Yuya Hitomi, Kazuya Kumagai, Akiko Miyazaki, Aiko Nakato, Masahiro Nishimura, Hiromichi Soejima, Ayako Suzuki, Toru Yada, Daiki Yamamoto, Kasumi Yogata, Miwa Yoshitake, Shogo Tachibana, Hisayoshi Yurimoto

    Science   379 ( 6634 )   eabn7850   2022.6

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    Carbonaceous meteorites are thought to be fragments of C-type (carbonaceous) asteroids. Samples of the C-type asteroid (162173) Ryugu were retrieved by the Hayabusa2 spacecraft. We measure the mineralogy, bulk chemical and isotopic compositions of Ryugu samples. They are mainly composed of materials similar to carbonaceous chondrite meteorites, particularly the CI (Ivuna-type) group. The samples consist predominantly of minerals formed in aqueous fluid on a parent planetesimal. The primary minerals were altered by fluids at a temperature of 37 ± 10°C, (Stat.) (Syst.) million years after formation of the first solids in the Solar System. After aqueous alteration, the Ryugu samples were likely never heated above ~100°C. The samples have a chemical composition that more closely resembles the Sun’s photosphere than other natural samples do.

    DOI： 10.1126/science.abn7850

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  • Extreme continental weathering in the northwestern Tethys during the end-Triassic mass extinction Reviewed

    Tetsuji Onoue, Jozef Michalík, Hideko Shirozu, Misa Yamashita, Katsuyuki Yamashita, Soichiro Kusaka, Katsuhito Soda

    Palaeogeography, Palaeoclimatology, Palaeoecology   594   110934 - 110934   2022.3

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    DOI： 10.1016/j.palaeo.2022.110934

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  • Calcium and strontium stable isotopes reveal similar behaviors of essential Ca and nonessential Sr in stream food webs Reviewed

    Kai Nils Nitzsche, Shigeyuki Wakaki, Katsuyuki Yamashita, Ki‐Cheol Shin, Yoshikazu Kato, Hiromitsu Kamauchi, Ichiro Tayasu

    Ecosphere   13 ( 2 )   2022.2

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    DOI： 10.1002/ecs2.3921

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    Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/ecs2.3921

  • Sr Isotopic Composition of NIES Certified Reference Material No. 28 Urban Aerosols Reviewed

    Akane Yamakawa, Kimiyo Nagano, Miyuki Ukachi, Kaoru Onishi, Katsuyuki Yamashita, Tomoki Shibata, Kazunari Takamiya, Tomomi Kani, Sylvain Bérail, Olivier F.X. Donard, David Amouroux

    Frontiers in Environmental Chemistry   2   771759   2021.11

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  • The δ 13 C – δ 18 O variations in marble in the Hida Belt, Japan Reviewed

    Hironobu Harada, Tatsuki Tsujimori, Keitaro Kunugiza, Katsuyuki Yamashita, Shogo Aoki, Kazumasa Aoki, Hideko Takayanagi, Yasufumi Iryu

    Island Arc   30 ( 1 )   e12389   2021.1

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    DOI： 10.1111/iar.12389

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  • Chondrules reveal large-scale outward transport of inner Solar System materials in the protoplanetary disk Reviewed

    Curtis D. Williams, Matthew E. Sanborn, Céline Defouilloy, Qing-Zhu Yin, Noriko T. Kita, Denton S. Ebel, Akane Yamakawa, Katsuyuki Yamashita

    Proceedings of the National Academy of Sciences   202005235 - 202005235   2020.9

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    Dynamic models of the protoplanetary disk indicate there should be large-scale material transport in and out of the inner Solar System, but direct evidence for such transport is scarce. Here we show that the ε50Ti-ε54Cr-Δ17O systematics of large individual chondrules, which typically formed 2 to 3 My after the formation of the first solids in the Solar System, indicate certain meteorites (CV and CK chondrites) that formed in the outer Solar System accreted an assortment of both inner and outer Solar System materials, as well as material previously unidentified through the analysis of bulk meteorites. Mixing with primordial refractory components reveals a “missing reservoir” that bridges the gap between inner and outer Solar System materials. We also observe chondrules with positive ε50Ti and ε54Cr plot with a constant offset below the primitive chondrule mineral line (PCM), indicating that they are on the slope ∼1.0 in the oxygen three-isotope diagram. In contrast, chondrules with negative ε50Ti and ε54Cr increasingly deviate above from PCM line with increasing δ18O, suggesting that they are on a mixing trend with an ordinary chondrite-like isotope reservoir. Furthermore, the Δ17O-Mg# systematics of these chondrules indicate they formed in environments characterized by distinct abundances of dust and H2O ice. We posit that large-scale outward transport of nominally inner Solar System materials most likely occurred along the midplane associated with a viscously evolving disk and that CV and CK chondrules formed in local regions of enhanced gas pressure and dust density created by the formation of Jupiter.

