Silicon self-diffusion in MgSiO3 perovskite at 25 GPa

Silicon self-diffusion coefficients in MgSiO3 perovskite were measured under lower mantle conditions. The MgSiO3 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 x 10(-10) exg(-336 [kJ/mol]/RT) and delta D-gb [m(3)/s] = 7.12 x 10(-17) exp(-311 [kJ/mol]/RT), respectively, where delta 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, (C) 2000 Elsevier Science B.V. All rights reserved.