THERMOCHRONOLOGICAL CONSTRAINTS ON ORE FORMATION AT THE GAYS RIVER PB-ZN DEPOSIT, NOVA-SCOTIA, CANADA, FROM APATITE FISSION-TRACK ANALYSIS

Fission tracks in detrital apatites from the Cambro-Ordovician metasedimentary basement in the vicinity of the Carboniferous-hosted Gays River Pb-Zn deposit, Nova Scotia, provide a record of final cooling during uplift and erosion of the Meguma Zone and constrain the timing of ore formation. An inferred thermal history involving regional heating to paleotemperatures >110°C during late Paleozoic burial followed by cooling to ~110°C prior to 240-220 Ma is suggested. A more recent phase or regional heating to paleotemperatures probably in the range of 60-80°C during Late Cretaceous-early Tertiary (c100-50 Ma) burial is also indicated by the track length data. Apatite fission track ages and mean track lengths from drill-core samples immediately beneath the Gays River orebody are similar to those for regional outcrop samples. -from Authors