EVIDENCE OF REDOX DISEQUILIBRIUM IN AN OROGENIC GOLD DEPOSIT FROM THE YELLOWKNIFE GREENSTONE BELT, CANADA

The Yellowknife Greenstone Belt (YGB), located within Canada’s Slave Province in the Northwest Territories (NWT), hosts several orogenic gold deposits including the world class Giant and Con mines. The composition of the mineralizing fluids, mechanisms of gold transport, and some of the controlling factors related to precipitation remain actively debated. Precipitation mechanisms proposed for gold in the YGB include fluid mixing and fluid-rock reactions associated with redox changes and sulfidation. Although mineralization style within the YGB is highly variable, there is a spatial correlation between gold mineralization and fluid inclusions containing high-pressure volatiles (i.e. CO₂ ±CH₄±N₂). This correlation suggests a link between mineralization and high-pressure volatile-rich fluids.

The Discovery-Ormsby Property is located approximately 90 kilometers north of Yellowknife, NWT. Mineralization on the property is associated with water-absent monophase carbonic fluid inclusions (CO₂±CH₄±N₂) as well as graphite-bearing inclusions (C±CO₂±CH₄±H₂O). Thermodynamic modeling of the mineralizing fluids and the host rock indicate the system was in a state of redox disequilibrium. Redox disequilibrium processes have long been recognized as a mechanism for gold precipitation and may be responsible for triggering precipitation at Discovery-Ormsby. Furthermore, the presence of high H₂S concentrations within fluid inclusions may hold further implications for gold solubility and transport within the region.