    DOI： 10.1073/pnas.2005235117

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    Other Link： https://syndication.highwire.org/content/doi/10.1073/pnas.2005235117

  • 子供だってジオ・エコ研究者

    中野孝教, 荒矢大輔, 飯田史哉, 石本達成, 伊戸康清, 猪嶋清文, 今村智子, 江川勇飛, 小澤弘幸, 帰山寿章, 片瀬靖規, 酒井元哉, 佐藤 実, 澤田誠司, 下島浩平, 野田博幸, 松田智幸, 松本高志, 山田明弘, 山田佳裕, 山下勝行, 岡野 修, 岸本圭祐, 勝見尚也, 山中 勝, 城間吉貴, 大河内博

    みんなの地学   1   10 - 15   2020.6

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  • Exploring the efficiency of stepwise dissolution in removal of stubborn non- radiogenic Pb in chondrule U-Pb dating Reviewed

    Renaud Merle, Yuri Amelin, Qing-Zhu Yin, Magdalena H. Huyskens, Matthew E. Sanborn, Kazuhide Nagashima, Katsuyuki Yamashita, Trevor R. Ireland, Alexander N. Krot, Melanie J. Sieber

    Geochimica et Cosmochimica Acta   277   1 - 20   2020.3

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  • Geographic variation of Sr and S isotope ratios in bottled waters in Japan and sources of Sr and S Reviewed

    Nakano, T, Yamashita, K, Ando, A, Kusaka, S, Saitoh, Y

    Science of The Total Environment   704   2020.2

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    DOI： 10.1016/j.scitotenv.2019.135449

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  • Revisiting Pb isotope signatures of Ni–Fe alloy hosted by antigorite serpentinite from the Josephine Ophiolite, USA Reviewed

    Mayu KAKEFUDA, Tatsuki TSUJIMORI, Katsuyuki YAMASHITA, Yoshiyuki IIZUKA, Kennet E. FLORES

    Journal of Mineralogical and Petrological Sciences   115 ( 1 )   21 - 28   2020

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  • Sequential chemical separation of Cr and Ti from a single digest for high precision isotope measurements of planetary materials Reviewed

    Hibiya Y, Iizuka T, Yamashita K, Yoneda S, Yamakawa A

    Geostandards and Geoanalytical Research   2019

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  • Sr isotope variations in the Upper Triassic succession at Pizzo Mondello, Sicily: Constraints on the timing of the Cimmerian Orogeny Reviewed

    Tetsuji Onoue, Katsuyuki Yamashita, Chise Fukuda, Katsuhito Soda, Yuki Tomimatsu, Benedetto Abate, Manuel Rigo

    Palaeogeography, Palaeoclimatology, Palaeoecology   499   131 - 137   2018.6

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    DOI： 10.1016/j.palaeo.2018.03.025

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  • Geochemical characteristics of hydrous basaltic magmas due to assimilation and fractional crystallization: the Ikoma gabbroic complex, southwest Japan Reviewed

    N. Koizumi, T. Okudaira, D. Ogawa, K. Yamashita, Y. Suda

    MINERALOGY AND PETROLOGY   110 ( 5 )   639 - 662   2016.10

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    DOI： 10.1007/s00710-016-0423-9

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  • Paleoenvironmental changes across the Carnian/Norian boundary in the Black Bear Ridge section, British Columbia, Canada Reviewed

    Tetsuji Onoue, John-Paul Zonneveld, Michael J. Orchard, Misa Yamashita, Katsuyuki Yamashita, Honami Sato, Soichiro Kusaka

    PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY   441   721 - 733   2016.1

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    DOI： 10.1016/j.palaeo.2015.10.008

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  • Tectonic influence on chemical composition of ocean island basalts in the West and South Pacific: Implication for a deep mantle origin Reviewed

    Gen Shimoda, Osamu Ishizuka, Katsuyuki Yamashita, Miwa Yoshitake, Masatsugu Ogasawara, Makoto Yuasa

    GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS   12   2011.7

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    DOI： 10.1029/2011GC003531

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  • Mn-53-Cr-53 CHRONOMETRY OF CB CHONDRITE: EVIDENCE FOR UNIFORM DISTRIBUTION OF Mn-53 IN THE EARLY SOLAR SYSTEM Reviewed

