THE RELATIVE HISTORY OF FLUID FLOW AND MINERALIZATION ALONG THE KENO FAULT, EAST CENTRAL NEVADA

Syntectonic veins deposited along the moderate-displacement Keno fault in east central Nevada record the history of fluid flow along that fault, as well as the late stages of mineralization in a Carlin-type gold deposit. The concentration of hydrocarbon inclusions decreased as mineralization occurred indicating that the oxidation state of the system increased with time. Sulfide mineralization was followed by sulfate mineralization, which was followed by oxide mineralization, which, along with the confocal laser scanning microscopy observations of the distribution of hydrocarbons, also indicates that the fluid regime became more oxidizing with time. Small-scale d¹⁸O and d¹³C analyses of the syntectonic calcite veins show that the veins formed due to the mixing of fluids from three distinct reservoirs: a mineralizing fluid that migrated along the Keno Fault, a reservoir of formation water contained within the deposit, and minor Tertiary meteoric water.