Petrogenesis and Tectonic Setting of Granitoids in the Mahe Molybdenum Deposit, North Qinling Terrane, Central China: Constraints From Geochemistry, Zircon U–Pb Geochronology, and Hf Isotope

ABSTRACT The Mahe molybdenum deposit, located in the western Mangling Mo‐polymetallic orefield of the North Qinling terrane (NQT), is a porphyry deposit associated with Late Mesozoic granitic magmatism. Compared to other regions in the East Qinling, porphyry molybdenum deposits in the NQT are relatively rare. Therefore, determining the geochronology and genesis of igneous rocks outcropped in the mining area is crucial for understanding the formation of the Mahe molybdenum deposit. This study investigates the Taoguanping, Chuanggou, Xigou, and Qitoushan plutons at Mahe through petrography, zircon U–Pb dating, geochemistry, and zircon Hf isotope analysis to elucidate their emplacement ages, petrogenesis, magmatic sources, tectonic setting and magma fertility. Zircon U–Pb dating indicates that the Taoguanping monzogranite, Chuanggou porphyritic monzogranite, Xigou monzogranite, and Qitoushan quartz porphyry were emplaced at 150.1 ± 2.0, 147.6 ± 1.3, 148.7 ± 1.3, and 149.4 ± 1.8 Ma, respectively. Geochemically, these rocks exhibit a peraluminous nature (A/CNK = 1.01–1.23), with high concentrations of SiO 2 (72.6–79.0 wt%), K 2 O (3.89–5.13 wt%), and Na 2 O (2.76–3.83 wt%), along with high differentiation index values (DI = 89.6–96.0). Chondrite‐normalised REE patterns display enrichment in light rare earth elements (LREEs) and depletion in heavy rare earth elements (HREEs). In mantle‐normalised multielement variation diagrams, the samples are characterised by depletions in high‐field‐strength elements (HFSEs). Petrological and geochemical features of these plutons uniformly display highly fractionated affinity of I‐type granitoids. The estimated pressure‐temperature‐oxygen fugacity ( P ‐ T ‐ f O2 ) conditions are low pressure ((La/Yb) N = 2.32–18.4), 724°C–790°C, and relatively oxidised conditions (average Ce 4+ /Ce 3+ and ΔFMQ values of 65.7–118 and 1.35–3.30, respectively). Zircon Hf isotope analysis reveals varying negative ε Hf ( t ) values from −27.8 to −5.65, with corresponding two‐stage model ages between 1563 and 2954 Ma, suggesting derivation from the partial melting of ancient crustal materials. Considering the regional tectonic and magmatic evolution, these granitoids at Mahe likely formed during the Late Jurassic transition from continental compression to extension in the Qinling Orogenic Belt (QOB). Differences in magma source area, oxygen fugacity, and water content significantly influence the magma fertility of these granitoids.