Dislocation microstructures of MgSiO3 perovskite at a high pressure and temperature condition

Dislocation microstructures of polycrystalline MgSiO3 perovskite, synthesized in a multi-anvil type high-pressure apparatus at 26 GPa and 2023 K for 600 min, have been investigated using transmission electron microscopy (TEM). The recovered MgSiO3 perovskite displayed deformation lamellae under cross-polarized optical microscopy, suggesting that the sample was deformed during the high-pressure experiment. TEM observations showed that curved dislocations with Burgers vectors lying in the {1 1 0} plane, potentially b = 〈1 1 0〉 and [ 0   0   w ] (orthorhombic symmetry) were nucleated. Low-angle tilt boundaries controlled by 〈1 1 0〉 dislocation climb were also activated at high temperature and pressure. The potential Burgers vector of b = 〈1 1 0〉 is consistent with previous results of slip to 〈1 0 0〉cubic, [1 0 0]pc and [0 1 0]pc (cubic symmetry and pseudo-cubic symmetry) on non-silicate perovskite analogues deformed at high temperatures and ambient pressure. The microstructures of climb-accommodated dislocation creep controlled by diffusion in the MgSiO3 perovskite can provide useful information on the rheology at high temperatures and slow strain rates corresponding to the Earthʹs lower mantle.