Contributions to Mineralogy and Petrology

, Volume 76, Issue 1, pp 92–97 | Cite as

Geobarometry and geothermometry of plagioclase-biotite-garnet-muscovite assemblages

  • Edward D. Ghent
  • Mavis Z. Stout
Article

Abstract

The assemblage, plagioclase-biotite-garnet-muscovite is widespread in garnet to lower sillimanite zone metasedimentary rocks. The equilibria, (1) pyr+gr+mu=3an+phl and (2) alm+gr+mu=3an+ann, involve a change in Al coordination from 6 to 4 and in Mg-Fe coordination from 8 to 6 and should be strongly pressure dependent. Using an ionic solution model we can define solid activity products for (1) and (2). Using a linear least squares analysis of activity products and estimated P-T from natural assemblages we can derive equilibrium constant equations for (1) and (2). Combining either of these equations with that for Mg-Fe exchange for garnet-biotite from Ferry and Spear (1978) allows estimation of P and T of metamorphism. Pressures estimated from these equilibria compare favorably to pressures estimated from garnet-plagioclase-Al2SiO5-quartz equilibria.

Keywords

Mineral Resource Activity Product Solution Model Ionic Solution Sillimanite 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag 1981

Authors and Affiliations

  • Edward D. Ghent
    • 1
  • Mavis Z. Stout
    • 1
  1. 1.Department of Geology and GeophysicsUniversity of CalgaryCalgaryCanada

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