Petrogenesis of Dengfuxian granites in Hunan Province, SE China: Insights from U-Pb zircon ages and geochemistry

Granitoids are prevalent in southeastern China and are associated with numerous renowned polymetallic deposits. The mineralization is thought to have a close genetic linkage with granitic magmatism in this region. However, the petrogenesis of these granites remains a subject of debate. Dengfuxian granites in the eastern Hunan Province, a representative granitic pluton, formed during this geological period and are linked with tungsten deposits. To constrain their magmatic origins and petrogenesis, analyses were conducted, including whole-rock geochemistry, SIMS zircon geochronology, oxygen isotope studies, and LA-ICPMS zircon Lu–Hf isotopic analyses on selected samples of Dengfuxian granites.The Dengfuxian granitic pluton predominantly consists of biotite granite, two-mica granite, and muscovite granite. Age determinations of the various granite types indicate the existence of two distinct episodes: the Late Triassic (221–226 Ma) and the Late Jurassic (150–151 Ma). Granites from both periods consistently exhibit high concentrations of SiO₂, Al₂O₃, total alkalis, K₂O, and P₂O₅, while showing low levels of MgO, TiO₂, and MnO₂, exhibiting a range from weak to strong peraluminous characteristics. Geological and geochemical evidence supports that the Dengfuxian granites are highly fractionated I-type granites, although some features typical of S-type granites are present, likely due to significant magmatic fractionation.Zircon Hf and O isotopic data reveal that the granites from both episodes originated from ancient crustal material, undergoing partial melting and substantial fractionation. The Late Triassic granites, in particular, appear to have incorporated a greater proportion of ancient crustal material into their magma.