Recognition and tectonic significance of previously named Balonggongge'er Formation in West Qilian Mountain

Balonggongge'er Formation is a Paleozoic stratigraphic unit distributed in southern Qilian Mountain. The authors disintegrated a typical schist unit in Balonggongge'er Formation which is located in West Qilian Mountain and named Guaizhangshan Complex-Group. LA-ICP-MS zircon U-Pb geochronology reveals 3 age spans, i.e., 2540±5Ma, 1662.8±5.7Ma and 962.9±4.4Ma respectively. Regional structural analysis shows that the Precambrian metamorphic basement rocks in southern Qilian Mountain was probably the basal components of ancient Qaidam massif, and was the tectonic window of Qaidam massif which was thrust southward and lay over southern Qilian Mountain through napping.