内蒙古陈旗断陷东部伊敏组沉积相及铀成矿作用

摘要

陈旗断陷是位于内蒙古东部海拉尔盆地群的一个早白垩世断陷盆地,盆地盖层由铜钵庙组、南屯组、大磨拐河组和伊敏组构成,盆地近东西向展布,为地层倾向南东的单断式盆地.在伊敏组沉积时期,陈旗断陷进入萎缩阶段,盆地南部扇三角洲向盆地中心推进,盆地被淤浅并出现大量沼泽沉积,形成含煤地层,同时湖面向北萎缩,盆地北部缓坡形成小型河流三角洲沉积.铀矿化出现在前第四纪时期的沟谷附近,前第四纪沟谷或河道提供的含铀含氧水垂向侧向渗入到隔水层顶板处氧化褐煤,被炭质吸附而形成煤层上部的次生铀矿化,属于潜水氧化型铀矿化.%The Chenqi fault depression in eastern Inner Mongolia is an Early Cretaceous basin among the Hailar basin group.It is covered by the Tongbomiao,Nantun,Damoguaihe and Yimin formations.This mono-faulted basin is distributed nearly east to west,with strata inclining to southeast.During the depositional period of the Yimin Formation,the Chenqi fault depression entered the stage of reduction,when the fan delta in the south advanced to the center of the basin.The basin then was filled with a large number of marsh deposits to form coal-bearing strata.Simultaneously,with the northward regression of the lake,small river delta was formed on the northern slope of the basin.The water with uranium and oxygen from the pre-Quaternary gully and river channels vertically or laterally infiltrated into the oxidized lignite layer at the top of the watertight stratum.Uranium was then adsorbed by carbon deposits with secondary mineralization in the upper part of the coal seam.Therefore,this uranium mineralization belongs to phreatic water oxidation type.