Identification of Eolian Sandstone in Cretaceous Uraniferous Sandstone in Ordos Basin,ChinaEI北大核心CSCD

Uraniferous rocks in the lower part of Cretaceous Luohe Formation of Well XX located at the southwestern Ordos Basin have been investigated through core logging, microscopic observation, scanning electron microscope and granularity analyses. The desert (lower part) and ephemeralalluvial (upper part) sedimentary facies, composed of dune, interdune, sandsheet, wadi, and channel, bank subfacies are identified. The lower part of the Luohe Formation consists of red, yellow, and grayish green coarse- to fine-grained sandstone. The sandstone lacks cement and matrix, and quartz grains as the main mineral component are commonly clean and bright, with a small amount of debris (sedimentary debris) and feldspar (microcline and striped feldspar), indicating a high composition maturity. These particles are mostly medium-fine, sub-angular to sub-rounded, and the grain size distribution is mainly concentrated between 2.2? and 3?. The grain size curve shows that the sandstone is mainly composed of jumping transport components, with a small amount of suspended transport components, which means that the sandstone is well sorted and structurally high mature. Large scale and high angle cross bedding, parallel bedding, and wavy bedding are common, and tongue shaped grain flow with upward or downward pinching, wind ripple strata with reverse grain sequence, pin stripe lamination with dark color can be identified in the layer. Under scanning electron microscope, a series of dished and crescent impact craters, pockmarks, chemical dissolution and precipitation, desert paint, and other phenomena are identified on the surface of sandstone particles. Comparing with the characteristics of typical fluvial sandstone and eolian sandstone, the uraniferous sandstone in the lower part of the Luohe Formation in the southwestern Ordos Basin is of typical eolian sandstone. The eolian uraniferous sandstone is a new type of uranium-bearing sandstone reservoirs in the world, and this discovery expands the exploration space and potential for uranium deposits in North China, and provides new direction for further exploration of sandstone type uranium deposits. Further research is still underway. © 2020, Science Press. All right reserved.