Massive Sulphide Deposits of the Eagle Bay Assemblage , Adams Plateau , South Central British Columbia ( 082

The Eagle Bay assemblage in south central British Columbia contains numerous polymetallic massive sulphide deposits, mainly within highly deformed and metamorphosed Devonian felsic volcanic rocks. A number of these, including Rea and Homestake, have had limited past production, and others have undergone extensive exploration and development. Less known and understood are the sediment-hosted massive sulphide deposits that occur on Adams Plateau near the southern extent of exposures of the Eagle Bay assemblage. These deposits are thin sheets of dominantly lead and zinc sulphides within carbonaceous and calcareous phyllites. Their age is unknown, but based on regional correlations and geochemistry of underlying mafic volcanic rocks, host successions may be equivalent to phyllites and quartzites of the EoCambrian Hamill Group exposed farther east. This paper describes these deposits, their structural and stratigraphic setting, and compares them to other deposits in the Kootenay Terrane. The paper is part of a regional study of massive sulphide deposits and mineral potential of the Kootenay Terrane of southern British Columbia and the correlative Yukon-Tanana Terrane in the northern part of the province and Yukon Territory (see Lett et al., 1999; Paulen et al., 1999). It summarizes six weeks of regional mapping and deposit studies in July and August, 1998. The Kootenay Terrane, and correlative rocks of the Barkerville subterrane farther north, comprise dominantly Paleozoic metasedimentary and metavolcanic rocks that are inferred to have been deposited on the distal western edge of ancestral North America. Major rock packages of the Kootenay Terrane include the Lardeau Group, the Eagle Bay assemblage, eastern assemblages of the Late Paleozoic Milford Group, and equivalent rocks within the Shuswap metamorphic complex. Massive sulphide deposits in the Kootenay Terrane include Besshi style volcanogenic massive sulphide deposits (VMS) of the Goldstream camp, formed during episodic extension along the western North American margin in Early Paleozoic time, and the Devonian polymetallic VMS deposits of the Eagle Bay assemblage, deposited in arc volcanic rocks in response to eastward subduction of a paleopacific ocean. Other important deposits or mineral camps within the Kootenay Terrane include numerous vein deposits in Lardeau Group rocks, such as the lead-zinc-silver veins of the Beaton-Camborne camp (Church, 1999), and within the Barkerville subterrane, the gold veins in the WellsBarkerville area. The Adams Plateau is a moderately high, low-relief plateau located southeast of Adams Lake in southern British Columbia (Figure 1). It is accessible by a well maintained gravel logging road that leaves the Scotch Creek road at Shuswap Lake park. The plateau is heavily treed, but with extensive logged areas. Numerous logging roads provide access to most of the area. Outcrops are relatively rare, and are largely restricted to roads and, less commonly, creeks. Mineral exploration on the plateau has focused on the sediment-hosted massive sulphide deposits, and two of these, the Mosquito King and Lucky Coon have had limited past production. Published reserves of these, and others on the plateau, are listed in Table 1. These deposits have locally high gold and copper content and exhibit close spatial association with