    Katsuyuki Yamashita, Seiji Maruyama, Akane Yamakawa, Eizo Nakamura

    ASTROPHYSICAL JOURNAL   723 ( 1 )   20 - 24   2010.11

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    DOI： 10.1088/0004-637X/723/1/20

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  • CHROMIUM ISOTOPE SYSTEMATICS OF ACHONDRITES: CHRONOLOGY AND ISOTOPIC HETEROGENEITY OF THE INNER SOLAR SYSTEM BODIES Reviewed

    Akane Yamakawa, Katsuyuki Yamashita, Akio Makishima, Eizo Nakamura

    ASTROPHYSICAL JOURNAL   720 ( 1 )   150 - 154   2010.9

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    DOI： 10.1088/0004-637X/720/1/150

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  • Precise determination of Cr, Mn, Fe, Co and Ni concentration by an isotope dilution-internal standardization method employing high resolution MC-ICP-MS Reviewed

    Akio Makishima, Akane Yamakawa, Katsuyuki Yamashita, Eizo Nakamura

    CHEMICAL GEOLOGY   274 ( 1-2 )   82 - 86   2010.6

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    DOI： 10.1016/j.chemgeo.2010.03.018

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  • クロム同位体から探る初期太陽系の姿 Reviewed

    山下勝行

    遊星人   2010

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  • Measurement of chlorine stable isotopic composition by negative thermal ionization mass spectrometry using total evaporation technique Reviewed

    Tatsuya Fujitani, Katsuyuki Yamashita, Masahiko Numata, Nobuyuki Kanazawa, Noboru Nakamura

    GEOCHEMICAL JOURNAL   44 ( 3 )   241 - 246   2010

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    DOI： 10.2343/geochemj.1.0053

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  • Chemical Separation and Mass Spectrometry of Cr, Fe, Ni, Zn, and Cu in Terrestrial and Extraterrestrial Materials Using Thermal Ionization Mass Spectrometry Reviewed

    Akane Yamakawa, Katsuyuki Yamashita, Akio Makishima, Eizo Nakamura

    ANALYTICAL CHEMISTRY   81 ( 23 )   9787 - 9794   2009.12

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    DOI： 10.1021/ac901762a

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  • Sm-Nd isotopic systematics of lherzolitic shergottite Yamato-793605 Reviewed

    Misawa, K, Yamada, K, Nakamura, N, Morikawa, N, Yamashita K, Premo, W.R

    Antarctic Meteorite Research   19   45 - 57   2006

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    We have undertaken Sm-Nd isotopic studies on Yamato-793605 lherzolitic shergottite. The Sm-Nd internal isochron obtained for acid leachates and residues of whole-rock and separated mineral fractions yields an age of 185±16Ma with an initial εNd value of +9.7±0.2. The obtained Sm-Nd age is, within analytical errors, identical to the Rb-Sr age of this meteorite as well as to the previous Rb-Sr and Sm-Nd ages of Allan Hills-77005 and Lewis Cliff 88516, although the ε_(Nd) values are not identical to each other. Elemental abundances of lithophile trace elements remain nearly unaffected by aqueous alteration on the Martian surface. The isotopic systems of lherzolitic shergottites, thus, are considered to be indigenous, although disturbances by shock metamorphism are clearly observed. "Young ages of 〜180Ma" have been consistently obtained from this and previous Rb-Sr, Sm-Nd and U-Pb isotopic studies and appear to represent crystallization events.

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  • A short timescale for terrestrial planet formation from Hf-W chronometry of meteorites Reviewed

    QZ Yin, SB Jacobsen, K Yamashita, J Blichert-Toft, P Telouk, F Albarede

    NATURE   418 ( 6901 )   949 - 952   2002.8

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    DOI： 10.1038/nature00995

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  • Diverse supernova sources of pre-solar material inferred from molybdenum isotopes in meteorites Reviewed

    QZ Yin, SB Jacobsen, K Yamashita

    NATURE   415 ( 6874 )   881 - 883   2002.2

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1038/415881a

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  • Origin and evolution of mid- to late-Archean crust in the Hanikahimajuk Lake area, Slave Province, Canada; evidence from U-Pb geochronological, geochemical and Nd-Pb isotopic data Reviewed

    K Yamashita, RA Creaser, JE Jensen, LM Heaman

    PRECAMBRIAN RESEARCH   99 ( 3-4 )   197 - 224   2000.2

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/S0301-9268(99)00058-3

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  • Integrated Nd isotopic and U-Pb detrital zircon systematics of clastic sedimentary rocks from the Slave Province, Canada: evidence for extensive crustal reworking in the early- to mid-Archean Reviewed

