The Pi's propose to continue investigations of the Salton Sea Geothermal system and particularly the interaction between deep hypersaline brines and Shallower, more dilute brines. These two reservoirs seem to be stratified within the sediment reservoir with a sharp density controlled interface paralleling the 250C isotherm. Isotopic data reveal that the two fluids may have different sources, and their distinctive chemical compositions imply different water-rock interaction histories along their respective flow paths. Both hydrothermal circulation and ore deposition are controlled by the salinity stratified nature of these fluids. Further work is intended to add to the existing data base using samples from commercial production wells. The ultimate goal is to understand the evolution of the two fluid reservoirs and their role in controlling metallogenesis.