Geochemical Study Of The Bairendaba Ag-Pb-Zn Polymetallic Deposit,Inner Mongolia

The Bairendaba silver-lead-zinc polymetallic deposit is the largest non-ferrous metal deposit in northern China,located in the south-central section of the western slope of the Greater Xing'an Range.Predecessors have done a lot of work on this deposit,but there are still controversies in the division of mineralization stages,the genesis of the deposit,and the spatial distribution of geogas.In order to solve these problems,this paper studies the geochemistry of the deposit,the genesis of the deposit,and the geogas measurement from four aspects:mineralogical characteristics,fluid inclusions,sulfur-lead isotope characteristics,and spatial distribution of geogas.The specific results are as follows:The metallic minerals of the ore in Bairendaba mining area are sulfide represented by sphalerite,galena,and silver-carrying compounds represented by arginetrahedrite and pyroxene.Non-ore minerals are represented by quartz and fluorite.In the ore,Pb,Zn,Cu and Ag are the main ore-forming elements,and As,Cd,Sb,Mn,Bi and Sn are the main associated elements.According to the observation of the hand specimen,the analysis under the microscope and the interspersing relationship between the various minerals,the metallogenic stages of the Bairendaba polymetallic deposit are divided into pyrite-arsenopyrite-quartz stage,gangue minerals-sulfide stage,silver polymetallic sulfide,and fluorite-calcite-mica stage.The density and salinity were calculated by measuring the homogenization temperature of single mineral inclusions in gangue at each mineralization stage.Finally,it is concluded that the ore-forming fluids in Bairendaba are mainly medium-low temperature and medium-low salinity fluids in general.The ?³⁴S_CDT%(value)of mineral crytalization in the Bairendaba lead-zinc polymetallic deposit is-2.5?2.9%,and the average value is-0.46%.Lead isotopes²⁰⁶Pb/²⁰⁴Pb=18.386?18.437,²⁰⁷Pb/²⁰⁴Pb=15.590?15.698,²⁰⁸Pb/²⁰⁴Pb=38.326?38.606.According to the results of fluid inclusions and sulfur and lead isotopes,the Bairendaba polymetallic deposit is a magmatic hydrothermal deposit with medium-low temperature and medium-low salinity.The geogas measurement results show that the elements Ag-Fe-Au-Bi-Pb-Zn-Sb-Cu-Co-V-W-Ni in the geogas samples collected perpendicular to the upper part of the ore body are obviously abnormally high and have obvious spatial distribution characteristics.By comparing the variation characteristics of rare earth elements in geogas samples and ore samples,it is found that the variation curves of rare earth elements are very consistent,which indicates that the mineralization information carried by geogas samples comes from the deep orebody,and it is completely feasible to use geogas survey method to search for ore in areas like Bairendaba.