鄂尔多斯盆地西北部特拉敖包矿产地铀成矿机理研究  

Study on the Metallogenic Mechanism of Telaaobao Occurrence in the Lower Cretaceous,Northwestern Ordos Basin

作　　者：贺锋[1] 李子颖[1] 刘鑫扬 张字龙[1] 王龙辉 刘持恒 张艳 邱林飞[1] 韩美芝 HE Feng;LI Ziying;LIU Xinyang;ZHANG Zilong;WANG Longhui;LIU Chiheng;ZHANG Yan;QIU Linfei;HAN Meizhi(CNNC Key Laboratory of Uranium Resources Exploration and Evaluation Technology,Beijing Research Institute of Uranium Geology,Beijing 100029,China;China Nuclear Geology Bureau,Beijing 100013,China;Geologic Party No.208,CNNC,Baotou,Inner Mongolia 014010,China)

机构地区：[1]核工业北京地质研究院中核集团铀资源勘查与评价技术重点实验室,北京100029 [2]中国核工业地质局,北京100013 [3]核工业二〇八大队,内蒙古包头014010

出　　处：《铀矿地质》2023年第6期859-874,共16页Uranium Geology

基　　金：中核集团集中研发项目“砂岩型铀矿多重耦合地质成矿作用与时空定位”(编号:中核科发2021-143号);中核集团青年英才项目“鄂尔多斯盆地西南部下白垩统厚大灰绿色砂体对铀成矿制约关系”(编号:地QNYC2301)联合资助;中国核工业地质局项目“鄂尔多斯盆地白垩系远景预测与找矿方向”(编号:202201-08)。

摘　　要：文章分析了鄂尔多斯盆地西北部下白垩统环河组铀成矿环境和特拉敖包矿产地铀成矿特征,开展了砂岩致色原因和灰绿色砂体成因分析,对下白垩统砂岩型铀成矿机理和成矿模式进行了探讨。西北部环河组铀矿体位于巨厚层辫状河砂体内部,发育由成岩作用形成的致密-疏松-致密的砂岩结构。下白垩统红色砂岩铀本底值非常低,灰绿色和褐灰色砂体存在后期铀富集。特拉敖包矿产地铀矿体主要呈多层板状、透镜状发育于灰绿色砂体中。铀矿物主要以铀石为主,铀矿物叠加富集与铁的氧化物共存。Fe^(3+)和Fe^(2+)的相对含量是砂岩致色的主要因素,后期渗出流体还原改造是灰绿色砂岩主要成因。西北部下白垩统铀成矿可划分为沉积期、渗出-渗入成矿和渗出保矿三个阶段,铀矿物与铁的氧化物共存是深部富铀还原性流体与含氧含铀水相对强弱变化、渗入-渗出交汇面上升和下降、不同蚀变带相互叠加的结果,是特拉敖包铀矿产地多层板状、透镜状矿体形成的主要因素。This paper carried out a detailed study on the uranium metallogenic environment of the Lower Cretaceous Huanhe Formation in Northwestern Ordos Basin,and the uranium ore characteristics of the Telaaobao uranium occurrence.Firstly,we analyzed the chromatism reason of various colors on sandstone,especially the gray-green sand body.And then,we discussed the uranium metallogenic mechanism and the metallogenic model.The uranium ore body of the Huanhe Formation is located in the huge thick sand body of the braided river with a tight-loose-tight structure by diagenesis.The uranium content of red sandstone(background value)in the Lower Cretaceous is extremely low,and uranium in grayish green and brownish gray sandstones is enriched in later stage.The uranium ore body of the Telaaobao uranium occurrence occurs in the gray-green sand body with the shape of a multi-layer plate and lens.The uranium minerals exist mainly in the form of coffinite and coexist with iron oxides by superimposing.Thus,it was believed that the content ratio of Fe3+and Fe2+is the key factor causing the coloration of sandstone,and the later transformation by hydrocarbon reduction is another consequence of gray-green sandstone.Finally,the uranium mineralization process of the Lower Cretaceous in the northwestern Ordos Basin can be divided into three stages:sedimentary stage,infiltrated-exudative mineralization stage,and exudative preservation stage.The coexistence of uranium minerals and iron oxides is multiple effects of the balance between deep reducing fluid with uranium and the meteoric water containing oxygen and uranium,the fluctuation of the infiltrated-exudative interface,and superposition of different alteration zones.These multiple coupling effects result in the multi-layer and plate-like uranium ore bodies in the Telaaobao uranium occurrence.

关 键 词：成矿特征 成矿机理 下白垩统环河组 灰绿色砂岩 特拉敖包矿产地 

分 类 号：P619.14[天文地球—矿床学]