鄂尔多斯盆地纳岭沟地区直罗组砂岩粘土矿物特征及初步对比研究

纳岭沟铀矿床位于鄂尔多斯盆地东北部，含铀岩系为中侏罗统直罗组。文章通过薄片鉴定、扫描电镜、X射线衍射 等分析测试手段，对纳岭沟地区直罗组砂岩粘土矿物的镜下特征、成分及含量进行了系统的观察和研究，探讨了直罗组砂 岩粘土的矿物特征，并初步与伊犁盆地及二连盆地做了对比。研究表明，纳岭沟地区直罗组砂岩的粘土矿物主要为蒙皂 石，其次为高岭石、绿泥石，少量伊利石 。蒙皂石与高岭石存在相互转化现象，部分绿泥石由蒙皂石和高岭石转化而来， 成岩过程中蒙皂石并未大规模自发的向伊利石转化。砂岩的粘土总量较高，与伊犁盆地相比，富含蒙皂石，高岭石含量较 低，粘土矿物的吸附能力较强。在直罗组砂岩的成岩过程中，粘土矿物的吸附作用为直罗组富集了大量的铀，这是鄂尔多 斯盆地东北部地区能形成众多铀矿床乃至超大型铀矿床的重要条件。

Features of Clay Minerals in the Middle Jurassic Zhiluo Formation Sandstones of the Nalinggou Area in the Ordos Basin and A Preliminary Comparison with Adjacent Areas

The Nalinggou uranium deposit is located in the northeastern Ordos Basin and the U-bearing rock series occur in the Middle Jurassic Zhiluo Formation. In this paper, method of microscopic identification, scanning electron microscopy and X-ray diffraction were used to systematically observe and study the microscopic characteristics, composition and content of clay minerals in the Zhiluo Formation sandstones of the Nalinggou area. Then, characteristics of the clay minerals were discussed in detail and compared preliminariy with those of the adjacent Yili and Erlian basins. Results show that the clay minerals are mainly smectites, followed by kaolinites, chlorites and illites. There is a mutual transformation between smectites and kaolinites, while some chlorites are transformed from smectites and kaolinites. In contrast, smectites did not spontaneously transform to illites during the diagenesis. The total amount of clay minerals in sandstones is relatively high. Compared with those in the Yili Basin, the sandstones in the study area are rich in smectites, with less content of kaolinites, and have a strong adsorption capacity caused by clay minerals. During the diagenesis, the adsorption of clay minerals led to a large amount of pre-enrichment of uranium, which is an important prerequisite for the formation of many uranium deposits and even super-large uranium deposits in the northeastern Ordos Basin.