The Study Of Fluid Inclusions Geochemistry And Tectonic Geochemistry Of Lead-zinc Deposits: Taking Huize And Songliang Lead-zinc Deposits For Examples, In The Northeast Of Yunnan Province, China

Huize and Songliang lead-zinc deposits, which located in the northeast of Yunnan province, were taken as study object in this doctoral dissertation. Based on the system summary of regional geology and geological features, infrared microthermometric technique was used to study fluid inclusions in sphalerite of Huize lead-zinc deposit, then the source and character of ore-forming fluid and ore-forming material was discussed, as well as the genesis of deposit. Fracture mechanics of fracture structure plane and geochemical feature of fault tectonite was studied based on the field observation, microscopic identification, analysis and test. On the basis of R-type factor analsis of testing data, geological anomalous map and anomaly model of tectonic geochemical was established, which is of help to the location forecasting of concealed orebody. The main conclusions that we got are as follows:1. Five types of fluid inclusions can be observed in sphalerite, pure gaseous inclusions, pure liquid inclusions, gas-liquid inclusions with rich liquid, gas-liquid inclusions with rich gas and three-phase inclusions containing a daughter. The homogenization temperature of fluid inclusions in sphalerite range from 100.2℃to 344.5℃, for the average homogenization temperature 179.5℃, which have two change temperature sectors obviously,150℃～200℃and 250℃～350℃, and the average capture temperature for 231.7℃. Salinity of fluid inclusions in sphalerite is similar to homogenization temperature, which range form 1.06wt%NaCleq to 18.04wt%NaCleq, for the average salinity 179.5℃, and have two change sectors, 1～13wt%NaCleq and 13～20 wt%NaCleq. The densities of ore-forming fluid in fluid inclusions range from 0.8884 g·cm-3 to 1.0507 g·cm-3, average fluid densities for 0.9735 g·cm-3. For calcite, fluid inclusions dominated by liquid and pure liquid types, homogenization temperature range from 164℃to 221℃and salinity range from 6.6wt%NaCleq to 12wt%NaCleq. Compare with gangue mineral, fluid inclusions in sphalerite contains more information of ore-forming fluid, and the infrared micro-thermometric technique has provided an ideal method to study the ore-forming fluid of Pb-Zn deposits in the northeast of Yunnan province.The metallogenic pressure estimated by fluid inclusions of Huize lead-zinc deposit is about 362.7×105Pa in average, equivaluent to a depth of 1370m. The liquid components of fluid inclusions are mainly Ca2+, Mg2+, Na+, Cl-; with minor amounts of F-, K+, Li+. The gas components of fluid inclusions are mainly H2O and CO2, the CO and CH4 areless abundant. The ore-forming fluid is weak acid to neutral with pH value of 5.6-7.1, and rich in CO2 of Ca2+-Mg2+-Na+-Cl--HCO3--SO42- system.2.Three mineralization stage of Huize lead-zinc deposit can be divided, in the first mineralization stage, the homogenous temperature of fluid inclusions ranged from 200℃to 350℃, with salinity of 15wt%NaCleq or above; in the second mineralization stage, the homogenous temperature of fluid inclusions ranged from 150℃to 250℃, with salinity from lwt%NaCleq to 185wt%NaCleq; in the last mineralization, the homogenous temperature of fluid inclusions ranged from 100℃to 220℃, with salinity of less than 10wt%NaCleq.3. In Huize lead-zinc deposit, the ore-bearing dolomite formed in the relatively strong oxidizing sedimentation-diagenesis environment. Its rare earth element content is low, with a narrower range of total REE contents, negative Eu anomaly and no remarkable Ce anomaly. Whereas in Songliang lead-zinc deposit, the ore-bearing dolomite formed in the weak oxidizing and reducing environment, with characteristics of low content of rare earth elements, a wider range of REE contents, positive Eu anomaly and weak negative to negative Ce anomaly.4. The formation of Huize lead-zinc deposit experienced three stages of sedimentation-diagenesis, post-magmatic hydrothermal superimposition and structural reactivated mineralization, with a variety of sources of ore-forming materials, carbonate strata, metamorphic basement and magma provides ore-forming materials. Ore-forming fluid is mixed fluid of magmatic water, hot brine and metamorphic water.5. The axial zonal elemental sequence of No.①orebody in the Songliang lead-zinc deposit: Li-P-Cu-Ba-Cd-Ga-Zn-V-Ag-Mn-Ge-In2→U-Sn-Th-Be-∑REE-Pb-Bi->Cs-In-Ta-Tl-Ti-Co-Nb-Mo-W-Li2-V2→Zr-Ni-Sr-Rb-Hf-Cr-Cs2-∑REE2. axial zonal elemental sequence of tectonic primary halo in the Songliang lead-zinc deposit is concluded, which indicates that the structure of primary halo is complex, the No.①orebody may be superposed by many intermittent orebody, and the ore-forming process may experience more than one Stage of mineralization. The analyses also forecast that the No.①orebody may has a good extend and there may exist concealed orebody in the deep of No.1 orebody. On this basis, the ideal model for tectonic primary halos of Songliang lead-zinc deposit was built.6. Trace elements of tectonites shows three principal factors element association by factor analysis, on behalf of the strata rock elements, medium-high temperature ore-forming fluid and medium-low temperature ore-forming fluid respectively. The distribution of tectonic geochemical anomaly can reflect the migration direction of ore-forming fluid, and to provide evidence for metallogenic prediction. In this thesis, geological, geochemical and geophysical prospecting marks of Songliang lead-zinc deposits are summarized respectively; many targets are given on the basis of those prospecting marks, partial prospecting targets has been engineering verification.