    K Yamashita, RA Creaser, ME Villeneuve

    EARTH AND PLANETARY SCIENCE LETTERS   174 ( 3-4 )   283 - 299   2000.1

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/S0012-821X(99)00265-4

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  • Geochemical and Nd isotopic constraints for the origin of Late Archean turbidites from the Yellowknife area, Northwest Territories, Canada Reviewed

    K Yamashita, RA Creaser

    GEOCHIMICA ET COSMOCHIMICA ACTA   63 ( 17 )   2579 - 2598   1999.9

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/S0016-7037(99)00167-2

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  • Geochemical and Nd-Pb isotopic systematics of late Archean granitoids, southwestern Slave Province, Canada: constraints for granitoid origin and crustal isotopic structure Reviewed

    K Yamashita, R Creaser, J Stemler, T Zimaro

    CANADIAN JOURNAL OF EARTH SCIENCES   36 ( 7 )   1131 - 1147   1999.7

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1139/e98-047

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  • GENESIS OF CONTINENTAL-CRUST UNDER ISLAND-ARC CONDITIONS Reviewed

    T YANAGI, K YAMASHITA

    LITHOS   33 ( 1-3 )   209 - 223   1994.10

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/0024-4937(94)90061-2

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  • U-PB AND RB-SR DATING OF THE OKI METAMORPHIC ROCKS, THE OKI ISLAND, SOUTHWEST JAPAN Reviewed

    K YAMASHITA, T YANAGI

    GEOCHEMICAL JOURNAL   28 ( 4 )   333 - 339   1994

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.2343/geochemj.28.333

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Presentations

  • 隕石から太陽系の歴史を学ぶ Invited

    山下勝行

    西はりま天文台・五月夜の星まつり  2025.5.4 

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    Event date： 2025.5.4

    Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

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  • ユークライトJuvinasの鉱物学的特徴とMn-Cr年代の解釈

    山下勝行, 原湧樹, 米田成一, 澤田順弘

    日本地球化学会 第71回年会  2024.9.18 

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    Event date： 2024.9.18 - 2024.9.20

    Language：Japanese   Presentation type：Oral presentation (general)  

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  • 地球化学的手法による福井県大野市における水質形成の研究

    石田 正貴, 山下 勝行, 岡野 修, 岸本 圭祐, 梶川 華奈子, 宮本 愛梨, 中野 孝教, 山田 佳裕, 城間 吉貴

    日本地球惑星科学連合2024年大会  2024.5.29 

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    Event date： 2024.5.26 - 2024.5.31

    Language：Japanese   Presentation type：Poster presentation  

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Research Projects

  • 遠洋性堆積岩から探る宇宙物質流入が地球表層環境に及ぼす影響の解明

    Grant number：25H00695  2025.04 - 2030.03

    日本学術振興会  科学研究費助成事業  基盤研究(A)

    尾上 哲治, 佐藤 峰南, 冨松 由希, 山下 勝行, 高畑 直人

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    Authorship：Coinvestigator(s) 

    Grant amount：\45760000 （ Direct expense: \35200000 、 Indirect expense：\10560000 ）

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  • 古代マヤ文明の基層形成と発展におけるヒトの移動に関するバイオアーキオロジーの研究

    Grant number：24H00102  2024.04 - 2028.03

    日本学術振興会  科学研究費助成事業  基盤研究(A)

    鈴木 真太郎

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    Authorship：Coinvestigator(s) 

    Grant amount：\46540000 （ Direct expense: \35800000 、 Indirect expense：\10740000 ）

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  • 地球外物質のMn-Cr年代測定に向けた初期太陽系における53Mnの空間分布の解明

    Grant number：24K07116  2024.04 - 2027.03

    日本学術振興会  科学研究費助成事業  基盤研究(C)

    山下 勝行

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    Authorship：Principal investigator 

    Grant amount：\4550000 （ Direct expense: \3500000 、 Indirect expense：\1050000 ）

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  • 顕生代における宇宙塵大量流入イベントと地球環境への影響

    Grant number：20H00203  2020.04 - 2025.03

    日本学術振興会  科学研究費助成事業  基盤研究(A)

    尾上 哲治, 曽田 勝仁, 山下 勝行, 高畑 直人, 佐藤 峰南

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    Grant amount：\44850000 （ Direct expense: \34500000 、 Indirect expense：\10350000 ）

