The coefficients of heterovalent NaSi-CaAl interdiffusion in plagioclases

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{13.14−0.354NPl+40.721+PH2O2−116095−1037NPl+139732/(1+PH2O2)RT}.