The Copper Cliff Mine, part of Sudbury Operations, is owned and operated by Vale Canada Limited, a wholly-owned subsidiary of Vale Base Metals Ltd., the holding entity of Vale’s Energy Transition Metals business.
On April 30, 2024, Vale S.A. announced the completion of the sale of Vale Base Metals Ltd. (“VBM”) to Manara Minerals, under which Manara Minerals acquired a 10% interest in VBM.
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Summary:
The Copper Cliff deposit consists of numerous mineralized zones. The major zones include the actively-mined 120, 100, 900, 880, 865, 860, 830, 810 orebodies, and the currently inactive 191, 178, 138, 890, 850, 790, 740, 725, and 712 zones.
Copper Cliff is predominantly an Offset-style deposit with associated minor Contact- and Footwalltype mineralization styles. Mineralization is hosted in a quartz–diorite dyke, the Copper Cliff Offset, which strikes 15 km south into footwall rocks from the base of the SIC, is steeply dipping, and averages 40 m wide. The Copper Cliff Offset is cut by narrow aplitic, quartz diabase, and olivine diabase dykes, locally referred to as “trap dykes”.
Contact-style mineralization associated with Sublayer norite is present in the North Copper Cliff mine area. Sudbury Breccia occurs in footwall rocks adjacent to the Copper Cliff Offset.
Structure
The Copper Cliff Offset is affected by post-impact displacement along the Creighton and Murray faults and several smaller splay faults.
The Copper Cliff Offset is folded about northeasterly-trending open fold axes that have steeplydipping axial planes. Folding of the quartz–diorite dyke is confined to part of the dyke south of the Creighton fault. West-trending diabase and northwest-trending olivine diabase dykes post-date the folding.
Mineralization
The sulphide mineralization is mainly associated with coarser grained quartz diorite and rarely crosscuts footwall rocks. Mineralization consists of disseminated and ragged disseminated sulphides, interstitial sulphides, inclusion massive sulphides, gabbro peridotite inclusion sulphides, contorted schist inclusion sulphides and massive sulphides.
The major sulphides are pyrrhotite, chalcopyrite and pentlandite. Minor sulphides include pyrite, cobaltite, sphalerite, galena, and gersdorffite (NiAsS). The precious metal mineral assemblage includes sperrylite, froodite (PdBi2), michenerite, hollingworthite ((Rh, Pt, Pd) AsS), native gold, argentite (Ag2S) and hessite (Ag2Te).
Sulphide content increases towards the centre of the ore zones and also increases with depth. Typically, chalcopyrite content increases from the centre along strike and down-dip. The Copper Cliff mine zones have variable copper to nickel and pyrrhotite to nickel ratios.