Petrogenesis of the Jurassic Guiping Complex in the Southwestern South China Block: Insights into the Subduction Processes of the Paleo-Pacific Slab

Late Jurassic NE-trending A-type granitoids are widespread in the Shihang belt, South China, though their petrogenesis and geodynamic settings remain controversial. The Guiping complex is located on southwest margin of belt. In this study, petrography, major trace element geochemistry, whole-rock Sr-Nd isotopes, zircon U-Pb geochronology were investigated. composed Fenghuangling Xishan plutons; both plutons yielded ages ca. 160 Ma. pluton has low SiO2 content 54.26% to 60.31%, whereas exhibits high 65.19% 71.18%. Both them metaluminous belong high-K calc-alkaline series enriched large-ion lithophile elements (LILEs) such as Rb, Th, U, Pb. showed enrichment light rare earth (LREEs) high-field strength (Nb, Ta, Zr, Hf) depletion heavy (HREEs). Marked Nb Ta negative anomalies not observed. Due contents Zr + Ce Y Ga/Al ratios, all samples belonged group granites. had ISr (mainly range 0.7046–0.7058) εNd(t) (−0.60 1.94) values, obviously different from those Precambrian basement China. Furthermore, they lie between ocean island basalt (OIB) asthenosphere arc basaltic rocks lithospheric mantle. Therefore, we proposed that parental magma originated partial melting mantle, which was metasomatized by asthenosphere-related OIB-type magma. Mafic microgranular enclaves displayed positive anomalies, consistent with basalts. also similar isotopic compositions pluton. That indicated probably formed mixing conclusion, formation granite belt attributed back-arc extension a result rollback Paleo-Pacific Plate.