STRUCTURAL FEEDERS AND GOLD TRAPS EXPLAINED AT TURQUOISE RIDGE MINE, NORTHERN NEVADA USA

Turquoise Ridge (TR) is a large Carlin-type Gold Deposit in Northern Nevada. It lies on the east flank of the Osgood Range, proximal to the Rodinian rift margin and Miocene Northern Nevada Rift. District Gold mining began in 1934 and TR is one the largest regional gold producers since opening in 1998. Stratigraphy is Cambrian Prebble Formation, terrigenous mudstones interlain with mafic OIBs; and mid to upper Cambrian Comus Formation, slope limestones with OIBs. The allochthonous package was thrust over by Ordovician Valmy and Permian Havallah formations during the Antler and Sonoman orogenies. The deposit formed in Cambrian stratigraphy between igneous bodies including a Cambrian syenite body, Silurian MORB North Pillow Basalt (NPB), and Cretaceous dioritic Osgood stock (OS) and associated low-angle E-dipping dikes. The Long-lived deformation and magmatic history created significant rheological contrasts between sediments and resistant intrusive bodies forming a connected, complex network of steep and low-angle faults that focused hydrothermal fluid flow.

East-verging Paleozoic Antler-Sonoman shortening created thrust faults forming an asymmetric antiform on the west margin of the massive NPB. The later, high-angle, BBT fault system formed axial planar to this fold. The OS and associated metasomatism altered the sediments, increasing fracturing and permeability. Laramide-aged SW-NE shortening refracted stratigraphy about the south margin of the NPB, forming the bedding-parallel, steeply N-dipping Atlantic fault and associated fold. Eocene mineralization is syn-extensional with displacement focused along the moderately E-dipping Getchell fault which exploits the OS/wall-rock contact. Mineralizing fluids travelled up the reactivated thrusts, Getchell fault and K dikes until they intersected the steeper Atlantic and BBT faults, reacting with deformed Fe-bearing intrusives and metasomatized carbonates and creating a vertically extensive, high-grade Gold deposit.