Structural evolution and controls on gold mineralization at the Great Bear deposit, Red Lake, Ontario

Abstract

The Great Bear property is located 25 km south of the productive Red Lake gold camp in the Archean Superior craton, Ontario. It hosts the 6.6 Moz structurally-controlled Great Bear gold deposit. The property is bisected by the NW-striking LP deformation zone, which straddles a ca. 2710.2 ± 1.2 Ma northern felsic domain and a southern mafic domain of unknown age. The LP deformation zone is a ~3.5 km wide high-strain zone, characterized by a NW-striking, steeply NE-dipping foliation, transposed isoclinal folds, and a steeply to moderately NE-plunging mineral stretching lineation. Late Z-shaped folds strike E-W and are associated with steeply dipping dextral shear bands. These structures formed during a long-lived dextral transpression event, which began after 2710.2 ± 1.2 Ma and continued post-2692.4 ± 4.5 Ma. Gold-bearing veins are invariably folded and transposed parallel to the foliation, indicating that the deposit formed prior to this transpression event.