Abstract

Simple pegmatites that occur in granitic and metamorphic rocks of Precambrian age are present in the Haystack Range. The bodies are described with regard to composition, zoning, and mode of occurrence, and evidence is presented to show that they were emplaced by one or more of 3 mechanisms: permissive filling, forceful displacement, and replacement of the host rock. Closely-spaced specimens of microcline were taken across 4 of the larger pegmatites and analyzed spectroscopically for Ba, Cu, Fe, Ga, Ge, Pb, Sr, Tl, V, and Y. No persistent trends could be detected toward an increase or decrease in the minor element content from the border zones to the centers of the pegmatites. The 4 pegmatites are characterized by an abundance of Pb. The pegmatites in the granitic host rock contain more Ga and less Pb than the pegmatites in the metamorphic host rock. Three samples of microcline from the granitic host rock contained less Pb and more Ba than the microcline from the pegmatites. Discussion is given to the problem of origin of these pegmatites.

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