The Tongling district is one of the most important non‐ferrous metal producers in China. The origin of Cu–Au deposits in the region is closely related to Late Mesozoic intermediate intrusions, which are mainly high‐K calc‐alkaline and shoshonitic series. Geochemical characteristics indicate that these granitic rocks are mixtures of more than two compositional end‐members, i.e. mantle‐derived melts and crust components incorporated through assimilation. Three important magmatic intrusions related to the Cu–Au deposits in the Tongling region – the Jiguanshi quartz monzodiorite, the Xishizishan quartz diorite and the Miaojia diorite porphyry – were selected for this study. Zircon U–Pb dating by LA ICP‐MS yielded two groups of ages (∼130–132 and 138–140 Ma) for these intrusions. Pyrite Re–Os age for the Xinqiao Cu–Fe–S deposit in the Tongling region is 126±11 Ma. Trace elements of zircon grains show that the earlier Cu–Au mineralization event was associated with adakitic rocks characterized by high positive Ce anomalies, produced at an elevated oxygen fugacity range. In contrast, later iron‐sulphur mineralization was closely related to low positive Ce anomalies, reflecting low oxygen fugacities. Considering that Pacific lithospheric subduction was the dominant factor that controlled major tectonic evolution in eastern China during the Early Cretaceous, the geochemical characteristics of these coeval ore‐forming intermediate intrusive rocks in the Tongling district were likely the result of Pacific plate underflow.

Large-scale Cu–Au mineralization is associated with Late Mesozoic intrusive rocks in the Tongling region of eastern China, which mainly comprise pyroxene monzodiorite, quartz monzodiorite, and granodiorite. To constrain the petrogenesis of the intrusive rocks and Cu–Au mineralization, detailed analyses of the geochronology, apatite in situ geochemistry, whole-rock geochemistry, and zircon Hf isotopic compositions were performed. Magmatic zircons from pyroxene monzodiorites, quartz monzodiorites, and granodiorites yield U–Pb ages of 136–149 Ma, 136–146 Ma, and 138–152 Ma, respectively, indicating that their formation ages are contemporaneous. Quartz monzodiorites and granodiorites (SiO₂ = 57.9–69.5 wt.%) are highly potassic calc-alkaline rocks with adakitic affinity and have low MgO and Y contents, low zircon ε_Hf(t) values (−11.7 to −39.0), high apatite Cl contents (>0.2 wt.%), and log fO₂ values (−23.2 to −8.23), indicating that they may have formed when metasomatized mantle-derived magmas mixed with slab-derived magmas before undergoing crustal assimilation and fractional crystallization. Pyroxene monzodiorites (SiO₂ = 48.4–53.0 wt.%) are shoshonitic and record high MgO, P₂O₅, and Y contents, high zircon ε_Hf(t) values (1.55 to −7.87), high oxygen fugacity, low Nb and Ta contents, and low apatite Cl contents (mainly <0.2 wt.%), suggesting that they were primarily derived from a metasomatized lithospheric mantle-derived magma that experienced the assimilation of lower crustal materials. The results indicate that the intrusive rocks and associated large-scale Cu–Au mineralization of the Tongling region resulted from the partial melting of the subducted oceanic slab in an oxidizing environment.

Late Mesozoic granitoids are widely distributed in southern Anhui Province, southeastern China, which also contains significant W–Mo–Cu mineralization. This study presents new geochronological and geochemical data that reveal the petrogenesis and tectonic affinity of the granitoids in this region. These granitoids can be divided into a high-K calc-alkaline and peraluminous I-type granodiorites, and an alkaline and metaluminous A-type granites, with zircon U–Pb dating indicating that they formed at 150–138 and 133–124 Ma, respectively. The early stage I-type granodiorites are adakitic, enriched in the light rare earth elements, and depleted in Nb, Ta, P, and Ti. They have negative zircon ε_Hf(t) values (–19.8 to –2.5) that correspond to Hf crustal model ages of 2.4–1.4 Ga. These early stage granodiorites were derived from partial melting of thickened Palaeoproterozoic–Mesoproterozoic lower crust. The late-stage A-type granites with strong depletion in Sr, P, and Ti, contain higher Zr, Y, and Yb contents, higher zircon ε_Hf(t) values (–1.5 to +2.1), and younger zircon Hf model ages (1.1–1.3 Ga) than the early stage granodiorites. The geochemistry of these A-type granites indicates they were likely generated by the reworking of Mesoproterozoic to Neoproterozoic juvenile crustal material that experienced the fractional crystallization of plagioclase and accessory minerals. Combining these data with other geological data from the study area indicates that the early stage granodiorites formed in a continental arc setting, whereas the late-stage granites formed in an extensional setting associated with roll-back of the subducted Palaeo-Pacific slab. The results indicate that zircon Ce⁴⁺/Ce³⁺ value can provide useful insight into oxygen fugacity conditions during magmatism.

The Anqing region in Lower Yangtze River metallogenic belt is one of the important Cu polymetal producers in China. The origin of Cu polymetallic deposits in the region is closely related to Early Cretaceous adakitic intrusions. To constrain the petrogenetic and metallogenic significance of the adakitic rocks, a detailed geochronological, geochemical, and Sr–Nd–Pb–Hf isotopic study was performed. The Anqing adakitic rocks (SiO₂ = 57.4–64.2 wt.%) consist mainly of quartz monzodiorite, formed at 138.2 ± 1.7 Ma (Mean Standard Weighted Deviation (MSWD) = 0.61). They have high MgO, Al₂O₃, Sr, and low Rb, Y, Yb contents, together with high Sr/Y (50.5–222) and La/Yb (31.9–46.9) ratios. They also show negative whole-rock ε_Nd(t) (−9.8 to −8.5) and zircon ε_Hf(t) (−10.0 to −5.4), and high oxygen fugacity (mainly −17.0 to −8.01) values and radiogenic Pb isotopic compositions with (²⁰⁶Pb/²⁰⁴Pb)_i = 17.692–17.884, (²⁰⁷Pb/²⁰⁴Pb)_i = 15.413–15.511, and (²⁰⁸Pb/²⁰⁴Pb)_i = 37.611–37.943. Coupled with negative Nb–Ta anomalies, low K₂O/Na₂O ratios (0.39–0.62), and high Mg# values (0.44–0.71), these data suggest the adakitic rocks and associated large-scale Cu–Au mineralization of the Anqing region resulted from partial melting of the high oxidized subducted oceanic crust. Addition of mantle-derived magmas and assimilation of crustal materials during emplacement are also possible.