Fluid Inclusions In The Keyue Pb-Zn-Sb-Ag Deposit,Lhunze County,Tibet

Keyue Pb-Zn-Sb-Ag deposit is located in the Lhunze County,Tibet.It is an imp-ortant part of the Sb-Au ore belt in the South Tibet.This papper takes fluid inclusio-ns as study objects,by studying petrography,microthermometry,Laser Raman Spec-tra,thermodynamic calculation,we discussed the characters of ore-forming fluid and the mineralization.The main ore-bearing stara is Ridang Group in Lower Jurassic.Steeply dipping Zn–Pb–Sb–Ag-bearing veins,lenses are hosted by SN trending fractures.The main ore minerals are sphalerite,galena,stibnite and sulphosalts On behalf of jamesonite,boulangerite etc.The Gangue minerals are quartz,calcite,rhodochrosite,siderite an-d so on.Ore textures are Residual,Interstitial,Milky-like,Euhedral-subhedral granu-lar etc.The ore structures are Massive structure,banded structure,druse-like structu-re,disseminated structure,brecciated structure etc.The main types of alteration are silicification,siderition/rhodochrosition,ferritization,pyritization,chloritization,etc.Mineralization process is divided into three stages:followed by the siderite/rhodoch-rosite-sphalerite-pyrite stage???;the quartz-siderite/rhodochrosite-sphalerite-ga-lena-sulphosalts stage???;the quartz-Stibnite stage???.stage?is the main mine-ralization stage.There are eight types of fluid inclusions in the Keyue Pb-Zn-Sb-Ag deposit,includeing liquid H₂O inclusions,vapor-liquid H₂O inclusions,daughter mineral-bearing inclusions,pure CO₂ inclusions,H₂O-rich CO₂-H₂O inclusions,CO₂-rich CO₂-H₂O inclusions,daughter mineral-bearing CO₂-H₂O inclusions and“empty”inclusions.It shows that the observed fluid inclusions assembalges are consistent with a model involving CO₂-H₂O immiscibility.The homogenization temperatures,salinities of the H₂O inclusions ranged from 172.8?to 282.7?,from3.06 to 33.19?wt%NaCl?,showing that the ore-forming fluid was charactered by medium-low temperature,medium-low sality,but partly presence of high salinity fluids,And from?to?stage,homogenization temperatures and salinity are decreasing.The homo-genization temperatures and the pressures of CO₂-rich CO₂-H₂O inclusions ranged from 247.8?to 272.2?,from 413.8bar to 1324.2bar;The homogenization tempera-tures and the pressures of H₂O-rich CO₂-H₂O inclusions ranged from 214.3?to289.5?,from 316.9bar to 1161.6 bar.They have the same the homogenization tempe-ratures and the pressures,indicating that CO₂ and H₂O are immiscible fluid inclusio-ns having been trapped in the same period.In the period of Himalayan,tectonic movement was active in this area.The EW crustal extension resulted in NS trending extensional faults,which controlling Veins,lenticular ore deposit.Ore-forming fluids migrated NS normal fault system,As the pressure plummeted,the occurrence of immiscible fluids,resulting in a large number of mineral precipitation is the main reason of the deposit formation.