Qinling-Kunlun triple junction and isotope chronological evidence of its tectonic process

Abstruct：The conjunctional and transitional relation between the West Qinling and East Kunlun orogenic belts, both of which belong to the Central Orogenic System, has long been a focus of dispute in the study of the Central Orogenic System of China. Based on many previous studies of the Buqin Mountain, A′nyêmaqên and Kuhai-Sêrtang ophiolitic mêlange zones in the junction between the two orogenic belts and through further survey and isotope chronological study, the authors find that the three ophiolitic mélange zones are not independent but form a typical triple junction with respect to the composition, textures and structures, geometry and isotope chronology, i.e. the Qinling-Kunlun triple junction. This tectonic system generally experienced a temporal-spatial transition process from the Devonian graben-graben-graben (GGG) type through the Carboniferous-Permian ridge-ridge-aulacogen (RRA) type to the Late Permian subduction-subduction-subduction (SSS) type of triple junction. In the Late Triassic, the process ended, and thus the junction between the West Qinling and East Kunlun was finally completed.