Sources of fluids and metals and evolution models of skarn deposits in the Qimantagh metallogenic belt: A case study from the Weibao deposit, East Kunlun Mountains, northern Tibetan Plateau

The Weibao Cu-Pb-Zn deposit is typical of skarn deposits in the Qimantagh metallogenic belt (QMB), East Kunlun Mountains, northern Tibetan Plateau. It comprises three ore blocks from west to east, known as Weixi, Main and Weidong. Mineralization in the Weibao deposit is intimately related to Late Triassic intrusions occurring at Weixi and Weidong, and orebodies are predominantly hosted by the Langyashan Formation (marine carbonate rocks), and to a lesser extent the Devonian volcanic rocks. Skarns from Weixi and Weidong are characterized by a high garnet/pyroxene ratio and diopside- and andradite-rich composition of pyroxenes and garnets, indicating a proximal, oxidized type. In contrast, skarn mineralogy of Main indicates a slightly reduced condition, typical of Pb-Zn skarn deposits. At least five hydrothermal mineralization stages can be identified and the microthermometric study indicates a general trend of cooling and dilution of the magmatic-hydrothermal fluids. Significant precipitation of Cu-Fe sulfides commenced from the fluid with the temperature of 340–448 °C and the salinity of 2.1–15.0 wt% NaCl equiv. Pb-Zn sulfides however mainly precipitated when the temperatures declined to