Petrologic Studies in Southwestern New England

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The research proposed here comprises an integrated study of metamorphic and associated felsic plutonic rocks in the multiply deformed and polymetamorphosed southwestern New England terrane. The goal of this project is to use this classic Appalachian terrane to characterize the petrologic and thermal processes resulting from the tectonic overthickening that accompanied the Taconian (Ordovician) collisional event described in tectonic models of western New England. The study will also provide a detailed picture of Acadian (Devonian) thermal evolution in the eastern portion of the southwestern New England highlands. Most important, our efforts will also be concentrated on examining the exact nature of the overprinting of later on earlier metamorphisms in the zone of overlap between the Taconian and Acadian events. The techniques we intend to use include: quantitative geothermobarmometry based on mineral chemical analyses by electron microprobe, to determine fluid-rock inter- action histories and to help constrain uplift histories; argon isotopic analysis of key minerals to deduce temperature-time evolution of key areas. Because our emphasis in applying our results is in determining the evolution of an orogenic belt, the study is focussed on three geographic areas: southwestern Connecticut and adjacent southeastern New York where we can document predominantly Taconian metamorphic effects; the central and eastern belt of the western highlands where the polymetamoprhic overlap is best displayed.