Geologic setting of recently discovered stratiform barite-sulphide deposits in northeast British Columbia

CIM Bulletin, Vol. 75, No. 840, 1982

D.G. MaclNTYRE, Project Geologist, Geological Branch, Mineral Resources Division, Ministry of Energy, Mines and Petroleum Resources, Victoria, British Columbia

Potentially economic stratiform barite-sulphide deposits have recently been discovered in Devonian basinal fades rocks of the Kechika Trough of northeast British Columbia. This new mineral district is over 180 kilometres long and includes nine major occurrences, namely Driftpile Creek, Bear, Mount Al-cock, Cirque, Fluke, Pie, Elf, Kwadacha and Sika. The Cirque is the largest known deposit, with reserves of at least 30 million tonnes averaging 10 per cent combined lead-zinc and 47 grams per tonne silver. The footwall rocks for the Cirque and other stratifrom barite-sulphide deposits in the area are rhythmically bedded baritic and pyritic carbonaceous black shales, siliceous argillites and cherts of probable Mid to Late Devonian age. These siliceous rocks overlie a succession of proximal to distal turbidites which are the basinal equivalent of Early to Mid Devonian carbonate reefs to the east. The siliceous fades is overlain by deeper-water black shales of probable Late Devonian to Mississippian age.Preliminary stratigraphic and sedimentological investigations suggest that the stratiform massive pyrite and bedded barite deposits formed in third-order euxinic basins within a northwest-trending structurally controlled trough which, in the southern part of the district, was bounded by carbonate reefs. The exhalative event, which appears to have been accompanied by synsedimentary faulting, took place during the early stages of a major eastward-directed marine transgression that was probably related to rapid crustal subsidence. De-watering of metal-enriched shales and subsequent brine discharge along fault zones within the trough, with the exhaled brines accumulating in seafloor depressions, is the mechanism envisaged for formation of the deposits. Convective circulation systems may have been established about the more deep-seated faults, in response to elevated heat flow levels.
Keywords: Mineral exploration, Stratiform deposits, Barite deposits, Sulphide deposits, British Columbia, Kechika Trough, Driftpile Creek occurrence, Bear occurrence, Mount Alcock showing, Cirque deposit, Pie claims, Fluke claims, Elf claims, Kwadacha deposit, Sika deposit.