Petrologic Studies in Southwestern New England

本文提出的研究包括对新英格兰西南部多重变形和多变质地体中变质及其伴生的长英质深成岩的综合研究。该项目的目标是利用这一经典的阿巴拉契亚地体来描述由新英格兰西部构造模型中描述的伴随着塔肯(奥陶纪)碰撞事件的构造增厚所导致的岩石学和热过程。这项研究还将提供新英格兰西南部高地东部阿卡迪亚(泥盆纪)热演化的详细图景。最重要的是，我们的努力还将集中在检查塔克期和阿卡迪亚事件之间的重叠区后来早期变质作用的确切性质。我们打算使用的技术包括：基于电子探针矿物化学分析的定量地质温差测量，以确定流体-岩石相互作用历史并帮助约束隆升历史；关键矿物的Ar同位素分析，以推断关键地区的温度-时间演化。由于我们在应用我们的成果时侧重于确定造山带的演化，所以这项研究集中在三个地理区域：康涅狄格州西南部和邻近的纽约东南部，在那里我们可以记录主要是塔科纪变质作用的影响；西部高地的中部和东部带，那里是多变质叠加的最佳展示区。

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.