[S-CG50] Rheology, fracture and friction in Earth and planetary sciences

[SCG50-10] Toward a SOR study of deep rock dynamics using MA-type deformation apparatus at high spatiotemporal resolution

★Invited Papers

*Tomoaki Kubo¹, Rikuto Honda¹, Yuta Goto¹, Yumiko Tsubokawa¹, Noriyoshi Tsujino², Yuji Higo², Yuki Shibazaki³ (1.Kyushu Univ., 2.JASRI, 3.KEK-PF)

Reaction-deformation coupling in deep rocks are potentially important processes to understand the plate-tectonic mantle convection in the Earth. Recent developments of high-pressure deformation techniques with D-DIA and D-111 type multi-anvil devices enable us to conduct in-situ observations of the coupling processes up to lower mantle pressures combined with synchrotron radiation at PF-AR NE7A and SPring-8 BL04B1 beamlines. We briefly report some experimental results on the reaction-induced shear instability and rheological weakening related to the deep slab processes (e.g., Honda+ and Goto+, this meeting). In these studies, the stress-strain and transformation-time curves were simultaneously obtained to reveal "bulk rock dynamics". The weak point of this method is that the spatial and temporal resolutions for in-situ X-ray observations are low (~10^2 µm and ~10^2 sec, respectively). To overcome these limitations, we are planning to introduce some strategies developed in materials science into the MA-type high-pressure deformation techniques to observe "grain-scale dynamics" on sub-second time scales. One is an in-situ observation of individual-grain behaviors by utilizing Mode I 3D-XRD method (e.g., Poulsen, 2012). Statistical information of the dynamics of grains such as time evolution of the number of grains can be obtained by taking 2D-XRD patterns with oscillating the sample (i.e., the apparatus) by a few degrees. By using an high-angular resolution 2D detector with a camera length of ~3m, in-situ obs. of grain dynamics down to sub-micron scales can be expected (e.g., Jakobsen+, 2006). This would be a powerful tool for detecting the grain-size evolution in deep rocks during transformation, dynamic recrystallization, and shear localization controlled by grain nucleation and growth processes. Another is to utilize a high-flux and high-energy X-ray beam from ID beamline for MA high-pressure deformation study. Recent preliminary experiments conducted at SPring-8 BL05XU beamline revealed a new dehydration mechanism of antigorite in time scales of ~10^-1 sec at high pressures. Combining these new methods with MA-type deformation techniques enable us to conduct in-situ observation of both bulk-rock and grain-scale dynamics at high spatiotemporal resolution. We will briefly present recent attempts and some preliminary results obtained.