The evolution of continental crust in the northern Appala- chians involved subduction, arc magmatism, erosion and sedimen- tation, metamorphism, anatexis, and microplate accretion. This project will investigate aspects of these processes by examining the chemistry and isotope geochemistry of igneous rocks associ- ated with the two major tectonic events in the region, the Taconic and Acadian orogenies. Between ~460-430 Ma ago, a bimodal volcanic sequence and two distinct calcalkaline plutonic series were emplaced in an island-arc and Andean-type continental margin, presently known as the Bronson Hill Anticlinorium, during the closure of the Iapetus ocean. Detailed trace element and Sr, Nd- and Pb- isotope studies of these rocks can resolve the relative roles of mantle and crustal components involved in magmagenesis. In rocks whose crustal contributions are high, Nd and Pb isotope studies combined with ongoing U-Pb zircon work can reveal the nature and age of underlying and hitherto hidden continental crust. The results of this study will constrain models dealing with head and mass transfer from the mantle and within the crust during orogenic episodes.
