Elasticity of Hydrated Al‐Bearing Stishovite and Post‐Stishovite: Implications for Understanding Regional Seismic V S Anomalies Along Subducting Slabs in the Lower Mantle

Zhang, Yanyao; Fu, Suyu; Karato, Shun‐ichiro; Okuchi, Takuo; Chariton, Stella; Prakapenka, Vitali B.; Lin, Jung‐Fu

doi:10.1029/2021JB023170

Abstract Seismic anisotropy of the Earth's mantle has been mostly attributed to crystallographic preferred orientation (CPO) generated during subduction and convection of an anhydrous mantle. But some hydrous phases are also stable at mantle conditions. Here we present results from diamond‐anvil cell deformation experiments at high pressure and temperature on hydrous phases Egg [AlSiO₃(OH)], δ [AlO(OH)] and hydrous stishovite [Si_1‐nH_4nO₂], transformed from the clay mineral kaolinite. They develop strong CPO during axial compression, suggesting that they likely contribute to seismic anisotropy and heterogeneity in the mantle. Comparing experimental results with viscoplastic polycrystal plasticity models suggest that phase Egg deforms dominantly by (001) slip, δ by (010) slip and stishovite by {100} slip which could be incorporated in future models of mantle geodynamics.

More Like this