GEOTECTONIC EVOLUTION OF THE GREAT BASIN AND METALLOGENY

Geotectonic evolution of the Great Basin bears on metallogeny because ore-forming processes are just normal geologic processes writ large. Issues of crustal and mantle sources of metals, formation of protore, ground preparation, and fluid migration paths enter into any analyses of ore systems. The geologic history of the Great Basin is as complex as for any area of comparable size in the world, exerting multiple potential influences on ore-bearing host rocks and ore bodies. Precambrian crustal genesis in the eastern Great Basin concluded with development of an arcuate suture belt between Archean crust of the Wyoming craton and Paleoproterozoic crust to the south. Abortive Mesoproterozoic rifting north and south of the Great Basin may have extended into buried Great Basin basement. Neoproterozoic rifting led to thinning of Precambrian crust westward, where it is absent in the northwestern Great Basin, and to marine deposition of the Cordilleran miogeocline as far west as the central Great Basin until mid-Paleozoic time. Late Paleozoic to earliest Mesozoic overthrusting of oceanic allochthons from the west tilted the Cordilleran miogeocline to induce updip foreland fluid migration eastward. Mid-Triassic to Late Cretaceous batholiths of the Cordilleran magmatic arc overprinted the western Great Basin from mid-Triassic to Late Cretaceous time, a Triassic-Jurassic backarc basin was inverted by Early-Middle Jurassic thrusting in the central Great Basin, and in the eastern Great Basin an incursion of widespread backarc Middle-Late Jurassic plutonism was followed by development of the structurally linked Eureka and Sevier retroarc thrust belts in Cretaceous time. Cretaceous-Paleocene Laramide magmatism later swept eastward across the Great Basin, and was succeeded after a magmatic null by migratory Eocene-Oligocene arc volcanism that swept southward across the Great Basin before Miocene establishment of the extensional regime of the modern Basin and Range province. Each step in the tectonic history of the Great Basin had the potential to influence the distribution of protore if not ore.