Formation conditions of gold-quartz veins of the Mechnikovskoe and Altyn-Tash deposits, South Urals: fluid inclusion and isotopic study
I.Yu. Melekestseva, A.M. Yuminov
Fluid inclusions and oxygen isotopic composition of auriferous quartz were studied in quartz from the Mechnikovskoe and Altyn-Tash gold deposits associated with listvenites, South Urals. The gold-quartz veins at the deposits were formed at similar temperatures (207–306 and 229– 294 °С), salinity of the fluids (10.6–16.7 and 9.8–1.6 wt. % NaCl-eq.), and major salt composition of the fluids (NaCl + NaHCO3 and KCl) at different pressure (0.4–0.8 and 1.1–1.5 kbar, respectively). The oxygen isotopic composition of auriferous quartz from both deposits is similar (14.7–15.4 ‰ for Mechnikovskoe deposit; 13.2–13.6 ‰ for Altyn-Tash deposit). The calculated oxygen isotopic composition of water (5.7–6.4 and 4.2–4.6 ‰) is similar to δ18ОH2O values for the early quartz from Berezovsk deposit (Bortnikov, 2006) and corresponds to the oxygen isotopic composition of magmatic water.
Figures 5. Tables 2. References 20.
Key words: gold, fluid inclusions, O isotopic composition, South Urals.
МINERALOGY № 2 2015