内蒙古巴彦乌拉铀矿床赛汉组砂岩地球化学特征及古环境意义  

Geochemical Characteristics and Paleoenvironmental Significance of the Saihan Formation in Bayanwula Uranium Deposit,Inner Mongolia

作　　者：刘成东[1] 黄晓宇 万建军[1] 赵严 LIU Chengdong;HUANG Xiaoyu;WAN Jianjun;ZHAO Yan(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China)

机构地区：[1]东华理工大学核资源与环境国家重点实验室,江西南昌330013

出　　处：《东华理工大学学报（自然科学版）》2023年第2期101-112,共12页Journal of East China University of Technology(Natural Science)

基　　金：国家自然科学基金项目(41972043)。

摘　　要：内蒙古巴彦乌拉铀矿床位于二连盆地,是我国北方砂岩型铀矿床的重要组成部分。研究表明,古气候条件能直接影响砂岩型铀矿成矿作用,而其对巴彦乌拉砂岩型铀矿形成的影响还存在争论。以内蒙古巴彦乌拉铀矿床赛汉组不同类型砂岩为研究对象,通过岩相学和地球化学的研究,还原赛汉组沉积时期古沉积环境,进而探讨古气候条件对该矿床的影响。赛汉组砂岩主要为中、细粒砂岩,成分成熟度较低,反映物源区相对稳定;稀土元素北美页岩标准化图解较为平坦且一致,指示该区具有统一的物源;B含量为8.04×10^(-6)~195.43×10^(-6)和n(Sr)/n(Ba)值为0.08~0.46等特征均指示沉淀水体为淡水,反映沉积初期为温暖潮湿环境;n(V)/n(V+Ni)值为0.21~0.73、δU值为1.27~1.99以及较富集的氧化-还原环境敏感元素U和Mo特征等表明,沉积时水体中含氧量较低,为还原环境。结合n(Sr)/n(Cu)值为1.42~24.45和w(SiO_(2))/w(Al_(2)O_(3))值为3.03~8.24,认为内蒙古巴彦乌拉铀矿床赛汉组砂岩沉积末期处于干热气候条件。综合研究认为赛汉组初期为温暖潮湿的还原条件,有利于黄铁矿和有机质富集,并为地层中铀的富集提供了良好条件,而沉积末期为干热气候条件,有利于铀的活化迁移,为内蒙古巴彦乌拉铀矿床的形成奠定了基础。Bayanwula uranium deposit located in Erlian basin Inner Mogolia,is an important sandstone-type uranium deposit in northern China.In recent years,more and more attention has been paid to the study of the influence of paleoclimate on sandstone-type uranium deposits.Some key ore-controlling factors created by paleoclimate can directly affect mineralization.The sandstone of the Bayanwula Saihan Formation is taken as the research object.Through the study of lithofacies and the main and micro analysis of whole rock,the ancient sedimentary environment of Saihan Formation is restored.The results show that the samples are mainly medium to fine sandstone,and the overall composition maturity is low,reflecting that the source area is relatively stable.The normalized distribution pattern of rare earth elements in north American shale is parallel,indicating that the area has a unified source.The content of B(8.04×10^(-6)~195.43×10^(-6))and the ratios of n(Sr)/n(Ba)(0.08~0.46)indicate that the sedimentary water is fresh water,reflecting the warm and humid climate in the initial stage of deposition.The values of n(V)/n(V+Ni)(0.21~0.73),δU(1.27~1.99)and the enrichment characteristics of redox environment sensitive elements U and Mo show that the water body has low oxygen content and is in a reducing environment.The ratios of n(Sr)/n(Cu)(1.42~24.45)and w(SiO_(2))/w(Al_(2)O_(3))(3.03~8.24)indicate that the Saihan Formation sandstones of Bayanwula uranium deposit in Inner Mongolia were deposited in a dry-hot climate in the late sedimentary period.The early stage of the Saihan Formation was warm and humid,which was conducive to the enrichment of pyrite and organic matter,and provided good conditions for the enrichment of uranium in the strata.The dry and hot climate conditions at the end of deposition are beneficial to the enrichment of uranium.

关 键 词：地球化学 砂岩型铀矿 古气候 赛汉组 巴彦乌拉 

分 类 号：P619.14[天文地球—矿床学]