Fluid inclusions in quartz of the gold-ore occurrences and gold-quartz intergrowths from placers in the Sololi uplift of the Olenyok arch (Yakutia)

Abstract

Fluid inclusions have been studied 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 overlapping gold mineralization on the Early and Middle Permian sandstones, as well as in the gold quartz intergrowths from the Sololi River placer. It has been revealed that formation of quartz breccias occurred within a wide temperature interval from 230 to 425 ºC, with predominance of carbon dioxide and nitrogen in the vapor phase. It is suggested that the increased nitrogen content may be associated with a chemical reaction between the fluid and ammonium-containing silicates of 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 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 meta-rocks and meta-rhyolites indicate the synchronism of their formation and attribute them to the common stage of ore formation. Quartz veins with gold sulfide mineralization were the primary sources of pebbles with gold-quartz intergrowths from the Sololi River, this is evidenced by similarity of principal characteristics of fluid inclusions. Oxidizing conditions of the mineralization serve as favorable factor for the Au deposition, it is indicated by the predominant CO2 content in fluid inclusions, keeping role of a geochemical barrier and leading to an elevated gold content in quartz veins.