Characteristics of isotopic compositions and genesis of the Lianjiagou polymetallic ore deposit in Chichen County, Zhangjiakou

Lead, zinc and silver polymetallic deposits are intimately associated with the hypabyssal acidic rock mass in northern Zhangjiakou area. Middle-Upper Proterozoic carbonate strata are widely distributed in southern Zhangjiakou. Some polymetallic ore deposits (ore spots) have been found in carbonate strata, such as Liangjiagou, Huoshigou and Changzhuangzi. Dolomite formation of Gaoyuzhuang Group and Wumisan Group of Jixian System constitute the major ore-host rocks. Contrary to polymetallic deposits located in northern Zhangjiakou area, polymetallic deposit lies in the dolomite strata where intermediate-acid intrusive masses are not developed in the mining area. In addition, the orebody characteristics, ore fabric and ore deposit geochemistry have significant difference from the polymetallic deposits related to the hypabyssal acidic rock mass in northern Zhangjiakou area. Taking the Liangjiagou polymetallic deposit as an example, based on the field observation of the geological characteristics of ore deposit and ore, and taking into consideration various isotope test results for such elements as Pb, S, Rb, Sr, the authors have reached the conclusion that the sources of ore-forming material might have come from dolomite strata or substrata, the formation of the deposit was related to the large-scale overthrust nappe tectonic system, and the genetic type of ore deposit belongs to the Mississippi valley type (MVT) ore deposit.