    2021年度の研究では、これまでの研究により3Heが高濃度で含まれることがわかっている古生代ペルム紀および中生代三畳紀の深海底堆積岩(層状チャート)試料を確保し、分析に用いる試料を作成した。具体的には、岐阜県坂祝町の三畳系チャートを中心に試料採取を進めた。採取したチャート試料の一部については、フッ化水素酸法で放散虫およびコノドント化石を抽出し、属種の同定および堆積年代の決定を進めた。
    採取した試料の一部は、3He濃度および3He/4He比を分析し、宇宙塵フラックスの時代変化を見積もる研究を進めた。試料からのHe抽出は、バルク試料の加熱法で行い、測定は東京大学大気海洋研究所のHelix SFTを用いた。また本年度は、チャート試料に含まれる地球外3Heのホスト鉱物を濃集させたヘリウム同位体分析を行うため、主に採取した三畳系チャート試料を対象として、試料の酸・アルカリ溶解実験を同時並行で行った。実験では酸・アルカリ溶液処理を行った16試料について3He、4Heの含有量及びヘリウム同位体比を測定した。その結果、強アルカリ溶液を用いて分析試料を前処理することにより、従来のバルク分析に比べて、地球外3Heを最大で10倍程度濃集させることができた。今後はこの手法を中古生代層状チャート試料に用いることで、より広い時代範囲の地球外3Heフラックスの変動を高精度で復元することが可能になる。また、2021年度は予察的に三畳紀試料に対してCr同位体分析の化学処理から分析までを行なっており、表面電離型質量分析計(TIMS)を使用してCr同位体分析を進めた。現在は、三畳紀岩石の比較対象となる隕石試料についてのCr同位体比に関するデータ収集を、同時並行的に進めている。

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  • High-precision isotopic study of primitive meteorites

    Grant number：24340137  2012.04 - 2015.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    YAMASHITA Katsuyuki, TOMIOKA Naotaka, NAGAO Keisuke, HIDAKA Hiroshi, YONEDA Shigekazu, YIN Qing-Zhu

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    Grant amount：\14950000 （ Direct expense: \11500000 、 Indirect expense：\3450000 ）

    Multiple-isotope study of primitive meteorites including chondrites and primitive achondrites was undertaken in order to shed light on the origin and evolution of early solar system planetary bodies. To achieve this goal, emphasis was given to technical development leading to high-precision isotope analyses using TIMS and MC-ICP-MS. Meteorites with distinct petrological and geochemical properties were investigated, and important isotope data leading to high-precision chronology of the early solar system objects were obtained.

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  • 希ガス同位体を用いた「Old Rock Geochemistry」の展開

    Grant number：21244085  2009 - 2012

    日本学術振興会  科学研究費助成事業  基盤研究(A)

    松本 拓也, 松田 准一, 辻森 樹, 太田 努, 山下 勝行, 宮川 千絵

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    Grant amount：\38220000 （ Direct expense: \29400000 、 Indirect expense：\8820000 ）

    本年度は、中国東南部各地から採取したマントル捕獲岩の希ガス同位体分析を完了した。この地域の大陸下lithosphereは比較的最近に大規模な剥奪過程を経験したことが先行研究などにより提唱されており、希ガス同位体がどのような特徴を示すかで、大陸中央部のlithospbereの進化過程に制約条件を与えうると期待できる。分析した試料の特徴としては一様に希ガス含有量がオーストラリアで産出する同様の岩石と比べて少なく、結果として同位体分析もかなり困難であった。ヘリウムの同位体が典型的な上部マントルの億よりも10-20%低い億を示すものもあったため、比較的最近のガスの寄与というよりは、ある程度の期間マントル内で放射集変起源成分の蓄積された領域が存在し、その領域に起因する流体が付加されたものであると推定できる。また、インド洋意の玄武岩試料の分析も完了し中央インド洋海嶺のセグメント毎に明確なヘリウム同位体比の特徴の違いを発見した。一部のセグメントで明確にレユニオンマントルブルームに起因する成分の寄与を発見するとともに.あるセグメントでは上部マントルの値よりも低い3He/4Heが発見され、その様な値は脱ガスを経験した上部マントルがその後少なくとも1000万年以上の期間放射起線のヘリウムを蓄積し、その領域からのガスが特定のセグメントにヘリウムを供給する必要がある。上記2つの研究は対象は異なっているが、いずれも上部マントル内でのローカルな同位体進化を反映した同位体不均一の存在を示唆しており、地球内部の同位体進化を探る上で今後考慮すべき事柄である。また、一部のダイアモンドで見られるネオン同位体の特徴を解釈するために、ネオンの同位体進化曲線をモデル計算し論文として発表した。昨年度来から継続したオーストラリア東部の研究については論文を発表するとともに国際学会にて発表を行った。

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  • Mn-Cr法を使ったユレイライトの起源と年代に関する研究

