The pressure scale at multimegabar and the implication to the center of the Earth

• Project/Area Number: 21740374
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Single-year Grants
• Research Field: Petrology/Mineralogy/Science of ore deposit
• Research Institution: Tohoku University
• Principal Investigator: SAKAI Takeshi 東北大学, 国際高等研究教育機構, 助教 (90451616)
• Project Period (FY): 2009 – 2010
• Project Status: Completed (Fiscal Year 2010)
• Budget Amount: ¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000); Fiscal Year 2010: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2009: ¥2,860,000 (Direct Cost: ¥2,200,000、Indirect Cost: ¥660,000)
• Keywords: 地殻 / マントル / 核 / 地球中心核 / 高温高圧 / 圧力スケール / ダイヤモンドアンビルセル

Research Abstract

We compressed NaCl-B2 to 304 Gpa and presented a pressure scale based on the Birch-Murnaghan and Vinet equations of state for this phase. The phase relations of Fe, Fe_<90>Ni_<10> and Fe_<87.9>Ni_<4.4>Si_<7.7> were investigated up to 273(6) Gpa and 4490(560) K, 250(19) Gpa and 2730(110) K and 304(3) Gpa and 2780(210) K, respectively, and the hexagonal close-packed structure was found to be stable in all of these compounds under the pressure and temperature conditions studied. The weak temperature dependency of the axial ratio of hcp-Fe-Ni-Si alloy indicates that the c-axis is still harder than the a-axis at high temperature condition. Therefore the alignment of hcp-Fe-Ni-Si alloy with the c-axis parallel to the Earth's rotation axis could account for the observation of the seismic wave anistropy of the inner core. On the other hand, Fe_<88.1>Ni_<9.1>S_<2.8> alloy was compressed up to 335 Gpa, and the hexagonal close-packed structure was found to be stable. Our results indicate that the hcp Fe-5 at.% Ni-7.9-10.3 at.% S alloy can account for the density of the inner core at 330 Gpa, assuming a linear relationship exists between the density and the nickel and sulfur content.

