TECTONIC SETTING OF THE SLIDE MOUNTAIN TERRANE, SOUTHERN BRITISH-COLUMBIA

The Slide Mountain terrane (SMT) in southern British Columbia consists of rocks of continental and oceanic affinity that are juxtaposed with parautochthonous rocks of the North American continental margin. In s outhern British Columbia, SMT consists dominantly of Fine-grained quar tzose elastic rocks, limestone and lesser amounts of conglomerate and volcanic rocks of the Carboniferous McHardy assemblage, and predominan tly mafic volcanic rocks of the Permian Kaslo Group. U-Pb ages of indi vidual detrital zircons from the McHardy assemblage are 1.7 Ga to 3.1 Ga and are similar to published ages of zircons from sedimentary rocks of the adjacent Kootenay terrane and the North American continental m argin. These data and the petrology of McHardy assemblage sandstones a nd conglomerate suggest Kootenay terrane and the North American miogeo cline as sources for McHardy assemblage detritus. U-Pb zircon ages of granitoid clasts within McHardy assemblage conglomerate indicate that Silurian granitic rocks also provided detritus to the SMT. Mafic volca nic, ultramafic, and sedimentary rocks of the Kaslo Group conformably overlie the McHardy assemblage. New geochemical data demonstrate that the Kaslo Group consists of light rare earth element depleted basalts. On the basis of geochemical and geologic data, we suggest that Kaslo Group volcanics were erupted within an ocean ridge proximal to the Nor th American continental margin and probably represent the eastern (con tinental) margin of a Permian marginal basin. Lithologic, stratigraphi c, and U-Pb geochronologic data suggest that the SMT was deposited on autochthonous, distal miogeoclinal rocks of the adjacent western North American craton and in close proximity to an early Paleozoic are terr ane. We infer that correlative late Paleozoic basinal terranes in west ern North American were deposited in a similar tectonic setting.