The material composition and LA-ICP-MS zircon U-Pb age of East-Kunlun tectonic melange in Xiaonanchuan area, Golmud City, Qinghai Province, and its geological significance

Depending on the NS-trending structural section in Xiaonanchuan area of East Kunlun, south of Golmud, the authors have recognized six different tectonic slices based on field detailed contact relationship, composition characteristics, metamorphic-deformation features and microstructures. From north to south, these six tectonic slices are amphibolitic lenses-bearing greenschist, blocky marble, silty slate, foliated pyroclastic rock, platy tuffite and schist, and each of them were bounded by brittle or ductile faults. Zircons in amphibolitic schist and foliated dacite from the tectonic melange belt are dated by LA-ICP-MS U-Pb method and yield weighted ages of 1123 ± 110 Ma and 499 ± 11 Ma. A comparative analysis shows that amphibolitic lenses-bearing greenschist and blocky marble should be part of Mesoproterozoic Wanbaogou Group and formed in the setting of continental rift. Silty slate, foliated pyroclastic rock and platy tuffite are the components of a suite of volcanic arc and arc-related fore-back basins, and schist is the petrologic constituent within the accretionary wedge. Petrologic constituent and geochronology of the tectonic melange belt in southern Kunlun can provide the fundamental substance and precise constraints for the establishment of the accretionary complex belt and the process of accretion and emplacement, which may furnish basis to the study of the tectonic progress of the Kunlun orogenic belt and even the northern margin of the Tibetan Plateau.