The development of shape- and crystallographic-preferred orientation in CaPtO3 post-perovskite deformed in pure shear

Abstract

Knowledge of the deformation mechanism of post-perovskite is important for interpreting observed seismic anisotropy in terms of mantle flow. Experiments on post-perovskite MgSiO3 and the low-pressure analog material CaIrO3 yield different textures, leaving the interpretation of the observed seismic signatures unclear. Here we present results of deformation experiments on CaPtO3 post-perovskite that may be a better analog to MgSiO3. Post-perovskite CaPtO3 deforms by glide of [100] dislocations on the (010) plane, consistent with previous experimental results on CaIrO3. In addition, samples containing a weak minority phase also display shape-preferred orientation with grains elongated in the crystallographic a-direction forming a planar fabric perpendicular to the compression direction. This shape-preferred orientation strengthens the observed crystallographic-preferred orientation and results in a rapid development of texture during deformation. This observation supports the recent suggestion that the D '' reflector might be due to a rapid generation of texture in post-perovskite. Furthermore, the role of shape-preferred orientation in generating seismic anisotropy in multi-phase assemblages should be considered for the D '' assemblage.