Abstract

The Salisbury pluton, composed chiefly of albite adamellite, is the most leucocratic and has the most anomalous trace element assemblage of 96 igneous bodies studied thus far in the Piedmont of the southeastern United States. Major element composition and textural evidence indicate that (l) the pluton originally underwent "eutectic point" crystallization in the system Ab-Or-An-Q-H2O; and (2) extensive metasomatic alteration occurred near the end of crystallization. The whole-rock Rb-Sr isochron age is 411 ± 6 m.y. The initial Sr87/Sr86 ratio of 0.7032 ± 0.0010 indicates that the original magma from which the Salisbury magma fractionated was derived from the mantle and was not contaminated by older crustal rocks.

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