Characteristics Of Fluid Inclusions And Its Significance In Mengya'a Pb-Zn Deposit,Tibet

The mengya'a lead-zinc deposit is located in Lhari County of Tibet autonomous region,located in the longgeer Niangqing tanggula Mesozoic uplift belt.Based on the study of the basic geological characteristics of the Pb-Zn deposit,the ore deposits are divided into stages.The inclusion geochemistry theory,the deposit of three stages(skarn stage,sulfide stage and carbonate stage)of the inclusion of detailed test temperature,salinity,density,summarize the characteristics,present evidence for the study of the characteristics of metallogenic fluid.Combined with geochemical isotope study,the source of ore-forming fluid in mining area is further studied.The mengya'a lead-zinc deposit of skarn minerals are widely distributed,with calcareous skarn dominated by mineral paragenesis and interpenetration relationships can be the mengya'a lead-zinc deposit formation process is divided 5 stages:(1)early skarn stage: the main form of garnet,pyroxene and wollastonite as anhydrous silicate minerals.Garnet formed early,mostly yellow-brown,euhedral degree is good and the content more;less pyroxene and wollastonite content.(2)late skarn stage: the main generation of tremolite,actinolite,epidote and biotite aqueous silicate minerals and magnetite,has obvious effect on early metasomatic skarn stage forming minerals such as tremolite metasomatism of wollastonite,diopside,biotite garnet and metasomatism.(3)the quartz sulfide stage: with the change of temperature,pressure and acid leaching,formed mainly galena,sphalerite and pyrite,chalcopyrite,pyrrhotite,Huang Xikuang and other metal sulfide and chlorite,sericite,calcite,quartz and other non-metallic minerals.According to the metal mineral metasomatism relationship determine its metallogenic sequence,a metallogenic period: magnetite,pyrrhotite,pyrite,sphalerite(chalcopyrite),chalcopyrite and galena;two(Huang Xikuang)mineralization: pyrrhotite,chalcopyrite.(4): late stage carbonate rock alteration carbonation development,the formation of a large number of small amounts of calcite and pyrite.(5)supergene oxidation stage: pyrite,pyrrhotite,chalcopyrite,etc.,which were formed in early stage,were oxidized to lead,limonite,malachite,common on the surface.The inclusion test shows that the mengya'a skarn deposit's homogenization temperature are concentrated between 360?-420?,the salinity is between 7.72% ~ 16.80% NaCleq;sulfide stage mineralization temperature mainly between 280?-320 ?,the salinity is between 2.07% ~ 8.81% NaCleq;carbonate stage mineralization temperature concentrated is between 160?-260?.The salinity of fluid inclusions between 0.88% ~ 6.88% NaCleq showed that from early stage to late stage,the mengya'a mining area of metallogenic fluid temperature gradually decreased,the salinity of fluid has been gradually reduced,characteristics of the main mineralization stage flow with middle temperature and low salinity.According to the study on hydrogen oxygen and carbon oxygen isotopes,the author speculate that the ore-forming fluid is mainly magmatic water early,late mixed with a lot of precipitation of different metal sulfides;rare earth elements show abnormal characteristics of different shop,reflects the physical and chemical properties of fluids mineralization happened in different degree of change.Study on Geochemistry of stable isotopes indicate that ore-forming hydrothermal carbon mainly from magma,partly from carbonate strata,magmatic rock and rock stratum strong oxygen isotopic exchange;sulfur isotope characteristics of the ore has the deep magmatic sulfur,sulfur is mainly magmatic source;high forest the value of lead isotope characteristics and tectonic evolution in Zartman Pb isotope pattern diagram and delta gamma delta beta samples point of origin classification diagram,show that the ore-forming materials come from the upper crust(basement),lead the living and the early Cretaceous granitic intrusion events are closely related.The mengya'a deposit mainly through the early high temperature and influence of oxidizing environment(both skarn stage),then change into low temperature metallogenic environment,and reducing environment(both sulfide stage),the origin of ore-forming fluid deposits are mainly of deep magmatic hydrothermal mineralization and mineralization in early late Tianshui,which magmatic hydrothermal mineralization in the dominant position,the ore genesis of presumed deep melting magmatic intrusion and accompanied by Tianshui mixed with magmatic hydrothermal and surrounding formation reaction,the nature of the ore-forming fluid changed,which led to the mineral deposits.