ABSTRACT
Five separate porphyry intrusions have been mapped on the basis of crosscutting relations between dikes and veins. Each intrusion was followed by a cycle of quartz vein formation, potassic alteration and copper-gold deposition. The first porphyry is coeval with the bulk of the copper-gold ore in the deposit, and metal introduction decreased through later cycles. Deposition of bornite-digenite-chalcopyrite and gold occurred relatively late within each porphyry cycle, after the main stage of quartz vein formation at 400 to >575°C. Cathodoluminescence petrography shows that copper-iron sulfides, minor quartz, and minor K-feldspar were deposited in fractures and irregular vugs within early formed quartz veins and wallrock, and preliminary fluid inclusion data indicates that sulfide deposition occurred at temperatures below 400°C. Fluid inclusions in quartz veins spanning a 1500m vertical range show that initially homogeneous CO2-rich magmatic-hydrothermal fluids underwent phase separation within the porphyry conduit at estimated paleodepths of 2-3 km. Molybdenite-quartz veins formed after termination of dike emplacement, and are in turn cut and offset by quartz-sericite-pyrite veins.
