ALLOCYCLIC AND THERMOCHRONOLOGICAL CONSTRAINTS ON THE EVOLUTION OF THE MARITIMES BASIN OF EASTERN CANADA

The tectonic and metallogenetic evolution of the Maritimes Basin is co nstrained by its thermochronology, structure, and stratigraphy. Allocy clic sedimentary deposition occurred within the basin and reflects the shifts in tectonic subsidence from local rapid events to regional slo wer events. Apatite thermochronology combined with vitrinite reflectan ce data suggest that an additional 1.5 to 4 km of strata were deposite d prior to 280 Ma and subsequently eroded. The organic maturation and the apatite fission track modelling indicate that the exhumation took place from 280 to 200 Ma. The thermochronology data are consistent wit h a paleogeothermal gradient of approximately 25-degrees-C/km. The str ucture of the Maritimes Basin and the paleogeographic reconstructions based on paleomagnetics and sediment dispersal studies suggest that th e basin developed as a continental wrench-fault basin. The exhumation of the basin may be the result of pre-rift bulging or due to the erosi on of strata deposited above sea level following a waning in the sedim ent supply into the basin. The timing of basin-brine expulsion events which have been hypothesized to explain Pb-Zn-Ba deposits in the basin are constrained to pre 280 Ma, prior to the onset of exhumation. Redb ed Cu mineralization can be explained as being related to a period of reddening of the sandstones of the basin during the exhumation of the strata.