Creation of the best model of the Earth's core

2019 Fiscal Year Annual Research Report

• Project/Area Number: 15H05748
• Research Institution: Tohoku University
• Principal Investigator: 大谷 栄治 東北大学, 理学研究科, 学術研究員 (60136306)
• Co-Investigator(Kenkyū-buntansha): 坂巻 竜也 東北大学, 理学研究科, 助教 (30630769) ; 平尾 直久 公益財団法人高輝度光科学研究センター, 利用研究促進部門, 研究員 (70374915) ; 福井 宏之 兵庫県立大学, 物質理学研究科, 助教 (90397901) ; 宮原 正明 広島大学, 理学研究科, 准教授 (90400241)
• Project Period (FY): 2015-05-29 – 2020-03-31
• Keywords: 地球核 / 軽元素 / 相平衡 / 放射光 / 高温高圧 / 音速 / 状態方程式 / 磁性

Outline of Annual Research Achievements

本研究では，相平衡実験・元素分配実験，放射光X線非弾性散乱法による音速測定，放射光メスバウア分光法，中性子回折法などを用いて，高温高圧下において鉄・軽元素合金の相関係・元素分配関係，密度・音速・磁性などの物性を解明した，それにもとづいて，地球核は鉄ニッケルともに，ケイ素，酸素，硫黄，水素が軽元素の候補として有力であること，また，内核と外核は軽元素の存在度が異なり，ケイ素が固体の内核の主要な軽元素であることが明らかになった．さらに， FeNi系およびFeNiSi系の高温高圧相平衡実験にもとづいて，内核はこれまで有力であったhcp構造相のみではなく，hcp構造相とbcc構造に類似のB2構造相の混合物からなるという地球核のモデルを構築した．このモデルは，これまで説明が困難であった内核の特徴である低い横波速度や大きなポアソン比を説明できる．
この研究によって，超高圧高温実験と放射光X線・中性子線を用いた測定方法の技術開発を行いつつ，地球核を構成する物質の諸物性を解明し，上記のような地球核の新たなモデルを構築した．これによって，地球型惑星の構造とその形成過程の理解を増進した．さらに，本研究において開発された実験方法は，関連する物理学・材料科学分野において使用されるなど，地球惑星科学のみならず，広く物性科学，材料科学分野においても貢献をした．

