Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Lange, R. A. Search for Related Content GeoRef GeoRef Citation

The density and compressibility of KAlSi₃O₈ liquid to 6.5 GPa

Department of Geological Sciences, 1100 N. University Avenue, University of Michigan, Ann Arbor, Michigan 48109-1005, U.S.A.

Correspondence: ^* E-mail: becky{at}umich.edu

The thermodynamic properties of crystalline and liquid KAlSi₃O₈ are used to calculate the fusion curve of sanidine to 6.5 GPa. New values for the enthalpy and entropy of fusion of sanidine at one bar and 1200 °C (H_Tf = 63.0 kJ/mol, S_Tf = 42.8 J/mol-K) are recommended on the basis of improved heat-capacity equations for KAlSi₃O₈ crystal, glass, and liquid. On the basis of phase-equilibrium experiments on the congruent melting reaction between 2 and 6.5 GPa, the pressure dependence of the liquid compressibility (K₀ ’ = dK₀/dP, where K₀ = 1/ß₀) is constrained to be 12.2 ± 1.0 in a third-order Birch-Murnaghan equation of state (EOS). The metastable, one-bar melting temperature (T_f ) is additionally constrained to be 1203 ± 26 °C. Determination of the liquid K₀ ’ allows the density and compressibility of KAlSi₃O₈ liquid to be calculated to 6.5 GPa (2.709 ± 0.014 g/cm³ at 1600 °C). The uncertainty in K₀ ’ of ±1.0 leads to an error in melt density at 6.5 GPa of ±0.52%. With a K₀ ’ = 12.2, the relatively high compressibility of KAlSi₃O₈ liquid at 1600 °C (K₀ = 15.8 GPa) drops rapidly with increasing pressure. The dominant mechanism of compression for KAlSi₃O₈ liquid between 0 and 6.5 GPa most likely involves topological changes and increases in network connectivity with pressure. It is probable that highly compressible liquids, such as hydrous, silica-rich liquids formed by partial melting of a subducted slab, may have K₀ ’ values that exceed 12 (at pressures 6.5 GPa).

Key Words: Sanidine • fusion curve • enthalpy of fusion • topology • equation of state

This article has been cited by other articles:

				T. J. Tenner, R. A. Lange, and R. T. Downs The albite fusion curve re-examined: New experiments and the high-pressure density and compressibility of high albite and NaAlSi3O8 liquid American Mineralogist, October 1, 2007; 92(10): 1573 - 1585. [Abstract] [Full Text] [PDF]