Geochemistry, zircon U–Pb geochronology and Lu–Hf isotopes of the Late Jurassic granitoids from the Shuangyuangou deposit, South Qinling, China: Implications for petrogenesis and porphyry Cu metallogeny

• Published in: Geological journal (Chichester, England) England), 2024-03, Vol.59 (3), p.1039-1055
• Main Authors: Zhao, Feng‐Yun, Tang, Li, Guo, Xu‐Fei, Santosh, M., Zeng, Tao, Chen, Long‐Long, Sheng, Yuan‐Ming, Zhao, Jiang‐Lin
• Format: Article
• Language: English
• Subjects: Belts; Copper; Diorite; Fractionation; Geochemistry; Geochronology; Geochronometry; Granite; Hafnium; Intrusion; Isotopes; Jurassic; Juveniles; Lava; Lead; Magma; magma source; Magmatic water; magmatic water content; Metallogenesis; Mineralization; Moisture content; Orogeny; Petrogenesis; Plagioclase; Porphyry copper; Qinling orogenic belt; Quartz; Radiometric dating; Rocks; Shanyang area; Shuangyuangou porphyry Cu deposit; Trace elements; Water content; Zircon
• ISSN: 0072-1050; 1099-1034
• DOI: 10.1002/gj.4908

The Shuangyuangou copper deposit is located in the southern segment of the Qinling orogenic belt in central China. The ore‐related intrusions include quartz diorite porphyry, granite porphyry and lamprophyre. In this study, we present whole‐rock geochemistry, zircon U–Pb geochronology, trace elements and Lu–Hf isotope data on the Shuangyuangou intrusions which provide critical constraints on the emplacement age, magma origin, petrogenesis and implications for porphyry Cu mineralization in this newly discovered deposit. Zircon U–Pb dating constrains the emplacement age of quartz diorite porphyry, lamprophyre and granite porphyry at 150–147 Ma. The quartz diorite porphyry and granite porphyry display high‐K calc–alkaline I‐type granite affiliation. The rocks show enrichment of LREE and LILE (Rb, Ba), depletion in HREE and HFSE (Nb, Ta, Ti) and absence of Eu anomaly. Zircon εHf(t) values of quartz diorite porphyry, lamprophyre and granite porphyry range from −7.5 to −1.7 with TDM2 ages of 1.3–1.6 Ga. Our data suggest that the parental magma was derived from partial melting of juvenile lower crust and metasomatic lithospheric mantle, with more involvement of mantle material for the lamprophyre. The zircon Eu/Eu* values of 0.55–0.78 suggest high magmatic water content which suppresses the fractionation of plagioclase. In addition, the ΔFMQ values calculated from zircon trace elements range from −0.90 to 2.96 which is a favourable factor for porphyry Cu mineralization at Shuangyuangou. The Late Jurassic Shuangyuangou intrusion and associated Cu mineralization were formed within an intracontinental setting after the collisional assembly of the Qinling orogenic belt. The emplacement age of quartz diorite porphyry, lamprophyre and granite porphyry in shuangyuangou is 150–146 Ma. The quartz diorite porphyry and granite porphyry are less evolved Ι‐type granites with magma originated from partial melting of juvenile lower crust. The lamprophyre is the product of the partial melting of enriched lithospheric mantle metasomatized by the multi‐stages of subduction in Qinling. The magmas of quartz diorite porphyry, granite porphyry and lamprophyre have high water content, high oxidation state and low zircon saturation temperatures, which are favourable factors for the formation of porphyry Cu deposit in the intra‐continental setting.