| Ke-Yue Pb-Zn-Sb-Ag polymetallic deposit is an important part of the Southern Tibet Sb-Au mineralization belt,which is located in the southern Tibet metallogenic belt with the favorable metallogenic conditions and unique mineral.The exposed Strata in the mining area is relatively simple,mainly for the J1r and the J2z,and part of the Quaternary distributed along the valley areas.The folds,faults in the Mining area are developmental,and control the output of lead and zinc,antimony polymetallic ore body.And magmatic activity and volcanic activity are well developed in the mining area,basic rocks and acid rocks distributed in the J1r.Volcanic rocks are mainly altered basalt to formation of interlining.The total of five banded and lenticular antimony polymetallic Pb-Zn ore bodies were circled in mining area.which distributed unevenly along the faults.?ore body as the main ore body,the exploration degree is relatively high at present.The frequent tectonic activity,and developmental volcanic-magmatic activity caused the rock in the mine with more alteration type.Mainly including silicification,siderition/rhodochrosition and pyritization,etc.This work was based on previous work,combining macro and micro measurement,mainly studied in detail at the characteristics of KeYue deposit?which include ore type,ore fabric characteristics,chemical composition of ores and ore minerals composition and so on?.According to the type of mineral assemblages,alteration types and relationship of veins interspersed,and divided the KeYue antimony-lead-zinc-silver deposit metallogenic stages and its mineral sequence.Studied the occurrence-mode of Ag in ore preliminarily by using testing methods such as electron microprobe and scanning electron microscope.Discussed the Ore-forming process of KeYue deposit preliminarily.The main achievements obtained in this paper are as follows:?1?The ore types can be divided into primary sulfide ore,oxide ores,mixed ore?semi oxidized ore?,according to oxidation degree,Dominated by primary sulfide ore.Ore useful components can be divided into Pb-Zn ore,Pb-antimony ore,Galena ore,Sphalerite ore and Stibnite ore.Main types are Pb-Zn ore and Pb-antimony ore.According to ore fabric characteristics,it can be divided into Disseminated ore,Stringer ore,NET vein ore,Massive ore,Banded ore,The main ores are Disseminated ore and Stringer ore.?2?According to their different causes,ore textures can be divided into Euhedral-subhedral granular texture,Allotriomorphic granular texture,Poikilitic texture,what cuased by crystallization;Emulsion texture,what caused by Separation of solid solution;Metasomatic relict texture,edge-solution structure,Interstitial texture etc,what caused by metasomatism;Framboidal texture,what cuased by sendimentation;Crumpled texture and Granoblastic texture etc,what cuased by pressure effect.According to different causes of formation,Ore structure can be divided into Synsedimentary function ore structure,metamorphic process ore structure,hydrothermal-metasom-atism-ore-structure,Hot liquid filling ore structure and weathering-effects-ore-structure.?3?The main elements in the ore have S,Pb,Zn,Sb,Ag,with Pb,Zn,Sb-based,Ag can appear as associated elements.Minerals have many types,S content is relatively high,ore minerals are mainly in the form of sulfides.Metal minerals are common sulfide?pyrite,sphalerite,galena,arsenopyrite chalcopyrite,stibnite?,sulfur-salt minerals?tetrahedrite,jamesonite and Bournonite,Boulangerite,Lillianite?,oxideandoxygensaltcontentminerals?Siderite/Rhodochrosite,valentinite,goethite,Angelesite,cerussite?;Nonmetal minerals are common quartz,calcite,mica,etc.?4?Ag of the deposits with non-uniform distribution,and its distribution is closely related to Pb,and Ag mineralization present from north to south,from west to east of weakening trend.Ag to isomorphism?galena,lillianite,jamesonite,boulangerite,arsenopyrite and pyrite?and independent silver minerals?freiberqite,silver tetrahedrite?two forms exist,and in the form of galena crystal lattice as the main modes of occurrence of silver.The enrichment of Ag in ore solution experienced two main precipitation process,first Ag+in the form of isomorphous substitutes precipitated sulfides Pb,Cu,Sb,Fe ions,which in the form of lattice silver hoeted in galena,lillianite,chalcopyrite,boulangerite,jamesonite and arsenopyrite and other metal sulfides.With the continued decreasing of temperature and pressure conditions,silver sulfide hydrogen complex become large disintegration,more freedom Ag+began to appear in the fluid,when the temperature drops to a certain range,the Ag+combined with Cu+,Sb3+ions that in the solution,direct precipitation formation of independent silver minerals which contains freiberqite,and silver tetrahedrite.?5?According to the geological characteristics of the deposits,ore fabric characteristics,Ore mineral paragenesis and the relationship of penetrating veins,Metallogenic period can be divided into Rock-Forming Period,Meso-Epithermal mineralization period and supergene period.Meso-Epithermal mineralization period can also be divided into the the siderite/rhodoch-rosite-sphalerite-pyrite stage???;the quartz-siderite/rhodochrosite-sphalerite-ga-lena-sulphosalts stage???;the quartz-Stibnite stage???.stage?,the quartz-siderite/rhodochrosite-sphalerite-galena-sulphosalts stage of Meso-Epithermal mineralization period is the main mine-ralization stage.?6?The output of the ore bodies of Ke Yue deposit strictly controlled by structural fracture zone,mainly is north to south transtension shear fracture zone.The study of the ore characteristics and causes of Keyue deposit shows it belongs to sedimentary-transformation ore deposit,constantly going with tectonic activities in the ore-forming process which has a modification effect on the deposit.The main metallogenic period is middle-low temperature hydrothermal stage,and the main ore-forming fluid is underground brine,part of the ore-forming material comes from the host strata and takes into by the magmatism.The ore-forming fluid evolutionaffected by the sudden drawdown of pressure,immiscible fluid,underground water,mixing of high salinity hot brine etc.When these conditions change,it can cause the equilibrium conditions of ore-forming fluid changes,resulting in a large number of metal sulfides,sulfate minerals sediment in turn. |
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