    Grant number：18740345  2006 - 2007

    日本学術振興会  科学研究費助成事業  若手研究(B)

    山下 勝行

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    Grant amount：\3300000 （ Direct expense: \3300000 ）

    本研究の目的はユレイライト母天体の起源とタイムスケールをMn-Cr同位体を用いて明らかにすることを目的としている。平成18年度までの研究ではALH77257、MET78008とY791538の3つのユレイライトの全岩及び鉱物フラクション(Y791538のみ)の同位体分析を行った。その結果、全てのユレイライトにこれまで発見されていなかった負の54Cr同位体異常があることを発見した。このことはユレイライトが正の同位体異當を持つ炭素質コンドライトの部分溶融によって形成されたものではないことを意味する。また同様の同位体異常は他のエコンドライトからも報告されており、初期の太陽系がクロムの同位体に関して不均一であったことが明らかになりつつある。ただしその不均一性が空間的なものなのか時間的なものなのかは分かっておらず、今後さらなる精密同位体分析が必要である。この問題に対応するために平成19年度はさらに少量の試料からクロムだけではなく、ニッケル、鉄、亜鉛などを高い回収率で分離するための方法を開発した。クロムの同位体分析に関してはこれまでよりもさらに精度の高いデータを約1/3の分析時間で得ることが可能になった。またニッケルについても表面電離型質量分析装置を使った精密同位体分析ができるようになった。
    年代に関しては現時点で得られているデータはMn/Cr比の開きが小さいため精密な年代を得るにいたっていない。しかし上記の分析方法が可完成したことで今度さらに純度の高い鉱物フラクションの分析が可能になり、精密な年代が得られることが期待される。

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  • 岩石に由来する安定同位体を用いた食品の産地判別法の開発

    Grant number：17651023  2005 - 2007

    日本学術振興会  科学研究費助成事業  萌芽研究

    中野 孝教, 山下 勝行

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    Grant amount：\3300000 （ Direct expense: \3300000 ）

    食の偽表示は近年ますます顕在化し、環境問題の一つとしてクローズアップされるようになった。農水産物に含まれる様々な成分は、地域の水を通してもたらされる。水に含まれる金属元素の究極の起源は岩石にある。岩石や鉱物の安定同位体組成は地域的に変化することから、それらはミネラル水や農産物などの産地を高い確度で判別しうる指標として利用できる可能性があり、そのための方法の確立を目的として本研究は実施された。
    申請書の所属する機関に設置された表面電離型質量分析装置により、数ナノグラムであっても高精度でストロンチウム(Sr)、鉛(Pb)、ネオジミウム(Nd)の同位体分析が可能となった。日本のミネラル水のSr同位体組成は大きく変化(0.7035-0.713)するが、基本的には流域の地質環境の違いで説明できる。富士山麓のミネラル水の値は特に低く、このことは同山塊が低い^<87>Sr/^<86>Srを有することと調和的であった。ミネラル水の硫黄同位体や微量成分も地域によって変化しており、その原因も主に地質に関係すると考えられるが、より詳細な検討が必要である。
    農産物としてはショウガやニンニクを対象に検討した結果、中国産と日本産を地質由来の安定同位体を利用することによって、高い確度で識別できることが明らかとなった。これに対して、窒素や炭素では明瞭な違いを識別できない。このことは、両国がともに化学肥料に依存している可能性を示唆している。マルチ安定同位体と微量元素を組み合わせることにより、食品の産地を高精度で識別できる可能性がある。

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  • Mn-Cr・Pb-Pb法を用いた初期太陽系物質の年代学的研究

    Grant number：16740305  2004 - 2005

    日本学術振興会  科学研究費助成事業  若手研究(B)

    山下 勝行

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    Grant amount：\2900000 （ Direct expense: \2900000 ）

    本研究では、初期太陽系における物質進化のプロセス及びタイムスケールを明らかにするために、隕石やその構成物質(CAIやコンドリュールなど)の精密同位体分析および年代測定を行った。年代測定では、絶対年代を求めるためのPb-Pb年代測定法の開発、そしてPb-Pb法だけでは年代測定が困難な試料に対応するためのMn-Cr年代測定法の開発を行った。Pb-Pb法では主に炭素質コンドライトの年代測定を行った。その結果、Allendeのような、熱変成の影響をあまり受けてない隕石がコンドリュール・CAIともに非常に古い年代(>4566Ma)を示すのに対し、神戸隕石のような熱変成を受けているものは、コンドリュールでも4512Maという非常に若い年代が得られることが明らかになった。これはPb-Pb法が熱変成に極めて敏感に反応することを意味しており、Pb-Pb年代の解釈に注意が必要であることを示している。一方、Mn-Cr法では主として分化した隕石(メソシデライトのマトリックスやユレイライトの全岩試料)の精密同位体測定・年代測定を行った。その結果、これまで炭素質コンドライト以外には存在しないと考えられていた54Crの同位体異常がメソシデライトやユレイライトにも存在することが明らかになった(ただし異常の方向は逆)。この同位体異常の発見は、今後さらに分析試料を増やすことでこれらの隕石の起源を明らかにするためのトレーサーになりうると考えている。またメソシデライトに関しては、その内部アイソクロンから、53Mnが消滅した後にMn-Cr系がリセットされた事が明らかになった。

