An empirical model for predicting diffusion coefficients in silicate minerals.

An empirical model describing the diffusion kinetics of oxygen in silicate minerals under hydrothermal conditions has been established for temperatures between 773 and 1073 Kelvin at 100 megapascals of water pressure. The equation, log D = alpha + (beta/T) + [(gamma + (delta/T))Z], where D is the diffusion coefficient, alpha, beta, gamma, and delta are constants, T is the Kelvin temperature, and Z is the total ionic porosity, may be used to predict diffusion coefficients, in most cases to within the reported experimental reproducibility of a factor of 2. For oxygen diffusion, alpha = -2, beta = -3.4 x 10(4)K, gamma = -0.13, and delta = 6.4 x 10(2)K, for D in square centimeters per second. Limited data for the diffusion of argon in silicates suggest that the model describes this system as well.