Home – Home – Jornals – Russian Geology and Geophysics 2002 number 12

Fluid inclusions in minerals from more than 22 Au-Hg deposits (Central Asia, Urals, East Sayan, Gorny Altai, northeastern Russia, Mongolia, etc.) have been examined by thermobarogeochemical methods (thermo- and cryometry, Raman spectroscopy of gas phase). It has been established that Au-Hg deposits are low-temperature (280-50 ^oC) hydrothermal objects which formed in subsurface (volcanogenic-hydrothermal) or shallow-depth (plutonogenic-hydrothermal) conditions, under pressures lower than 500-600 bars. The volcanogenic-hydrothermal Au-Hg deposits were formed with participation of weakly concentrated (10-0.5, less frequently to 14 wt.%) chloride or chloride-bicarbonate-sodium hydrothermal fluids with low-density N₂-CO₂ (CH₄) gas phase. The ore-forming fluids of plutonogenic-hydrothermal deposits are characterized by wider variations in concentration (from 0.2 to 25 wt.%), complex salt composition (NaCl, CaCl₂, FeCl₂, KCl, etc.), and dense highly CO₂ gas phase (CO₂ N₂ CH₂); in salt composition and reduced character they similar to magmatic fluids. The characteristic feature of the fluid regime of ore-forming systems of volcanogenic- and plutonogenic-hydrothermal Au-Hg deposits is the heterogenous state of ore-forming fluids. In particular ore districts, the physicochemical parameters of formation of volcanogenic- and plutonogenic-hydrothermal Au-Hg deposits are generally close to the parameters of formation of similar Au-Sb, Sb and Sb-Hg deposits. The results obtained from the thermobarogeochemical study stress the polygene nature of Au-Hg deposits.