Lithophile Metals and the Cordilleran Tin Belt
R. MULLIGAN, Economic Geologist, Geological Survey of Canada, Ottawa, Ont
The Cordilleran tin belt extends from the Seward Peninsula in westernmost Alaska to Mexico. Throughout the Canadian section, tin occurrences are mainly confined to a belt along the northeastern fringe of the Western Cordilleran sub-region; the boundary of this sub-region with the Eastern Cordilleran sub-region is most simply defined as the practical eastern limit of granitic and metamorphic rocks. The stratified rocks underlying this restricted belt are mainly late Precambrian and early Paleozoic miogeosynclinal sedimentary rocks, which are more or less metamorphosed but otherwise are generally equivalent to the less severely deformed rocks underlying the Eastern Cordilleran sub-region. They contrast with Late Paleozoic - Mesozoic eugeosynclinal volcanic-sedimentary assemblages farther west, but the granitic intrusions throughout are mainly of Late Mesozoic age. Thus, narrowly defined, the tin belt largely coincides with a lead-zinc-silver metallogenic province, whereas copper deposits characterize the eugeosynclinal regions to the west. In addition to the tin occurrences, which include the Sullivan lead-zinc-silver mine, Canada's only significant producer, the belt contains all the beryllium, most of the tungsten and many Iithophile-type molybdenum occurrences. Several types of occurrences of each metal are represented. Lithium occurrences in the Canadian Cordillera are notably rare, and these few are insignificant.
batholith, Beryllium, granitic, scheelite, Tin Belt, Deposits, Intrusions, Mine, Mines, Rock, Rocks, tin