Geochemical constraints on origin of high-silica granite and volcanic-plutonic connection: An example from Ningwu volcanic basin, Eastern China

High-silica granites (HSGs), commonly associated with felsic volcanic rocks, preserve key information on origin and differentiation of the continental crust through geological time. However, a typical distribution area of Cretaceous HSGs and felsic volcanic rocks in southeast China, origin of the HSGs, their volcanic-plutonic connection, and the causes of mineralization differences remain poorly constrained. This study systematically presents petrological, zircon UPb geochronological, and whole-rock major and trace element, whole-rock Sr-Nd-Pb, and zircon Hf isotopic data of the HSGs in Ningwu volcanic basin, eastern China. Zircon UPb ages indicate that the HSGs (SiO₂ = 73.5–76.4 wt%) are coeval (ca. 130–128 Ma) with the low-silica granites and volcanic rocks (60.2–70.2 wt% SiO₂) in the Ningwu basin. The similar NdHf isotopes, high radiogenic Pb isotopes, and identical trace elemental evolution trends suggest that their parental magmas possibly were originated from partial melting of pre-existing Paleo-Mesoproterozoic accreted crust which was modified and replaced by Cretaceous enriched basic magma involving limited subducted sediments. The HSGs studied have low Eu/Eu* (0.45–0.67) and Zr/Hf (26.9–29.6) ratios, low Eu (0.33–0.83 ppm) and Ba contents (47.6–714 ppm). Combined with the corrosion structures of quart and K-feldspar, these trace-element variations (whole-rock and zircon) and geochemical features suggest that the Ningwu HSGs are the extracted melt of a crystal mush. The low-silica granite porphyries and volcanic rocks have high Eu/Eu* (> 0.7) and Zr/Hf (> 30) ratios, and high Eu (mainly >0.80 ppm) and Ba contents (mainly >800 ppm), showing a cumulate residue. We propose that injection of mantle-derived basaltic magma rejuvenated partial melting of the pre-existing Paleo-Mesoproterozoic crust, generating intermediate to felsic magma. Progressive crystallization produced a crystal-rich mush, which evolved into a shallow silicic magma chamber. The extracted crystal-poor high-silica melts ascended to shallower crustal levels, forming the Ningwu HSGs, whereas the residual silicic cumulates crystallized as the low-silica granites and volcanic rocks. Comprehensive discriminant analysis further suggests that magma source and evolutionary processes likely were key controls on iron mineralization, while high tungsten contents (580–1620 ppm) in the HSGs reflect strong magmatic fractionation in the Ningwu region.