Structure of the Ferderber gold deposit, Belmoral Mines Ltd., Val d'Or, Quebec

CIM Bulletin, Vol. 80, No. 907, 1987

L VU, Belmoral Mines Ltd. Val d'Or, Quebec, R. DARLING, Ecole Polytechnique, Montreal, Quebec, J. BELAND, Universite de Montreal Montreal, Quebec, and V. POPOV, Belmoral Mines Ltd., Toronto, Ontario

The Ferderber gold deposit is of Archean age. It consists of a series of gold-bearing quartz lenses within a shear zone that crosscuts the central part of the quartz dioritic Bourlamaque batholith. On average, this zone strikes N70E and dips 65SE. The Ferderber shear zone, which hosts the ore lenses, has been affected by a succession of tectonic events. A possible early period of brittle shear, accompanied by the formation of quartz lenses, resulted from strike slip movement along the zone. These early quartz veins were subsequently folded and boudinaged during reverse movement that accompanied a prolonged period of ductile shear. More quartz veins were emplaced in the shear zone at this time; these were also deformed by the thrusting. The latest tectonic event to affect the shear zone was a period of brittle fracture. Early dextral strike-slip movement on the shear zone is suggested by the local occurrence of Riedel shears, the preferred association of ore with east-northeast oriented segments of the zone, and by the apparent en echelon arrangement of some ore lenses. The most important event, a reverse movement, is indicated by the attitudes of foliation, folds, boudins, C-S tectonites and slip planes. The late brittle fracturing formed narrow gouge-filled faults, locally flanked by breccia zones, which run generally within and parallel to the shear zone, and also conjugate fractures that crosscut the zone. The Ferderber and six other adjacent gold deposits were formed in a structural regime dominated by a generally horizontal north-south regional compression. The Y axis of the strain ellipsoid is east-west and varies from horizontal to a plunge of 25°W.
Keywords: Structural geology, Gold deposits, Ore reserves, Exploration, Economic geology, Ferderber gold deposit.