Late Cretaceous-Cenozoic intraplate extension and tectonic transitions in eastern China: Implications for intraplate geodynamic origin

The geodynamic origin of intraplate extension remains poorly understood. For the case of the Late Cretaceous-Cenozoic intraplate extension in eastern China, its driving mechanism remains highly controversial due to the absence of a comprehensive understanding of significant tectonic transitions. This study uses the well-documented Cretaceous tectonic evolution as a background and integrates extensive multidisciplinary data in the Jianghan Basin, Bohai Bay Basin and Zhejiang area, to develop an integrated view of the Late Cretaceous-Cenozoic geodynamic origin for the first time. During the Late Cretaceous, rifting and depocentres were distributed in the Jianghan Basin and were located in the central Bohai Bay Basin. During the Cenozoic, rifting and depocentres were initially focused in the western basins and then progressively migrated eastward, rather than continuing migrating eastward. The rifting and volcanism during the Middle Cenozoic (50-23 Ma) significantly increased, and all rift basins in eastern China were abandoned at the end of the Middle Cenozoic (~26-23 Ma). The volcanism in the Zhejiang area was markedly enhanced during the Late Cenozoic (23-0 Ma). The asthenospheric mantle sources beneath the two rift basins were isotopically more depleted with an increased extent of melting from the Late Cretaceous (100-65 Ma) to Early Cenozoic (65-50 Ma); however, they became isotopically more enriched and heterogenous with a decreased melting extent (significantly reduced volatile content) from the Early Cenozoic to Middle Cenozoic. The mantle source beneath the Zhejiang area during the Late Cenozoic was isotopically more depleted and heterogeneous than during the Middle Cenozoic, with an increased extent of melting. These three-phase tectonic transitions together with tectonic correlations directly constrain the causal relationships between the intraplate extension in eastern China and the motions of the adjacent plates. Consequently, we propose that the Late Cretaceous-Cenozoic intraplate extension and tectonic transitions in eastern China were successively driven by the Paleo-Pacific slab rollback during the Late Cretaceous, the India-Asia collision during the Early-Middle Cenozoic and by the combination of the subduction of the Pacific Plate and India-Asia collision during the Late Cenozoic. Our study provides an integrated perspective for unraveling the geodynamic origin of intraplate extension. •Three-phase tectonic transitions together with tectoni