| The Qilian Early Palaeozoic metallogenic belt dominated by nonferrous and precious metal mineral deposits can be tectonically divided into North, Middle and South Qilian units. As for ore-forming regionalization, it is divided into North Qilian and South Qilian metallogenic subbelts, with the latter composed of the North and the Middle Qilian tectonic units. On the whole, the Early Palaeozoic marine volcanic rocks are considered to be rocks of island arc, deep sea trench and back-arc basin facies and rift remnants, which were formed in an environment of the northward North Qilian ocean-ocean subduction and contained polymetallic massive sulfide deposits. However, the western part of the North Qilian Mountains seems to be an environment of continental magmatic arc-facies formed by ocean-continent collision, with some skarn tungsten deposits in it. The South Qilian consists of flysch formations and pyroclastic rocks of continental and intracontinental rift-environments as well as the Middle Qilian old basement, and contains some magmatic copper-nickel deposits and chromium deposits and large-size orogenic type gold deposits. In the early stage of Middle Porterozoic, the Qilian Mountains seemed to be the “hot point” position of ultra-plume, and the Jinchuan superlarge Cu-Ni-PGE deposit resulted from the ultra-plume action, by which the deposit was moved to the northern side of the North Qilian due to the Early Palaeozoic accretion. The Lashuixia area in the South Qilian is possibly an important area in search for the Jinchuan type deposits. In Early Palaeozoic stage the North Qilian ocean basin was a marginal sea environment induced from Paleo-Asiatic Ocean, and the special withering history of the marginal sea caused the formation of characteristic metallogenic associations. The crust shortening of the Qi-lian Mountains in northern Qinghai-Tabit plateau led to the intense transformation of the pre-orogenic structures and mineralized petrofacies and the formation of “orogenic type” mineral deposits. |