Geologic map of the Barre Granite District, Vermont: Supplement 1 from "Mode of emplacement of the Barre granite, Vermont" (Thesis)

Description

The Barre granite district, three to six miles southeast of Barre, Vermont, covers an area of less than thirty square miles. The main quarries were mapped on a scale of 200 feet to the inch, and an areal geologic map was prepared on a scale of 1500 feet to the inch. This region is underlain by phyllites, impure limestones, impure quartzites, and calcareous mica schists of the Waits River formation, at least a portion of which is Ordovician in age. The Barre granite, probably of late Devonian age, cuts these metasedimentary rocks. It is a fine to medium-grained gray granite with two distinct phases; the earlier of these, the "dark Barre", occupies the southern part of the exposed granite masses; the later phase, the "light Barre", is slightly lighter in color, and is a comagmatic member of the sequence. It occupies the bulk of the exposed granite masses. Previous workers have ascribed the emplacement of these plutons to forceful injection. Results of the present investigations suggest that a large portion of the space required for the pluton probably was gained by stoping processes. The factors which support this conclusion are: the small amount of doming in the granite, the small expansion across the schistosity, the uniformity of schistosity in the country rock, the complete removal of a large portion of the metasedimentary section by the granite, and the lack of orientation of inclusions in the granite.

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