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    鄂尔多斯盆地东北部侏罗纪含铀岩系三维地质结构与铀成矿规律浅析

    A brief analysis on the three-dimensional geological structure and uranium mineralization of Jurassic uranium-bearing rock series in the northeastern Ordos Basin

    • 摘要:
      研究目的 为了更加直观、准确地揭示鄂尔多斯盆地东北缘侏罗纪含铀岩系直罗组三维空间展布规律,开展铀成矿规律研究和找矿预测工作。
      研究方法 本文利用首次建立的钻孔-测井综合数据库,精细构建了东胜铀矿集区多尺度、多类型的三维地质模型并实现其可视化功能。
      研究结果及结论 综合地质建模研究发现本区铀成矿具有以下特征:(1)受直罗组沉积期"北高南低、东高西低"古地貌格局的影响,纳岭沟-大营地区直罗组下段存在区域性沉积相变,由北部呼斯梁-唐公梁古隆起区向西、向南方向,沉积体系由冲积扇-砾质辫状河向砂质辫状河、辫状河三角洲沉积有序转变,大营铀矿化集中产于辫状河向辫状河三角洲沉积过渡部位的分流河道一侧,纳岭沟铀矿化主要产于砾质辫状河之上的砂质辫状河道中;(2)自东部呼斯梁向西部大营地区,直罗组下段铀储层的非均质性增强,具体表现为砂体厚度明显减薄、含砂率降低、泥岩层数量和厚度均显著增加、内部开始发育薄层煤线。这种组合的出现在大营西侧形成了规模较大的横向泥质隔挡层和垂向还原层,在后期成矿过程中极大地抑制了层间氧化带向西推进的速率和里程,从而在大营一带形成稳定的层间氧化带前锋线和持续的铀矿化;(3)矿床尺度的三维地质建模显示,大营弧形展布的铀矿化体与东部相邻的纳岭沟-塔然高勒铀矿化几乎相连,且两矿床之间的伽马三维属性模块亦有较强的放射性异常显示,指示着大营与纳岭沟之间的塔然高勒-乌定布拉格地区具有很好的找矿潜力。

       

      Abstract:
      This paper is the result of mineral exploration engineering.
      Objective In order to more intuitively and accurately reveal the three-dimensional spatial distribution of the Jurassic uranium-bearing rock series (the Zhiluo Formation) in the northeastern margin of the Ordos Basin, the research on the uranium metallogenic characteristics and the prospecting and prediction work were carried out.
      Methods In this paper, we used the first established comprehensive database consists of drills, logging to construct the three-dimensional geological models with different scales and types and realized its visualization function in the Dongsheng uranium area.
      Results and Conclusions Comprehensive geological modeling shows that uranium mineralization in this area has the following characteristics: (1) Under the influence of the paleogeomorphic pattern of "high in the north and low in the south, high in the east and low in the west" during the depositional period of the Zhiluo Formation, there was a regional sedimentary facies transition in the lower section of the Zhiluo Formation in the Nalinggou-Daying area. From the northern Husliang-Tanggongliang paleo-uplift area to the west and south, the sedimentary system gradually changed from alluvial fan-gravel braided river to sandy braided river and braided river delta deposition. Uranium mineralization in Daying area is concentrated in the distributary channel of braided river to braided river delta, while uranium mineralization in Nalinggou is mainly in the sandy braided river which was above the gravel braided river; (2) The heterogeneity of uranium reservoir in the lower member of Zhiluo Formation increased from Husiliang in the east to Daying area in the west, which is manifested as a significant reduction in the thickness of the sand body, a decrease in the sand content ratio, a significant increase in the number and thickness of mudstone layers, and the inner coal-line began to develop. The occurrence of above combination formed a large-scale lateral argillaceous barrier layer and vertical reduction layer on the west side of Daying, which greatly inhibited the westward propulsion rate and distance of the interlayer oxidation zone. Therefore, a stable front line of interlayer oxidation zone and continuous uranium mineralization are formed in the Daying area; (3) By the three-dimensional geological modeling of ore deposits, it can be found that the arc-shaped uranium mineralization body in Daying area is almost connected with the uranium mineralization in Nalinggou- Tanggongliang. Meanwhile, the three-dimensional γ property model between the two deposits also shows strong radioactive, which indicate that the Tarangaole- Wudingbulage area between Daying and Nalingou diposits has a good prospecting potential.

       

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