A Study of Na/K Feldspar Solid Solution Using Statistical Mechanics

Thermal behavior of various solid feldspars are different, namely those of bivalent cations show no change in the distribution of Al and Si atoms, whereas feldspars of univalent cations become more disordered with raising temperature. In the latter case Al atoms migrate from the sites they occupe at low temperatures and interchange positions with the Si atoms. At high temperatures (but still below the melting point) the mixture of the two feldspars forms a solid solution, while at low temperatures two almost pure phases separate out from each other. The behavior of pure feldspar (like albite) have been theoretically studied by various methods, while solid solutions of feldspars of univalent cations have not been studied (due to their complexity). In this paper statistical mechanical methods are used to study sodium and potassium feldspar solutions.