Study On The Mineralization Of Zhaxikang Lead-zinc-antimony Polymetallic Deposit In Longzi County,Tibet

The Zhaxikang lead-zinc-antimony polymetallic deposit is located in the eastern part of the Northern Himalaya Metallogenic belt of the Qinghai-Tibet Plateau.It is the largest lead-zinc deposit in Tibet at present.Many experts and scholars have conducted in-depth studies on the geological features,ore characteristics,and metallogenic model of the deposit.However,no consensus has been reached on the genesis of the deposit.Therefore,on the basis of combining previous researches,this paper applies the multiple methods to this deposit again in order to explain the genesis of the deposit.The ore-bodies of the deposit area are mainly occurred within the nearly NS-and NE-striking faults in Lower Jurassic Ritang Formation,with the rocks being carbon-bearing calcareous slate,The extension direction of the ore vein is basically the same as that of the fault.Ore structure types are mainly reticulate,veinlike,and reticulate.The ore minerals are mainly galena,sphalerite and stibnite.The gangue minerals are mainly arsenosides,rhodochrosites,quartz and calcite.Wall rock alterations are mainly silicified,limonite,pyrite,and calcine.According to the vein-cutting relationship and mineral symbiotic combination in the deposit,the deposit is divided into two metallogenic phases(intermediate and low-temperature hydrothermal phase and epigenetic phase).According to the elemental earth data,it is likely that the strata in the mining area is strongly enriched with metallogenic elements such as Cs,As,Pb,Zn,and Sr,which may be related to the hydrothermal input during deposition.The elemental differences between the strata in the mining area and the outer strata of the mining area may be related to the migration of elements in the deposit.The inclusion study shows that the main type of inclusion in the deposit is gas-liquid two-phase water inclusions.From the early metallogenic stage to the late mineralization stage,there is a small difference in the homogenization temperature of the inclusions,and the salinity has the tendency of first decreasing and then increasing.Overall,it has the characteristics of low temperature,low salinity,and low density.The precipitation ofsulphide may be the result of the boiling effect of the fluid.Hydrogen and oxygen isotope studies indicate that the ore-forming fluid comes from geothermal water supplemented by atmospheric precipitation.The H isotopes indicate that the Zhaxikang mining area has risen to near-modern altitude(3723m to5185m)during the ore-forming process.Combined with previous research results,the ore-forming period was limited to the Miocene.According to a comprehensive study,the mineralization of Zhaxikang lead-zinc-antimony polymetallic deposit is driven by the thermal dynamics of metamorphic nuclear complexes.The groundwater hydrothermal cycle has extracted various geological bodies including sedimentary strata,crystalline basement and pale-colored granites.The ore-forming material in the medium precipitates the final formed medium-low temperature hydrothermal deposit at or near the SN fracture site.