砂体特征对地浸砂岩型铀矿成矿的制约——以扎赉诺尔坳陷带为例

摘要

砂体是制约地浸砂岩型铀矿成矿的重要条件之一.扎赉诺尔坳陷带内诸凹陷具有不同的沉积特征和砂体特点,查干诺尔凹陷砂体形成于冲积扇沉积体系,砂体厚度变化大、相变快、粒度粗、有机质含量低,其顶、底板泥岩均不发育;克鲁伦凹陷砂体形成于扇三角洲沉积体系,砂体厚度较稳定,中前缘发育泥-砂-泥地层结构;呼伦湖凹陷以发育曲流河三角洲平原相砂体为主,具有较稳定的泥-砂-泥地层结构,有机质含量高,砂体厚度和横向延伸较稳定;胡列也吐凹陷砂体以辫状河三角洲体系产出为主,砂体厚度大,延伸稳定,底板泥岩发育,顶板泥岩发育不完全.扎赉诺尔坳陷带各凹陷砂体的不同特点,决定了它们具有不同的找矿潜力.通过砂体综合条件的对比分析,笔者认为呼伦湖和克鲁伦凹陷砂体铀成矿条件最好,胡列也吐凹陷次之,查干诺尔凹陷砂体成矿条件最差.%Each sag in Zalailuoer depression has its own characteristics of sedimentary system and sand-bodies. The sandbodies in Chaganluoer sag were formed in alluvial fan and delta sedimentary system with coarse grain sediments which varies very much in thickness and change very fast in fades, and have low content of organic materials and poorly developed upper and bottom mud set. The sandbodies in Kelulun sag were formed in delta sedimentary system with stable thickness and mudstone - sandstone - mudstond stratigrafic composition. Sandbodies in Hulunhu sag were mainly formed in small delta which bear mud-stone - sandstone - mudstone composition and high organic materials content and are fairly stable in thickness of transver strench. Sandbodies in Huleyetu sag were mainly formed in braided delta sedimentary system and with a relatively thick sandbody, the sandbodies is stable in distribution and developed well bottom mud set but poor upper one. Different characteristics of sandbodies in each sag of Zalailuoer depression have defferent potential for uranium mineralization. On the basis of comprehensive contrast, the authors concluded that uranium mineralization in Huleyetu sag and Kelulun sag are the best, but Hulunhu sag is not good, while Caganluoer sag are bad.