Telluride Mineralogy of the Kochbulak Epithermal Gold Deposit, Tien Shan, Eastern Uzbekistan

The Kochbulak gold deposit is situated on the northern slope of the Kurama range of eastern Uzbekistan and is one of the largest Tellurium-rich epithermal gold deposits in the world. Based on a detailed field and petrological investigation, three stages of mineralization can be classified, including, from early to late, quartz-pyrite vein stage, quartz-telluride-sulfide-sulphosalt-native gold stage, and pyrite-chalcopyrite vein stage. Abundant tellurides, including tellurobismuthite, rucklidgeite, tetradymite, altaite, volynskite, and hessite, have been well recognized in the second (main) mineralization stage. Based on the mineral assemblages and petrogenetic occurrence, the sequence of tellurides in the second mineralization stage can be approximately identified as altaite+calaverite+native tellurium, calaverite+native gold, Bi-telluride (e.g., tellurobismuthite and rucklidgeite)+petzite+native gold, Ag-Bi telluride (e.g., volynskite), and Ag-telluride (e.g., hessite)+native gold. By depicting the Log f(Te2)-Log f(S2) relationship diagram of the Kochbulak gold deposit under 250 degrees C and 200 degrees C, the Log f(S2) value ranges from -14.7 to -8.6 and from -16.7 to -10.9, respectively, with Log f(Te2) value varies from -12.3 to -7.8 under 250 degrees C and ranges from -13.8 to -11.2 under 200 degrees C.