Preliminary report on the geology and controlling parameters of the Goldcorp Inc. High Grade zone, Red Lake mine, Ontario

The association of axial planar carbonate veins, high-grade ore zones, and an F2 fold hinge deforming the basalt-ultramafic contact in the Goldcorp Inc. High Grade zone suggests a local geological control by an F2 fold. The development of such an F2 fold was potentially critical in forming the structures hosting the veins and in controlling fluid circulation allowing formation of the carbonate extensional veins within the basalt and their subsequent Au-rich silicic replacement. The CO2-rich and auriferous silica-rich fluids were preferentially focused in a low-pressure F2 hinge due to a combination of factors including competence contrast, tangential longitudinal strain associated with F2, and east-southeast-trending high-strain zones. The altered ultramafic rock acted as a less permeable barrier controlling fluid migration along the folded contact, allowing supralithostatic fluid pressure to build up and inducing a ponding effect in the basalt underneath, to create wide, high-grade ore zones in low-pressure hinges. The Au-rich silicic replacement of the carbonate veins was potentially synto late-D2. Subsequent strain remobilized gold in late, extremely high-grade structures. 2001-C18 B. Dubé et al. 1 CURRENT RESEARCH RECHERCHES EN COURS 2001 Article Article Titles Titres Purchase Information Information pour acheter 1 Contribution to Western Superior NATMAP Project 2 INRS Géoressources, 880 chemin Sainte-Foy, C.P. 7500, Sainte-Foy (Québec) G1V 4C7