Lead-zinc-silver polymetallic mineralization and prospecting potential in East Tianshan, Xinjiang

The East Tianshan orogenic belt, located in the southwest margin of the Central Asian Orogenic Belt, represents an important part of the Central Asian Orogenic Belt where develops a series of lead-zinc-silver polymetallic deposits such as Qiongkuduke, Aqishan, Weiquan, Caixiashan, and Hongyuan. The lead-zinc-silver polymetallic deposits in the East Tianshan, Xinjiang are mainly distributed in the Harlik island arc, the Aqishan-Yamansu island arc and the Central Tianshan block, and are dominated by epithermal, skarn and reworked sedimentary types. The lead-zinc-silver ore formation is concentrated in the Neoproterozoic and Carboniferous periods, while the peak period of mineralization is the Carboniferous. The ore-forming fluids are generally characterized by medium-high temperature and salinity, with two main composite types of fluid sources, including magmatic fluid and meteoric water, and metamorphic fluid and magmatic fluid as well as meteoric water. Cooling of the ore-forming hydrothermal system, fluid mixing, and the water-rock interaction are key factors for the precipitation of ore-forming metal elements. The ore-forming materials of epithermal and skarn types mainly derive from the magmatic-hydrothermal, while the reworked sedimentary lead-zinc-silver deposits in the central Tianshan show a primary source from the Precambrian basement rocks. Whole-rock geochemical signatures indicate that the related magmatic rocks are metaluminous to weakly peraluminous, calc-alkaline to high-K calc-alkaline dioritic to granitic rocks, which were originated from partial melting of the mixed crust and mantle components during the evolution of the Paleo-Asian Ocean. The lead-zinc-silver ore explorations in the East Tianshan should mainly focus on the contact zone between Carboniferous calc-alkaline magmatic rocks and calcareous volcaniclastic rocks and carbonates in the Aqishan-Yamansu island arc; meanwhile, the distribution area of carbonates and fine-grained clastic rocks in the Central Tianshan block is also a favorable prospecting target for finding large sized lead-zinc-silver deposits.