Fluid Pathways at the Turquoise Ridge Carlin-type Gold Deposit, Getchell District, Nevada

Fluid pathways at the Turquoise Ridge Carlin-type gold deposit are deduced from patterns of lithology, structure, hydrothermal alteration, gold grade, carbonate oxygen isotopes and trace elements. Auriferous fluids migrated up the NNW-striking Getchell fault and entered antithetic and NE-striking small-displacement faults in the hanging wall, which, along with a pre-ore dike, served as conduits to high-grade ore bodies located up-dip. Flow was mainly fracture-controlled; evidence for extensive pervasive fluid flow is lacking. The base of the largest ore zone coincides with the footwall of a reactive sedimentary carbonate breccia unit, the base of ferroan calcite-bearing rocks, and a gradient in the organic carbon content of the host rocks. Abundant late ore-stage realgar occurs along the west side of Turquoise Ridge and marks the collapse of the hydrothermal system by incursion of meteoric waters down and into the Getchell fault zone. The patterns of fluid flow agree with percolation theory, whereby at low strain, flow along the Getchell fault linked the source of fluids and metals with sites of discharge into reactive host rocks. Small strain changes likely occurred during the change from compressional to extensional tectonics in the Eocene in northern Nevada.