Shear Deformation of Upper Mantle Minerals: The Role of Water, Dynamic Recrystallization and Deformation

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9706329 Karato The PI proposes to provide new experimental constraints on the geodynamical interpretation of seismic anisotropy in upper mantle minerals. The focus will be on the role of water and of dynamic recrystallization. Simple shear deformation techniques developed in the PI's laboratory will be used in the experiments and electron backscatter pattern analysis (EBSP) will be utilized to investigate lattice preferred orientation. Synthetic polycrystalline specimens of upper mantle minerals will be prepared and deformed to large strains (~100-300 %) at high temperature and pressure in simple shear under water-rich and water-poor conditions. The microstructural development including the lattice preferred orientation will be investigated by the EBSP technique and seismic anisotropy corresponding to specific deformation mechanisms and deformation geometry will be predicted. The results will be compared with seismological observations to place new constraints on the flow pattern in the upper mantle. ***