Mineralizing age of the Rushan lode gold deposit in the Jiaodong Peninsula: SHRIMP U-Pb dating on hydrothermal zircon

摘要

Zircons from the auriferous quartz vein in the Rushan gold deposit, Jiaodong Peninsula, have high common Pb contents (~(206)Pb_c = 2.00%--5.88%) and Th/U ratios (0.31--.35), and trap primary CO_2-H_2O fluid inclusion similar to ore-forming fluids, indicating that they grew from high Th/U ratio ore-forming fluids responsible for gold mineralization. SHRIMP U-Pb analyses of these zircons gave an age of 117±3 Ma comparable with the ages reported by the former researches in the other areas in the Jiaodong Peninsula, which is interpreted as the age of gold mineralization at Rushan. The age of SHRIMP zircon U-Pb dating with 160±3 Ma from host rock Kunyushan monzogranite is different from that of the gold mineralization, indicating that there is no genetic relationship between gold mineralization and the granitic magmatism. SHRIMP U-Pb dating on hydrothermal zircons from auriferous quartz veins could be used to constrain the timing of lode gold mineralization and the relationship to relevant hydrothermal event.