PHYSICOCHEMICAL CONDITIONS OF MINERALIZIN G PROCESSES AT THE KARIISKOE GOLD DEPOSIT, EASTERN TRANSBAIKALIA

Detailed cryo- and thermometric studies of fluid and melt inclusions c onfirmed the genetic links established earlier between the gold minera lization and granitic rocks of the Amudzhikan-Sretenskii Complex. The obtained results made it possible to constrain the boundary physicoche mical parameters of the ore-magmatic system. The granitic melt was ric h in water (up to 11.3 wt %) and chlorine (up to 0.48 wt %) and crysta llized at temperatures of 800-690 degrees C and water pressures of 4.8 -4.2 kbar. The conditions under which the hydrothermal ore mineralizat ion formed varied over wide ranges of parameters: temperature 575-85 d egrees C, pressure 2820-85 bar, and solution salinity 56-0.5 wt % NaCl equiv., with carbon dioxide playing a significant role in the process . During the initial stages of the hydrothermal activity, the solution boiled off, which resulted in an increase in its salinity and enrichm ent in ore-forming components. The fluid salinity rapidly decreased at temperatures below 350 degrees C, probably because of the opening of fractures and addition of meteoric waters to the system. These process es brought about massive ore deposition.