Geothermometry and geobarometry of Dalradian metapelites and metabasites from the Central Scottish Highlands

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Abstract
Synopsis: Temperatures and pressures of metamorphism have been estimated for a suite of Dalradian garnetiferous mica schists, calcareous pelites, and hornblende schists (‘Green Beds’) from Central Perthshire. Garnet-biotite, calcite-dolomite, and muscovite-paragonite geothermometers indicate temperatures ranging from about 500°C, corresponding to the lowest grade, to a maximum of about 580°C, corresponding to the highest grade. Garnet-kyanite-plagioclase-quartz, and epidote-plagioclase-garnet-quartz equilibria indicate pressures of 8–11 kb. These temperature, pressure estimates agree well with the experimentally determined phase stabilities. A thermal gradient of 60–65°C/kb (20–22°C/km geothermal gradient) characterizes this area.