Geochemical and Isotopic Properties of Fluids from Gold-Bearing and Barren Quartz Veins of the Sovetskoye Gold Deposit (Siberia, Russia)

摘要

This paper reports on the comparative study of fluids trapped in inclusions in gold-bearing and barren quartz veins at the Sovetskoye gold deposit, Yeniseisky ridge, Siberia, Russia. The host rocks are greenschist facies metasedimentary rocks of Upper Proterozoic age. Within the deposit, some veins contain 10 to 25 ppm of Au (gold-bearing veins); others contain less than 1 ppm of Au (barren veins). Fluid inclusions trapped in barren veins are predominantly low-salinity-H₂O (4.0–8.0 mass % NaCl equiv.) with variable contents of dissolved CO₂ (<12.5 mol %), CH₄ (<1.3 mol %), and N₂ (<1.7 mol %). Homogenization temperatures vary from 200° to 410°C, and the calculated pressures of entrapment are <1.5 kbars. Inclusion fluids trapped in the host schists are predominantly aqueous (97.6–99.3 mol % H₂O), with CO₂ contents below 2.4 mol percent.