Skarn garnets of the Novonikolaevskoe copper deposit (South Urals)

The paper describes the composition of skarn garnets of the Novonikolaevskoe Cu deposit (South Urals) in comparison with that of garnets of the Gumeshki and Tarutino skarn copper porphyry deposits in the Urals. Three generations of the andradite-grossular group garnets typical of skarn depositsare distinguished at the Novonikolaevskoe deposit. The median TiO2 content of garnet-1 and garnet-2 is 0.37 wt. % reaching 2.38 wt. % in garnet-3. This TiO2 content of garnets and relatively low Fe contents in some garnets from exoskarns (And40–54) possibly indicates a temperature increase during the skarn formation stage of garnets at the Novonikolaevskoe deposit, as well as relatively higher-temperature conditions of formation of garnet at the deposit compared to those from the Tarutino and Gumeshki deposits. Low fluid redox conditions during the formation of skarns at the Novonikolaevskoe deposit compared to the Tarutino deposit may be another reason for the low Fe contents in exoskarn garnets. According to the composition of garnet, the Novonikolaevskoe and Gumeshki deposits can be classified as Au-Fe-Cu skarn deposits, whereas the Tarutino deposit can be ascribed to a Cu-skarn deposit.