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 Earth's lower mantle. (C) 2008 Elsevier B.V. All rights reserved.