| Tibet Dulong Deqing Lietingang iron-copper?molybdenum? polymetallic deposit is located on the east side of the Gangdise orogenic belt and belongs to the Ladakh-Gangdese-Xiachayu magmatic arc zone.The magmatic arc zone starts from Gangdise Mountain near the Yarlung Zangpu River stretches all the way southeast into Myanmar.The composition of the Precambrian metamorphic rocks in the belt is the base of the island arc zone,and the magmatic arc zone has experienced a total of Jurassic-Cretaceous subduction volcano-magmatic arc,Paleogene collision type volcano-magmatic arc,and Neogene post-collision magma Event Three times of tectonic-magmatic events formed intermediate-acid magmatic intrusive rock masses and volcanic rocks.It provides favorable geological basis and conditions for many porphyry and skarn polymetallic deposits in the Gangdise metallogenic belt.The main exposed strata in the Lietingang iron-copper?molybdenum?polymetallic deposit area are the Triassic Chaqupu Formation and Quaternary residual slope deposits and alluvial deposits.The Chaqupu Formation is mainly composed of four lithological sections of marble,with skarn at the bottom.Magmatic rocks dominated by intrusive rocks are widely developed in the mining area,mainly medium-acid rock bodies.The ore body mainly occurs on the contact zone of the marble,skarn,granite and granodiorite of the Chaqupu Formation.The boundary between the ore body and the surrounding rock is mainly a gradual relationship.There are nine main ore bodies in the mining area,mostly lenticular,cystic and layer-like.The distribution of minerals in the ore body is characterized by the upper part being iron ore and the lower part being copper ore.As a newly discovered polymetallic deposit in recent years,the Leitingang deposit has only started to carry out corresponding exploration work in 2006.The entire deposit is not well researched,there are few previous data,and there is no systematic model of the genesis of the deposit research.Therefore,this article starts from the aspects of ore deposits,fluid inclusions,isotope geochemistry,etc.,based on the mineral deposit data collected by the field exploration and the C,O,S,Pb and other element isotope combinations of the collected rocks,combined with the fluids tested by predecessors Inclusion data is used to explore the geological background of the mining area,the source of ore-forming materials,and the evolution of ore-forming fluids,etc.,and then to establish the genesis model of the deposit,which provides theoretical support for the exploration of the outer and deep areas of the mine area and the study of other similar deposits on the Gangdise Orogenic Belt.In this paper,through the field survey and the mobile phone of the predecessors'census data,we grasped the geological background and tectonic movement of the study area,and understood the occurrence,scale,type of ore body,surrounding rock alteration and main ore-controlling factors of the ore body in the mining area.Based on field sampling,the order of formation of different minerals in the ore body and the relationship between vein bodies and the division of metallogenic phases were found out.This article tested the C and O isotope content of five calcite samples.The C and O isotope content tested by the predecessors was cast on the ?18O-?13C map,which basically fell near the granite composition,but all received the influence of atmospheric precipitation.The overall content Similar to the isotopic composition in the mantle,it is speculated that the ore-forming fluid may be the source of the mantle and was affected by atmospheric precipitation in the later period of mineralization.In this paper,the origin of water in ore-forming fluids is determined by studying the H-O isotope composition tested by previous people.Putting the ratio into the ?D-?18O diagram,it can be found that the point of calcite is closer to the atmospheric precipitation line,which proves that there is atmospheric precipitation mixed into the fluid at the later stage of mineralization,and the change in ?D value of garnet is much greater than ?18O,indicating that the water in the early stage of mineralization The source is dewatered magma water.In this paper,22 single minerals such as pyrrhotite,chalcopyrite,molybdenite,sphalerite,etc.were selected for S isotope test.The test results show that the ?34 SCDT value of all sulfur isotopes is negative and the change range is small.In the histogram,the number of samples near the zero value is the largest,and it has a tower-type distribution.Its performance is different from the sulfur of metamorphic and sedimentary sources.The source of the sulfur element reflects the deep-source magmatic sulfur.In this paper,17 metal sulfides were selected for lead isotopic composition analysis and testing.The range of changes in the lead isotope combinations of all minerals tested is very small,indicating that the source of lead is very stable.Putting the ratio of lead isotope composition into the206Pb/204Pb-207Pb/204Pb diagram shows that almost all the points are near the orogenic point line,indicating that the sample has multiple segments to provide the lead source at the same time.The ratio of ore lead isotope ratio and relative mantle isotope relative thousandth deviation value ?? and ?? are plotted.The data basically falls in area 3a,indicating that the source of lead is the subduction zone where the upper crust and mantle are mixed under magma.The metallogenic time of the Lietingang deposit can be inferred that during the main collision between the Indian plate and the Eurasian plate,the rollback of the Tethys plate caused the upwelling of the mantle and intrusion of the mixed magma formed by the melting of the crust.That is the source of lead.By studying the data of the mineral fluid inclusions of the predecessor Leitingang deposit,it can be concluded that no matter the mineralization stage,the mineral inclusions are very developed and the morphology is also very diverse.It can be divided into two types:gas-liquid two-phase inclusions that can be homogenized and inclusions containing daughter minerals.Through research and analysis of the data,it can be seen that the temperature and salinity of the inclusions gradually decrease with the progress of mineralization,and the variation range of salinity varies greatly in the middle and later stages of mineralization.The gas-liquid compositions of the inclusions in the Lietingang are relatively similar,mainly composed of H2O in the liquid phase and H2O and CO2 in the gas phase.Finally,in combination with related studies of other inclusions,it can be inferred that the fluids of the Lietingang polymetallic deposit have undergone processes such as magmatic leaching,supercritical fluid differentiation,fluid cooling and pressure boiling and mixing of atmospheric precipitation fluids to cause secondary boiling.In summary,the study of this paper believes that the geological characteristics of the Lietingang iron-copper polymetallic deposit have obvious characteristics of skarn type deposits.. |
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