Abstract

Use of Al content geobarometry on clinopyroxene inclusions in plagioclase from the Carboniferous Liberty Hill pluton, South Carolina, yields pressure estimates of 8-10 kbar. Amphibole crystallization pressures are 3.1-4.7 kbar; contact metamorphic pressures are 4.5 kbar. Clinopyroxenes could be early crystallization products from the melt, restite crystals from the source region, xenocrysts from the magma conduit walls, or xenocrysts from a more mafic magma. Compositional uniformity of granitoid clinopyroxenes but dissimilarity with those in contemporaneous gabbroids is evidence against a xenocrystic origin. The deeper depths are interpreted as either the source region or a pausing place important in the crystallization history of the magma during its ascent to the upper crust. Early crystallization assemblage of the granitoid, and possibly the assemblage of the source region, was amphibole + clinopyroxene ± plagioclase-bearing. An amphibolitic lower crustal source is consistent with the Sr and O isotopic and rare-earth-element studies of this and many other similar-age granitoids in the southern Appalachians.

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