Title: Thermodynamics of pyrope‐grossular garnets and their stabilities at high temperatures and high pressures
Abstract: Activity expressions for Mg 3 Al 2 Si 3 O 12 and Ca 3 Al 2 Si 3 O 12 in pyrope‐grossular garnets that include explicit enthalpy, entropy, and volume terms have been formulated from measured thermodynamic properties. Predicted Ca 3 Al 2 Si 3 O 12 activities agree well with those given by Hensen et al. (1975) based on high‐pressure phase equilibrium experimentation, when the latter activities are corrected to 1 bar with the measured partial molar volumes. Calculations of the stabilities of garnets in the CaO‐MgO‐Al 2 O 3 ‐SiO 2 system reproduce fairly accurately the most reliable phase equilibrium data at 1000°–1200°C that do not heavily involve a clinopyroxene phase. Though the calculation of garnet‐clinopyroxene stability relations is in general agreement with available experimental observations, a critical comparison is hindered by the uncertainties in the high‐temperature heat capacities of the garnet and clinopyroxene components. The predicted solvus in the garnet join develops a ‘spike’ at high pressures which is displaced toward pyrope‐rich compositions.
Publication Year: 1980
Publication Date: 1980-12-10
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 73
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