Recent developments at the Mount Polley porphyry copper-gold mine

CIM Vancouver 2006
Lee Ferreira, Patrick McAndless, Chris Rees, Steve Robertson,
Abstract Mount Polley, 56 km northeast of Williams Lake, B.C., is a copper-gold alkalic porphyry, hosted in Late Triassic Nicola Group intrusive rocks. In March 2005, open-pit mining and milling operations resumed after a 3.5 year hiatus, stimulated by the discovery in 2003 of the Northeast Zone (NEZ). Reserves are 40.7 million tonnes grading 0.43 % copper and 0.31 g/t gold (NEZ, Bell and Springer; M200 permit application, July 2005). High-grade ore from the NEZ (Wight Pit) is supplemented by lower grade mill feed from the Bell Pit and stockpiles. The first shipment of concentrate was made in July 2005, less than two years after discovery of the NEZ. Chalcopyrite-bornite mineralization in the NEZ is hosted by a magmatic-hydrothermal breccia. Deeper extensions of the ore body containing locally high grades of copper (around 5%) and gold (up to 3 g/t) may support underground mining after the Wight Pit is completed. Exploration is continuing on the property, including adjacent to the smaller but relatively gold-rich Southeast Zone. Other deposit sub-types reveal a diversity of mineralization settings, requiring a flexible exploration strategy. Also planned for 2006 is further delineation of the still undeveloped Springer deposit, which will sustain mining for the longer term.
Keywords: Mount Polley, Copper, alkalic porphyry, Gold, Northeast Zone
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