Physical-chemical conditions and composition of ore-building fluids of Russian oroganic gold deposits

The detailed research of fluid inclusions and stable isotopes in minerals of industrial ore veins large-scale orogenic gold deposits of different regions of Russia was carried out. The deposits under investigation are Berezovsk and Kochkarskoye (Ural), Olympiada (the Yenisei Ridge), Mayskoye (Chukotka), Nezhdaninskoye (Yakutiya) and Sukhoy Log (Eastern Siberia). Temperatures of industrial ores formation for all investigated deposits are stacked in an interval 190-485 ºС. Fluid pressure under ore formations changed from 1.0 up to 3.6 kbar. The hydrothermal fluid of all orogenic gold deposits under investigation is a low-mineralized water solution with the general concentration of salts 2-17 % in weight, and sodium and potassium chlorides are prevailed. For fluids from the majority of deposits the high concentrations of dissolved CO2 (3-7 mol/kg H2O) with a small impurity of other gases are characteristic. Variations of geochemical ratio volumes for K/Rb, Br/Cl and others which can serve as indicators of the ore-forming fluid natures are established. Au-bearing fluid from all deposits had the magmatic nature and had mixed up with formation solutions under ore sediments.