Ore deposits as a guide to the tectonic evolution in the East Tianshan Mountains, NW China

Abstract： Ore deposits are an important indicator for the tectonic evolution. The characteristics and space-time distribution pattern of ore deposits provide new constraints for reconstructing the tectonic evolution in the East Tianshan Mountains. Study indicates that the Paleozoic East Tianshan orogenic belt, sandwiched in between the Tuha block and Central Tianshan block, may be divided into three tectonic-strata (magmatic)-metallogenic belts in terms of spatial distribution, i.e.： the southern Tuha basin marginal copper metallogenic belt (north belt), Kanggur gold metallogenic belt (central belt) and Aqishan-Yamansu Fe (-Cu)-Ag- polymetallic metallogenic belt (south belt). The temporal evolution of the East Tianshan orogenic belt is distinctly characterized by three stages. (1) The southern margin of the Tuha Basin was an Ordovician-Devonian active continental margin, where there occurred a paleocontinental-margin metallogenic system including VMS Cu-Zn deposits and porphyry copper deposits. In the terminal Late Devonian-initial Early Carboniferous, the paleo-oceanic crust was subducted northward, closing the ocean, and the Central Tianshan block accreted and was amalgamated to the southern margin of the Tuha block (which belongs to the Kazakhstan-Junggar plate). (2) In the Early Carboniferous (Visean), the East Tianshan again underwent extension along the Kanggur suture, forming Carboniferous aulacogen volcanic-sedimentary rocks and a corresponding stratabound metallogenic system (including VMS type Cu-Zn deposits and volcanic-hosted Fe (-Cu) deposits and native copper deposits), and skarn type Ag polymetallic deposits formed during the closing stage of the aulacogen. (3) In the Early Permian, a Cu-Ni sulfide metallogenic system related to mantle-derived magma underplating and spanning tectonic units and gold deposits related to shearing formed in this area. Based on the above discussion, new suggestions about mineral prospecting in the East Tianshan area are put forward in this paper.