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在鄂尔多斯盆地东北部 ,铀成矿与直罗组底部砂体的非均质性关系密切。砂体非均质性主要表现在平面和垂向上 ,其中 ,砂体平面非均质性可以通过砂分散体系来表征 ,而垂向非均质性则可以通过隔挡层和沉积物粒度来表征。在平面上 ,铀成矿主要分布于辫状河沉积体系向辫状河三角洲沉积体系过渡的辫状分流河道一侧 ,最佳成矿区则位于辫状分流河道砂体的频繁分岔处和从无隔挡层到隔挡层突发区的河道砂体边缘 ,且随着隔挡层数量和厚度的增加 ,铀成矿几率和品位逐渐降低 ;在垂向上 ,隔挡层的存在可以导致多个垂向序列单元、层间氧化带和铀矿卷头的发育。统计发现 ,中砂岩和细砂岩是铀成矿的最佳载体 ,所以在每个垂向序列单元中 ,铀矿通常位于辫状分流河道砂体的中下部。铀的成矿机理一方面可能是砂体非均质性通过对成矿流体运移状态的影响进而实现对铀成矿的控制 ,另一方面可能与沉积环境相变导致还原性物质的增加有关。通过砂体非均质性研究而总结的铀成矿规律是进行铀成矿空间定位和预测的基础。
Uranium mineralization is closely related to the heterogeneity of the sand body at the bottom of Zhiluo Formation in the northeastern Ordos Basin. Sand body heterogeneity is mainly manifested in the plane and the vertical, where the sand body heterogeneity can be characterized by sand dispersion system, while the vertical heterogeneity can be characterized by the barrier layer and sediment size . On the plane, uranium mineralization is mainly distributed on the braided distributary channel side of the braided river sedimentary system to the braided river delta sedimentary system, and the optimal metallogenic zone is located at the frequent bifurcation of the braided distributary channel sand body and from There is no barrier layer to the edge of the channel sand body in the barrier zone, and with the increase of the number and thickness of the barrier layer, the probability and grade of uranium metallogenesis gradually decrease; in the vertical direction, the barrier layer can lead to more Vertical sequence unit, interlayer oxidation zone and uranium deposit head development. Statistics show that medium sandstone and fine sandstone are the best carriers for uranium metallogenesis. Therefore, uranium ore is usually located in the middle and lower part of braided distributary channel sandstone in each vertical series unit. On the one hand, the ore-forming mechanism of uranium may be that the sand body heterogeneity can control uranium metallogenesis through the influence on the migration state of ore-forming fluid and on the other hand it may be related to the increase of reducing materials caused by the phase change of sedimentary environment . The uranium mineralization rule summarized through the study of sand body heterogeneity is the basis for the localization and prediction of uranium metallogenic space.