巴音戈壁盆地乌力吉凹陷白垩系含铀岩系层序地层及铀成矿作用  

Sequence Stratigraphy and Uranium Mineralization of Cretaceous Uranium Bearing Rock Series in Wuliji Sag,Bayingebi Basin

作　　者：郭煦劼 刘波 郝朋 秦彦伟 李鹏 GUO Xujie;LIU Bo;HAO Peng;QIN Yanwei;LI Peng(Geologic Party No.208,CNNC,Baotou,Inner Mongolia 014010,China)

机构地区：[1]核工业二〇八大队,内蒙古包头014010

出　　处：《铀矿地质》2025年第2期272-291,共20页Uranium Geology

基　　金：中国核工业地质局项目(编号:201903);核工业二〇八大队自主科研项目联合资助。

摘　　要：巴音戈壁盆地是中国北方重要的产铀盆地,在乌力吉地区发现了大量铀矿化异常点。为了解乌力吉凹陷下白垩统巴音戈壁组层序地层及铀成矿作用,文章在野外调查和大量钻孔测井的基础上,划分了下白垩统高分辨率层序地层,建立了不同时期的体系域,讨论了沉积、层间氧化与铀富集的关系。研究表明,下白垩统巴音戈壁组可分为两个四级层序,即巴音戈壁组下段(Sq1)和巴音戈壁组上段(Sq2),其中Sq1层序在研究区只见到强制水退体系域(FSST),Sq2层序由低位体系域(LST)、湖扩体系域(TST)和高位体系域(HST)组成。巴音戈壁组上段的高位体系域与上覆海侵体系域的湖相泥岩形成有利的格挡层,低位体系域发育厚大扇三角洲砂体,形成稳定的泥-砂-泥结构,有利于含铀含氧水的运移;扇三角洲砂体中的有机质和黄铁矿以及分流湾的暗色泥岩为铀矿化提供了还原介质;铀矿化主要赋存于分流河道、水下分流河道或扇三角洲河口坝中。文章在层序地层学研究的基础上,建立了铀矿的层序、沉积、成矿模式,丰富了铀成矿理论,为同类型铀矿的找矿提供了参考。Bayingebi Basin is an important uranium producing basin in north China.A large number of uranium anomalies have been found in Wuliji.The main target layer is the Lower Cretaceous Bayingebi Formation,which developed fan delta-shallow lake facies deposition.The distributary channel sandbodies in the fan delta plain and the distributary channel sandbodies in the fan delta front are favorable uranium reservoirs.On the basis of field investigation and analysis of a large number of borehole logging data,the authors divided the lower Cretaceous high resolution sequence stratigraphy and established the system tracts of different periods.The relationship between deposition,interlayer oxidation and uranium enrichment was discussed.The Lower Cretaceous Bayingebi Formation can be divided into two quaternary sequences(Sq1 and Sq2).Lower member of Bayingebi Formation(Sq1),Upper Member of Bayingebi Formation(Sq2).Sq2 is composed of lowstand system tract(LST),lacustrine expanding system tract(TST)and highstand system tract(HST).The lacustrine mudstones in the high system tract and overlying transgressive system tract form the favorable aquiclude.The sandbodies of thick big fan delta developed in the lower system tract and formed stable mudsand-mud structure,which was beneficial to the migration of uranium-containing oxygen water.Organic matter and pyrite in fan delta sand body and dark mudstone in fan bay provide reduction medium for uranium mineralization.Mineralization occurs mainly in distributary channels,subaqueous distributary channels or fan delta mouth bars.Based on the study of sequence stratigraphy,a model of uranium deposit sequence,sedimentation and mineralization has been established,which provided reference for the prospecting of the same type of uranium deposit in the study area.

关 键 词：层序地层学 剥蚀天窗 铀成矿作用 巴音戈壁盆地 

分 类 号：P619.14[天文地球—矿床学]