Research Sandstone-type Uranium Ore - Controlling Factors Niger Chapman Creek Area

After studies on outcrops and drill cores and logs associating with thin sectionanalysis under microscope,the conclusion is that the sedimentary facies of Assaouasfromation is braided river delta and subfacies is delta front; distributary channelssandstone characters medium-coarse grains and rich acid volcanic debris and poorlyargillaceous material whose compositional maturity and textural maturity arelow;channel sandstone bodies are high porosity and permeability and goodcommunication horizontally and vertically which favor circulation of mineralizingfluids and provide favorable host room and uranium resource for uraniummineralization.Alterations are analyzed by methods such as optical microscope and electronmicroprobe and scanning electron microscope,based on studies on alterations in thefield.There mainly are reduction and micrite carbonatization and analcitization anddevitrification of acidic volcanic glasses which are relational with uraniummineralization. Analcitization of acidic volcanic and devitrification of acidic volcanicglasses provide uranium for uranium mineralization.The paper studies existent forms of uranium by utilization of electronmicroprobe and optical microscope and scanning scanning electronmicroscope.Uranium mainly existence as forms of uranium minerals which cementand infill intergranular pore and fissures and cavities corroded of clastics. Pitchblendeand coffinite associate with pyrite and chalcopyrite and chalcocite and native copperet al.Origins of mineralizing fluids are traced by analysis of fluid inclusion and C-Oisotope of calcite and O isotope of pitchblende. Mineralizing fluids comes fromatmospheric water and reducing fluid from the deep. δ18O of mineralizing fluidsfrom O isotope of calcite and pitchblende are-0.01and-1.05which revealatmospheric water signifies uranium mineralizing. δ¹³C of mineralizing fluids fromcalcite is-6.63which is close to the boundary value of mantle carbon(δ¹³C=-7³‰)and indicates reducing fluid from the deep probability blends with mantle carbon. H2is detected form fluid inclusion which reveals one type of reductants is H2from the deep. Atmospheric water fluid provides uranium as well as fluid from thedeep does reductants.Ore controling fectors of uranium mineralization are concluded based on analysisof the Azelik uranium deposit. Structure and sedimentarion and mineralizing fluidstogether control uranium mineralization. Channel sandstone badies providefavourable host room; NW faults control the rang of reduced sandstone badies; Thesuperposition of three types of fluids contros forms of mineral ore which is at the topof sandstone and tablet and discrete.Pitchblende minerogenic age is dated by utilization of pitchblende mineraldilution method and LA-ICP-MS pitchblende microzone U-Pb isotope dating which is101.3⁷6.6Ma.With theories of sandstone type uranium deposit,the theory of the superpositionof three typies of fluids and metallogenetic model is established,based on analysis ofgeotectonic and basin’s structure setting, after multidisciplinary analysis of structurescharacteristics and sedimentation and mineralization features and geochemicalbehavior and mineralizing fluids characteristics and ore controling fectors ofmineralization and minerogenic age.