Late Archean regional deformation and structural controls on gold-quartz vein mineralization in the northwestern Slave Province, N.W.T., Canada

Abstract

Late Archean crustal accretion in the northwestern Slave Province is suggested to have involved approximately west-northwest–east-southeast directed horizontal compression that produced three episodes of deformation recognizable in the northwestern Anialik River igneous complex (ARIC) and Anialik River greenstone belt (ARGB). Observations show that the ARIC was probably emplaced as a series of synvolcanic sills prior to the earliest deformational event. Regional shortening produced a pervasive foliation, downdip lineations and folding in the ARGB, and an early, subsequently folded, foliation in the northwestern ARIC. Postfold ductile and brittle–ductile deformation produced regional- and outcrop-scale shear zones including the Sheeted Zone, which defines the ARIC–ARGB contact. Younger rocks of the northwestern ARGB appear to have been tectonically juxtaposed along the Sheeted Zone against the older rocks of the northwestern ARIC. Greater brittle response, enhanced permeability, and cyclical increases in fluid pressure led to the development and concentration of an anastamosing network of gold-quartz vein bearing shear zones in the ARIC. Steep to subvertical shear-related linear fabrics show that regional-scale and mineralized shear zones have a large component of vertical shear with predominantly east-side-up movement. The age relationships, proximity, and similarity of deformational structures in the Kangguyak gneiss belt, containing a craton-scale ductile deformation zone, and shear zones within the Arcadia Bay area, suggest contemporaneous development and regional late Archean structural relationships similar to those of shear zone hosted gold-quartz vein mineralization seen in the Abitibi Subprovince (Canada) and Yilgarn Craton (Australia).