On the Proterozoic Longshan Group in the Eastern Qilian Orogen
Abstract:The Longshan Group,which is a metamorphic rock series separated from the lower part of thebarren rock series of the original“Niutouhe Group”,consists of the marble rock formation and gneissicrock formation in ascending ordcr.According to isotopic geochronological studies,the gneissic rockformation dates 813 881 Ma earlicst age values in the area,corresponding to the Middle-Upper pro-terozoic. Based on the exposure and spreading of the rock group ,it is considered to be an uplifted partof the basement of the Qilian orogen.The characteristic features and geological implications of theChenjiamiao Fe-Cu ore deposit occurring in the gncissic rock formation is also discussed in this paper.