Research Of Mineralizing Fluid Characteristics And Genesis Of Shizidong Copper Deposit,Guizhou Province

On the basis of geological background, petrology, geochemistry, fluid inclusionand H-O isotope studies of basalts and basaltic copper deposits in Emei Mountain,combining the previous researching results, the characteristics of mineralizing fluidsand mineralization of basaltic copper deposit in Emei Mountain are researched.Results are as follows:(1) Shizidong Basaltic Copper Deposit is hosted in the fourth lithologic sectionof Basaltic Formation and in the contacts between basalts and Zhenwei Formation,whose ores are mainly hosted in basalts and charcoal-bearing sedimentary rocks,with the mineral associations being native copper+malachite+quartz and nativecopper+carbonaceous material+zeolite+quartz+calcite respectively.(2) Fluid inclusions can be subdivided into pure liquid phase (I type) andliquid-vapor two phase(II type) fluid inclusions.(3) The mineralizing fluids of Shizidong Basaltic Copper Deposit are one ofmiddle-low salinity(0.5~23.5％NaClWt%), middle-low density (0.45~1.11g/cm~3)and shallow environment, whose mineralizing temperature ranges from60to523℃.(4) Fluid inclusion and H-O isotope researches show mineralizing fluids in theearly period are originated from magmatic waters in Emei Mountain Basalts, withsome meteoric waters mixing them in the shallow crust. High salinities and CH4influid inclusions indicate the characteristics of basin brine waters. Fluid mixing,boiling and organic reduction can be the main precipitation mechanisms ofShizidong Basaltic Copper Deposit.(5) In the end of Emei Mountain basalt eruptions, there were continuoushigh-temperature heat flux environments in the areas adjacent to craters, whichcould form high grade copper deposits. Emei Mountain basalts accepted sedimentswithin swamp environments, laid down and underwent burial metamorphisms. Thefault-fracture networks formed by compressed deformations along withrubble-bearing amygdaloid basalts in the top of basaltic flows and sedimentary rocks between basaltic flows, constituted a mineralizing system, in which mineralizingfluids migrated upwards and concentrated.(6) With respect to prospecting, the old craters should be the key explorationareas because the early mineralization formed in volcano syngenetic hydrothermalfluids. In addition, we should pay more attention on the controls of faults onmineralizing fluid migrations and the blockings and absorptions of ZhenweiFormations...