The initiation of Paleo-Pacific subduction in Northeast Asia: Key evidence from the Yuejinshan accretionary complex

The late Paleozoic−Mesozoic tectonic evolution of eastern Eurasia has long been a subject of debate. While it is widely accepted that the subduction-accretion processes of the Paleo-Pacific Ocean significantly shaped the tectonic framework of the region, uncertainties remain regarding the specific timing and mechanisms of these processes. Fortunately, the Nadanhada Terrane stands out as a crucial geological unit that provides direct insights into this subduction-accretion history. Comprising the Yuejinshan and Raohe accretionary complexes, with the former located at the forefront of the subduction zone, the Nadanhada Terrane is an ideal target for determining the initiation of Paleo-Pacific subduction. In this paper, we present novel geochronological and geochemical data obtained from various lithologies within the Yuejinshan accretionary complex to constrain the timing and nature of its emplacement. Our new results, when integrated with previous studies, document the complete history of the subduction-accretion process from Panthalassa to the onset of Paleo-Pacific subduction. Based on these findings, we propose a three-stage model that illuminates the complex tectonic evolution of the region during the late Paleozoic to Mesozoic era: (1) bidirectional subduction of Panthalassa during the early Permian, (2) initiation of the Paleo-Pacific subduction in the Early−Late Triassic, and (3) subduction-accretion of the Paleo-Pacific Ocean beneath eastern Eurasia from the Late Triassic to Early Jurassic.