Some thermodynamic and experimental constraints on the melting of albite at atmospheric and high pressure.

A. Navrotsky, C. Capobianco, J. Stebbins

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23 Scopus citations

Abstract

Recent redetermination of the melting curve of albite, NaAlSi3O8, has raised questions about possible nonequilibrium states in viscous silicate liquids near their liquidus temperatures and about the thermodynamic description of albite melt at high P and T. Solid solubility of excess nepheline in albite, and of excess silica in anorthite and celsian (on the order of 1-4wt%) has been reported in the literature. In analogy to similar cases in semiconductors, it is proposed that this homogeneity range of the feldspar phase may explain the melting behavior if the composition of maximum melting point does not correspond to stoichiometric NaAlSi3O8 (CHI NaAlO2 = 0.25). A schematic phase diagram is proposed in which stoichiometric NaAlSi3O8 melts over a temperature interval (1100-1120oC), and the composition of maximum melting point (more nepheline-rich than albite) has its liquidus near 1145oC. The results of some additional melting experiments and calorimetric experiments are presented and discussed. An internally consistent set of parameters describing the heat capacity of liquid and crystal, the volume of liquid and crystal, and the heat of fusion is proposed for stoichiometric NaAlSi3O8.-Authors

Original languageEnglish (US)
Pages (from-to)679-698
Number of pages20
JournalJournal of Geology
Volume90
Issue number6
DOIs
StatePublished - 1982

ASJC Scopus subject areas

  • Geology

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