The Paleo-Pacific Plate subduction and episodic magmatism: Evidences from the Lianhuashan granitic composite batholith in the eastern Guangdong, China

<p indent="0mm"> The Late Mesozoic episodic magmatism along the southeastern coast of China provides key insights into the dynamics of the Paleo-Pacific Plate subduction. Compared to the coastal areas of Zhejiang and Fujian provinces, the research on magmatism in the eastern Guangdong is still relatively limited. This study conducts detailed petrographic, zircon U-Pb dating, whole-rock geochemical, and Sr-Nd-Hf-O isotopic studies of granites and their dark enclaves around the Lianhuashan Fault Zone in the eastern Guangdong. Combined with all relevant previous dating data, we have revealed four stages of magmatism, including the Early Jurassic <sc>(192–180 Ma),</sc> Middle-Late Jurassic <sc>(172–150 Ma),</sc> early stage of the Early Cretaceous <sc>(148–130 Ma),</sc> and late stage of the Early Cretaceous <sc>(106–94 Ma).</sc> The variations of geochemical compositions of these granites are mainly controlled by the crystallization differentiation of their magmas. Especially, the Early Jurassic/Early Cretaceous dark enclaves are cogenetic enclaves rather than products of the magma mixing, as they have consistent Sr-Nd-Hf isotopes comparing to their host rocks. The Early Jurassic diorite porphyries are characterized with low SiO₂, high Al₂O₃, enriched K, metaluminous-weakly peraluminous compositions, right-declined REE patterns (weak Eu anomalies), <italic>δ</italic>¹⁸O values of 5.1‰–5.4‰, and depleted <italic>ε</italic>_Hf(<italic>t</italic>) values (+8.52–+11.06), indicating that they have arc magmatic characteristics. These findings suggest that the Paleo-Pacific subduction to the southeastern coast of China was initiated before <sc>180 Ma.</sc> Magmatic activities of four episodic stages reflect that the subduction process has an intermittent feature of alternating plate advance and stagnation.