MINERALOGY OF SUPERGENE CARBONATE-HOSTED NONSULPHIDE ZN-PB MINERALIZATION IN SOUTHERN AND CENTRAL BRITISH COLUMBIA

Carbonate-hosted nonsulphide base metal (CHNSBM) deposits form in supergene environments when base metal sulphides are oxidized and chemical weathering causes the metals to be leached out and deposited as metal-bearing gossans. The metals can be deposited by “direct replacement” as nonsulphide minerals directly above the sulphide ore, or can travel away from the underlying sulphides with percolating water and be deposited as “wall-rock replacement deposits”. Direct replacement deposits are known as “red ores” and are usually rich in iron oxides and contain economic concentrations of zinc and lead. Wall-rock replacement deposits, known as “white ores”, typically contain higher concentrations of zinc but lesser amounts of lead. Both forms of mineralization have been recognized as valid exploration targets in B.C., but detailed mineralogy and chemistry of representative deposits is needed to better establish exploration models. Petrography, XRD and SEM analyses were completed on select nonsulphide deposits, i.e., Redbird, Lomond, and Oxide in the Salmo district of the Kootenay terrane, and Cariboo Zinc in the Quesnel Lake district of the Cariboo terrane. All of the deposits studied fit the direct replacement style of nonsulphide mineralization with the exception of the Oxide property, which shows traits of wallrock replacement style mineralization. Though different, both deposits fit the general supergene model of nonsulphide mineralization and further characterization can assist in creating an exploration model for similar deposits in BC and the rest of the Cordillera.