Precambrian Crustal Composition and Reworking in the Western Margin of the Yangtze Craton: Constraints from Sr-Nd-Hf Multi-Isotope Mapping

Regional multi-isotope mapping provides an effective means of investigating deep crustal composition and crustal reworking processes. The western margin of the Yangtze Craton has experienced multiple episodes of magmatism, crustal reworking, and mineralization since its formation, making it an ideal region for exploring the relationship between deep crustal evolution and metallogenic systems. In this study, Sr-Nd-Hf isotopic and whole-rock geochemical mapping was conducted based on compiled geochronological, geochemical, and isotopic datasets, integrated with deep geophysical data, to reconstruct the Precambrian crustal composition and reworking processes of the region. The results reveal significant crustal heterogeneity in the western margin of the Yangtze Craton. West of the Anninghe Fault Zone, rocks exhibit depleted Nd-Hf isotopic signatures (εHf(t) = 0 to +17; εNd(t) = 0 to +6), low ISr values (0.702–0.710), and high Nb/Ta (14–26) and Zr/Hf (36–46) ratios, indicating derivation from the remelting of juvenile mafic lower crust and providing direct evidence for Proterozoic underplating of mantle-derived magmas. In contrast, rocks east of the Anninghe Fault Zone show enriched Nd-Hf isotopic signatures (εNd(t) = −9 to 0; εHf(t) = −7.5 to 0), higher ISr values (0.711–0.726), and lower Nb/Ta and Zr/Hf ratios (8–13 and 21–35), suggesting remelting of ancient continental crust. Mineralization is closely associated with crustal architecture. IOCG deposits mainly occur in juvenile crustal domains, whereas Sn polymetallic and phosphate deposits are associated with ancient reworked crust. Under the Precambrian subduction setting, continuous arc magmatism promoted juvenile crust growth, whereas asthenospheric upwelling facilitated ancient crustal reworking, jointly controlling the spatiotemporal distribution of metallogenic systems along the western margin of the Yangtze Craton.