华南粤东盆地晚三叠世—中侏罗世沉积岩碎屑锆石物源分析及对构造体制转换的指示OA

The transition of South China Block from the Paleo-Tethyan to the Paleo-Pacific tectonic domain ex-erted a profound influence on regional tectonic evolution,sedimentary basin architecture,and magmatic activity.However,the timing of this critical tectonic regime transition remains contentious.This study focused on the Late Triassic-Middle Jurassic sedimentary rocks in Heyuan area of Eastern Guangdong Basin in South China,and conducted U-Pb chronology research on detrital zircons from the Late Triassic-Early Jurassic Yinpingshan For-mation and the Middle Jurassic Zhangping Formation.The sedimentary environment and provenance distribution characteristics were analyzed and the regional tectonic evolution were integrated for comparative analysis,provi-ding new evidence for the study of tectonic domain transformation of South China Block.The results showed that Yinpingshan Formation formed in a littoral sedimentary environment,with detrital zircon age spectrums displaying peaks at 247 Ma,422 Ma,and 2 492 Ma.The youngest zircon age was(226.3±1.99)Ma,showing its deposi-tional age to no earlier than the Norian stage of the Late Triassic.Provenance analysis indicated dominant sedi-ment derivation from the southwest,including Jinshajiang-Ailaoshan suture zone,Songma belt,and Hainan Is-land,exhibiting the structural characteristics of NW-trending folds superimposed by NE-trending folds.In con-trast,Zhangping Formation representsed a lacustrine depositional environment,characterized by multi modal de-trital zircon age peaks at 173 Ma,273 Ma,442 Ma,781 Ma,1 858 Ma,and 2 472 Ma.The youngest zircon age was(173.1±1.56)Ma,suggesting deposition no earlier than the Aalenian stage of the Middle Jurassic.Prove-nance shifted to a multi-directional supply system,including the eastern Nanling Range,Wuyi Uplift Zone,Jiangnan Orogen,the southeastern coastal magmatic belt,and Hainan Island,showing a NE-trending fold pat-tern.It demonstrated that Eastern Guangdong Basin was in a transitional stage from the Paleo-Tethyan to Paleo-Pacific tectonic domains during the early Middle Jurassic,combined with the evidence from provenance shifts,fa-cies changes,and differential tectonic features demonstrates.