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Geological Characteristics And Genesis Of The Tongkuangyucopper Deposit In Zhongtiao Mountain,Shanxi Province

Posted on:2016-07-31Degree:MasterType:Thesis
Country:ChinaCandidate:J G SunFull Text:PDF
GTID:2180330461494837Subject:Mineralogy, petrology, ore deposits
Abstract/Summary:PDF Full Text Request
Tongkuangyu copper deposit is located in Zhongtiao Mountain copper metallogenic belt, which is one of China’s oldest porphyry Cu(Mo) deposit. Through detailed field geological survey, the characteristics of the wall rock alteration and their zoning were identified. Microscopy and electron microprobe were used to study the alteration minerals. The granodiorite porphyry were studied by zircon LA-ICPMS U-Pb dating, Lu-Hf isotope and geochemical analysis. The fluid inclusions petrography, microthermometry, group inclusions composition and H, O, S isotope were used to study the source, nature and evolution of the ore-forming fluids and the source of the minerals. By all of these, the genesis of the Tongkuangyu copper deposit were revealed.Studies have shown that early alteration include sodium silicate alteration, potassium silicate alteration and propylitization alteration, late alteration mainly is feldspar-destructive alteration. Spatially,sodium silicate located inside the porphyry body, potassium silicate rock located in and around the area of propylitic rocks,propylitization alteration located outside of potassium silicate,potassium silicate alteration superimposed on the earlier sodium silicate alteration, the latter feldspar-destructive alteration superimposed on the earler potassium silicate and locate between potassium silicate and propylitization alteration. The chalcopyrite mineralization of Tongkuangyu copper deposit began to precipitate in the late stage of the potassium silicate alteration,the stage of quartz-sulphide is the most important stage of mineralization, the quartz carbonate stage followed, the carbonate stage also contributed some copper to the ore.The discordia upper intercept age of porphyry in Tongkuangyu copper deposit were 2159 ± 19 Ma and 2148 ± 39 Ma. The Re-Os model ages of molybdenite in the granite porphyry were 2129 Ma, which show that the time of Diagenesis and mineralization were consistent. The εHf(t) values of the granodiorite porphyry were negative, and two-stage model ages range from 2706 Ma to 3007 Ma, which indicate that the primary magma was derived from the remelting Late-Archaean Palaeocontinental crust,with little mantle-derived materials.The ore-forming fluid was magmatic fluid with midium-high temperature, high oxygen fugacity, rich CO2. After the stages of boiling, lower the temperature, oxygen fugacity reduced, CO2 escaping, the fluid tend to be reducing fluid, resulting in a large number of metal sulfide precipitation. Then through the processes of continuously fed by atmospheric precipitation and cooling, the hydrothermal meteoric with low-temperature, low oxygen fugacity, low salinity, low in CO2 were formed.Hydrogen-oxygen isotopic show that in the early stages of mineralization, the ore-forming fluid is given priority to primary magma water, as the process of mineralization stage, in the late stages of mineralization, the proportion of mixed precipitation is increasing. Characteristics of carbon and oxygen isotopes suggest that the relationship between the ore-forming fluid and granite porphyry is more close, and effected by the late alteration and hybrid, with characteristics of multiple source. Characteristics of sulfur isotopes suggest that the ore-forming material main come from deep region.
Keywords/Search Tags:Porphyry copper deposit, Wall rock alteration, Fluid inclusions, Ore-forming fluid, Diagenetic and Metallogenic age
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