Formation Conditions of the Yugo-Konevskoe and Porokhovskoe Tungsten Deposits (Southern Urals) Based on Microthermocryometry and Mineralogical Thermometry Data

The article is devoted to the assessment of the formation conditions of the Yugo-Konevskoye and the Porokhovskoye deposits belonging to the same ore zone, localized in granites and in a metamorphosed volcanogenic-sedimentary sequence, respectively, and separated by a large thrust. According to the results of the study of fluid inclusions in quartz, the formation of quartz ± fluorite ± muscovite veins with hubnerite at both deposits was under similar conditions at minimum true temperatures of 245-540 °C and a pressure of ~ 350 bar, from carbon dioxide -water fluids of sodium-chloride composition with an admixture of KCl, KF and Ca and Mg carbonates, with a salt concentration of 0.54 to 16.13 wt. % NaCl-eq. CO2 predominates in the gas phase and impurities of CH4, N2 and H2S are recorded. The similarity of the mineral composition, fluid and muscovite composition in the ore veins indicates a single source of ore-bearing fluid for both deposits and an insignificant influence of the host rocks on it. The simultaneous presence of low-mineralized inclusions and inclusions with a solid phase indicates a phase separation, which is more pronounced at the Yugo-Konevskoye deposit. Late quartz in the skarns of the Porokhovskoye deposit was formed at lower temperatures than the ore veins and from solutions that contained a sulfate component, reflecting the probable assimilation of limestones from the host stratum during skarnification. Low pressures estimated from FI are due to the formation of ore veins as a result of brittle deformations of consolidated rocks. The obtained PTX parameters of the fluids correspond to those characteristic of greisen formation objects, falling into the relatively low-pressure and low-temperature region.