Phase relationships in the system NaAlSiO 4 -SiO 2 -H 2 O to 35 kilobars pressure

Abstract

Phase relationships in the system are first presented on P-T projections of three different composition joins. Crystalline phases encountered include albite, analcite, coesite, jadeite, nepheline, and quartz. Vapor-saturated melting curves proceed with negative dP/dT slopes to invariant points of pressures between 10 and 13 kb. Together with chemographic methods of Schreinemakers and experimental data for the system NaAlSiO 4 -SiO 2 , univariant and invariant equilibria for the ternary system are presented on P-T projection. Isobaric polythermal diagrams, constructed on the basis of the melting relationships and solubility data illustrate the primary fields for the crystalline phases and disclose that critical phenomena will intervene only for compositions rich in SiO 2 .