Pressure-Temperature-Time Evolution of the Acadian Orogen, Central New England: Constraints from Detailed Petrologic and Geochronologic Studies: Collaborative Research

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This proposal represents a collaborative effort between F.S. Spear of Rensselaer Polytechnic Institute and T.M. Harrison of SUNY-Albany. The objective of the proposed research is the determination of pressure-temperature-time paths for metamorphic rocks from central New England during the Acadian orogeny. The areas chosen for study comprise four transects across central Massachusetts, southern New Hampshire and Vermont, and northern new Hampshire. Pressure-temperature paths of metamor- phism will be determined for rocks of different structural levels utilizing a combination of petrologic techniques including geothermobarometry, zoned metamorphic prophyroblasts, petrogenetic grids, and textural analysis. P-T paths will be correlated with structural evolution through analysis of mineral growth in relation to fabric development. Age constraints on the cooling histories of the rocks will be obtained from analysis of 40 Ar/39 Ar release spectra in hornblende, muscovite, biotite and K-feldspar. Zircon chronology on the ANU SHRIMP ion microprobe will be used to obtain absolute ages on pluton emplacement and to constrain the timing of structural development. The ultimate goal of this research is to obtain 4- dimensional (x-y-z-time) control on the thermo-tectonic behavior of the crust during the Acadian orogeny. It is anticipated that these results will lead to an improved understanding of the evolution of the continental lithosphere during collisional orogenesis in general.