北山地区残留盆地砂岩型铀成矿潜力分析

Analysis of Metallogenic Potential of Sandstone-type Uranium Deposit in Residual Basin of Beishan Area

北山地区位于天山-兴蒙造山带北山褶皱带内,由7个大小不同的中-新生代沉积盆地组成,晚白垩世以来,本区长期处于隆升状态,下白垩统遭受剥蚀,现今为残留盆地。文章通过盆地沉积-构造演化的研究,分析了各盆地填充物和成矿有利层位,确定下白垩统下沟组为主要找矿目的层。对比各盆地下沟组残留厚度、规模和岩性-岩相特征,分析铀矿化特征和控矿因素,认为总口子盆地、公婆泉盆地和黑鹰山盆地下沟组残留厚度大,有利相带保存较好,潜水及层间氧化带发育,且在氧化带上下翼发现有较好的铀矿化,显示层间氧化带型找矿潜力较大;扎格高脑盆地下沟组不整合于富铀岩体之上,底部发育厚层砂体,岩体风化壳厚度大,且后生氧化作用强烈,显示具有古河道砂岩型铀矿找矿前景。

Beishan area is located in Beishan fold belt of Tianshan-Xingmeng orogenic belt,which is composed of seven Mesozoic-Cenozoic sedimentary basins with different sizes.Since Late Cretaceous,the study area has been uplifted for a long time,and the Lower Cretaceous has suffered denudation,which is now a residual basin.Based on the study of basin sedimentary-tectonic evolution,this paper analyzed the favorable horizons for filling and mineralization in each basin,and determined Xiagou Formation of Lower Cretaceous as the main prospecting target.By comparing the residual thickness,scale and lithology-lithofacies characteristics of Xiagou Formation in each basin,Xiagou Formation in Zongkouzi basin,Gongpoquan basin and Heiyingshan basin was found thick and large with favorable well preserved facies,well developed phreatic water and interlayer oxidation belts.Good mineralization was discovered in the upper and lower wings of oxidation belts,indicating great prospecting potential for interlayer oxidation mineralization.Xiagou Formation in Zhagegaonao basin is unconformity on uranium-rich pluton,with thick sand body at the bottom,thick weathering crust and strong epigenetic oxidation,indicating that there is a prospecting prospect for sandstone-type uranium deposits in paleochannel.