Krausite, rhomboclase and parabutlerite found for the first time in the Hongshan high-S epithermal Cu-Au deposit, Xinjiang, and their significance

Abstracts：The oxidized zone of the Hongshan high-S epithermal Cu-Au deposit in the Hami area, Xinjiang, NW China, occurs as a funnel in the upper part of the primary sulfide orebody, extending downward for 50-60 m. Many supergene minerals were found by X-ray diffraction (XRD), differential thermal analysis (DTA) and thermal gravimetric analysis (TGA), of which three sulfate minerals, krausite, rhomboclase and parabutlerite, were for the first time found in China. The chemical analysis of krausite gives the following results (%): H2O 6.35, SO3 49.72, Na2O 0.15, Fe2O3 26.00, K2O 12.47, FeO 0.25, SiO2 3.25, insoluble residue 0.85 and CaO 0.11 with a total of 99.15, and its XRD analysis presents the following characteristic spectra: 4.40 (100), 4.26 (70) and 6.58 (47). The results (%) of chemical analysis of rhomboclase are H2O 26.51, SO3 49.91, Na2O 0.03, Fe2O3 22.52, MgO 0.01 and CaO 0.03 with a total of 99.01；and the characteristic spectra of its XRD analysis are 9.16 (100), 3.29 (9) and 4.06 (8). The results (%) of chemical analysis of parabutlerite are H2O 24.82, SO3 38.53, Al2O3 0.18, Fe2O3 36.10, MgO 0.02 and CaO 0.04 with a total of 99.69, and its characteristic spectra of XRD analysis are 5.00 (100), 3.11 (41) and 5.85 (39). DTA further verified the reliability of these chemical data and explained the thermal reaction mechanism of these sulfates. These sulfate minerals have been used as a new type of acid resource for wet smelting of copper, showing great advantages in mineral beneficiation and environmental protection. So the paleoenvironment and paleoclimate may be deduced through an intensive study of the assemblages, sequence of occurrence and formation conditions of such sulfate minerals in the oxidation zone.