鄂尔多斯盆地东北部延安组铀异常与沉积体系的关系

在鄂尔多斯盆地东北部,延安组第V成因单元存在着多处铀异常,这对铀的后备战略基地建设有重要意义。从沉积学的角度重建了第V成因单元的沉积体系,识别出两种沉积体系,分别是位于研究区西北部的辫状河沉积体系和东南部的曲流河沉积体系。通过对铀异常信息的成功提取及平面编图,发现延安组中铀异常呈一个又一个具有自我中心的单元出现,且与曲流河沉积体系的关系密切:通常发育于河道分岔或转弯处;普遍发育于薄砂带(区),一般砂体厚度在30 m以下,含砂率小于40%;铀异常单元与厚煤层关系密切;主要赋存于粒度较细的岩性中,部分也富集于煤中,但铀异常最高值富集于中砂岩中。

Relationship between Uranium Anomaly and Depositional System of Yan''''an Formation, North-east Margin of Ordos Basin

Several uranium anomalies in Yan'an Formation,Unit V,have been found in the north-east margin of Ordos Basin,which are important for building the prospective uranium reserve base.According to sedimentology,the depositional system of Unit V,Yan'an Formation,has been reconstructed,it is revealed that there is braided stream system in the northwest of study area, and meandering stream system develops in the southeast.According to successfully extracting and graphing of uranium anomalies,the self-center uranium anomalies and their close relationship with meandering stream systems have been observed.The uranium anomaly always(develops) in the distributary and turning place of meandering stream system,and is related with thin sand area(whose sand thickness and sand ratio are less than 30 meters and 40% respectively),thicker coal,fine lithology,but the highest value of uranium anomaly exists in middle sandstone.