Objective Tethys can be divided into Proto−Tethys, Paleo−Tethys and Neo−Tethys according to its evolutionary history, roughly corresponding to the Early Paleozoic, Late Paleozoic and Mesozoic oceans, respectively. In recent years, a large number of studies in the southern Xizang Plateau, Iran, Pakistan and other areas have shown that the (post−) collisional granite formed after the closure of the New Tethys Ocean is generally characterized by high oxygen fugacity and high water contents, which has led to the formation of many large to super−large porphyry copper deposits in these areas. How about the metallogenic potential of Proto−Tethys and Paleo−Tethys porphyry deposits? Does the (post−) collisional stage after the closure of the two paleo−oceans also have the metallogenic potential of large to super−large porphyry copper deposits? These problems have not been systematically studied before. The Qimantagh area in the East Kunlun Orogenic Belt records the tectonic evolution and metallogenic history of Proto− and Paleo−Tethys from subduction to closed stages. Thus, this area is a natural laboratory and excellent place to study the porphyry mineralization of Proto−Tethys and Paleo−Tethys.

Methods In this paper, the age and geochemical data of granites previously reported in Qimantagh area of the East Kunlun Orogenic Belt are reviewed, and the granite characteristics related to porphyrie−skarn deposits are particularly studied. The purpose of this paper is to reveal the metallogenic regularity of Proto−Tethys and Paleo−Tethys porphyry and serve a new round of prospecting breakthrough strategy.

Results The granites in the Qimantagh area of the East Kunlun Orogenic Belt mainly occurred in two periods, i.e., 435~370 Ma and 245~196 Ma. These granites formed in the collisional stage after the closing of the Proto−Tethys and the Paleo−Tethys Oceans, respectively. In contrast, the granites related to oceanic subduction were rarely found. The two stage collisional granites have similar geochemical characteristics, mainly fall into the range of high−K calc−alkaline and shoshonitic series, belong to metaluminous to weakly peraluminous rocks with depleted Nb and Ta, and display characterisitics of crustal−mantle mixing in the sources of parental magmas.

Conclusions Based on the results of previous studies, this paper proposes that the Proto−Tethys and Paleo−Tethys experienced similar evolutionary processes. ① During the subduction stage, the Proto−Tethys and Paleo−Tethys subducted to the continent in the form of flat subduction, which inhibited arc magmatism and resulted in the scarcity of arc granites in Qimantagh area, East Kunlun. ② During the collisional stage, the subduction plate was detached which led to the upwelling of the asthenosphere mantle, forming a large number of collisional granites of crustal−mantle mixing origin. However, compared with the Neo−Tethys collisional granites, the Proto−Tethys and Paleo−Tethys collisional granites generally have lower oxygen fugacity and water content. These characteristics may explain why no large and super−large porphyry copper deposits have been found in the northern part of the Xizang Plateau. In spite of this, the skarn copper polymetallic deposits in the north of the Qinghai−Xizang Plateau have great prospecting potential and should be the main type and direction of prospecting in the future.