Detrital zircon evidence for the evolution of the Paleo-Asian Ocean and Pangea scenarios during late Paleozoic times

The Central Asian Orogenic Belt (CAOB) is one of the Earth's largest and longest-lived accretionary orogenic collages, consisting of numerous accretionary prisms, magmatic arcs, ophiolites and microcontinents. The Solonker and Hegenshan suture zones in the eastern CAOB record the Late Paleozoic closure of the Paleo-Asian Ocean; however, closure times and variability remain uncertain, and there are ongoing disputes about how East Asian blocks linked with the Pangea supercontinent. In this paper, we report detrital zircon U-Pb ages and trace elements from the eastern CAOB, which indicate that the Northern Orogenic Belt received sediment from the Uliastai active continental margin of the Mongolia Block during Pennsylvanian times. In Early to Middle Permian times, the Northern Orogenic Belt exhibited an internal detrital source with a single age cluster, demonstrating its isolation on both north and south sides, flanked by the Solonker and Hegenshan oceans. However, from Late Permian to Early Triassic times, the sediments of the Northern Orogenic Belt along with adjacent areas displayed a mixed exotic provenance derived from both the North China Block and Mongolia Block, providing evidence for the simultaneous closure of both the Solonker and Hegenshan oceans. The source-to-sink system during the assembly of the Mongolia Block and North China Block further demonstrates a weak connection to the Laurussia supercontinent. These findings highlight the global tectonic evolution from Pangea B to A during the Late Paleozoic.