Abstract:

Hydrothermal vein type of PbZn polymetallic ore deposits is one kind of important deposit in Deerbugan meatallogenic zone, Inner Mongolia, China. Their oreforming ages and geological backgrounds are still unclear. Six pieces of sphalerites collected from Dongjun hydrothermal vein type of PbZnAg deposits were analyzed for Rb, Sr and their isotopes. The 87Rb/86Sr and 87Sr/86Sr ratios fall into the ranges of 0.2838 to 6.5030 and 0.713685 to 0.725241, respectively, and they show good linear relationship, defining a RbSr age of 130.2±4.4 Ma (2σ, MSWD=16), (87Sr/86Sr)0=0.713176±0.000057, indicating that the mineralization age of Dongjun PbZnAg deposit is in the Early Cretaceous. As the Da Hinggan Mountains and its adjacent region were in an extensional setting in the early Cretaceous, so this type of ore deposit was formed in an extensional tectonic regime in the early Cretaceous, and its mineralization was related to hypabyssalultra hypabyssal magmatic intrusion. This type of ore deposit represents an important metallogenic period and type in the Deerbugan metallogenic belt.

Key words: Dongjun PbZnAg deposit, sphalerites, RbSr age