The magmatic copper-nickel sulphide deposits at Sudbury are part of the Paleoproterozoic Sudbury Structure which comprises the Sudbury Igneous Complex (SIC); breccias, mudstones siltstones and wackes of the Whitewater Group which occupy the centre of the Sudbury Basin; and a ring of brecciated and shockmetamorphosed Archean and Paleoproterozoic footwall rocks which surrounds the SIC. All rocks defined as footwall to the Sudbury Structure are cut by occurrences of Sudbury Breccia. This breccia occurs as small veins, irregularly shaped patches and large, laterally extensive, crudely tabular bodies, which may extend for many kilometres along strike. The rocks of the SIC, dated at 1.85 Ga, are exposed within an elliptical or beanshaped ring with a NE-rending long axis of 60 km and a short axis of 27 km.

North Range contact-type Ni-Cu deposits occur at the base of the SIC in association with a noritic to gabbroic inclusion-bearing contact phase termed the sub-layer, and within the metamorphic textured footwall breccia/granite breccia below the sub-layer in embayment features. These deposits include the Coleman Mine (formerly McCreedy East), Main, West and East orebodies.

The sub-layer inclusions consist of footwall and mafic to ultramafic rocks with the volumetric distribution of the sub-layer controlled by the shape and morphology of the basal contact of the SIC. Sulphide mineralization within the sub-layer consists of disseminated to massive sulphide genera ........

The primary mining methods used at Coleman Mine are Post Pillar cut-and-fill mining in the massive contact orebodies and mechanized cut-and-fill mining in the narrow vein footwall orebodies. For mining sill pillars in the Coleman main orebody (MOB) and the 150 orebody, Blasthole Stoping and/or underhand cut-and-fill mining methods are used.

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