Role of Sulfidation in Deposition of Gold, Twin Creeks Sediment-Hosted Micron Gold Deposit, Nevada
David P. Stenger, Stephen E. Kesler, John Fortuna, Dean R. Peltonen, 1997. "Role of Sulfidation in Deposition of Gold, Twin Creeks Sediment-Hosted Micron Gold Deposit, Nevada", Carlin-Type Gold Deposits Field Conference, Peter Vikre, Tommy B. Thompson, Keith Bettles, Odin Christensen, Ron Parratt
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Despite important advances in our understanding of sediment-hosted micron gold deposits, debate continues over the processes that deposited their gold. Possible processes include cooling or boiling of the ore fluid, dilution, oxidation or other changes caused by mixing two fluids, or wallrock reactions such as carbonate dissolution and sulfidation. Several recent studies have called attention to the role of sulfidation in deposition of SHMG ores. At Jerritt Canyon, support for fluid mixing and sulfidation was provided by the relation between δ18O values and gold grades in ore-stage jasperoids (Northrop et al, 1987) and chemical reaction-path modeling of ore and alteration mineralogy (Hofstra et al, 1991). At Carlin, studies of fluid inclusions by Kuehn and Rose (1995) suggested that mineralization accompanied by sulfidation took place when an acidic, CO2-rich, mineralizing fluid mixed with cooler, gas-poor meteoric(?) water as it underwent episodic leakage from a deep overpressured reservoir.
The best way to assess the role of sulfidation in SHMG deposits is through comparison of the abundance and distribution of elements at the scale of a deposit. We report here the results of comparisons of this type based on a database comprised of 20-foot composite samples from hundreds of drillholes at Twin Creeks, all of which were analyzed for Au, Fe, S (total and reduced) and other elements of interest and labeled according to rock type and degree of oxidation. From the standpoint of chemical compositions, one of the most important differences among the depositional mechanisms listed above is the degree to which