Research Products

• [Journal Article] Equation of state of the NaCl-B2 phase up to 304 Gpa (2011)
  • Author(s): Sakai, T., E. Ohtani, N. Hirao, Y. Ohishi
  • Journal Title: J. Appl. Phys. Volume: 109 Pages: 84912-84912
  • DOI: 10.1063/1.3573393
  • Peer Reviewed
• [Journal Article] Stability field of the hcp-structure for Fe, Fe-Ni, and Fe-Ni-Si alloys up to 3 Mbar (2011)
  • Author(s): Sakai, T., E. Ohtani, N. Hirao, Y. Ohishi
  • Journal Title: Geophysical research letters Volume: 38
  • DOI: 10.1029/2011gl047178
  • Peer Reviewed
• [Journal Article] Equation of state of the NaCl-B2 phase up to 304 GPa (2011)
  • Author(s): Sakai, T., E.Ohtani, N.Hirao, Y.Ohishi
  • Journal Title: Journal of Applied Physics Volume: (In press)
  • Peer Reviewed
• [Journal Article] Stability field of the hcp-structure for Fe, Fe-Ni, and Fe-Ni-Si alloys up to 3 Mbar (2011)
  • Author(s): Sakai, T., E.Ohtani, N.Hirao, Y.Ohishi
  • Journal Title: Geophysical Research Letters Volume: (In press)
  • Peer Reviewed
• [Journal Article] Phase relationships of the Fe-FeS system in conditions up to the Earth's outer core (2010)
  • Author(s): Kamada, S., Terasaki, H., Ohtani, E., Sakai, T., Kikegawa, T., Ohishi, T., Hirao, N., Sata, N., Kondo, T.
  • Journal Title: Earth Planet. Sci. Lett. Volume: 294 Pages: 94-100
  • Peer Reviewed
• [Journal Article] Phase relationships of the Fe-FeS system in conditions up to the Earth's outer core (2010)
  • Author(s): Kamada, S., Terasaki, H., Ohtani, E., Sakai, T., Kikegawa, T., Ohishi, Y., Hirao, N., Sata, N., Kondo, T.
  • Journal Title: Earth and Planetary Science Letters (In press)
  • Peer Reviewed
• [Journal Article] Phase stability and compression curve of Fe-Ni-S alloy and(Fe,Ni)_3S under multimegabar pressure (2009)
  • Author(s): Sakai, T., Kamada, S., Terasaki, H., Ohtani, M., Murakami, A., Hirao, N.
  • Journal Title: SPring-8 User Experimental Report 2009A
• [Presentation] 内核相当圧力までのNaCl-B2状態方程式 (2011)
  • Author(s): 境毅, 大谷栄治, 平尾直久, 大石泰生
  • Organizer: 第51回高圧討論会
  • Place of Presentation: 仙台
• [Presentation] Phase stability of subsolidus phases in Fe-Ni-S system at the core pressure (2011)
  • Author(s): Sakai, T., E. Ohtani, H. Terasaki, S. Kamada, N. Sata, Y. Ohishi
  • Organizer: 日本地球惑星科学連合2010年大会
  • Place of Presentation: 幕張, 千葉
• [Presentation] Temperature profile of the outer core based on X-ray diffraction of Fe-Fe3S and (Fe, Ni)-(Fe, Ni)3S system (2010)
  • Author(s): Kamada, S., Ohtani, E., Terasaki, H., Sakai, T., Ohishi, Y., Hirao, N., Sata., N.
  • Organizer: AGU fall meeting 2010
  • Place of Presentation: USA, California, San Fransisco, Moscone Convention Center
• [Presentation] Compression of Fe-Ni-S alloy up to the pressure of the center of the Earth (2010)
  • Author(s): Sakai, T., Ohtani, E., Terasaki, H., Kamada, S., Hirao, N., Sata, N., Ohishi, Y.
  • Organizer: IMA2010
  • Place of Presentation: Budapest(INVITED)
• [Presentation] Density of Fe-Ni-S alloy at the pressure of the center of the Earth (2010)
  • Author(s): Sakai, T., Ohtani, E., Terasaki, H., Kamada, S., Hirao, N., Sata, N., Ohishi, Y.
  • Organizer: Dynamic Earth and Heterogeneous Structure
  • Place of Presentation: Japan, Sendai
• [Presentation] Compression study of S-bearing Fe-Ni alloy and (Fe, Ni)3S up to the core pressure conditions (2010)
  • Author(s): Sakai, T., E. Ohtani, H. Terasaki, S. Kamada, N. Hirao, N. Sata, Y. Ohishi
  • Organizer: Global-Network Symposium on Earth's Dynamics
  • Place of Presentation: Japan, Sendai
• [Presentation] Melting Relationships of Fe-FeS System based on X-ray Diffraction (2010)
  • Author(s): Kamada, S., E. Ohtani, H. Terasaki, T. Sakai, T. Kikegawa, Y. Ohishi, N. Hirao, N. Sata
  • Organizer: Global-Network Symposium on Earth's Dynamics
  • Place of Presentation: Japan, Sendai, New Mitoya hotel
• [Presentation] Phase stability of subsolidus phases in Fe-Ni-S system at the core pressure (2010)
  • Author(s): Sakai, T., E.Ohtani, H.Terasaki, S.Kamada, N.Hirao, N.Sata, Y.Ohishi
  • Organizer: 日本地球惑星科学連合2010年大会
  • Place of Presentation: 幕張,千葉
• [Presentation] Temperature profile of the outer core based on X-ray diffraction of Fe-Fe_3S and (Fe,Ni)-(Fe,Ni)_3S system (2010)
  • Author(s): Kamada, S., Ohtani, E., Terasaki, H., Sakai, T., Ohishi, Y., Hirao, N., Sata., N.
  • Organizer: AGU fall meeting 2010
  • Place of Presentation: USA, California, San Francisco, Moscone Convention Center
• [Presentation] Compression study of S-bearing Fe-Ni alloy and(Fe,Ni)_3S up to the core pressure conditions (2010)
  • Author(s): T.Sakai, E.Ohtani, H.Terasaki, S.Kamada, N.Hirao, N.Sata, Y.Ohishi
  • Organizer: Global-Network Symposium on Earth's Dynamics
  • Place of Presentation: Japan, Sendai、New Mitoya hotel
• [Presentation] Phase stability of S-bearing Fe-Ni alloy and (Fe, Ni)3S at the core pressure conditions (2009)
  • Author(s): Sakai, T., H. Terasaki, E. Ohtani, S. Kamada, N. Hirao, N. Sata, Y. Ohishi
  • Organizer: Americal Geophysical Union 2009 Fall Meeting
  • Place of Presentation: America, California, San Fransisco
• [Presentation] Micro sample preparation using Focused Ion Beam system for the experiment at multimegabar pressure (2009)
  • Author(s): Sakai, T.
  • Organizer: Laser Heating the DAC:Where we are and where we are going
  • Place of Presentation: America, California, Berkeley、Lawrence Berkeley National Laboratory
• [Presentation] Phase stability of (Fe, Ni)3S at ultra high pressure conditions (2009)
  • Author(s): Sakai, T., S. Kamada, H. Terasaki, E. Ohtani, N. Hirao, H. Asanuma, N. Sata, Y. Ohishi
  • Organizer: Joint AIRART-22 & HPCJ-50
  • Place of Presentation: Japan, Tokyo
• [Presentation] Stability of Fe3S under the core conditions (2009)
  • Author(s): Kamada, S., H. Terasaki, T. Sakai, E. Ohtani, M. Miyahara, H. Asanuma, H. Hayashi, T. Kikegawa, Y. Ohishi, N. Hirao, N. Sata
  • Organizer: Joint AIRAPT-22 & HPCJ-50
  • Place of Presentation: Japan、Tokyo
• [Presentation] Phase stability of(Fe,Ni)_3S at ultra high pressure conditions (2009)
  • Author(s): T.Sakai, S.Kamada, H.Terasaki, E.Ohtani, N.Hirao, H.Asanuma, N.Sata, Y.Ohishi
  • Organizer: Joint AIRAPT-22 & HPCJ-50
  • Place of Presentation: Japan, Tokyo, Tokyo International Exchange Center
• [Presentation] Micro sample preparation using Focused Ion Beam system for the experiment at multimegabar pressure (2009)
  • Author(s): T.Sakai
  • Organizer: Laser Heating the DAC : Where we are and where we are going
  • Place of Presentation: America, California, Berkeley, Lawrence Berkeley National Laboratory
• [Presentation] Phase stability of S-bearing Fe-Ni alloy and(Fe,Ni)_3S at the core pressure conditions (2009)
  • Author(s): T.Sakai, H.Terasaki, E.Ohtani, S.Kamada, N.Hirao, N.Sata, Y.Ohishi
  • Organizer: American Geophysical Union 2009 Fall Meeting
  • Place of Presentation: America, California, San Francisco, Moscone Center
• [Presentation] Stability of Fe_3S under the core conditions (2009)
  • Author(s): S.Kamada, H.Terasaki, T.Sakai, E.Ohtani, M.Miyahara, H.Asanuma, H.Hayashi, T.Kikegawa, Y.Ohishi, N.Hirao, N.Sata
  • Organizer: Joint AIRAPT-22 & HPCJ-50
  • Place of Presentation: Japan, Tokyo, Tokyo International Exchange Center