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  • Plio-Pleisatocene environmental changes in Java and hominind evolution and dispersion

    Grant number：15403015  2003 - 2006

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    HYODO Masayuki, SATO Hiroshi, MATSU'URA Shuji, KONDO Megumi, KUMAI Hisao, YAMASHITA Katsuyuki

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    Grant amount：\14100000 （ Direct expense: \14100000 ）

    Javan hominid fossils are important to study hominid dispersion, namely "Out-of-Africa" problem. However, their ages have not been established, and still disputed. In this study, we reconstructed paleoenvironmental changes from the Sangiran hominid fossil-bearing formation, central Java, and discuss the relationship between hominid dispersion and environment changes. In addition, a new paleomagnetic dating technique was studied, and tried to apply to the Javan paleomagnetic stratigraphy data. The following results were obtained:
    (1) A technique of environmental magnetism was first applied to the black clay of the Pucangan (Sangiran) Formation in Sangiran, central Java. As a result, we found a large environmental change that occurred just above the T11 tuff horizon, coincided with the occurrence of the earliest Homo erectus fossil in Sangiran. We confirmed the method was valid to the sediments with less content of biological fossils like pollen or diatom, often used for paleoenvironmental study.
    (2) Detailed paleoenvironmental study with pollen and diatom fossils is difficult because of poor content, except some parts of the Pucangan (Sangiran) Formation.
    (3) The magnetostratrigraphy data in Sangiran show that the Upper Olduvai transition represents a number of geomagnetic fluctuations. The same field behavior was observed in the Chinese loess in Baoji, south-central China. Thus we confirmed that it is a real geomagnetic feature, and that the magnetostratigraphic correlation by Hyodo et al. (1992; 1993; 2002) is reasonable.
    (4) We revealed millennial to submillennial-scale features for the Matuyama-Brunhes polarity transition using a 1700-m core from Osaka Bay. The features are utilized to confirm the magnetostratigraphic correlation in Sangiran.

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  • Cosmochemical and isotopic study of the origin and evolution of chondrites and achondrites, their genetic relationship and timescales.

    Grant number：14340171  2002 - 2004

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    NAKAMURA Noboru, YAMASHITA Katsuyukii, OKANO Osamu

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    Grant amount：\13200000 （ Direct expense: \13200000 ）

    In order to obtain new evidences constraining the timing, origin and evolution of primitive and differentiated meteorites and their genetic relationships, we have carried out chemical, petrological and isotopic analyses for chondrites and achondrites. Results are summarized bellow :
    (1)Under international consortium for the Kobe (CK) meteorite, we obtained a unique REE pattern and detailed chemical and petrological features, which constrains nebular fractionations and meteorite parent body processes of CK chondrites yielding silicate-darkening of the meteorites. The age determination by U-Pb and Rb-Sr methods were carried out for the meteorite, indicating complicated thermal histories of CK chondrite parent body.
    (2)REE and Rb-Sr isotopes were analyzed for the most pure matrix materials or chondrules from the Allende (CV) meteorite, respectively. REE results suggest that the precursor of matrix formed by nebular processes. The 4.4Ga alteration event was newly discovered from Rb-Sr system of Allende.
    (3)The precise Sm-Nd isotopic analyses were carried out for 5 acapulcoites : We obtained a significantly young age (4.13±0.10Ga) for one acapulcoite, indicating young thermal event on the parent body.
    (4)The low Pb blank technique for U-Pb dating was established and precise U-Pb ages as well as Sm-Nd and Rb-Sr ages and REE patterns were obtained for three newly found Antarctic Martian meteorites.
    (5)The Mo isotopic anomalies derived from stellar processes were discovered in primitive meteorites. Precise Cr and Ba isotopic analysis techniques were established and new isotopic anomalies were found for primitive and differentiated meteorites.
    (6)Precise chlorine isotopic analyses were carried out for Allende and 9 standard rocks using thermal ionization mass spectrometry (TIMS). We also established a high sensitivity negative TIMS for Cl.

