Thermodynamics of aluminosilicate garnet solid solution: New experimental data, an optimized model, and thermometric applications

Jibamitra Ganguly, Weiji Cheng, Massimiliano Tirone

Research output: Contribution to journalArticle

290 Citations (Scopus)

Abstract

We have experimentally determined the displacement of the equilibrium Grossular + 2 Kyanite + Quartz ⇄ 3 Anorthite (GASP) as a function of garnet composition in the systems Mg-Ca-Mn, Fe-Mg-Ca and Fe-Mg-Ca-Mn at 1000°C. The results were treated along with selected experimental and observational data available in the literature as well as binary parameters from other workers to obtain a set of mutually compatible binary mixing parameters of the quaternary (Fe,Mg,Ca,Mn)- aluminosilicate garnet solid solution. Attempts to determine equilibrium garnet composition in the GASP equilibrium in the Ca-Mg binary were unsuccessful due to the formation of pyroxene. Calculations of binary and ternary miscibility gaps show that the P,T,X combination required for unmixing of garnet solid solution is not realized by natural samples. The solution model was applied to account for compositional effects on Fe-Mg exchange between garnet and ortho- or clinopyroxene. Applications of the revised thermometric formulations to selected natural assemblages yield P-T conditions which are much less sensitive to compositional effects compared to the other available formulations, and are consistent with independent constraints. ΔV̄ and ΔV°: Partial molar volume change and end-member molar volume change of a reaction, respectively. WijG, WijH, and WijS: Subregular free energy, enthalpic and entropie binary interaction parameter, respectively, between the components i and j. WG(i-j), WH(i-j), and Ws(i-j): Regular solution or simple mixture free energy, enthalpic and entropie interaction parameter, respectively, between the components i and j. ΔW1: W(Mg-i) - W(Fe-i). X1α: Atomic fraction of the component i in the phase α in the site of mixing.

Original languageEnglish (US)
Pages (from-to)137-151
Number of pages15
JournalContributions to Mineralogy and Petrology
Volume126
Issue number1-2
StatePublished - 1997

Fingerprint

Garnets
aluminosilicate
solid solution
garnets
Solid solutions
garnet
solid solutions
thermodynamics
Thermodynamics
Global Air Sampling Program
volume change
Density (specific gravity)
Free energy
free energy
formulations
grossular
miscibility gap
Quartz
anorthite
kyanite

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

Thermodynamics of aluminosilicate garnet solid solution : New experimental data, an optimized model, and thermometric applications. / Ganguly, Jibamitra; Cheng, Weiji; Tirone, Massimiliano.

In: Contributions to Mineralogy and Petrology, Vol. 126, No. 1-2, 1997, p. 137-151.

Research output: Contribution to journalArticle

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