Ore-Forming Fluids of Gold Porphyry and Skarn Deposits in Central Aldan (Southern Yakutia) Based on Fluid Inclusion Study

The Late Mesozoic alkaline magmatic rocks (160-120 Ma, Ar-Ar and U-Pb dating) are widely distributed in the SE part of the Siberian craton. The formation of large Au, Pt, U, rare metal deposits and deposits of high quality raw materials for jewelry are temporally linked with alkaline magmatism. The largest ore district with such types of mineral deposits is located in the Central Aldan. A number of large gold deposits have been discovered in this district, most of which are now being mined. A fluid inclusions study in minerals of the Ryabinovoe and Samolazovskoe deposits was performed with the aim to indicate specific features of composition and estimate the metal-bearing capacity of the ore-forming fluids. Using recent methods of fluid inclusions study it has been found that ore-forming fluids are characterized by high salt concentrations, chloride carbonate-sulphate composition, high metal-bearing capacity, and high value of the redox potential corresponding to the sulfate-sulfide equilibrium. The detection of different forms of sulfur in the inclusion fluids (SO42-, HSO4-, HS-, H2S and S-0) is allowing us to consider the possibility of presence of the other sulfur compounds such as thiosulfates and sulfites in the ore-forming solutions.