Collaborative Research: COMPRES Grand Challenge for Experimental Study of Plastic Deformation under Deep Earth Conditions

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Green0135411Quantitative rheological measurements on Earth materials have been conducted only under relatively low-pressure conditions corresponding to the depth of ~60 km or less. The main thrust of this project is to extend this limit, through technical developments, at least to ~800 km covering not only the upper mantle but also the transition zone and the lower mantle. We propose to establish a new inter-institutional program coordinated with COMPRES (Consortium for Materials Property Research in the Earth Sciences) by utilizing the infrastructure for operation of national facilities and educational program, and we will expand the capabilities of these facilities for the broader scientific community. Through inter-institutional collaboration, we will develop two new types of apparatus (a modified cubic apparatus (D-DIA) and a rotational Drickamer apparatus (RDA)) in addition to further improvements to the well-established deformation techniques using a multianvil apparatus (MA). Both D-DIA and RDA (as well as MA) can readily be fitted to synchrotron radiation facilities to allow quantitative measurements of stress and strain at high-pressure and temperature conditions. D-DIA is suited for quantitative rheology measurements including shear localization and resultant instabilities while RDA has a unique capability of large strain deformation experiments at high-pressures, an important feature for study of lattice preferred orientation. These apparatus will be used to obtain the first quantitative data set on rheological properties and deformation-induced microstructures of Earth and planetary materials under high-pressure, high-temperature conditions (to ~15-25 GPa, ~2000 K). The results of such measurements will contribute to better understand (i) the radial and lateral variation of rheological properties for whole mantle, (ii) the interaction of rheological behavior with chemical reactions including phase transformations, and (iii) the nature of deformation-induced microstructures such as lattice preferred orientation (which causes seismic anisotropy). The unique facility thus developed will be accessible to a large mineral and rock physics community and will significantly enhance the contribution of mineral and rock physics research to a wide range of solid Earth sciences.