Double subduction of the Early Paleozoic North Qilian oceanic plate: Evidence from granites in the central segment of North Qilian, NW China

Abstract：This paper deals with zircon SHRIMP dating of the Niuxinshan and Minleyaogou granites in the central segment of the North Qilian Mountains, NW China. The dating results indicate that the ages of the Niuxinshan granite and Minleyaogou granite are 476 and 463 Ma respectively. Petrogeochemistry shows that both granite intrusions have the features of active continental-margin magmatism. On the basis of these features, combined with the tectonic locations of granite occurrence and field observation data, the authors think that south- and north-directed subductions of the North Qilian oceanic plate took place in the Early Paleozoic, of which the southward subduction resulted in the formation of the Nixinshan granite (476 Ma) and the northward subduction gave rise to the Minleyaogou granite (463 Ma).