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 generally zoned from massive sulphide at the footwall to disseminated sulphide ore towards the hangingwall. The PGE-Au content of the contact deposits is variable but low.

The bulk of the economic North Range Ni-Cu occurs within the granite breccia. This footwall breccia consists of fragments of country rock, exotic ultramafic inclusions and rare sub-layer and mafic norite xenoliths in a metamorphic-textured quartzo-feldspathic matrix. Mineralization occurs as blebby disseminations and fragments of sulphide, veins and stringers, and as accumulations of massive sulphide within bodies of footwall breccia. A transition zone exists between the footwall breccia and non-brecciated footwall rock with the greatest amount of sulphide found at the base of the footwall breccia.

Two types of footwall deposits have been defined in the North Range. These are massive stockwork style sulphide Cu-PGE-Au deposits (Coleman Mine 153 and 170 orebodies) and disseminated low sulphide high PGE-Au zones and deposits (Coleman 148 Zone and lenses within the 153 Orebody). Footwall mineralization is highly fractionated compared to the contact mineralization and is emplaced within or near thermally metamorphosed Sudbury Breccia into dilatant fractures. A physical connection between the contact sulphide and footwall sulphide is not always preserved or recognized.

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.

Ore is transported from the Ontario Operations mines and third party ore suppliers by rail and/or truck to Clarabelle Mill where it is blended together. The ore is crushed and ground, with the majority of the pyrrhotite removed through magnetic separation and sent to a designated waste storage area in the Copper Cliff tailings impoundment area. The remaining ore undergoes selective flotation to produce a bulk nickel and copper concentrate grading 14% Ni equivalent and approximately 8.5% Cu and 11% Ni. The concentrate is dewatered, mixed with custom concentrate feed and high-grade silica flux and conveyed to the smelter. The rock tailings are used for mine backfill, building dams in the Tailings area, or disposed of in the Copper Cliff tailings impoundment area.

Concentrate produced from the flotation process is used to generate a high copper concentrate by depressing the pentlandite, thus allowing the copper to float. The concentrate is then filtered to produce a filter cak ........