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One of the largest and richest Canadian Archaean gold deposits, with more than 20 000 000 oz Au, the Campbell-Red Lake deposit includes the Goldcorp zone with reserves of 1 775 000 t at an average grade of 80.6 g/t Au and production since 2001 of 1 500 000 oz Au at 88 g/t. Such mineralisation provides an opportunity to define the geological parameters controlling high-grade ore formation and to develop exploration guidelines for similar targets. The deposit is proximal to a folded regional unconformity, a palaeosurface that represents a key target in the district and elsewhere in greenstone belts. New U-Pb data and detailed mapping of cross-cutting dyke relationships show that the main stage of the high-grade mineralisation predated c.2712 Ma and that a second stage, much smaller in terms of total gold content but spectacular in terms of grade, postdated c.2702 Ma. It is proposed that the first stage may have been synchronous with the emplacement of various stocks and intrusions while the seond stage is attributed to new or remobilised gold contemporaneous with emplacement of the 2699 Ma Walsh Lake pluton or a c.2660-2630 Ma post-collisional regional thermal event., One of the largest and richest Canadian Archaean gold deposits, with more than 20 000 000 oz Au, the Campbell-Red Lake deposit includes the Goldcorp zone with reserves of 1 775 000 t at an average grade of 80.6 g/t Au and production since 2001 of 1 500 000 oz Au at 88 g/t. Such mineralisation provides an opportunity to define the geological parameters controlling high-grade ore formation and to develop exploration guidelines for similar targets. The deposit is proximal to a folded regional unconformity, a palaeosurface that represents a key target in the district and elsewhere in greenstone belts. New U-Pb data and detailed mapping of cross-cutting dyke relationships show that the main stage of the high-grade mineralisation predated c.2712 Ma and that a second stage, much smaller in terms of total gold content but spectacular in terms of grade, postdated c.2702 Ma. It is proposed that the first stage may have been synchronous with the emplacement of various stocks and intrusions while the seond stage is attributed to new or remobilised gold contemporaneous with emplacement of the 2699 Ma Walsh Lake pluton or a c.2660-2630 Ma post-collisional regional thermal event.

The Goldcorp high-grade zone has reserves of 1 775 000 t at an average grade of 80.6 g/t Au. Geochronologic data combined with mapping and crosscutting relationships showed that the main mineralisation stage occurred before 2712 Ma and that a second stage, much smaller in total Au content but high in grade, occurred after 2702 Ma. The second stage is attributed to Au remobilisation caused by the enhanced thermal gradient and deformation associated with the emplacement of the Cat Island pluton (2699 Ma) or by the about 2.63-2.66 Ga postorogenic regional thermal event indicated by hornblende, muscovite and biotite Ar-Ar cooling ages from the Uchi sub-province. A folded and metamorphosed polymictic conglomerate located stratigraphically above the Campbell-Red Lake deposit is correlated with the newly recognised Huston assemblage. Areas of high potential for Au exploration occur in the Balmer assemblage rocks within 500-1 000 m of the unconformity., The Goldcorp high-grade zone has reserves of 1 775 000 t at an average grade of 80.6 g/t Au. Geochronologic data combined with mapping and crosscutting relationships showed that the main mineralisation stage occurred before 2712 Ma and that a second stage, much smaller in total Au content but high in grade, occurred after 2702 Ma. The second stage is attributed to Au remobilisation caused by the enhanced thermal gradient and deformation associated with the emplacement of the Cat Island pluton (2699 Ma) or by the about 2.63-2.66 Ga postorogenic regional thermal event indicated by hornblende, muscovite and biotite Ar-Ar cooling ages from the Uchi sub-province. A folded and metamorphosed polymictic conglomerate located stratigraphically above the Campbell-Red Lake deposit is correlated with the newly recognised Huston assemblage. Areas of high potential for Au exploration occur in the Balmer assemblage rocks within 500-1 000 m of the unconformity.

The zone was discovered 1 520 m below surface in the hangingwall of the existing orebody in Ontario, 46 years after it was first mined. The very rich ore is characterised by abundant visible native gold. Textural observations of ore within carbonate veins as well as cross-cutting relationships suggest that at least some of the gold was emplaced during peak metamorphism. Remobilisation after lamprophyre dyke emplacement is locally observed. Ore occurs where a fault trend intersected folded ultramafic volcanic rocks that created a semi-permeable cap-rock to ore fluids ascending the feeder structure. This was enhanced by strong competency contrasts between eastern ultramafic rocks, felsic volcanic rocks to the west and the mafic volcanic host rocks, so that protracted dilatant pathways developed. The zone was developed in 2000 at a capital cost of US, The zone was discovered 1 520 m below surface in the hangingwall of the existing orebody in Ontario, 46 years after it was first mined. The very rich ore is characterised by abundant visible native gold. Textural observations of ore within carbonate veins as well as cross-cutting relationships suggest that at least some of the gold was emplaced during peak metamorphism. Remobilisation after lamprophyre dyke emplacement is locally observed. Ore occurs where a fault trend intersected folded ultramafic volcanic rocks that created a semi-permeable cap-rock to ore fluids ascending the feeder structure. This was enhanced by strong competency contrasts between eastern ultramafic rocks, felsic volcanic rocks to the west and the mafic volcanic host rocks, so that protracted dilatant pathways developed. The zone was developed in 2000 at a capital cost of US