Simultaneous development of arc-like and OIB-like mafic dikes in eastern Guangdong, SE China: Implications for late Jurassic – early Cretaceous tectonic setting and deep geodynamic processes of South China

The Mesozoic South China is characterized by extensive magmatism, transition from Jurassic intraplate magmatism to Cretaceous active continental margin magmatism. However, the time and deep geodynamic processes accounting for the Mesozoic magmatism remains controversial. In this study, we presented new SIMS zircon UPb ages, in-situ Sr isotope of plagioclase, whole-rock geochemical and Sr–Nd–Pb isotopic data on three suites of mafic dikes in eastern Guangdong, namely Anliu (AL) and Sanjiaowo (SJW) and Jishuimen (JSM) mafic dikes. The AL (154.3 ± 3.4 Ma) and SJW (141.3 ± 4.0 Ma and 143.2 ± 2.3 Ma) dikes show arc-like geochemistry and “crust-like” isotopic signatures, likely derived from partial melting of a subduction metasomatized lithospheric mantle. Meanwhile, the JSM dikes (141.7 ± 3.2 Ma) exhibit OIB-type geochemical and isotopic features, and were likely derived from partial melting of an enriched asthenospheric mantle. The development of late Jurassic AL lamprophyre may represent the oldest Paleo-Pacific subduction-related arc-type mafic rocks so far recorded in South China. Development of dikes (SJW vs JSM) with different geochemical signatures (Arc vs OIB) at the same time within a limited space indicates that asthenosphere-related process overprint and co-operate with subduction-related magmatism and imply the initiation of Paleo-Pacific subduction roll-back was potentially at least ca.141 Ma.