Silicon self-diffusion in MgSiO 3 perovskite at 25 GPa

Abstract

Silicon self-diffusion coefficients in MgSiO 3 perovskite were measured under lower mantle conditions. The MgSiO 3 perovskite was synthesized and diffusion annealing experiments were conducted at pressure of 25 GPa and temperature of 1673–2073 K using a MA8 type high-pressure apparatus. The diffusion profiles were obtained by secondary ion mass spectrometry. The lattice and grain boundary diffusion coefficients ( D 1 and D gb) were determined to be D 1 [m 2/s]=2.74×10 −10 exp(−336 [kJ/mol]/ RT) and δD gb [m 3/s]=7.12×10 −17 exp(−311 [kJ/mol]/ RT), respectively, where δ is the width of grain boundary, R is the gas constant and T is the absolute temperature. These diffusion coefficients play a key role for understanding the rheology of the lower mantle.