Phase Equilibria in Three Assemblages of Kyanite-Zone Pelitic Schists, Lincoln Mountain Quadrangle, Central Vermont

Abstract

Petrologic and geologic arguments suggested that a close approach to chemical equilibrium at a single temperature and pressure might be found in the rocks near Mt. Grant in central Vermont. An area 2,800 feet by 4,000 feet was selected and studied in detail. The major assemblages are: kyanite-chloritoid-chlorite-quartz-muscovite-paragonite-rutile; garnet-chloritoid-chlorite-quartz-muscovite-paragonite-ilmenite; and garnet-chlorite-biotite-quartz-muscovite-albite-ilmenite. All minerals were separated from a primary sample for each of these assemblages and purified, complete gravimetric and spectrographic analyses performed, and optical properties, X-ray properties, and densities measured. Chlorite, garnet, and chloritoid or biotite were separated from an additional nine samples of these assemblages and spectrographic and partial gravimetric analyses performed.