Study On Fluid Geochemistry In ZHAOTONG Lead-Zinc Deposit,Yunnan

This thesis is based on the project of National Natural Science Foundation of China "Study on sphalerite fluid inclusions geochemistry on large lead-zinc ore-concentrated areas in the northeast of Yunnan province" and the project of School-enterprise cooperation in Yunnan province "The study of deep and periphery concealed ore forecast and increase production in Zhaotong Large lead-zinc deposit".On the basis of summarizing regional geological background and deposit geology characteristics, this thesis focuses on the fluid inclusion of sphalerite-host, quartz-host and calcite-host. Based on the study of sulfide mineral typomorphic features and stable isotope, the charactistics and evolutions of ore-forming fluid will be used to describe the ore-forming process of this deposit. The conclusions we got are as follow:1) There are five types of fluid inclusions can be observed in various minerals. They are pure gaseous inclusions, pure liquid inclusions, aqueous inclusions, vapor-riched inclusions and CO2-riched inclusions. The homogenization temperatures by microthermometry for sphalerite-hosted fluid inclusions vary104℃to352℃with two peak interval:200-215and260-300℃,which have a wide range of interval that include the homogenization temperatures of calcite-host and quartz-host and reveals the exits of the high temperature fluid. The salinity ranges from0.8wt%NaCleq to19.2wt%NaCleq with an average value of11.2wt%NaCleq. The density is between0.89and1.05g·cm-3. The homogenization temperatures by microthermometry for calcite-hosted fluid inclusions vary73℃to172℃. The salinity ranges from1.5wt%NaCleq to12.3wt%NaCleq. The density is between0.88and0.96g·cm-3. The homogenization temperatures by microthermometry for quartz-hosted fluid inclusions vary169℃to214℃. The salinity ranges from6.7wt%NaCleq to16.7wt%NaCleq. The density is between0.97and1.07g·cm-3.2) There are four mineralization stage of Zhaotong lead-zinc deposit can be divided, in the first stage, the homogenization temperatures of fluid inclusions rangs from169℃to351℃with the main intervals between200℃and215℃and the salinity from4.39to17.95wt%Nacleq with the main intervals between9and11wt%Nacleq; in the second stage, the homogenization temperatures of fluid inclusions rangs from142℃to277℃with the main intervals between170℃and185℃and the salinity from5.2to18wt%Nacleq with the main intervals between10and11.5wt%Nacleq; in the third stage, the homogenization temperatures of fluid inclusions rangs from104℃to173℃with the main intervals between140℃and165℃and the salinity from0.8to19.2wt%Nacleq with the main intervals between10and18wt%Nacleq; in the last stage, the homogenization temperatures of fluid inclusions rangs from73℃to172℃with the main intervals between100℃and125℃and the salinity from1.5to18.8wt%Nacleq with the main intervals between5and11Wt%NaCleq;3) Based on the result of estimate pH and Eh from fluid inclusion, indicated that sulfide minerals is precipitate in the acid-leak to alkaline-leak environment in Zhaotong lead-zinc deposit.4) According to analysis of C-O and H-O isotope in fluid inclusions, considered that the formation of Zhaotong lead-zinc deposit for many sources, stratigraphic carbonate rocks, metamorphic basement and magmatic rocks. Ore-forming fluid is mixed fluid of magma water, metamorphic water and hot brine with experience the mineralization of superposition.