Atomic diffusion coefficients calculated for transition metals in olivine

Abstract

Atomic diffusion in minerals is one of the most important processes for obtaining information on the formation and subsequent cooling histories of minerals or recks. We have estimated the atomic diffusion coefficients of four transition metals in the forsterite structure on the basis of the potential energy map using the Born–Mayer type repulsive energy term in the WMIN program^1,2. The cation was assumed to migrate along the minimum energy pass of the map. We have estimated the activation energies for the M1 cation migration front the height of the saddle point at the pass, and the frequency terms for diffusion from the shape of the energy minimum around the M1 site. Our calculated values are in line with experimental results³. Although the diffusion phenomena give us information about the genesis and cooling histories of the minerals, the atomic diffusion coefficients in geologically important minerals such as pyroxene are often too low to measure experimentally; we show here how our theoretical approach may be applied to such minerals.