柴北缘冷湖砂岩型铀矿铀矿物赋存特征及成因机制  

Genetic mechanism and occurrence characteristics of uranium minerals in the Lenghu sandstone-type uranium deposit,northern Qaidam Basin

作　　者：张超[1] 王善博 俞礽安 程银行 奥琮 滕雪明 冯平[2] 于航 ZHANG Chao;WANG Shan-bo;YU Reng-an;CHENG Yin-hang;AO Cong;TENG Xue-ming;FENG Ping;YU Hang(Tianjin Center of Geological Survey,China Geological Survey,Tianjin 300170,China;The Nuclear Industry Geological Survey 283 Brigade in Sichuan Province,Dazhou 635000,China)

机构地区：[1]中国地质调查局天津地质调查中心,天津300170 [2]四川省核工业地质局二八三大队,四川达州635000

出　　处：《岩石矿物学杂志》2022年第1期47-60,共14页Acta Petrologica et Mineralogica

基　　金：中国地质调查局项目(DD20190119);青海省青藏高原北部地质过程与矿产资源重点实验室资助项目(2019-KY-02);青海省清洁能源矿产专项资金勘查项目(2021074006ky006)。

摘　　要：冷湖铀矿床是近年来在柴达木盆地北部新发现的具有工业价值的砂岩型铀矿床,为了研究该地区铀矿物的类型、成分特征、赋存形式及铀成矿作用,本文在野外地质调查的基础上,对下侏罗统小煤沟组相关蚀变矿物进行了矿相学、电子探针、背散射电子成像分析。研究发现,冷湖小煤沟组矿石主要包括杂砂岩型及碳质砂岩型两种,整体发育后生蚀变。铀矿物主要为铀石与沥青铀矿,含少量硒铅矿,与黏土矿物、有机质及黄铁矿密切共生,呈微细柱状、似胶状或不规则锯齿状产于石英、长石等蚀变岩屑矿物颗粒之间或蚀变矿物的解理缝隙中。后期多次流体作用携带的U^(6+)在Fe^(2+)提供的还原环境中发生还原-沉淀-吸附铀成矿作用。综合铀矿物存在高Y与低Y两种类型、蚀变序列及环境特征分析,推测铀矿物中的铀为原铀矿物残留,经不含Y元素或Y元素含量很低流体的多期改造而富集成矿。Lenghu uranium deposit is a newly discovered in recent years and have industrial value sandstone-type uranium deposit in the northern part of the Qaidam Basin.In order to study the classification,occurrence and mineralization of uranium minerals in this area,this paper conducted the mineralogical,electron probe,backscatter electron imaging analysis of the altered minerals in Xiaomeigou Formation of Lower Jurassic on the basis of field investigation.These studies found that the ore types of Xiaomeigou Formation in Lenghu are mainly composed of complex sandstone-type and carbonaceous sandstone-type,which have occurred overall epigenetic alteration.It is found that the main uranium minerals are uranite,pitchblende and minor of lead selenite,which is closely associated with clay minerals,organic matter,and pyrite,and lie in the intergranular space of quartz,feldspar and other altered lithic mineral grains or in cleavage joints of altered minerals occurs in fine columnar,gel-like or irregular sawtooth shape.In late multiple fluid processes,U^(6+) occurred reduction-precipitation-adsorption uranium mineralization in the reduction environment provided by Fe^(2+).Based on the analysis of high Y and low Y-types uranium minerals,alteration sequence and environmental characteristics,it is inferred that uranium in uranium minerals was the residual of original uranium minerals,which is enriched and mineralized by multi-stage transformation of fluids with no Y element or very low Y element.

关 键 词：砂岩型铀矿 电子探针 小煤沟组 冷湖 柴北缘 

分 类 号：P619.14[天文地球—矿床学]