Chronological evidence of Neoproterozoic volcanic rocks in the eastern segment of the North Qilian Mountains

According to the geological survey of 1∶50000Shimenchuan Sh eet and Laolongwan Sheet,vol-canic rocks different from those in the Early Or dovician Yingou Goup have been found in the Shandiao-diaopo area,Jingtai Count y in the eastern segment of the North Qilian Mountains .Sm-Nd isochron dat-ing of the volcanic rocks shows that they formed during the Neoproterozoic, about 723million years ago.REE and trace element and trace element geochem ical characteristics suggest that a compressional environ-ment resulting from subduction of oceanic crust occurred there at that time.