松辽盆地南部砂岩型铀矿储层结构与铀成矿作用

    Study on reservoir structure and mineralization type of the sandstone uranium deposits, southern Songliao Basin

    • 摘要: 以松辽盆地南部DL地区砂岩型铀矿为目标,在沉积学背景研究的基础上,开展铀储层结构与铀成矿作用研究。通过钻孔数据统计及系统的取样分析并编制铀储层非均质性图件,精细地刻画了姚家组铀储层的几何形态和复杂结构,充分展示了铀储层的定量非均质性。结果显示,区内灰色砂体多为原生灰色砂体,而下氧化带在沉积期后经历了较强的表生流体改造,为后生氧化带,矿体主要分布于河道砂体分岔处,以及从无隔挡层到隔挡层突然变厚的河道砂体边缘而非河道中央,其形态受氧化还原界面控制以板状为主。综合分析认为,表生流体成矿作用经历了晚白垩世姚家组含矿主岩预富集与表生流体叠加改造成矿2个阶段。通过对比DL地区储层结构对铀成矿的控制作用,在BL地区优选出3片找矿靶区,为下一步的勘查工作提供理论依据。

       

      Abstract: Exploring the sandstone-type uranium deposits in the DL area, located in the southern Songliao Basin, our research focuses on the sedimentological characterization, structure of the uranium reservoir and processes of uranium mineralization. Through drilling data statistics and systematic sampling analysis, a uranium reservoir heterogeneity map was drawn, which finely depicted the geometric shape and complex structure of the Yaojia Formation uranium reservoir, and fully demonstrated the quantitative heterogeneity of uranium reservoirs. The results show that the gray sand body primarily retains its original color, while the lower oxidation zone underwent modification by strong supergene fluid activity after the deposition, and transforming into an epigenetic oxidation zone. The ore bodies are mainly distributed in the bifurcation of the channel sand body, and along the edge of the channel sand body where the thickness transitions suddenly from no barrier layer to the presence of barrier layer, rather than in the center of the channel. Their plate-like shape is controlled by the redox interface. Comprehensive analysis shows that the mineralization of supergenetic fluids can be divided into two stages: the enrichment of the ore—bearing host rocks of the Yaojia Formation during the Late Cretaceous and the superimposed transformation of supergenetic fluids. By comparing the controlling effect of reservoir structure on uranium mineralization in DL area, three prospecting target areas were optimized in the BL area, providing a theoretical foundation for future exploration work.

       

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