THE P-T-t HISTORY OF A BARROVIAN SEQUENCE IN DUTCHESS COUNTY, NEW YORK, AND THE ADJACENT PART OF CONNECTICUT

Abstract

The P-T-t history of a Barrovian sequence in Dutchess County, New York and the adjacent part of Connecticut was studied. Using the average P-T mode in THERMOCALC, the following P-T results were calculated for the garnet, staurolite, kyanite and sillimanite-K-feldspar zones (1sigma uncertainties): 5.2±0.8 kbar, 570±12°C; 5.9±1.1 kbar, 557±12°C; 6.4±1.1 kbar, 600±29°C; and 7.4±1.4 kbar, 752±68°C, respectively. Phase equilibria modeling in the MnNCKFMASHTO system yields peak P-T results consistent with the average P-T results.

Monazite ages were obtained for the garnet, staurolite, kyanite and sillimanite-K-feldspar zones (2 sigma uncertainties): 455±6 and 453±10 Ma; 451±9 and 438±8 Ma; 478±6, 431±4 and 425±8 Ma; 533±7 Ma, 507±6, 506±4 Ma and 472±5 Ma, respectively. These ages help to constrain the timing of the Taconic and Salinic orogenic events.