Seismic Anisotropy in the Lower Mantle Transition Zone Induced by Lattice Preferred Orientation of Akimotoite

Abstract

AbstractSeismic anisotropy has been widely observed near the subducting slabs in the lower mantle transition zone (MTZ) and is often interpreted by the lattice preferred orientation (LPO) of constituent minerals. Akimotoite is one of the dominant minerals near the cold subducting slabs. Therefore, we conducted the well‐controlled uniaxial and shear deformation experiments on the MgSiO3 akimotoite aggregates at 21–23 GPa and 900–1300°C by using the D111‐type Kawai‐type multianvil apparatus. We observed strong LPOs and the most dominant slip system of akimotoite is suggested to be (0001). The elastic wave velocities of deformed samples were calculated to be strong azimuthal and polarization anisotropy with the velocities of horizontally polarized shear waves greater than that of vertically polarized shear waves for the horizontal mantle shearing. Our results provide important implications for the origin of observed seismic anisotropies and the mantle flow directions in the lower MTZ.