Stratigraphic and structural setting of stratabound lead-zinc deposits in southeastern B.C.

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

TRYGVE HOY Project Geologist, B.C. Ministry of Energy, Mines and Petroleum Resources, Victoria, B.C.

Important stratabound lead-zinc deposits in southeastern B. C. occur in rocks that range in age from Proterozoic Helikian to Middle Cambrian. The Sullivan deposit, and similar but smaller deposits in the Sullivan area are the only important deposits that occur in clastic rocks with little carbonate content. The highly deformed and metamorphosed Shuswap deposits, of probable Hadrynian to Helikian age, are in mixed marble, calc-silicate gneiss and pelitic schist assemblages, rocks transitional between elastics and carbonates. Deposits in younger rocks, such as the Kootenay Arc deposits in the Lower Cambrian Badshot-Reeves Formation and the Monarch -Kicking Horse deposits in Middle Cambrian dolomite, are hosted by platformal carbonate rocks.An important regional control for the distribution of deposits appears to be a northeast-trending tectonic zone that crosses the Rocky Mountains and the Purcell Mountains just south of the Sullivan area, and projects southwestward toward the Salmo camp at the southern end of the Kootenay Arc. Pronounced northeast-trending gravity and magnetic anomalies, basic volcanism of Hadrynian age (the Irene volcanics west of Creston) and a preferred alignment of Mesozoic granitic rocks indicates that the zone coincides with deep crustal structures. Within the zone are dramatic and abrupt thickness and fades changes in Hadrynian Windermere rocks and lower Paleozoic rocks, and on the east side of the Rocky Mountain Trench in Helikian Purcell Supergroup rocks, indicating that block-faulting was active intermittently within the zone from Helikian through to lower Paleozoic time. Right-lateral and reverse movements occurred on northeast-trending tear faults within the zone in Mesozoic time.All important lead-zinc deposits in the Helikian Aldridge Formation, including the Sullivan, North Star, Stemwinder and Kootenay King, are within or along the northern edge of the transverse zone, and many are associated with either a footwall conglomerate or anomalous concentrations of boron, both assumed related to "basement fractures", suggesting a direct genetic link between the deposits and the transverse zone. Furthermore, the largest concentrations of deposits in the Kootenay Arc, those of the Salmo camp, are located at the southwestern extension of the zone, and two of the larger placer gold camps of southeastern B.C., the Wild Horse and Perry River camps, are within the zone. It is, therefore, suggested that northeast-trending basement fractures that were the loci for syndepositional faults in Helikian, Hadrynian and lower Paleozoic time indirectly controlled the outflow of metal-charged convective fluids. Discharge onto the sea floor led to the formation of stratiform sulphide accumulations in both clastic and carbonate rocks. Locally, sulphides were also trapped in brecciated and dolomitized carbonate, resulting in epigenetic deposits with features similar to the so-called "Mississippi Valley" type.
Keywords: Mineral exploration, Stratigraphy, Stratabound deposits, Lead deposits, Zinc deposits, British Columbia, Purcell Group, Sullivan Mine, Kootenay King deposit, Shuswap Metamorphic Complex, Frenchman Cap deposits, Cottonbelt property, River Jordan property, Kootenay Arc deposits, Reeves-MacDonald Mine, Duncan deposit, Monarch deposit, Kicking Horse deposit, Shag Creek showings, Silver Giant Mine, Jubilee Mountain prospect, SOAB claims.