伊犁盆地南缘西段小泉沟群上段沉积特征与铀矿化关系

Relationship Between Sedimentary Characteristics and Uranium Mineralization in the Upper Part of Xiaoquangou Group in The Western Segment of Southern Margin of Yili Basin

伊犁盆地南缘是我国重要的可地浸砂岩型铀矿基地,前人针对盆地内含煤层系铀成矿理论研究较多,而对三叠系小泉沟群探索不足。通过对小泉沟群上段砂体、隔水层的统计,结合室内测试分析,研究了砂体垂向、平面与沉积相平面展布特征,总结了伊犁盆地南缘西段小泉沟群上段岩性、岩相及其层间氧化带发育特征,探讨了砂体粒度、厚度及其空间构形特征与铀富集之间的关系。研究表明,研究区内小泉沟群上段平面上自西向东发育洪海沟、克其克博拉、琼博拉3个规模较大的冲积扇,垂向上可划分为4个稳定的沉积旋回。在克其克博拉地段小泉沟群上段第Ⅱ旋回砂体成矿条件最好,但砂体粒度粗、缺乏煤或炭屑等有机质及吸附介质,铀矿化以翼部为主,还原介质的缺乏是铀富集成矿的不利因素。层间氧化带与铀矿化密切相关,为控矿的最关键因素,库捷尔太微凸使地下水存在侧流现象,导致含氧含铀水流动受阻,增加了水岩作用时间及效果,为铀矿化富集的有利条件。层间氧化带前锋线发育受砂体中泥质含量变化影响,精准划分各旋回砂体沉积微相是下一步找矿突破的关键因素。

The southern margin of Yili Basin is an important in-situ leachable sandstone-type uranium mineral base in China.Based on the statistical analysis of sand body and waterproof layer in the upper part of Xiaoquangou Group,the distribution characteristics of sand body were studied in the vertical,horizontal and sedimentary facies by combining the laboratory test and analysis,and the development characteristics of lithology,lithofacies and interlayer oxidation zone were summarized for the upper part of Xiaoquangou Group in western segment of southern margin of Yili Basin.The relationship between the grain size,thickness and spatial configuration of sand body and uranium enrichment was discussed.Comprehensive analysis showed that Honghaigou,Keqikebola and Qiongbola alluvial fans were developed in the upper part of Xiaoquangou Group in the research area from west to east.Among them,the sand bodies of the first and second rhythmic layers are well connected,and the interlayer oxidation zone extends farther along the trend.The ore-forming conditions of the second rhythmic layer sand bodies in the upper section of the Xiaoquangou Group in Kujiertai-Wukuer area are the best in lithology.However,the coarsegrains,the lack of reduction media such as coal or carbon chips and adsorption media affected the formation of uranium-rich integrated deposits.The Kuzier microconvexity leads to the side flow in groundwater,which hinders the flow of oxygen-bearing and uranium-bearing water,increases the time and effect of water-rock interaction which is a favorable condition for uranium mineralization enrichment.The development of the front line of the interlayer oxidation zone was affected by the change of argillaceous content in the sand body,and the accurate division of the sedimentary microfacies of the sand body in each rhythmic layer is the key factor for the next breakthrough in ore prospecting.