Located in the southern segment of the Great Hinggan Mts. (Da Hinggan Range, or Great Xing’an Mts.) in Hinggan—Mongolia Orogenic Belt (XMOB), the Shuangjianzishan Ag—polymetallic deposit in Balinzuo Qi(Balin Zuoqi; Baarin Left Banner) is a newly discovered superlarge scale epithermal deposit, which is closely related to the Mesozoic tectonomagmatic activities in space, age and genesis. The polymetallic mineralization (Ag, Zn, Pb, and Cu) hosted by the volcano—sedimentary rocks is composed of the layered, lenticular, wedge shaped and cystic orebodies occurring as disseminated, vein, sheet, and veinlets. Preliminary study showed that the sericite yielded an ArAr plateau age of 146.9 ± 1.9 Ma, and the molybdenite from the silver polymetallic ore yielded a model age of 162.6 ± 2.6 Ma. These two ages are identical with the age of regional Jurassic volcanic rocks (160~147 Ma). Therefore, the formation of the Shuangjianzishan silver polymetallic deposit is related to the Jurassic tectono—magmatic activities caused mainly by the remote effect of the subduction of the Mesozoic PaleoPacific plate during the tectonic transformation.