Silicon self-diffusion in MgSiO3 perovskite at 25 GPa

Silicon self-diffusion coefficients in MgSiO3 perovskite were measured unde r lower mantle conditions. The MgSiO3 perovskite was synthesized and diffus ion annealing experiments were conducted at pressure of 25 GPa and temperat ure 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 w idth of grain boundary, R is the gas constant and T is the absolute tempera ture. These diffusion coefficients play a key role for understanding the rh eology of the lower mantle, (C) 2000 Elsevier Science B.V. All rights reser ved.