On the history of the formation of the Tash-Yarsky pyrite-polymetallic deposit (South Urals)

Abstract

The article considers the geological structure of the Tash-Yarsky pyritepoly-metallic deposit located in the northern part of the Magnitogorsky megazone near the large (about 300 km2) Akhunovsky granite massif. The petrographic study of the hornfelses made it possible to identify a number of mineral parageneses containing cordierite, garnet, and biotite, which are installed respectively from the massif contact at a distance no further than 0,6-0,8; 1,2-1,5 and 2,3-2,5 km. Based on the temperature dependence of the maximum iron content of sphalerite, high temperatures of metamorphism (500-610 °С) were obtained for ores. According to garnet-biotite and garnet-cordierite thermobarometers for rocks close to the massif, the transformation temperature is 720-750 °С, and the pressure is 8,9-9,1 kbar. With a distance of 700-850 m from the contact of granitoids, the temperature does not exceed 620-640 °C, and the pressure is 5,3-5,4 kbar; at a distance of 1,3 km, respectively - 550-560 °C and 4,6-4,7 kbar.