The PureGold Mine is located within the Red Lake Greenstone Belt (RLGB) of the Archean Superior Province craton of the Canadian Shield.
The RLGB is approximately 50km by 40km, and comprises 2.99Ga to 2.70Ga deformed and metamorphosed supracrustal (volcanic and sedimentary) rocks intervening between three main granitoid batholiths.
The RLGB has a prolific history of gold production over a 90-year history. All major deposits in the RLGB are hosted within the ca. 2.99Ga to 2.96Ga Balmer Assemblage which includes the belt’s oldest volcanic rocks that are predominantly of submarine mafic tholeiite and ultramafic komatiite composition.
Gold deposits in the RLGB are classified as orogenic gold deposits (Groves et al., 1998) and characterized by an association with crustal-scale fault structures. Gold deposition in orogenic gold deposits is typically syn-kinematic and syn- to post-peak metamorphic, and is largely restricted to the brittle-ductile transition zone.
Rock units of the RLGB are multiply deformed and metamorphosed. On the PureGold Mine property, this complex deformation history is most readily explained through an early phase of tight upright folding (D1) and an overprinting minor folding event and associated widespread foliation development (D2).
Significantly, the PureGold Mine, Fork, Russet South, and Wedge deposits all occur within planar structures (shear zones) that developed generally axial-planar to property-scale D1 folds. These early planar mineralized structures are the main targets for further gold exploration at the PureGold Mine and, although they have been strongly overprinted by penetrative D2 deformation and metamorphism, they can be effectively identified by a distinct series of mineral phases (alteration), vein styles (blue-grey, deformed quartz veins), and quartz porphyritic intrusions that pre-date gold mineralization and occur within the D1 shear zones.
In some ways, the PureGold Mine deposits seem atypical in that they are strongly overprinted by deformation and metamorphism rather than being syn- to post-peak metamorphic. The age of D1 deformation and gold mineralization, however, is poorly constrained and, if the overprinting deformation is unravelled from the PureGold Mine deposits, they closely fit the orogenic gold deposit model – including an association with crustal scale structures, and an association with pervasive structurally-controlled carbonate alteration and quartz-carbonate.1