Bedrock underlying the Slab iron oxide-copper-gold occurrence consists of fine-grained sedimentary rocks and schist of the Fairchild Lake Group (oldest unit of the Early Proterozoic Wernecke Supergroup), intermediate to mafic Slab volcanics, dioritic Bonnet Plume River Intrusions, and Early Proterozoic Wernecke Breccia that crosscuts all other units. The Wernecke Breccia was divided into two units: Type 1 and Type 2. Type 1 is limited in extent and consists of sedimentary and locally abundant massive magnetite clasts in a carbonate-magnetite matrix. Type 2 cuts Type 1 and comprises sedimentary clasts in a micro-breccia matrix. Iron oxide-copper-gold mineralization is associated with Wernecke Breccia. It occurs disseminated in quartz-carbonate veins cutting metasomatized sedimentary rocks, as sulphide veins that cut Type 1 breccia, as sulphide clasts in Type 2 breccia, as well as disseminated in the matrix of Type 2 breccia, and finally as sulphide veinlets crosscutting Type 2 breccia.