Characteristics Of Ore Geology And Ore-forming Fluid In The Zhaxikang Sb-Pb-Zn-Ag Deposit, Southern Tibet, China

Due to the huge mineral resource potentials and complex deposit types, Zhaxikang Sb-Pb-Zn-Ag Polymetallic Deposit, in southern Tibet, has been caught more scholars’ attention in the past few years. By studying the geological characteristics and fluid inclusion in Zhaxikang Deposit, the mineralization and the possible ore deposit type are discussed in this paper.The ore bodies are hosted in Jurassic Ridang Formation and controlled by a S-N normal fault, followed by NE-SE rift. According to the paragenesis of minerals,Zhaxikang deposit can be divided into two pulses of mineralization, consisting of six separate stages, which can be recognized:(1) fine-grained ferromanganese carbonate and brown sphalerite, pyrite, and arsenopyrite;(2) coarse-grained ferromanganese carbonate and brown or black sphalerite, galena, pyrite, and minor arsenopyrite;(3) quartz, sphalerite, galena, pyrite, and minor chalcopyrite, and calcite;(4) quartz and sulfosalt minerals composed mainly of boulangerite;(5) quartz, stibnite and cinnabar; and(6) quartz and calcite.The studies of fluid inclusions suggeset that the type of inclusions are relatively simple in each of the mineralization stage, Mainly in the rich liquid two-phase aqueous inclusions, lack of two-phase CO2 inclusions and three-phase type inclusions.In the early mineralization, homogenization temperatures of inclusions vary from 220℃-240℃,the salinity(wt%Na Clequiv) vary from 12% ~15%;In the late mineralization, homogenization temperatures and the salinity of inclusions have a decreasing trend.The homogenization temperatures range from 230℃~310℃(II-1)、230℃~270℃(II-2)、230℃~270℃(II-3)、230℃~260℃(II-4); the salinities range from 6% ~10t%(II-1)、6% ~9%(II-2)、6% ~9%(II-3)、3% ~6%(II-4)。The early hydrothermal showing a low temperature, medium salinity, H2O–Na Cl system,the same as SEDEX and MVT type deposite;The late hydrothermal is a medium-low temperature, low salinity, H2O–Na Cl system, similar to the epithermal type.Consider of H-O isotope,the type of Zhaxikang deposite can be defined as a Sedimentary exhalative- epithermal superimposed deposits.