华南南雄盆地晚白垩世—古近纪红层的物源演化对区域构造体制转换的启示OA

The south China Block underwent intracontinental extension during the late Mesozoic driven by adjustments in the subduction angle of the paleo-Pacific plate,resulting in a series of northeast-southwest trending extensional basins,exemplified by Nanxiong Basin.These basins are characterized by terrigenous clastic strata that recorded provenance changes driven by regional tectonic activities.To investigate the geochemical characteristics and provenance of sediments from the Cretaceous to Paleogene in Nanxiong Basin,systematic sampling was conducted for the Zhenshui,Shanghu,and Nongshan Formations in the Luofuzhai and Ejingling sections of the basin.A total of 14 sandstone and mudstone samples were analyzed for major and trace elements,and three samples were examined for detrital zircon U-Pb ages and Lu-Hf isotopes.The whole-rock geochemical data reveal that the Zhenshui Formation was primarily sourced from felsic igneous rocks,and the Shanghu Formation was also dominated by felsic igneous sources,but with an increasing contribution from ancient metamorphosed sedimentary rocks.The Nongshan Formation exhibits a more diverse provenance,with a continued dominance of felsic igneous material mixed with mafic components.The detrital zircon U-Pb ages and Hf isotopic data indicate that the Zhenshui Formation primarily derives from Indosinian Qingzhangshan granite plutons to the south of Nanxiong Basin,while the Shanghu Formation was sourced from Caledonian granite plutons to the north and Precambrian ancient clastic rocks of the Cathaysia block.The Nongshan Formation,however,is mainly sourced from Caledonian and Indosinian granite bodies along the basin's periphery,with Cathaysia ancient clastic rocks representing only a minor source.The provenance change suggests a tectonic regime transition in Nanxiong Basin during the late Cretaceous to early Paleogene,from extension to compression.Subsequently,the compressional tectonic activity weakened during the deposition of the Nongshan Formation.