[S-CG62] Rheology, fracture and friction in Earth and planetary sciences

[SCG62-P09] High-strain deformation experiments on olivine aggregates using the rotational diamond anvil cell

*Keishi Okazaki^1,3, Shintaro Azuma², Masahiro Yasutake⁵, Bunrin Natsui², Kentaro Uesugi⁵, Naotaka Tomioka^3,1, Ryuichi Nomura⁴ (1.Earth and Planetary Systems Science Program, Hiroshima University, 2.Department of Earth & Planetary Sciences, Institute of Science Tokyo, 3.Kochi Institute for Core Sample Research, JAMSTEC, 4.Kyoto University, 5.JASRI/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.