Fluid Inclusion Evidences for the P-T Conditions of Quartz Veins Formation in the Black Shale-Hosted Gold Deposits, Bodaybo Ore Region, Russia

The P-T conditions of auriferous and barren quartz veins from Kopylovsky, Kavkaz and Krasnoye gold deposits in Proterozoic black shales of Bodaybo ore region are presented the first time in this study. Fluid inclusions trapped in auriferous quartz are aqueous Na±K-Mg chloride with salinity of 6 wt.%-8.8 wt.% NaCleqv. Homogenization temperatures vary from 260 to 350 °C, and calculated trapping pressures are 1.2–1.6 kbar. The fluids trapped in barren quartz have more complicated compositions with Na, K, Mg and Fe chlorides, salinity up to 13 wt.% NaCleqv, and homogenization temperatures ranging between 140 and 280 °C. The volatiles in fluids are dominated by H2O, followed by CO2 with minor amounts of CH4 and N2. We suppose that auriferous and barren quartz veins have been formed due to the basic metamorphogenic fluid as evidenced by the close slat and gas fluid composition.