[S-CG62] 地球惑星科学におけるレオロジーと破壊・摩擦の物理

[SCG62-P09] rDACによるカンラン石多結晶体の大歪変形実験

*岡崎 啓史^1,3、東 真太郎²、安武 正展⁵、夏井 文凜²、上杉 健太朗⁵、富岡 尚敬^3,1、野村 龍一⁴ (1.広島大学先進理工系科学研究科地球惑星システム学プログラム、2.東京科学大学理学院地球惑星科学系、3.海洋研究開発機構高知コア研究所、4.京都大学、5.高輝度光科学研究センター/SPring-8)

To understand the dynamics of the plate tectonics, it is important to constrain the rheology of olivine in the mantle peridotites, and how it evolves under high-strain deformation imposed during plate motions and mantle flows. We performed a series of high-strain deformation experiments on olivine aggregates using a rotational diamond anvil cell (rDAC). Experiments were conducted at the beamline BL47XU, SPring-8. The experimental conditions are the confining pressure of 8–22 GPa, the temperature of 300–1000 K, and the equivalent shear strain rate of ~10^–4 1/s. During the deformation experiments, X-ray diffraction (XRD) patterns and X-ray radiographs were taken every 2–3 minutes. Stresses in the olivine aggregates were calculated from the lattice strain estimated from XRD. Since we applied a torsional deformation to the sample, there are some stress and strain gradients in the sample. We adopted the stress at the position 2/3 of the radius from the center of the sample as a representative stress in the sample, because this position is the area-averaged radius of the sample. As the shear strain increased, the stress increased and then reached a steady-state stress condition. The steady-state shear stress and equivalent stress at the temperature of 300 K and the pressure of 8 GPa were about 1.8 GPa and 7.0 GPa, respectively. The steady-state shear stress and equivalent stress at the temperature of 673 K and the pressure of 12 GPa were about 1.2 GPa and 3.0 GPa, respectively. The steady-state stress obtained in the present study is consistent with a Peierls’s flow law reported in a previous study. We will also present data on crystallographic preferred orientations of olivine aggregates in this presentation.