Thermal Conductivity and Evolution of the Earth's Core Explored in High-Temperature and High-Pressure Experiments

• Project/Area Number: 17H04861
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Petrology/Mineralogy/Economic geology
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Ohta Kenji 東京工業大学, 理学院, 准教授 (20727218)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Project Status: Completed (Fiscal Year 2019)
• Budget Amount: ¥25,090,000 (Direct Cost: ¥19,300,000、Indirect Cost: ¥5,790,000); Fiscal Year 2018: ¥7,670,000 (Direct Cost: ¥5,900,000、Indirect Cost: ¥1,770,000); Fiscal Year 2017: ¥11,700,000 (Direct Cost: ¥9,000,000、Indirect Cost: ¥2,700,000)
• Keywords: 地球中心核 / 熱伝導率 / 鉄合金 / 高温高圧実験 / 異方性 / 地球・惑星内部構造 / 岩石・鉱物・鉱床学

Outline of Final Research Achievements

Although thermal conductivity is a fundamental physical property for investigating the temperature structure and thermal evolution of the Earth's interior, there are few actual examples of measurements under the temperature and pressure conditions of the Earth's core. The purpose of this study is to measure the thermal conductivity of iron-light element alloys under the temperature and pressure conditions of the core. The combination of the in-situ thermal conductivity measurement method under high pressure developed and put into practical use by the PI and the high temperature generation technology corresponding to the core condition made it possible to measure the thermal conductivity of iron and iron alloys under the Earth's core condition. To determine the thermal conductivity accurately, a method of observing the three-dimensional shape of a sample at high pressure in situ was also established.

Academic Significance and Societal Importance of the Research Achievements

本課題によって地球マントル、中心核条件での物質の熱伝導率測定手法が確立した。今後、この手法をもちいて地球・惑星深部物質の熱物性が広く計測されていくことで、惑星内部の温度構造や熱進化への理解が大きく進むと期待される。極限環境下での物質の熱物性測定法は高機能材料の開発や物性物理理論の検証などの他分野での応用も大いに期待が持てる。
本課題によって、鉄の高圧相の伝導度には結晶方位異方性があることや、溶融鉄の伝導度測定の困難さが浮き彫りにされた。地球中心核は液体、固体の２層構造を成しており、核の熱進化のさらなる理解のために取り組むべき新たなテーマが明らかにされたことも成果の一つと言える。

