Geochemical Characteristics Of Sandstone-type Uranium Ore Elements In Taikang Area Of Songliao Basin

Taikang area is one of the most abundant oil and gas reservoirs in northwest of Songliao Basin.At the same time,it is a main area for exploring sandstone-type uranium deposits.Many uranium mineralization points have been found,which has a good prospecting potential for exploration.Based on the detailed field geological investigation and previous research results,this article will focus on researching the sandstone body characteristics,wall rock alteration,major elements and trace element geochemical characteristics of sandstone bearing strata in key boreholes in Taikang area.Optical microscopy,XRF and ICP-MS are the main methods for this study.The results of this research are summarized in the rules of element migration in the uranium mineralization process and also discussed the tectonic background,material source environment and the properties of metallogenic fluids.The components of sandstone clastic are mainly quartz,feldspar and lithic debris,with a small amount of heavy minerals,mostly zircon and rutile.Based on the nature of the parent rock cuttings,rock debris can be divided into volcanic cuttings?occupied more?and metamorphic sedimentary rock cuttings.A small amount of intermediate-acid plutonic and metamorphic cuttings could be observed in some sample.The bedded sandstone in the study area is formed after burial and before mineralization,which also suffered by a variety of diagenesis,such as compaction,metasomatism and recrystallization.The contents of SiO₂,Al₂O₃ and K₂O gradually decrease from wall rocks to uranium ores,while the contents of CaO,MgO and MnO increase between wall rocks and uranium ores.That indicates Si,Al and other elements migrate out under the action of water-rock and Ca,Mg and other elements migrate with fluid.Uranium precipitates under hydrolysisThe main enriched elements in ore are Pb,Rb,Ba,Hf,U,Mo.The correlation coefficient between Mo,Cr,Rb,Ba,Ga and U is relatively high.Elements Mo and Cr are positively correlated with U and Rb,Ba,Ga are negatively correlated with U.From wall rock to uranium ore,U,Mo,Cr,V and other elements tend to be enriched,while Ba and high field strength elements Zr,Hf,Nb and Ta are relatively deficient.The values of?Eu and?Ce fluctuate slightly,showing no obvious Eu or Ce anomalies.The LREE from yellow sandstone to uranium ore decreases gradually,and HREE tends to enrich from yellow sandstone to uranium ore,which could indicate the change of oxidation-reduction environment.The curve form of rare earth elements is exactly the same as that of continental crust,and the metallogenic fluid shows the properties of Shell source,which is less affected by mantle and has the characteristics of low temperature hydrothermal fluid.Alkali metasomatism is the main alteration type of wall rock.Combined with trace element analysis,the enrichment of Ba elements and the loss of Zr and Hf indicate that the late ore-forming fluids should be less related to the mantle and show the characteristics of low-temperature hydrothermal fluids.