鄂尔多斯盆地北缘砂岩型铀矿板状矿体形成机制:来自含矿层不同分带砂岩中高岭石含量研究的约束  

The formation mechanism of tabular orebody of sandstone-type uranium in the northern Ordos Basin:constraints on the study of kaolinite content from different zones of ore-bearing sandstone

作　　者：丁波[1] 刘红旭[1] 张宾 易超[1] 刘洪军 王贵 任志勇 DING Bo;LIU Hongxu;ZHANG Bin;YI Chao;LIU Hongjun;WANG Gui;REN Zhiyong(CNNC Key Laboratory of Uranium Resources Exploration and Evaluation Techniques,Beijing Research Institute of Uranium Geology,Beijing,100029;China institute of Nuclear Industry of Strategy,Beijing,100048;Geologic Party NO.208,CNNC,Inner Mongolia,014010)

机构地区：[1]中核集团铀资源勘查与评价重点实验室,核工业北京地质研究院,北京100029 [2]中核战略规划研究总院,北京100048 [3]核工业二〇八大队,内蒙古包头014010

出　　处：《地质学报》2020年第10期2874-2882,共9页Acta Geologica Sinica

基　　金：鄂尔多斯盆地西北部砂岩型铀矿成矿作用与新区突破研究(地D1911);国家科技部973计划项目(编号2015CB453004);中核集团集中研发项目(龙腾二期)“鄂尔多斯盆地北部砂岩型铀矿关键因素识别与靶区优选”(编号地LTD1601-2)联合资助。

摘　　要：鄂尔多斯盆地北缘是中国北方最重要的砂岩型铀矿分布区之一。与层间氧化带砂岩型铀矿的卷状矿体不同,研究区矿体以板状、似层状为特征。国内中-东部盆地砂岩型铀矿矿带砂岩中高岭石含量相对偏高指示含矿层至少经历一期与成矿密切相关的偏酸性流体,这与国外学者在研究板状铀矿体的过程中关注含矿层上覆泥岩压实作用下排出富含有机酸的酸性流体具有相似的特点。因此,本文为探讨酸性流体活动与板状矿体形成的内在关系,选择纳岭沟铀矿床为例,通过采取含矿层不同地球化学分带砂岩样品,应用扫描电镜、X-衍射、U元素含量等分析手段,发现矿带与还原带砂岩中高岭石含量相对偏高这一特殊现象;系统研究后认为上述现象与含矿层下伏延安组煤层埋藏演化过程中产生的大量有机酸性流体垂向渗入含矿层有关;结合含矿层埋藏演化史,将板状矿体的形成过程分为封闭体系-有机酸性流体发育、开放体系-大规模铀成矿、油气大规模逸散-叠加改造保矿三个阶段,并认为板状矿体的形成是偏碱性含铀含氧大气降水与有机酸性流体长期稳定相互作用的结果,产于两种流体混合接触面上,其中含矿层砂岩厚度是控制矿体形态的关键因素。The sandstone-type uranium deposits in the northern Ordos basin are important in north China.They have the characteristics of tabular orebody,which is different from the roll orebody in the interlayer oxidation zone sandstone-type uranium deposits.The latest study shows that the kaolinite content is relatively high in the sandstone-type uranium ore belt sandstones of the central and eastern basins,indicating that the ore-bearing bed has experienced at least one period of acidic fluids closely related to mineralization.It has similar characteristics with recent ideas that the formation of tabular orebody was related to acidic fluids discharged from the compaction of overlying mudstone.In this paper,the sandstone-type uranium deposits in the northern Ordos basin are selected as an example,and the sandstone samples of different geochemical zonation of ore-bearing bed are collected for SEM,X-diffraction,and U element content analysis.The phenomenon of relatively high kaolinite content in sandstone-type uranium ore belt and reduction belt sandstone in the northern Ordos basin is considered to be related to organic acid fluid generated in the burial evolution process of the Yan’an Formation coal seam under the ore-bearing bed.Combined with the burial evolution history of ore-bearing bed,the formation of tabular orebody is divided into three stages:closed system-organic acid fluid development stage,open system-large scale mineralization stage,oil and gas large scale dispersion-superposition transformation ore-retaining stage.It is believed that the formation of tabular orebody is the result of long-term stable interaction between alkaline uranium-containing meteoric water and organic acid fluid,and occurs on the mixed contact surface of the two fluids.In addition,the overall thickness of ore-bearing sandstone is an important factor controlling orebody morphology.

关 键 词：鄂尔多斯盆地 砂岩型铀矿 板状矿体 酸性流体 高岭石含量 

分 类 号：P619.14[天文地球—矿床学]