Geochemistry and geochronology of granite-pegmatite in the Duxiushan deposit, Anqing ore district: Implications for petrogenesis and Li–Rb mineralization

The Duxiushan deposit in the Anqing ore district is a newly discovered granite-pegmatite system hosting significant Li–Rb–Nb–Sn mineralization, representing a style markedly different from those previously recognized in the Middle-Lower Yangtze River Metallogenic Belt, yet its genetic mechanism remains unclear. In this study, we integrate geochronology, geochemistry, and isotopes to constrain its petrogenesis and rare metal enrichment. Zircon U–Pb dating of the two-mica granite (138.3 ± 1.7 Ma) and barren pegmatite (136.7 ± 1.6 Ma), together with cassiterite U–Pb dating of the mineralized pegmatite (136.6 ± 1.9 Ma), indicate that magmatism and coeval Li–Rb–Sn mineralization occurred during the Early Cretaceous. The Duxiushan two-mica granite is classified as a highly fractionated, peraluminous S-type granite. Consistent isotopic compositions of zircon Hf, apatite Sr–Nd, and tourmaline δ 11 B across all three lithologies indicate a cogenetic origin, involving partial melting of Neoproterozoic juvenile crust followed by assimilation of ancient continental crustal components within an extensional tectonic setting. Systematic geochemical trends from granite through barren pegmatite to mineralized pegmatite, including increasing SiO 2 and Rb, decreasing TiO 2 , MgO, total REE, Ba, Th, Nd, and extreme depletion of Zr/Hf and Nb/Ta, record progressive fractional crystallization. The positive correlation between Fe and Al in tourmaline, combined with zircon Ce 4+ /Ce 3+ ratios, indicates a reduced magmatic system. Tourmaline exhibits significantly higher F contents in mineralized pegmatite, indicating F enrichment during magma evolution. Collectively, these processes efficiently concentrated incompatible elements (Li, Rb, Sn, Nb, Ta) into the residual melt, leading to the formation of the mineralized pegmatite in the Duxiushan deposit.