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Migmatization Of Archean Aluminous Metasediments From The Eastern Beartooth Mountains, Montana, U.S.A., Andrew T. Maas

LSU Master's Theses

Geothermobarometry, mineral compositions and textures, and thermodynamic models suggest biotite dehydration melting occurred in the peraluminous rocks of the eastern Beartooth Mountains. These Archean metapelitic migmatites are metatexites and diatexites, and have typical metamorphic assemblages of Qtz + Pl + Kfs + Bt + Sil +/- Grt +/- Crd. The subsequent in situ crystallization of the magma derived from the biotite dehydration created migmatitic leucosomes in the rocks. These leucosomes are primarily composed of quartz, plagioclase and potassium feldspar. Water derived from the dehydration of biotite was dissolved in the melted phase. Crystallization of the magma reintroduced this water to …