The Campbell mine, located in northwestern Ontario, Canada, is developed within a metamorphosed and deformed fault-controlled Archean gold deposit hosted predominantly within basalt and ultramafic rocks with lesser quantities of rhyolite and diorite. The sequence of hydrothermal alteration has been subdivided into three partially overlapping phases consisting of an early alteration phase, followed by the main-stage vein phase, and culminating in the mineralization phase. Early alteration consists of two substages represented by carbonatization and pervasive biotite (potassic) alteration, and early silicification and aluminosilicate-bearing alteration. Carbonate alteration is relatively wide-spread, whereas biotitic alteration occurs proximal to alteration-controlling structures in highly carbonatized and/or silicified rocks. Carbonate-biotite alteration grades into carbonate-chlorite alteration laterally outward.