Brief Study On The Fluid Inclusion Characteristics And Its Genetic Significance Of Tianbaoshan Pb-Zn Deposit In Huili County, Sichuan Province

Sichuan-Yunnan-Guizhou Pb-Zn polymetallic mineralization belt is situated inthe western margin of the Yangtze Block, periphery of Kangdian axis, in which areaTianbaoshan Pb-Zn deposit is a very represntive one.On the basis of large amount of geological research and survey results,we foundthat the predecessors have done a systematic work in Mineralogy, deposit geology,geochemistry and ore deposit models study,but when refers to the Aspects of theformation and evolution of ore-forming fluid, fluid properties, fluid dynamicsmechanism of migration,experts have different argument and academicperspectives.As a result,this article mainly research and study the mineral-fluid of thisdeposit.Through field investigation in Tianbaoshan Pb-Zn deposits, especially in theunderground mining tunnels and systematic sampling theore-bodies and ore veins.The geological characters and ore-body numbers, scale, output state of this Pb-Zndeposit have been roughly known. After systematic sampling quartz and calcite, lotsof thin sections, polished sections and fluid inclusion sections have been grinded.Based on previous data, through field investigation and sampling,usingmicroscope, hot and cold stage and Laser Raman Technique,combined with theknowledge of ore mineralogy and fluid inclusions related.The rock and mineralidentification, inclusion thermometry and composition measurement of the collectedsampleshave been researched. Then the properties, sources of ore-forming fluidmining area ore forming material, the migration and precipitation is discussed, andestablished preliminarily the metallogenic model of the region. The mainachievements are as follows:(1)Through the tests of inclusions homogenization temperature, quartzinclusions’ homogenization temperature in the region is concentrated in the area of120~220℃. The temperature range of metallogenic stage is120~160℃, the peak at 160℃,and metallogenic temperature is low; salinity range (NaCleqv) are locatedmainly in the area of5.11~8.45%, which is low but slightly higher than Seawatersalinity, and it may be the underground thermal brine; three metallogenic fluid densityrange is roughly in the period of time,which the main distribution range is0.75~0.85g/cm3and averages is0.85g/cm3, for middle-low density fluid.(2)The inclusion into the initial melt inclusions testing showed that the fluid isthe NaCl-H2O system, and in gas phase composition, H2O occupies the absolutenumber,followed by CH4、N2, and contain trace amounts of H2、CO and other gases;Cl-、HCO3-、Ca2+、Mg2+is contented more and high activity. A preliminarydetermination of the fluid type of the Tianbaoshan Pb-Zn deposit isCa2+-Mg2+-Na+-Cl--HCO3-type, similar to the atmospheric precipitation compositionof carbonate area.(3)The metallogenic pressure ranges in40~45Mpa, the depth of mineralization isabout the crustal depth1.5Km to2.0Km, for hypabyssal Pb-Zn deposit;the pH valueof fluid is between5.53~5.72,and the average is5.65, showing that weakly acidiccharacteristics and the Pb-Zn deposit in Tianbao Mountain was formed in weak acidicenvironment; Eh value range for the-0.273~-0.184,mean-0.238,showing reducibilityand it mainly form in the reducing environment.(4) The metallic ore deposits in the metallogenic fluid with source has multiplesource, mainly coming from the earth’s crust, and some are from deep source material,but also has a close relationship with the mining of ore rock images-upper siniandolomite rock. S sources are multidirection, part from carbonate rocks in the seawater,with a part of S reduction through biological function; C is from marine faciescarbonatite,and fluid is from hot geothermal brine.(5) Based on the discussion of metallogenic model, the Tianbaoshan Pb-Zndeposit in the ore controlling factors (formation lithology control)、sources andore-forming hydrothermal properties、pressure and depth etc has the property of MVTPb-Zn deposit type, thus initially identified as MVT Pb-Zn deposit type.