Magmatism And Metallogenesis Of The Super-large Shuangjianzishan Pb-Zn-Ag Deposit In Inner Mongolia, China

The Shuangjiangzishan Pb-Zn-Ag deposit in Inner Mongolia is located in the northeast section of the Huanggang-Ganzhuer silver polymetallic metallogenic belt.It is the largest silver deposit discovered in China at present.The reserves of symbiotic mineral resources are 15474.42 tons of silver and metal.The content of lead metal is392200 tons and that of zinc metal is 1.523 million tons.The relationship between magmatism and mineralization in the mining area of Shuangjiangzishan Pb-Zn-Ag deposit is not clear.The transport form and precipitation mechanism and the occurrence state of silve have not been systematically studied.On the basis of detailed field geological investigation and petrographic observation,electron probe technique,whole rock main microtest and analysis,LA-ICP-MS zircon U-Pb dating technique,sulfides?galena,sphalerite?are used in this paper.S Isotope and Pb Isotope Test of Pyrite),Re-Os dating of Pyrite,etc.The occurrence state,transport and sedimentation mechanism of Shuangjiaozi mountain silver were discussed.The diagenesis in the mining area was studied and analyzed.The following main understandings have been obtained.?1?The LA-ICP-MS U-Pb ages of zircon from magmatic rocks in Shuangjianzishan ore area include 261 249 Ma,169¹59 Ma and 137 ⁹Ma,mainly from late Permian to early Triassic,Middle to late Jurassic and early Cretaceous.The Re-Os isochron age of pyrite in Shuangjiangzishan mining area is133.0 ±1.9 Ma,indicating that Shuangjiangzishan mineralization mainly occurred in the early Cretaceous.?2?The Shuangjiangzishan Pb-Zn-Ag deposit is a medium and low temperature hydrothermal deposit,and the mineralization stage is medium temperature ? low temperature and high sulfur fugacity ? low sulfur fugacity.The precipitation order of metal minerals is:?pyrite,chalcopyrite,sphalerite,galena?? the sulfides of silver ?the natural metal of silver.?3?In Shuangjiangzishan rock mass,the felsic magmatic rock invasion of261²49 Ma is located in the late closed period of ancient Asia,that is,the partialmelting of the depleted mantle under the tectonic background of collision to extension transformation;The felsic magmatic rocks of 169¹59 Ma are formed by partial melting of the depleted mantle,which is related to the subduction of the Mongolia-Okhotsk Ocean.The felsic magmatic rocks of 137¹29 Ma are formed by partial melting of subduction oceanic crust,which is related to the subduction of the ancient Pacific Ocean.The mineralization of Shuangjiangzishan Pb-Zn-Ag deposit mainly occurred at this stage.