Ore Deposits Tectonics And Metallogeny In The Canadian Cordillera

This report provides a tectonic and mineral deposit overview, then discusses deposits in North American rocks, followed by deposits formed in accreted and suspect' terrains; deposits formed at or near the sea floor or from hot springs; and those formed in successively deeper zones as magmatic deposits, vein to replacement deposits, skarns, and porphyries. Deposits within and directly linked to intrusive rocks (magmatic, porphyries, skarns), replacement deposits, possible manto deposits, deep to shallow veins and related deposits formed at the surface, volcanogenic massive sulphides and sedex deposits are then discussed. Sedimentary-hosted deposits of gypsum, barite, phosphate and other industrial minerals are not covered, nor are coal, uranium, pegmatite-hosted deposits, molybdenum prophyries or some of the less common deposit types such as carbonatites, tin greisens, and placers.

This summary report commences with a brief metallogenic overview of the northern Pacific Rim, with particular attention paid to the world-class Mesozoic and Cenozoic ore deposits that define the region's premier metallogenic provinces. This is followed by a summary of the relative attractiveness of the region's various mining jurisdictions, as recorded by recent exploration activity.

Steep crustal-scale faults, having their origins in the Late Archean and Early Proterozoic and trending NE-SW, which define the fundamental block lithospheric structure of the North American craton, are seen from geological and geophysical evidence to continue far into the interior of the Late Proterozoic-Phanerozoic Canadian Cordilleran mobile megabelt. This suggests that variously reworked ex-cratonic basement blocks underlie much of the Cordillera. The western edge of the modern craton is probably near the Rocky Mountain-Omineca belt boundary; the Rocky Mountain fold-and-thrust belt on the east side of the Cordillera is evidently rootless and overlies the undisturbed cratonic basement. Phanerozoic differences between the Cordilleran tectonic belts, resulting from a long, dissimilar, multi-cycle history of waxing and waning orogenesis apparent from the rock record, lie chiefly in the degree of indigenous tectonic remobilization and reworking of the ancient crust.

Steep crystalline-basement faults, commonly indicated by potential-field anomalies, played a crucial role in evolution of continental cratonic platforms. In the Phanerozoic Western Canada Sedimentary Province, history of crustal block movements and warps is reconstructed from the distribution of depocenters, lithofacies and structures in structural-formational étages in sedimentary cover. Each étage is a rock succession formed during a particular tectonic stage; regional tectonic restructuring closes each stage, and the next stage represents a new tectonic regime. Practical tectonic analysis, based on observation of rocks and geophysical data, is a reliable guide for deciphering a region's geologic history and for resource exploration.