Abstract

Fluid inclusions were studied in some 300 samples of quartz, taken from quartz pods, lenses, and veins occurring in the biotite, garnet, and staurolite-kyanite zones of metamorphosed Paleozoic and Pre-cambrian rocks in eastern Vermont. Most of the samples were taken from conformable quartz pods within a 200-km2 area of detailed study on the east flank of the Chester and Athens mantled gneiss domes in the southeastern part of the state (Fig. 1). This area is dominated by a steeply dipping sequence of garnet-zone metamorphic rocks of Silurian-Devonian age which occurs stratigraphically above the Taconic unconformity (Fig. 1). The lower part of the Silurian-Devonian section in this area consists of a transgressive marine sequence, which begins with conglomeratic quartzite, dolomitic carbonate, and minor schist and amphibolite of the basal Shaw Mountain Formation, and it is overlain by interbedded metapelites and dolomatic carbonates of the Northfield and Waits River Formations. The Geologic Map of Vermont (Doll and others, 1961) and details field investigations by Hepburn (1972), Rosenfeld (1954, 1968), and Thompson (1950) provided the regional geological framework for the present study.

Within the field area, conformable quartz pods averaging several centimetres in length are abundant in Silurian-Devonian pelitic rocks of garnet zone or higher metamorphic grade. Where the same rock units are less metamorphosed, conformable quartz pods are rare or absent, and crosscutting quartz veins and lenses are common. This suggests that the conformable quartz pods in the study area developed during garnet one metamorphism. Fluid inclusions were looked for but not found in numerous grains of rock quartz; the present quartz pod sites therefore appear to have been loci of fluid-phase activity during the regional metamorphism.

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