Cambrian–Devonian reconstructions of East Asian blocks via detrital zircon big data and mixing models

The tectonic evolution of the Tethyan oceans and the subsequent accretion of East Asian blocks to Eurasia are central to deciphering the geodynamic assembly of the Asian continent. However, the precise paleogeographic configuration of these continental fragments along the northeastern Gondwanan margin remains a subject of intense debate, obscuring our understanding of the episodic lifecycles of the Proto-, Paleo-, and Neo-Tethys oceans and the sequence of Gondwanan fragmentation. Here, we present a robust quantitative paleogeographic reconstruction underpinned by a comprehensive large detrital zircon U-Pb geochronological dataset from key Cambrian to Devonian sedimentary successions of northeastern Gondwana. By employing inverse Monte Carlo mixture modeling to quantitatively partition sediment provenance and terrane affinities, integrated with existing paleomagnetic constraints, we demonstrate that these blocks were arranged in a concentric belt framework along the Gondwanan margin. Our modeling results delineate a structured spatial arrangement. The innermost blocks (Qiangtang, Baoshan, and Sibumasu) were situated proximal to the Indian margin, while the Lhasa terrane is interpreted to be situated adjacent to Australia. An intermediate belt, comprising Indochina and South China, bridged these sectors. The outboard Tarim and North China cratons, following their Cambrian isolation, were incorporated into the margin by the Ordovician, synchronous with the terminal closure of the Proto-Tethys Ocean. This spatial arrangement archives a spatio-temporally diachronous rift-drift narrative. Northward dispersal initiated with these outboard cratons during the Ordovician–Silurian, progressed to the intermediate blocks during the Devonian opening of the Paleo-Tethys Ocean, and culminated in the late Paleozoic rifting of the innermost blocks during the opening of the Neo-Tethys Ocean. We interpret this orderly, inboard-younging unzipping sequence as a first-order geodynamic response to sequential opening of the Tethyan oceans, likely driven by sustained subduction zone rollback. This model provides a unifying framework that reconciles disparate geological datasets and elucidates the staged northward transfer of continental fragments from Gondwana to Asia.