Research Products

• [Int'l Joint Research] ソルボンヌ大学(フランス)
• [Journal Article] An experimental examination of thermal conductivity anisotropy inツ?hcpiron (2018)
  • Author(s): Ohta Kenji、Nishihara Yu、Sato Yuki、Hirose Kei、Yagi Takashi、Kawaguchi Saori I.、Hirao Naohisa、Ohishi Yasuo
  • Journal Title: Frontiers in Earth Science, section Solid Earth Geophysics Volume: 6 Pages: 1-15
  • DOI: 10.3389/feart.2018.00176
  • Peer Reviewed / Open Access
• [Journal Article] Measurements of sound velocity in iron?nickel alloys by femtosecond laser pulses in a diamond anvil cell (2018)
  • Author(s): Wakamatsu Tatsuya、Ohta Kenji、Yagi Takashi、Hirose Kei、Ohishi Yasuo
  • Journal Title: Physics and Chemistry of Minerals Volume: - Pages: 589-595
  • DOI: 10.1007/s00269-018-0944-3
  • Peer Reviewed
• [Journal Article] The influence of sulfur on the electrical resistivity of hcp iron: Implications for the core conductivity of Mars and Earth (2017)
  • Author(s): Suehiro, S., Ohta, K., Hirose, K., Morard, G., Ohishi, Y.
  • Journal Title: Geophysical Research Letters Volume: 44 Pages: 8254-8259
  • DOI: 10.1002/2017gl074021
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] The effect of iron and aluminum incorporation on lattice thermal conductivity of bridgmanite at the Earth’s lower mantle (2017)
  • Author(s): Okuda Yoshiyuki、Ohta Kenji、Yagi Takashi、Sinmyo Ryosuke、Wakamatsu Tatsuya、Hirose Kei、Ohishi Yasuo
  • Journal Title: Earth and Planetary Science Letters Volume: 474 Pages: 25-31
  • DOI: 10.1016/j.epsl.2017.06.022
  • Peer Reviewed
• [Journal Article] Lithium polyhydrides synthesized under high pressure and high temperature (2017)
  • Author(s): Takahiro Matsuoka, Keiji Kuno, Kenji Ohta, Masafumi Sakata, Yuki Nakamoto, Naohisa Hirao, Yasuo Ohishi, Katsuya Shimizu, Tetsuji Kume, and Shigeo Sasaki
  • Journal Title: J. Raman Spectrosc. Volume: 48 Pages: 1222-1228
  • DOI: 10.1002/jrs.5183
  • Peer Reviewed
• [Presentation] Electrical resistivity of fcc phase iron hydrides at high pressures and temperatures (2018)
  • Author(s): Ohta, K., Suehiro, S., Hirose, K., Ohishi, Y.
  • Organizer: 第59回高圧討論会
• [Presentation] Simultaneous measurements of electrical and thermal conductivity of iron at high pressure and temperature in an internal heating method (2018)
  • Author(s): Suehiro, S., Ohta, K., Hasegawa, A., Yagi, T., Hirose, K.
  • Organizer: 第59回高圧討論会
• [Presentation] Thermal conductivity measurement under high pressure and high temperature conditions (2018)
  • Author(s): Hasegawa, A., Yagi, T., Ohta, K., Hirose, K.
  • Organizer: 第59回高圧討論会
• [Presentation] Experimental determination of the thermal and electrical conductivity of iron at Earth’s core conditions (2018)
  • Author(s): Ohta, K.
  • Organizer: High Pressure Research at Gordon Research Conference 2018
  • Int'l Joint Research / Invited
• [Presentation] Experimentally inferred thermal conductivity of planetary cores (2018)
  • Author(s): Ohta, K., Suehiro, S.
  • Organizer: Japan Geoscience Union Meeting 2018
  • Invited
• [Presentation] Anisotropic thermal conductivity of hcp iron and the implications for the Earth’s inner core (2018)
  • Author(s): Ohta, K., Nishihara, Y., Sato, Y., Hirose, K., Yagi, T., Kawaguchi, S., Hirao, N., Ohishi, Y.
  • Organizer: Japan Geoscience Union Meeting 2018
• [Presentation] Electrical resistivity of hcp Fe-Si alloy at high pressure and temperature (2018)
  • Author(s): Inoue, H., Suehiro, S., Ohta, K., Hirose, K., Ohishi, Y.
  • Organizer: AGU 2018 Fall Meeting
  • Int'l Joint Research
• [Presentation] Measurement of electrical conductivity of iron at high pressure and temperature in an internally-heated diamond anvil cell (2018)
  • Author(s): Suehiro, S., Ohta, K., Hirose, K., Ohishi, Y.
  • Organizer: AGU 2018 Fall Meeting
  • Int'l Joint Research
• [Presentation] Formation of non-stoichiometric fcc and hcp FeHx at high pressure and temperature conditions (2017)
  • Author(s): Tagawa, S., Ohta, K., Yagi, T., Hirose, K., Ohishi, Y.
  • Organizer: High-Pressure Mineral Physics Seminar (HPMPS-9)
  • Int'l Joint Research
• [Presentation] Lattice thermal conductivity of (Mg,Fe)O solid solutions (2017)
  • Author(s): Hasegawa, A., Ohta, K., Yagi, T., Hirose, K., Kondo, T.
  • Organizer: High-Pressure Mineral Physics Seminar (HPMPS-9)
  • Int'l Joint Research
• [Presentation] The influence of sulfur on the electrical resistivity of hcp iron: implications for the core conductivity of Mars and Earth (2017)
  • Author(s): Suehiro, S., Ohta, K., Hirose, K., Morard, G., Ohishi, Y.
  • Organizer: High-Pressure Mineral Physics Seminar (HPMPS-9)
  • Int'l Joint Research
• [Presentation] Measurements of sound velocity in iron-nickel alloys by femtosecond laser pulses in a diamond anvil cell (2017)
  • Author(s): Wakamatsu, T., Ohta, K., Yagi, T., Hirose, K., Ohishi, Y.
  • Organizer: High-Pressure Mineral Physics Seminar (HPMPS-9)
  • Int'l Joint Research
• [Presentation] Compressional and pressure-temperature dependence of the thermal conductivity of bridgmanite (2017)
  • Author(s): Okuda, Y., Ohta, K., Yagi, T., Sinmyo, R., Wakamatsu, T., Hirose, K.
  • Organizer: High-Pressure Mineral Physics Seminar (HPMPS-9)
  • Int'l Joint Research
• [Presentation] Is thermal conductivity of hcp iron anisotropic? (2017)
  • Author(s): Ohta, K., Sato, Y., Nishihara, Y., Yagi, T., Hirose, K., Kawaguchi, S., Hirao, N., Ohishi, Y.
  • Organizer: High-Pressure Mineral Physics Seminar (HPMPS-9)
  • Int'l Joint Research
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