Rheology in the Earth's inner core studied by high-pressure deformation experiments

2023 Fiscal Year Final Research Report

• Project/Area Number: 19H00723
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Medium-sized Section 17:Earth and planetary science and related fields
• Research Institution: Ehime University
• Principal Investigator: Nishihara Yu 愛媛大学, 地球深部ダイナミクス研究センター, 教授 (10397036)
• Co-Investigator(Kenkyū-buntansha): 西 真之 大阪大学, 大学院理学研究科, 准教授 (10584120) ; 大内 智博 愛媛大学, 地球深部ダイナミクス研究センター, 准教授 (60570504)
• Project Period (FY): 2019-04-01 – 2024-03-31
• Keywords: 地球中心核 / hcp鉄 / 高温高圧変形実験 / レオロジー

Outline of Final Research Achievements

In order to understand the Earth’s inner core dynamics which is probably responsible for its anisotropic structure, we have conducted deformation and diffusion experiments on hcp-Fe and related materials. Rheological property of hcp-Fe determined by deformation experiments suggested that the viscosity of hcp-Fe under the inner core conditions is around 10^19 Pa s or higher. We also determined that viscosity of bcc-Fe is ~5 orders of magnitude lower than that of hcp-Fe, and hcp- and dhcp-iron hydrides are weaker than hcp-Fe only slightly. Fe-Ni interdiffusion coefficients in Fe determined by our experiments were consistent with that by previous study at least below 25 GPa.

Free Research Field

地球深部物質科学

Academic Significance and Societal Importance of the Research Achievements

六方最密構造鉄(hcp-Fe)の実験結果に基づいて見積もられた地球内核の粘性率の高い値は、地球内核における構造形成メカニズムとして、異方的内核成長または並進運動がもっともらしいことを示唆している。固体金属の地球内核の複雑な異方的構造の成因については、数多くの仮説が提唱されており混沌としているが、この問題を強く制約することに成功した。