The Metallogenic Material's Migration And Metallogenetic Process Study Of Zhaxikang Lead And Zinc Polymetallic Deposit In Lonzgi Country, Tibet, China

Due to the complex deposit type and huge mineral resource potentials,Zhaxikang Lead and Zinc Polymetallic Deposit located in the west of Lonzgi Country,Tibet,China has been a hot topic for the past few years.Zhaxikang Deposit is controversial greatly in the metallogenesis and genetic type.It is concentrating in the underground thermal spring type,the sedimentary exhalative and hydrothermal modification type,the magmatic hydrothermal type,superimposed deformation type,etc.As a result,studying the metallogenesis and metallogenic regularity will be a great contribution to the exploration of other deposit in the mining zone.While the prospecting model based on it can also perform a career for the exploration on the deposit of the same type.In this study Zhaxikang Lead and Zinc Polymetallic Deposit had been selected for the research object.On the basis of the previous research,detailed field works,indoor ore microscopy study,fluid inclusions study,Pb and S isotopic analysis,primary halo research,source and migration patterns of ore-forming material,metallogenic characteristics,and zoning model had been discussed,and the some conclusions were made:There were two metallogenic periods of Zhaxikang Deposit: the lead-zinc-antimony hydrothermal mineralization period and the supergene period.The lead-zinc-antimony hydrothermal mineralization period was mainly composed of five stages like the pyrite-ferromanganese carbonate stage,the pyrite-galena-sphalerite ferromanganese carbonate-stage,the pyrite-arsenopyrite-ferromanganese carbonate stage,the antimony bearing sulfosalt-quartz stage,and the quartz stage.The mineral association from deep to shallow was: vein and massive galena was generally distributed below the altitude of 4700 meter,and the ones between the altitudes from4200 to 4500 meter had the highest degree of crystallization and the largest particles.The distribution range of sphalerite which was mainly vein is similar to the galena's,and the brecciated ones were concentrating near the altitude of 4200 meter.And thedistribution of the solid-solution separation of chalcopyrite in sphalerite reduced with height while the sphalerite gradually transformed into disseminated.Between the altitudes from 4300 to 4600 meter the distribution of arsenopyrite increase with height,which was mainly thin vein,the range had demonstrated the medium temperature phase.Antimony bearing sulfosalts minerals were generally distributed upon the altitude of 4300 meter,the distribution increase with height.Vein iron and manganese carbonate had a concentrated distribution in both sides of sphalerite,the distribution decrease sharply upon the altitude of 4700 meter.Large number of drusy and comb quartz vein occurred along with galena and antimony bearing sulfosalts minerals from the altitude of 4400 meter,indicating that the compressional mineral formation environment begin to turn into tensional environment.In the two zones of the altitudes from 4200 to 4500 meter and upon 4500 meter,from deep to shallow,the homogenization temperature of ore-forming fluid decrease gradually,showing a transition of high-middle-low temperature phase,the change of salinity and metallogenic pressure were corresponding to the homogenization temperature.It demonstrated that the power of hydrothermal fluid at depth were decreasing gradually with a higher involvement level of hydrothermal fluid from subsurface.The metallogenic depth decrease obviously in vertical direction.The Pb and S isotopic tracing results indicated that the ore-forming materials sources were mainly from upper crust which contained both Himalaya Basin source-the magma source at depth but also effected by the contamination of sedimentary and metamorphic strata,indicating that there were two different material sources system.According to the primary halo zoning characteristics,the strata had strong supply capability of As,Sb and Pb,but weak capability of Zn.The zoning regularity of main indicator elements along the axial direction of ore body(from deep to shallow)was:Pb and Zn had continuous zoning from deep to shallow;there were two seprate distributions for both typical hanging wall elements As,Sb and foot wall elements W,Sn,Mn in the deep and shallow position of studying.The continuous distribution of Pb and Zn might be the results of mutil-stage superposition process.The W-Sn-Mn zoning upon the altitude of 4600 meter indicated the tail part of previous ore body while the As-Sb zoning in the deep might be the head position of next ore body.At the meantime,as the zoning of Pb existed till the deepest part,there would be a high possibility that the ore body would extend downwards.On the basis of primary halo zoning characteristics and evaluation criteria,the zone of the altitudes from 4300 to4700 meter was the main zone of superposition process,and there were two different ore sources located in the deep part and the subsurface upon the altitudes of 4600 meter.On the basis of the zoning of minerals,ore;-forming fluid and primary halo,the metallogenesis zoning model was established,and the effect range of different hydrothermal fluids: the influence range of high temperature environment was mainly from deep to the altitude of 4300 meter,effected by the magmatic hydrothermal at depth mostly.The transition area located from the altitudes of 4300 to 4500 meter,showing changes from the high-temperature condition into middle-temperature condition,and the compressional environment into tensional environment.The subsurface hydrothermal system got involved upon the altitudes of 4600 meter with the weaker effect of magmatic hydrothermal at depth,and an end near the altitude of4700 meter,then the strata hydrothermal system was acting the leading role from this height.There might be two series of geochemical barriers altitude of 4100 and the range of 4500-4700 meter which had contributes to the mineralization.