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  • トリプルスパイク法を用いた鉄隕石の精密Pb同位体分析

    Grant number：13740316  2001 - 2002

    日本学術振興会  科学研究費助成事業  若手研究(B)

    山下 勝行

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    Grant amount：\2300000 （ Direct expense: \2300000 ）

    本研究はダブル・トリプルスパイク法を用いて鉄隕石のPb同位体比を精密に測定することにより、様々な鉄隕石の母天体が形成されたタイムスケールを明らかにする事を最終的な目的としている。本研究ではまずダブル・トリプルスパイクの実験に必要な実験器具や試薬・エミッターを作成し、10ナノグラム程度の鉛を0.01%以下の内部精度で測定できるようにした。次にダブル・トリプルスパイクの中でもオーバースパイクに対する誤差拡大率の小さい204-207Pbダブルスパイクを作成し、その同位体比をNBS982標準試薬を使って求めた。さらに求められたスパイクの同位体組成が正確であるかを確認するために標準試薬NBS981の同位体比をダブルスパイク法を用いて求めた。このようにして求められたNBS981の値は以下の通りである。206Pb/204Pb=16.9419(23;2σ_p),207Pb/204Pb=15.4987(32),208Pb/204Pb=36.7295(95).この値はGaler(1997)によって求められた16.9405,15.4963,36.7219と誤差範囲内で一致しており、ダブルスパイクを使った測定とデータ解析が正確に行われていることを示している。
    本研究では上記のスパイクを用いていくつかの鉄隕石やトロイライトインクルージョンの分析を行った(一部は進行中)。その中でも特に鉛含有量が高いNantan隕石中のトロイライトについては段階的な分解を行い、それぞれの同位体比を測定した。その結果、同位体比が最も低いフラクションでもCanyon Diablo中のトロイライトよりも高い同位体比を示すことが明らかになった。今後、さらに年代学的な理解を深めるためにはCanyon Diabloトロイライトの同位体比をダブルスパイク法を用いて求める必要がある。

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  • Cosmo and Geochemical studies of chlorine isotopes

    Grant number：11640489  1999 - 2001

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (C)

    NAKAMURA Noboru, YAMASHITA Katsuyuki

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    Grant amount：\1500000 （ Direct expense: \1500000 ）

    Stable isotopes such as hydrogen and oxygen have been used as an important tool in Cosmic and geochemistry and have significantly contributed to the solution of a wide variety of geochemical problems. Chlorine isotopes, however, have rarely been used for these purposes due to difficulties in precise isotopic analyses. Particularly, almost no isotopic data have been reported for meteorites. The purpose of this project is to establish high precision analytical technique of chlorine isotopes for planetary materials (including meteorites) by a thermal ionization mass spectrometry.
    In the first year, the mass spectrometric technique using molecular species of C_<s2>Cl^+ ions have been developed successfully and the precision of 0.1 permil (‰) for ^<37>Cl/^<35>Cl ratio was established using reagent standard (CsCl). We have carried out analyses of chlorine in many organic and inorganic chloride compounds and found large variations of δ^<37>Cl_<SMOC> from -5 to +3 ‰ for commercial chloride compounds. In the second year, mass discrimination processes during reductive dechlorination of chlorinated ethenes by anaerobic bacteria have been investigated and found ssite-dependent isotopic discrimination. Chlorine concentrations were determined using an ion chromatography. Replicate analyses have been carried for standard mean ocean chloride (SMOC) and reagent standard (CsCl) and then established ^<37>Cl/^<35>Cl ratio ; 0.319790±60, which was defined as reference (δ^<37>Cl_<SMOC> = 0.00 ‰) and one of reagents (CsCl) was employed as laboratory standard with the ratio of δ^<37>Cl_<SMOC> = -2.56±0.21 ‰. The HF-leaching method has been successfully developed for efficient extraction of chlorine from rock samples (recovery : 85-90%).
    In the 3^<rd> year, we have carried out analyses of meteorites and terrestrial standards. The results are ; δ^<37>Cl_<SMOC> = -0.74±0.24 (‰) for JR-1 ; δ^<37>Cl_<SMOC> = -2.87±0.32 (‰) for Allende chondrite ; ^<37>Cl_<SMOC> = +0.47±0.52 (‰) for Allegan ordinary chondrites. It is remarkable that isotopic compositions area clearly resolvable among these planetary materials including two chondrites, although the isotopic data area still preliminary. We, therefore, suggest that the high precision technique established in this project is now applicable to analyses for a wide variety of planetary materials including meteorites.

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