| Daying uranium deposit is the largest in china which discovered in recent years, it is located in north-central Yi-meng uplift, ordos basin.Dongsheng and Hangjinqi(Nalinggou) deposit have been found in decades in the east. Which discovered that Yi-meng uplift has the potential to be the world-class sandstone-type uranium deposits after United States and central Asia area. At present,The system study of Daying uranium deposit has just begun, so it is important to strengthen its geological characteristics, genetic types and metallogenic regularities.This paper based on the field geological investigation, drilled core observe, which through rock thin section identification, electron probe microanalysis, SEM and energy spectrum analysis, X-ray diffraction and geochemical analysis and so on, concentrating on formation distribution, material composition, types, geochemistry, U-Ra equilibrium metallogenic epochs, sources, interlayer oxidation zone characteristics has carried on the analysis of macro and micro. From the geology background of oil and gas, tectonic ore-controlling characteristics and mineralization of isotopic are discussed and Analysised its genesis.(1) Analysised its genesis:Uranium mineralization occurs in the middle-lower Jurassic zhiluo group, upper submember, which controlled by green sandstone alteration. This remnant contained a higher proportion of red oxidation sandstone, the ? and Orgc contents is low, Th/U ratios is small, which turned into green after the reduction of the gas dissipation. The reason of its that are many chlorite cement article epigenetic banded. Daying uranium deposit mainly for coffinite, a small number of brannerite, many ore exersits in the gap of calcite and pyrite and the microfracture, others associated with organic matter (coal),Associated with pyrite, calcite, kaolinite and chlorite, etc.; Closely associated with pyritization, carbonatization, chloritization, kaolinite (white sandstone)etc.Mo, V, Se and Re can be comprehensive utilize. U-Ra distribution model are partial basic ore of normal distribution characteristics of mineralized samples, others are turned to radium; The ore source may be in the north of Daqingshan granite and the mineralization of sandstone.(2) Has been cleared about (ancient) interlayer oxidation zone type uranium deposit of Daying. The largest character is controlled by green alteration zone (the ancient interlayer oxidation zone). The oxidation zone and transition zone (mineralized zone) and the reduction zone, constant elements is little change; U, V, Y, Pb and REE are riched in the transition zone; E S is lower in the oxidation zone and green sandstone, highest in the mineralized zone; Orgc is the highest in transition zone, lowest in oxidation zone; Th/U ratios is higher in the oxidation zone, the lowest in the mineralized zone; Clay minerals is the highest in the mineralized zone, primary zone has rich montmorillonite, green belt is chlorite; Transition zone are U, Mo, V, Se, Re and REE.(3)Discussed the formation of sandstone-type uranium deposits in northern ordos basin, Daying included, which related to the cretaceous gas dissipation function.The late-reformation is mainly occured in K-E, E3, late N1 and N-Q, which have e better coupling relationship with gas escape and the year of uranium mineralization. The C-O isotope is significantly negative, the characteristics of S isotope has obvious biological effect, and sulfur source, The natural gas calcite inclusion of hydrogen and oxygen isotope prove the existence of ore-forming fluid from atmospheric precipitation and hydrogen isotope drift phenomenon. These explained the cause of formation of sandstone uranium deposits in northern ordos basin,Daying inclued should be mixed with" escaping gas-water atmosphere" fluid effect of low temperature hydrothermal deposit. |
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