Fault-Controlled Lateral Fluid Flow Underneath and Into a Carlin-Type Gold Deposit: Isotopic and Geochemical Footprints

摘要

Many Carlin-type gold deposits in northern Nevada are found adjacent to steeply dipping faults that channeled hydrothermal fluids upward into mineralized regions. However, some Carlin deposits comprise gently dipping tabular ore zones lacking any obvious large, steeply dipping, feeder structure beneath them. The goal of this paper is to test whether fluid flow into such ore zones also involved largely vertical upwelling, or whether lateral fluid flow, particularly along low-angle fault structures, may have played a significant role in their formation. In this study we use carbon and oxygen isotopes in conjunction with trace element geochemistry to investigate pathways taken by hydrothermal ore-forming fluids into the tabular subhorizontal ore zones of the Pipeline deposit, a giant carbonate rock-hosted Carlin-type deposit in Nevada. We sampled deep drill holes within, below, and to the side of the main ore zone to assess the extent of lateral versus vertical fluid flow up to 600 m below mineralization.