Fluid evolution and timing of the Stibnite-Yellow Pine district, Idaho

Abstract

Gold, antimony, and tungsten resources of the Stibnite-Yellow Pine district, Idaho, are hosted in complexly faulted Late Cretaceous Atlanta Lobe of the Idaho batholith and surrounding Neoproterozoic-Paleozoic metamorphic rocks. This study utilizes detailed petrography and trace element chemistry of quartz to establish relative timing relationships between successive ore forming events and provide textural constraints for the interpretation of geochronologic data. Textures are discussed in the context of fluid inclusion populations that provide evidence into the P-T-X evolution of the hydrothermal system. Results reveal that the deposits contain multiple overprinting generations of hydrothermal quartz, each with distinct cathodoluminescence (CL) signature, trace element chemistry, and fluid inclusion populations. Quartz textures record a complex history of recrystallization, dissolution, and successive overgrowth as fluids evolved towards lower temperatures and CO2 contents. Quartz associated with the main stage of Au deposition contains relatively high concentrations of Ti, with low concentrations of all other elements measured. Later quartz generations are depleted in Ti, but show elevated Al concentrations, with significant concentrations of Sb measured in quartz associated with stibnite. Textural and geochemical evidence suggests that the system evolved from deeper mesozonal Au-W deposition towards more shallow epizonal Sb-(Ag) deposition during a period of rapid uplift.