东胜矿区深部直罗组氧化还原环境与砂岩型铀矿特征

Zhiluo Formation Redox Environment and Sandstone-type Uranium Deposit Characteristics in Deep Part Dongsheng Mining Area

鄂尔多斯盆地北部东胜地区中侏罗统直罗组下段古层间氧化型砂岩铀矿较为发育,铀矿化主要发育于层间氧化带氧化前锋附近(灰绿色砂体与灰色砂体的过渡部位)。通过对测井资料的解释发现,东胜矿区深部西南部乌审旗西南和北部杭锦旗附近直罗组下段砂体中也存在放射性异常。通过对东胜深部矿区50多个钻孔的数据统计与分析,重现了直罗组下段(下亚段、上亚段)的古层间氧化-还原砂体的分布。古氧化带大致呈NW-SE向展布,主要分布在研究区中北部;放射性异常主要出现在氧化-还原过渡带部位。研究区目的层砂体内放射性异常总体呈现出厚度较小(下亚段异常层平均厚度2.67 m、上亚段异常层平均厚度2.33 m)、埋深较大(下亚段异常层平均埋深1 025 m、上亚段异常层平均埋深921 m)的特征。

The middle Jurassic Zhiluo Formation lower member paleo-interstratified oxidized sandstone-type uranium deposit is relatively developed in Dongsheng area, northern Ordos Basin. The mineralization had happened near the front of interstratified oxidized zone（a transitional belt between grayish green sand mass and gray sand mass）. The interpretation and analysis of well logging data found that in the Zhiluo Formation lower member sand mass near southwestern Uxin Banner and northern Hanggin Banner in southwestern deep part Dongsheng mining area have also radioactivity anomalies. Through 50 more boreholes in deep part Dongsheng mining area data statistics and analysis, have revealed Zhiluo Formation lower member（lower and upper sub-members） paleo-interstratified redox sand masses distribution. Paleo-oxidation belt roughly presented NW-SE extending, mainly in mid-north study area; radioactivity anomalies mainly appeared in transitional oxidation-reduction belt. Radioactivity anomalous target sand masses in study area present characteristics of smaller thicknesses（average thickness of lower sub-member anomalous layer is 2.67 m, upper sub-member 2.33m）,deeper buried depths（average depth of lower sub-member anomalous layer is 1025 m, upper sub-member 921m）.