Neoproterozoic multilevel magmatism in response to Rodinia’s peripheral subduction: Insights from the Pengguan Complex in the western Yangtze Block, South China

The circum-Rodinia suprasubduction system maintained a dynamic equilibrium between extension and convergence along the periphery of the Rodinia supercontinent during its breakup. Although recent paleomagnetic data place the Yangtze Block at this margin, it remains unclear whether the Tonian tectonothermal events on its western edge are fully consistent with this configuration. This study examined a composite intrusive batholith of the Pengguan Complex on the western Yangtze margin, South China, comprising diorite, tonalite, granodiorite, biotite granite, and K-feldspar granite; however, a systematic synthesis of its properties for reconstructing the regional setting remains uncertain. Zircon U-Pb geochronology yielded consistent ages of ca. 801–794 Ma, representing the multiplex magmatic record of the western Yangtze Block during the middle Tonian. The various lithologies exhibit distinct zircon Hf-isotopic compositions, whole-rock geochemistry, Sr-Nd isotopes, and mineral geochemistry, reflecting partial melting at different levels across a continental-arc lithospheric profile. Diorite crystallized from an evolved hydrous magma ultimately related to a metasomatized mantle source, as evidenced by its arc-type trace element signatures and variable Nd-Hf isotopes. Tonalite and granodiorite display adakitic features, including elevated Sr/Y and (La/Yb)N ratios and reduced Ni and Cr concentrations, plus erratic Nd- and Hf-isotopic signatures. These features favor their derivation from partial melting of a thickened mafic lower crust. Distinct petrogenetic processes contributed to the formation of the biotite granite and K-feldspar granite, both of which are associated with transcrustal recycling. The former shows variable Nd- and Hf-isotope ratios derived from the reworking of ancient crust. In contrast, the latter has depleted Nd and Hf isotopes and younger model ages, resulting from partial melting of relatively juvenile lower-crustal components. These pieces of magmatism collectively represent multilevel partial melting of compositionally distinct domains in the mantle wedge and continental crust. The multilevel partial melting recorded by the studied batholiths in the Pengguan Complex within a continental arc setting, coupled with coeval Tonian subduction-related magmatism along the western Yangtze margin, constitutes a thermal manifestation of the convergent regime at the periphery of the Rodinia supercontinent during the early Neoproterozoic.