The relationship between the McLaughlin gold-mercury deposit and active hydrothermal systems in the Geysers-Clear Lake area, northern Coast Ranges, California

Active hot- and mineral-springs in the Coast Ranges of northern California are intermediate between the fluid- and vapor-dominated end-member systems. The chemical and isotopic compositions of these fluids are the result of thermal processes and are not explained by simple mixing models between connate fluids and meteoric groundwater. Their isotopic and chemical composition is best explained by meteoric-dominated systems with repeated non-equilibrium subsurface vapor loss (evaporation) in a near closed system, with the relative deuterium and 18O enrichment proportional to the reservoir temperature.