Geochemical and Sr–Nd–Pb–Hf–O isotopic compositions of Jurassic granites in central Guangdong, SE China: Constraints on petrogenesis and tectonic setting

The origin and tectonic regime of Jurassic granites in Southeast (SE) China have remained controversial for decades. This study focuses on the granites exposed in Fogang and Xinxing Batholiths in central Guangdong and conducts geochemical and geochronological analyses of whole-rock and zircon. Mineralogical and geochemical data show that these granites are high-K calc-alkaline I-type granites. SIMS U-Pb dating on magmatic zircons yields consistent ²⁰⁶Pb/²³⁸U ages ranging from 158 Ma to 163 Ma, suggesting that these granites were emplaced during this period. Whole-rock Sr-Nd isotopic analysis reveal that these granites are characterized by initial Sr⁸⁷/Sr⁸⁶ ratios of 0.6802 to 0.7072 and negative εNd(t) values of -9.5 to -8.2. In addition, in-situ zircon Hf-O isotopic analysis shows negative εHf(t) values of -12.34 to -0.56 and high δ¹⁸O values of 7.64 ‰ to 10.08 ‰. Above characteristics suggest that these granites were probably formed by mixing supracrustal sedimentary components with minor mantle-derived magma. Thus, the granites from the Fogang and Xinxing Batholiths in SE China are interpreted to have been generated by the reworking of Proterozoic crust triggered by asthenosphere upwelling or mafic magma underplating. These Jurassic granites represent anorogenic magmatism, probably generated in an intraplate extensional setting due to the flat slab foundering beneath SE China.