AR-40 AR-39 AGE OF SHEAR ZONES IN THE SOUTHWEST MEGUMA ZONE BETWEEN YARMOUTH AND METEGHAN, NOVA-SCOTIA/

The Cape St, Marys, Cranberry Point, and Chebogue Point shear zones li e within a zone of D2 deformation that overprinted D1 fabrics and reac tivated F1 folds between the shear zones. D2 was accompanied by greens chist-facies metamorphism that variably overprinted earlier metamorphi sm of varying grade. A collection of single muscovite grains from pres sure shadows defining L2 in a sample from the Cape St. Marys shear zon e yields an average apparent age of 316 +/- 5 Ma. The age obtained for these grains from an isotope correlation diagram is 320 +/- 5 Ma. Age s for muscovite separates for two samples from the Cranberry Point she ar zone are 325 +/- 4 and 319 +/- 4 Ma. An amphibolite from this zone yields a discordant spectrum interpreted to reflect the combined effec ts of Acadian metamorphism and excess argon. The muscovite ages approx imate the lime of syntectonic deformation because muscovite closure te mperatures approximate the temperature of metamorphism during D2. Thus , together with published data from the Chebogue Point shear zone, our data indicate a Mid-Carboniferous age, ca. 320 Ma, for D2 within this system of three shear zones and reactivated folds.