Abstract: The ZhashuiShanyang ore deposit cluster is a southern Qinling area with strong tectonic-magmatic activities. Many hypabyssalsuper hypabyssal granitoids, such as the Yuanzijie intrusion, are widely distributed in this area. In this contribution, we performed detailed petrological, whole-rock geochemical, LA-ICP-MS zircon U-Pb isotope, trace element and Lu-Hf isotope analyses on the Yuanzijie granitoid. Using trace and rare earth elemental (REE) compositions of zircon, we calculated the magma temperature and f(O2) conditions, and subsequently evaluated the petrogenesis, geodynamic setting and metallogenetic potential of the granitoid. The Yuanzijie corcovadite yielded zircon 206Pb/238U weighted average age of 141.7±1.7 Ma, with significant positive Ce and weak negative Eu anomalies, suggesting an oxidized environment for zircon formation. Zircon εHf(t) values of -1.58 to +2.18 indicated a mixed origin of crust- and mantle-derived materials with high degree of homogenization for the formation of the Yuanzijie intrusion. The corcovadite displayed Ti-in-zircon temperatures of 598841 ℃ (averaging 656 ℃), with an average lgf(O2) value of -18.0 and ΔFMQ values concentrating between 0 and 5—all similar to the values of Xiaohekou skarn copper deposit in the ore cluster. The intrusion also had significantly high Cu content (1705939 μg/g, averaging 1300 μg/g), obviously higher than that of granitoids in South Qinling (11 μg/g) and the world (20 μg/g) on average. Rock RbY+Nb, NbY and zircon YbU, HfU/Yb and U/YbY discriminant diagrams further suggested that the Yuanzijie intrusion was formed in a post-collisional orogenic setting. We conclude that the Yuanzijie mineralized spot is similar to those of typical porphyry-skarn deposits in the ZhashuiShanyang ore cluster and the world in diagenesis and metallogenic setting, mineralization characteristics, wall rock alteration, and magma f(O2) condition, implying its mineralization potential. The Yuanzijie intrusion and other Yanshanian intrusions in the Qinling Orogen occurred in a same geodynamic setting of a transitional regime from compression to extension during J3K1, triggering a intense crust-mantle mixing and granitic magmatism, and forming the ore-bearing intrusions and skarn-type mineralization.

Key words: zircon U-Pb age, zircon trace elements, zircon Lu-Hf isotope, Yuanzijie intrusion, mineralization potentiality