Elements Geochemistry Of Sandstone Type Uranium Deposit Northeast Ordos Basin

The Northeast Ordos basin is the main mineral area of sandstone type uranium deposits in China. Until now, it has been found several large to super large uranium deposits. Although the previous studies are numerous here, but the micro research, for example, the element geochemical study is still relatively weak, especially in the process of mineralization elements migration study is seldom reported. With the increasing difficulty in prospecting, how to get useful geological information and guide the mining area prospecting should be got more and more concerned.Based on the summarization of geological and mineral characteristics of sandstone type uranium deposits in northeast Erdos basin, this study choose the element geochemistry, isotope geochemistry and hydrogenic uranium deposit theory as the instruction, took the ICP-MS, electron probe, X ray diffraction as the methods, then made a detailed analysis of the element geochemical characteristics and change rules of sandstone, mineral sandstone and uranium ore in the sandstone type uranium deposits. The migration of elements during the uranium metallogenic process has been quantitatively studied. Combined with the characteristics of carbon and oxygen isotope geochemistry, the source of ore-forming fluid also has been researched, and a discussion has been done on the mineralization of the sandstone type uranium in northeastern Ordos Basin.Based on the contrast of the constant elements in different type sandstone, it has found that the content of SiO2, Al2O3. K2O and Na2O gradually decreased from primary grey sandstone to uranium ore, while the content of CaO, MgO and MnO gradually increased from primary grey sandstone to uranium ore, which indicated that the hydrolysis process lose Si and rich Ca, Mg; Fe2O3. FeO, TFe2O3were highest in grayish green sandstones and lowest in uranium ore. It also reflected a certain geochemistry zone. TiO2has a stability component which can be used to reflect the sediment source characteristics.The analysis results of trace elements show that Pb, Zn, Cr, Mo, Ba, V, Nb, Zr, Hf, U, Th and other elements have the main enrichment in sandstone. From gray sandstone, mineralization sandstone to uranium ore, the enrichment trace elements are radioactive elements (U), sulfur (Co. Ni dear), large ion dear stone elements (Rb, Ba, V) and properties of active elements of Mo, while the main loss elements are high field elements (Zr. Hf, Nb, Ta), stable elements are mainly Cu, Sr, Ga etc.. Rock and ore are rich in REE and light, heavy rare earth had obvious difference during the ore-forming process. The enrichment degree of LREE is higher than the HREE enrichment degree.The mass balance equations and diagrams indicate that during the formation of the original sandstone, sandstone rich in uranium, mineralization sandstone, low grade uranium ore and high grade uranium ore, SiO2and Fe2O3are the come out components, while the CaO, FeO and K2O are the getting into components. It reflects that calcium enrichment and Si lost during the uranium metallogenic process and the mineralization is related to carbonate. Mo, Ba, V, Y are the getting into components. Zn, Ni and Co are the come out components, while the Nb, Ta, Zr and Hf change different during the whole process. Rare earths elements are the getting into components, heavy rare earth elements migration was higher than that of light rare earth elements.The carbon and oxygen isotopes study of carbonate cements indicates that the source of carbon in sandstone is complex, which is mainly related to sedimentary organic matter and deep carbon source. Organic matter has two mainly kinds of sources, one is the sedimentary rock’s organic matter, and the other part comes from the coal formed gas. Deep carbon source is mainly related to the thermal fluid. Combined with the element geochemical characteristics the study considered that the sandstone type uranium in northeast Erdos basin mainly through the interlayer oxidation mineralization and cryogenic fluid reworking mineralization two main mineralization periods.