Abstract

Literature data on the coefficients of heterovalent NaSi–CaAl interdiffusion in plagioclases are analyzed. It is shown that activation energy and frequency factor decrease as the partial pressure of water and plagioclase basicity increase. A general expression has been derived for the interdiffusion coefficients of albite and anorthite components as a function of the plagioclase composition (NPl), temperature T (K), and water pressure PH2O (kbar):
D~[cm2s]=exp{13.140.354NPl+40.721+PH2O21160951037NPl+139732/(1+PH2O2)RT}.
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