Geochemical Characteristics of REE and Trace Elements in the Biliyagu Large Pb-Zn Ag Deposit of Eerguna Area,Inner Mongolia and Their Metallogenic Significance

Located in the northwest of Hailar-Genhe Mesozoic volcanic basin,the Biliyagu Pb-ZN-Ag deposit occurs in the Upper Jurassic Manketouebo Formation acidic volcanic and is controlled by the NW-trending faults,with the ore bodies being mainly of veined type.Analysis on REE and trace element between volcanic wall rock and main ore minerals show they have similar distribution trend:enrichment of large ion lithophile elements such as Rb and Th,depletion of high field-strength element such as Sr,Nb and Ta,which show both of them developed in Plate tectonic environment.The differences lie in two points:1Total REE and trace elements of the ore mineral are bviously less than those of volcanic wallrock;2The volcanic wallrock shows clear negative Eu anomalies,while the ore mineral show positive Eu anomalies with different grade.Comprehensive analysis show that the Biliyagu Pb-Zn-Ag deposit belong to volcanichypovolcanic hydrothermal type.The main metallogenic epoch was eorrelated to the volcanic activities during Upper Jurassic-Lower Cretaceous(140Ma±),and this period was corresponding to the late stage of regional tectonic transition in the northern areas of China.After this metallogenic period,the deposit was transformed by the large scale magmatic activities at 120Ma±,which was caused by the quickly regional lithospheric thinning.Magmatism in this stage caused deep metamorphism and deep fluid activities related to crust-mantle interantion which strong transformed the ores and led to the change of the REE and trace element in the ore minerals.