Phase-transition-induced texture of post-perovskite and D'' discontinuity

Magnesium silicate post-perovskite phase (PPv) is widely regarded as the most likely candidate to explain seismic anomalies observed at the Earth’s D’’ discontinuity. However, direct sound velocity measurements on isotropic polycrystalline MgSiO3 bridgmanite (Brg) and PPv showed no significant Vs positive jump at phase boundary which is inconsistent with seismic observations. Since PPv is known to develop strong fabrics upon transforming from Brg, we would like to combine synchrotron multigrain crystallography and Brillouin spectroscopy to investigate the nature of phase-transition-induced texture of PPv and its influence on sound velocity. Our results will help understand whether the transformation-textured PPv reasonably reproduces the observations of Vs jump and anisotropic features at the D’’ discontinuity. This will offer unprecedent evidence on the genesis of the D’’ discontinuity with implications for our views on the dynamics of the Earth’s lowermost mantle.