Phase-Equilibrium Studies in the System NaAlSiO4 (Nepheline)-KAlSiO4 (Kalsilite)-SiO2-H2O

D. L. Hamilton and W. S. MacKenzie
Department of Geology, Manchester University

Summary: Phase-equilibrium relations have been determined at 1000 kg/cm2 water pressure for compositions within the system NaAlSi3O8-KalSi3O8-NaAlSiO4-KAlSiO4 in the area adjacent to the temperature minimum. The composition and temperature of the minimum are Ne50Ks19Qz31 and 750° ± 7° C respectively. The compositions of 102 plutonic rocks and 122 extrusive rocks, from Washington's tables, that carry 80% or more of normative Ab + Or + have been plotted; the areas of high density show a marked similarity to the positions of the low-temperature regions of the synthetic system and suggest that many undersaturated rocks are derived by fractional crystallization from a trachytic magma.

Mineralogical Magazine; 1965 v. 34; no. 268; p. 214-231; DOI: 10.1180/minmag.1965.034.268.17
© 1965, The Mineralogical Society
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