Zircon U–Pb geochronology and geochemistry of the Late Jurassic granite porphyries from central-eastern Jilin Province, NE China: Petrogenesis and tectonic implications

Abstract

The recently discovered Yizuoying Mo deposit is located in central-eastern Jilin Province, NE China. The molybdenum (Mo) mineralization, mainly hosted in granite porphyry, is considered to be granite-related. Zircon U–Pb dating of the granite porphyry yielded concordant ages of 160.81 ± 0.62 Ma, which is consistent with the weighted mean U–Pb age of 160.53 ± 0.65 Ma, indicating that the emplacement of granitic plutons occurred in the Late Jurassic. The granite porphyry samples are peraluminous, high-K calc-alkaline and show an A-type geochemical signature with high Na₂O + K₂O and Zr + Nb + Ce + Y content, K₂O/MgO, Fe₂O₃^T/(Fe₂O₃^T + MgO), REEs (rare earth elements) and 10 000 Ga/Al ratios. Based on the trace element content of zircons, they have high Th, U, Zr, Hf, and Pb abundance and obvious La and Eu anomalies, and their distribution pattern is similar to that of A-type granites. The zircon εHf(t) values range from 4.5 to 10.5 with Neoproterozoic T_DM2 ages (536–922 Ma) for Hf isotopes, and they have relatively high values of εNd(t) (3.14 to 3.49; T_DM2 = 665–693 Ma) and initial ⁸⁷Sr/⁸⁶Sr (0.723260–0.734669). Detailed elemental and isotopic data suggest that the Yizuoying granite porphyry belongs to the A₂-subtype and was formed by partial melting of a crustal source with a neoproterozoic overall residence age. Integrating new data on the oxygen fugacity of zircons and published data on the tectonic evolution, we suggest that the granite porphyry and associated Mo mineralization in the Yizuoying deposit formed in an extensional environment at ~160 Ma, related to the subduction of the Paleo-Pacific plate. The evolution of granitic magma in this period contributed to Mo mineralization.