Fluid Inclusions in Quartz of Gold-Ore Occurrences and Gold-Quartz Intergrowths from Placers of the Sololi Uplift of the Olenyok Arch

Fluid inclusions (FI) have been researched in vein quartz with gold-sulfide mineralization from metamorphosed sandstones of the Eekite series and metarhyolites of the Early Proterozoic, in quartz breccia from the zone of overlying gold mineralization on the Early and Middle Permian sandstones, as well as in the gold quartz aggregate from the Sololi River placer. It has been established that the formation of quartz breccias occurred within a wide temperature interval from 230 to 425°C, with predominance of carbon dioxide and nitrogen in the gas phase. It is suggested that the increased nitrogen content may be associated with a chemical reaction between the fluid and ammonium-containing silicates of the host rocks, in which nitrogen in the form of NH4+ isomorphically replaces potassium at the regressive stage of metamorphism. At the same time, it is possible that mantle nitrogen, which was transported along the Anabar-Eekite deep fault, participated in the formation of the studied breccias. The close homogenization temperatures and similar nature of the water-salt composition for the fluid inclusions of quartz veins that inject the Eekite series metarocks and metarhyolites indicate the synchroneity of their formation and attribute them to the general stage of ore formation. Quartz veins with gold sulfide mineralization were the primary sources of quartz gravel with natice gold of the Sololi River, as evidenced by the similarity of fluid inclusions in the main characteristics. A favorable factor for the Au deposition was the oxidizing conditions of mineral formation, as indicated by the predominant CO2 content in the fluid inclusions, which played the role of a geochemical barrier and led to an increased Au content in quartz veins.