Characteristics Of The Ore Forming Fluid And Factor At The Songliang Vein-type Lead-zinc Deposit In Qiaojia County,Northeastern Yunnan Province,China

Sichuan-Yunnan-Guizhou adjacent area is one of the important concentrated areas of lead-zinc mine in China.There are many lead-zinc deposits in the region.Among them,the big vein lead-zinc deposit occurs in the Upper Sinian Dengying group is an important type.The mechanism,especially the role of ore fluid is not clear.The vein-like lead-zinc deposit in the Songliang Village of Qiaojia County is located in the siliceous dolomite of Dengying Formation.It is an ideal object to trace the ore-forming fluid and genetic evolution.Based on the previous research results,this paper uses the the system of mine mapping,tunnel and borehole logging,taking I orebody as the research object,uses fluid inclusions,electron probe and S-H-O isotope tracer to identify the characteristics of ore-forming fluids,chemical composition,and then analyzes its origin and evolution,and reveals its migration law,so as to provide the basis for the establishment of a reasonable metallogenic model.This article mainly draws the following understanding:1.The main strata exposed in the mining area are the Quaternary(Q),the Lower Cambrian Qiongzhusi Formation(?iq)and the Upper Sinian Dengying Formation(Z2dn).I ore body is mainly steeply inclined veins,which is located in the crushed zone of gray siliceous dolomite in the upper part of the Upper Sinian Dengying Formation(Z2dn2).2.Mineral minerals in the ore are mainly sphalerite,pyrite and galena.The gangue minerals are mainly composed of dolomite,calcite and quartz.3.Based on the analysis of the components of sphalerite,pyrite and galena in typical minerals of Songliang lead-zinc mine by using the electronic probe.It is found that the content of Zn element in sphalerite is slightly higher than that of standard sphalerite,and the content of S element is higher than that of standard sphalerite.The content of Zn element in sphalerite,pyrite and pyrite is higher than that of standard sphalerite The atomic ratio of S/Zn is lower than that of standard sphalerite,and the content of Fe is lower than that of standard sphalerite.It has similar characteristics with Fe element change in sphalerite of global MVT lead-zinc deposit.Zn/Fe atomic ratio shows that the ore-forming temperature of sphalerite is medium-low temperature.The atomic ratio of S/Fe atom ratio of pyrite is slightly higher than that of theoretical atomic ratio(?2),rich in As.Only when in the low temperature,will as replace the pyrite in the S.It is judged that the pyrite in the Songjiang lead-zinc deposit should be formed in the medium and low temperature environment.4.The total amount of trace elements in sphalerite and galena Songliang lead-zinc mining area(?ME)significantly decreased variation from the bottom to the top.The analysis may have the following reasons:?There is a certain relationship between the content of trace elements and ore rock in the more the content of trace elements in rock ore bodies in the lower part,and less content of trace elements in ore the upper.?There is a certain relationship with the migration of ore-forming fluids,influenced by geological effect,the lower part of the carrying fluid dissolved ore ore-forming substances and trace elements to the migration of ore body at the top,in the migration process of continuous unloading ore deposits,the ore body led to the bottom to the top of ore mineral trace elements appeared to be reduced.5.There are three types of primary inclusions in quartz of Song Liang lead-zinc ores:pure liquid inclusions(L-type),gas-liquid two-phase inclusions(L+V type)and salt-bearing inclusions(L+V+S type),but mainly gas-liquid two-phase inclusions.The average temperature of quartz is 158.9?,which is characterized by low-temperature fluid properties and a relatively stable metallogenic environment,indicating that no high-temperature magmatic fluid is involved,and the average salinity is 14.93wt%NaCleq,which is shown as low-salinity inclusions.The average pressure is 106.75MPa and the ore-forming depth is 1197m,which is shown to be shallow.The uniform temperature and pressure values show a decreasing trend from the bottom to the top of the ore body,suggesting that fluid migration is from the bottom to the top.6.The average pH value of the fluid is 5.71,which is weak acidity.It is concluded that the Songliang vein-like lead-zinc deposit is formed in the acidic environment.The Eh value is 0.08,which is shown as reducing condition.The deposits are mainly formed in the reducing environment.7.The results of fluid inclusions and hydrogen and oxygen isotopes show that the ore-forming fluids are derived from atmospheric precipitation,and have the fluid properties of low-temperature,medium-low salinity and medium density.8.Songjiang lead-zinc deposit belongs to MVT-type lead-zinc mine.