| By the studies of tectonic and sedimentary evolution, geochemical background of uranium metallogency, composition and properties of ore-forming fluid, geochemical characteristics of phreatic water alteration zone and so on, this dissertation has analyzed mineralized characteristics, formation conditions and location of the phreatic water oxidation sandstone uranium deposits in detail, established a model for uranium deposits of phreatic water oxidation zone in the region and summarized prospecting criteria for phreatic water oxidation uranium deposits. Based on this, this dissertation also discusses the prospecting direction of uranium deposits in Hailaer Basin and analyses its prospecting potential.Kelulun downfaulted basin is located in the Precambrian intermediary geoblock of Ergula-qiaobasha, belonging to southwestern part of Zalainaoer depression zone in Meso-Cenozoic Hailaer Basin. The base of Kelulun downfaulted basin consists of Precambrian moderate- and high-grade metamorphic rocks, chorismite and magmatitic granite, Hercynian acidic granite and Jurassic neutral ~ acidic volcanic rocks and its cover mainly consists of early Cretaceous Damoguaihe Formation. The evolution of the downfaulted basin can be divided into four stages: late Jurassic late Jurassic taphrogeny, early Cretaceous faulting, late Cretaceous shrinking, late Cretaceous -Tertiary differential uplift and planation. In the evolution of Kelulun downfaulted basin, ore-forming target strata were formed in early Cretaceous and late Cretaceous - Tertiary is the period of uranium mineralization. The target stratum for ore prospecting in Kelulun dwonfaulted basin is Upper Member of Damoguaihe Formation, which is widely outcropped or overlaid by extremely thin Quanternary in the study area. It is mainly a sedimentary system of fandelta – lake facies, vertically composed of several positive rhythmic units of coarse in the lower and fine in the upper. The lithology of sand body in the target stratum mainly consists of arkose and lithic arkose, its compositional and textural maturities are low, and its roundness is mainly angular – sub-angular, with matrix support.The uranium mineralization of Kelulun dwonfaulted basin is phreatic water oxidation sandstone type. The occurrence of mineralization is relatively concentrated, mainly distributed in Chudong and Chuzhong and the buried depth of ore body is low and its grade is low. In the region, the most favorable mineralization occurs in No.0 profile, the buried depth of ore body is 58.59～113.0m, and that of most ore bodies is 70.0～90.0m; the formation of uranium mineralization is closely related to the phreatic water oxidation zone. Ore bodies are mainly distributed near the water table and they are mainly lens, secondarily laminar and silllike in forms. There is also the possibility to form rolled ore bodies. The ore-bearing rocks are mainly lithic sandstone or pebbly lithic sandstone containing carbonaceous segments And the ore grade is 0.01～0.03%. The ore-forming fluid of phreatic water oxidation sandstone type uranium deposits in Kelulun downfaulted basin is surface infiltration water and the factors influencing the properties of ore-forming fluid are climatic factors and geologic factors. They control the properties of ore-forming fluid together. The alterations in the formation of the phreatic water oxidation sandstone type uranium deposits can be divided into two types. One is oxidized alteration and the other is reduced alteration. Uranium moved out from the oxidized subzone due to oxidized alteration and precipitated in the oxidation-reduction transitional subzone due to reduction. Oxidized alteration takes place mainly in oxidation zone. The sequence of oxidized alteration is generally organic substance → Fe- carbonate of ( siderite, Fe-dolomite ) →sulfide (pyrite, marcasite) →Fe-silicate (glauconite, biotite, chlorite).Reduced alteration takes place at the interface of oxidation and reduction. Reducer includes organic substance, H2S, pyrite. However, the most common one i...
|
PDF Full Text Request