Research Progress Status

令和元年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

令和元年度が最終年度であるため、記入しない。

Research Products

• [Int'l Joint Research] Bayeriches Geoinstitute(ドイツ)
  • Country Name: GERMANY
  • Counterpart Institution: Bayeriches Geoinstitute
• [Int'l Joint Research] California Institute of Technology(米国)
  • Country Name: U.S.A.
  • Counterpart Institution: California Institute of Technology
• [Journal Article] Phase and melting relations of Fe3C to 300 GPa and carbon in the core, Carbon in Earth’s Interior (2020)
  • Author(s): Takahashi, S., Ohtani, E., Sakai, T., Kamada, S., Ozawa, S., Sakamaki, T., Miyahara, M., Ito, Y., Hirao, N., Ohishi, Y.
  • Journal Title: Geophysical Monograph 249, First Edition Volume: 249 Pages: 25-36
  • DOI: doi:10.1002/9781119508229.ch3
  • Peer Reviewed
• [Journal Article] New developments in high-pressure X-ray diffraction beamline for diamond anvil cell at SPring-8 (2020)
  • Author(s): Hirao, N., Kawaguchi-Imada, S., Hirose, K., Shimizu, K., Ohtani, E., Ohishi, Y.
  • Journal Title: Matter and Radiation at Extremes Volume: 5 Pages: 018403
  • DOI: doi:10.1063/1.5126038
  • Peer Reviewed
• [Journal Article] Thermal equation of state of Fe3C to 327 GPa and carbon in the core (2019)
  • Author(s): Takahashi, S., Ohtani, E., Ikuta, D., Kamada, S., Sakamaki, T., Hirao, N., Ohishi, Y.
  • Journal Title: Minerals Volume: 9 Pages: 744
  • DOI: doi:10.1038/s41598-019-43601-z
  • Peer Reviewed / Open Access
• [Journal Article] Interstitial hydrogen atoms in face-centered cubic iron in the Earth’s core (2019)
  • Author(s): Ikuta, D., Ohtani, E., Sano-Furukawa, A., Shibazaki, Y., Terasaki, H., Yuan, L., Hattori, T.
  • Journal Title: Scientific Reports Volume: 9 Pages: 7108
  • DOI: doi:10.3390/min9120744
  • Peer Reviewed / Open Access
• [Journal Article] Sound velocity of Fe3C at high pressure and high temperature determined by inelastic X-ray scattering (2019)
  • Author(s): Takahashi, S., Ohtani, E., Sakamaki, T., Kamada, S., Fukui, H., Tsutsui, S., Uchiyama, H., Ishikawa, D., Hirao, N., Ohishi, Y., Baron, A. Q. R.
  • Journal Title: Comptes Rendus Geoscience Volume: 351 Pages: 190-196
  • DOI: doi:10.1016/j.crte.2018.09.005
  • Peer Reviewed / Open Access
• [Journal Article] Stability of Fe-bearing hydrous phases and element partitioning in the system MgO-Al2O3-Fe2O-SiO2-H2O in Earth's lowermost mantle (2019)
  • Author(s): Yuan, H., Zhang, L., Ohtani, E., Meng, Y., Greenberg, E., Prakapenka, V.B.
  • Journal Title: Earth and Planetary Science Letters Volume: 524 Pages: 115714
  • DOI: doi.org/10.1016/j.epsl.2019.115714
  • Peer Reviewed / Int'l Joint Research
• [Presentation] Inner core as a two phase mixture of the Fe-Ni-Si alloys (2019)
  • Author(s): Ohtani, E., Ikuta, D., Hirao, N., Sakamaki, T
  • Organizer: AGU2019 Fall meeting
  • Int'l Joint Research
• [Presentation] Inelastic x-ray scattering at extreme conditions and its geophysical applications (2019)
  • Author(s): Ohtani, E., Sakamaki, T., Fukui, H., Ikuta, D., Ishikawa, D., Uchiyama, H., Tsutsui, S., Baron, A. Q. R.
  • Organizer: 11th International Conference on Inelastic X-ray Scattering (IXS2019)
  • Int'l Joint Research / Invited
• [Presentation] Composition of the Earth’s Inner Core Inferred from the Sound Velocity Measurement of Iron-Nickel Alloy at High Pressure and High Temperature (2019)
  • Author(s): Sakamaki, T., Ohtani, E., Fukui, H., Kamada, S., Tsutsui, S., Uchiyama, H., Baron, A. Q. R.
  • Organizer: Goldschmidt conference 2019
  • Int'l Joint Research
• [Presentation] Sound velocity measurement of Fe-Ni-Si alloys at high pressure and high temperature (2019)
  • Author(s): Ikuta, D., Ohtani, E., Sakamaki, T., Fukui, H., Uchiyama, H., Tsutsui, S., Baron, A. Q. R
  • Organizer: 第60回高圧討論会
• [Presentation] Sound velocity and Mossbauer spectroscopy measurements of FeH2 (2019)
  • Author(s): Ikuta, D., Ohtani, E., Kawaguchi-Imada, S., Hirao, N., Ohishi, Y.
  • Organizer: 日本鉱物科学会2019年年会
• [Presentation] Phase relations in the Fe-Ni-Si system at high pressures and high temperatures (2019)
  • Author(s): Ikuta, D., Ohtani, E., Kawaguchi-Imada, S, Hirao, N., Ohishi, Y.
  • Organizer: JpGU Meeting 2019
  • Int'l Joint Research
• [Presentation] P-wave velocity of Fe3S under high pressure and temperature (2019)
  • Author(s): Kamada, S., Terasaki, H., Fukui, H., Sakamaki, T., Uchiyama, H., Tsutsui, S., Ohtani, E., Baron, A. Q. R.
  • Organizer: JpGU Meeting 2019
  • Int'l Joint Research
• [Presentation] B2 phase in the inner core: constraints from high pressure experiments (2019)
  • Author(s): Ohtani, E., Ikuta, D., Kamada, S., Sakamaki, T., Hirao, N.
  • Organizer: JpGU Meeting 2019
  • Int'l Joint Research
• [Presentation] Role of high pressure hydrous phase in lower mantle dynamics (2019)
  • Author(s): Ohtani, E., Ohira, I., Jackson, J., Ishii, T., Hsieh, W. P.
  • Organizer: GeoMuenster conference
  • Int'l Joint Research / Invited
• [Presentation] Role of Hydrogen on Composition, Structure, and Dynamics of the Lower Mantle (2019)
  • Author(s): Ohtani, E.
  • Organizer: Goldschmidt 2019
  • Int'l Joint Research / Invited
• [Book] CSJ35 有機・無機材料の相転移ダイナミクス―数理から未来のマテリアル開発まで. トピックス④ (2019)
  • Author(s): 大谷栄治
  • Total Pages: 4
  • Publisher: 日本化学同人
  • ISBN: 9784759813951
• [Remarks] Eiji Ohtani - Tohoku University
  • URL: http://epms.es.tohoku.ac.jp/minphys/ohtani/eindex_ohtani.html
• [Remarks] OHTANI Eiji - Tohoku University
  • URL: http://db.tohoku.ac.jp/whois/e_detail/9964bb514897cf4c21b0438da2929547.html
• [Remarks] Ohtani Laboratory
  • URL: http://epms.es.tohoku.ac.jp/minphys/index.html