Mineral Exploration

By FIONA KATAY Fall 20 1 6 13 PHOTO: DAVE GRIEVEGOVERNMENT OF BRITISH COLUMBIA T he unique geology of southeastern British Columbia has long been of interest for the mineral resources it contains. Not only does the region host good mineral potential, but the ease of access and well-developed infrastructure make it a favourable and profitable place for companies to work. Teck Resources Limited's zinc-lead smelter is also in operation there. Several mines and quarries operate within the region, contributing to both direct and indirect revenue and employment for surrounding businesses and communities, and for the entire province. The north-south-running Rocky Mountain Trench separates two major metallogenic provinces. On the western side, an older suite of Proterozoic greenschist facies rocks of the Purcell Supergroup (Belt-Purcell) and intrusive rocks host base and precious metals. To the east of the trench, largely unmetamorphosed Paleozoic to Mesozoic carbonate and clastic rocks of the Rocky Mountain fold and thrust belt are mined for coal and industrial minerals (gypsum, magnesite, tufa, limestone and silica). Belt-Purcell Basin The Mesoproterozoic Purcell Supergroup of southeastern B.C., dating from 1,500 to 1,300 million years ago, and the equivalent Belt Supergroup in Idaho and Montana, represent up to 12 kilometres of marine and non-marine sedimentary rocks that were project in 2015 and discovered the Berkey copper mineralized zone through prospecting. The property is underlain by the multi-phase alkaline Spout Lake intrusive complex and Nicola Group volcanic rocks. Near Kamloops, Tower Resources Ltd. announced the discovery of two new copper- gold targets, Kwil and KV, on its Rabbit North project, where copper mineralization is associated with the Durand Lake pluton. Near Merritt, Plate Resources Inc. drilled the Lucky Mike copper-tungsten skarn mineralization, hosted in Nicola Group volcanics and thought to be associated with a broad porphyry molybdenum-copper system. Despite a number of tough years for the industry, B.C.'s exploration and mining industry remains resilient. With seven operating mines, numerous encouraging prospects and strong support from researchers, government and explorers, the Quesnel terrane continues to grow its reputation as a highly prospective belt – particularly for porphyry-type ore deposits – for explorers in Canada and globally. The author thanks Paul Jago, regional geologist with the B.C. Ministry of Energy and Mines, for his generous contributions to this article. Quesnel Terrane Southeastern B.C. deposited in a north-northwest-trending intracontinental rift basin. Evidence of synsedimentary faulting during graben extension and sporadic magmatism characterize the lower Belt-Purcell stratigraphic successions (e.g., Moyie sills). Once deeply buried, these rocks were exposed at surface over an area of about 200,000 square kilometres during the Mesozoic contraction. About 10 per cent of this area is in southeastern B.C. The importance of the Belt-Purcell lies within its unusually high metal endowment, from both Mesoproterozoic and Jurassic-Cretaceous metallogenic events. Placer gold was discovered in the Belt-Purcell in the 1860s. With the influx of prospectors and miners, it wasn't long after that world-class discoveries were made: lead-silver at Coeur d'Alene, Idaho, and a copper-silver-gold-molybdenum porphyry-epithermal system at Butte, Montana. Within the Canadian portion of the Belt-Purcell, the North Star and Sullivan SEDEX deposits were discovered in 1892. Intracratonic rift systems that have been infilled by marine sediments such as the Belt-Purcell have long been recognized as the most favourable environment for the formation seafloor hydrothermal zinc-lead-(copper) sulphide, or SEDEX, deposits. These are prime exploration targets because of their large tonnage and grades. The Sullivan mine in Kimberley, B.C., operated from 1909 to 2001 and produced over eight megatonnes of zinc, 8.5 megatonnes of lead and 285 million ounces of silver over its lifespan. At the time of its closure, it had become both Canada's longest-lived continuously producing mine and one of the world's largest lead-zinc producers. Over its 92 years of active production, it contributed over $20 billion (in today's metal prices) to the economy, and the average number of employees each year exceeded 1,000. The early establishment of the phenomenal mineral endowment of the Belt-Purcell has supported an almost permanent mineral exploration interest in the area. Later discoveries included massive sulphide replacement deposits (Irish, Mississippi Valley and Manto); Mesoproterozoic intrusion and fault-related silver-lead-zinc and copper-silver veins; seafloor copper-cobalt deposits (Blackbird mining district and Sheep Creek); red-bed copper-silver deposits (Montana copper belt, such as at Spar Lake); and Mesozoic shear and vein gold. More recent work has also suggested potential for iron oxide copper-gold (Olympic Dam) type deposits and platinum group element mineralization in mafic intrusions. SEDEX-style sulphide mineralization within the Aldridge formation of the Purcell Supergroup

• Cover