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    中国北方砂岩型铀矿成矿作用与油气关系研究

    Research on relationship of oil-gas and sandstone-type uranium mineralization of northern China

    • 摘要: 油气与砂岩型铀矿的相互作用关系日益受到地质、特别是铀矿地质学者的重视,单个能源矿产的成矿理论已日趋成熟,但相互作用关系研究却十分薄弱,是亟需探究和解决的关键科学问题之一。本文通过中国北方典型砂岩型铀矿与油气时空分布特征分析、镜下微观分析、化学计算,表明油气主要通过吸附作用、还原作用、供铀作用和保铀作用促使铀的富集成矿。其中,油气的裂解产物沥青、有机酸层对铀有强烈的吸附作用;油气的还原作用主要是通过强还原气体(H2、CH4、CO、H2S等)将高价、活化的铀离子还原成四价、稳定的铀矿物;油气与硫酸根离子相互作用生成的有机酸能够通过酸溶、萃取和金属-有机络合作用将途经围岩的部分铀富集并在成矿部位释放,从而叠加改造铀成矿作用,增加铀的来源;油气逸出的强还原气体H2、CO能使地层产生酸化,形成高岭土化,从而使氧化带呈弱碱性、成矿带呈弱酸性特征。砂岩型铀成矿作用与油气的关系对砂岩型铀矿含矿目的层的厘定、铀矿床定位、补充完善砂岩型铀成矿理论、“烟囱效应”指导找油气等具有重要启示意义。

       

      Abstract: Interaction between oil-gas and sandstone type uranium has aroused much interest among geologists, especially uranium geologists. In spite of rapid development of mineralization theory for single energy mines, the study of interaction is very insufficient. Therefore, this problem should be regarded as the key frontier scientific issue which deserves investigation. Based on an analysis of distribution characteristics of uranium and oil-gas, microscope testing, geochemical calculation, it can be inferred that uranium enrichment can be improved by adsorption, reduction, uranium-supply and preservation of oil-gas, in which asphalt and organic acid, cracked by oil-gas, can adsorb uranium strongly. For reduction of oil-gas, high valence and activated uranium ion can be reduced to +4 valence and form stable uranium minerals by more reducing gas, such as H2, CH4, CO, and H2S. By means of acid dissolving, extraction and metallic-organic complexation, organic acid, produced by the interaction of oil-gas and SO42-, can accumulate partial uranium nearby surrounding rocks. And then this uranium can be released in mineralization location, which can reform mineralization and increase the source of uranium. Besides, more reducing H2, CO, escaping from oil-gas, can cause acidification and kaolinization of the formation, which leads to the feature that the oxidation zone is slightly alkaline and the metallogenic belt is slightly acidic. Therefore, the interaction between oil-gas and uranium can be very important for the determination of uranium-bearing beds, locating of uranium deposits, developing of mineralization theory, and oil-gas exploration guided by 'chimney effect'.

       

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