The Joining of North and South China During the Permian: Coherent Metamorphic Evidence From East Asia Orogenesis

The joining of the North and South China blocks marks the formation of the united East Asian continent, which is an integral part of Pangea. The amalgamation of these two continental blocks also resulted in the formation of the world-class ultrahigh pressure orogenic belt, namely the Dabie-Sulu orogenic belt. Figuring out the time of the initial collision between the two continents is critical for resolving questions such as the duration and the geodynamic processes of the orogeny. A Triassic joining time has been suggested by the geochronology of the eclogite facies rocks in this orogenic belt. However, paleomagnetic and paleontological studies suggested a Permian docking time for these continental blocks. In this paper, we present new metamorphic ages of rocks from northern Dabie and the Permo-Triassic intracontinental orogen of South China, which are all closely associated with this continental collisional event. New age dating results, as well as a synthesis of recent studies on metamorphic rocks occurring in southeastern North China and the Cathaysia Block of South China, show that the onset of the collisional orogenesis along the eastern part of the orogenic belt dates back to the Middle Permian (270-252 Ma). Considering these data and other geological records, we provide a new tectonic model for the major continents of East Asia, in which we show that the initial collision between North and South China occurred in the east during the Middle Permian, and then propagated westward. Continental collisions forming mountains and closing seaways in East Asia thus apparently occurred before the end-Permian mass extinction, suggesting these paleogeographic changes might have also preconditioned and facilitated the end-Permian biospheric crisis in the region.

Automated summary

The joining of North and South China formed the East Asian continent and the Dabie-Sulu orogenic belt. Determining the time of their initial collision is crucial for understanding the orogenic processes. New dating results suggest a Middle Permian collision, which indicates that continental collisions in East Asia occurred before the end-Permian mass extinction.