我国砂岩型铀矿分带特征研究现状及存在问题  

Current Status and Existing Problems of China's Sandstone-type Uranium Deposits

作　　者：付勇[1] 魏帅超 金若时[2] 李建国[2] 奥琮 

机构地区：[1]贵州大学资源与环境工程学院,贵阳550025 [2]天津地质矿产研究所,天津300170

出　　处：《地质学报》2016年第12期3519-3544,共26页Acta Geologica Sinica

基　　金：国家重点基础研究发展计划"973"项目(编号2015CB453000);中国地质大调查"我国重要矿产和区域成矿规律研究"(编号1212010633903)资助的成果

摘　　要：作为一种重要的国家战略资源,砂岩型铀矿床是当今世界上最重要的铀矿床类型之一。本文详细地介绍了砂岩型铀矿在国内外的分布特征及占比情况,并对外生地质作用矿床类型中表生流体作用形成的层间渗透砂岩型和潜水渗透砂岩型铀矿床进行了讨论,发现层间渗透砂岩型铀矿床在外表颜色、矿物组合以及地球化学等方面均具有明显的氧化-还原分带现象,此外,矿床内部还具有细菌分带现象。颜色分带在氧化带、氧化-还原过渡带以及还原带之间具有明显不同的特征;矿物组合在不同分带之间各不相同;地球化学分带表现为U、TOC含量以及Fe^(2+)/Fe^(3+)、Th/U比值在各分带之间差异较大。此外,硫酸盐还原菌、硫杆菌、铁细菌及硝化菌等细菌在不同分带之间的数量相差悬殊,而且硫酸盐还原菌数量与TOC呈明显正相关性。通过矿化带内的碳、硫同位素分析,发现硫酸盐还原菌参与了成矿过程,推测其可能是导致碳、硫同位素分馏的主要因素。总体来看,颜色分带、矿物分带、地球化学分带以及细菌分带均与氧化-还原分带呈耦合关系。本文通过总结层间渗透砂岩型和潜水渗透砂岩型铀矿床的成矿模式和当前分带研究中存在的问题,提出了由细菌、地球化学反应参与的砂岩型铀矿床成矿机理,以及未来亟需解决的若干关键科学问题。典型砂岩型铀矿床的分带现象在物、化、探、遥等领域的异常响应对寻找砂岩型铀矿床具有重要的指导意义。Asone key national strategic resource, sandstone type uranium deposits are one of the most important types in the modern world. This paper decribes in great detail the distribution and ratios of sandstone type uranium ore deposits at home and abroad, discussed interlayer permeability sandstone type and submerged permeability sandstone type uranium deposits formed by supergene fluids. The results show that distinct redox zoning of interlayer permeability sandstone typeuranium deposit occurs in terms of surface color, mineral combination and geochemistry, and moreover, bacteria zoning phenomenon. Color zoning show remarkable different characteristics among oxidized zones, redox transitional zones and reduced zones; mineral combination differs among the different zones; geochemical zoning is also defined by U, TOC contents and Fe2＋/Fe3＋ and Th/U ratios. In addition, the quantities of bacteria, such as sulfate reducing bacteria （SRB）, thiobacilli, ferrobacteria, and nitrobacteria, vary considerably among the different zones, and there is conspicuous positive correlation between the magnitude of SRB and TOC. By analysis of carbon and sulfur isotope in the mineralization belt, we find that SRB has involved in the metallogenic process and infer that SRB may be the dominant factor causing carbon and sulfur isotopic fractionation. As a whole, color, mineral, geochemical, and bacteria zonings all have coupling relationship with the redox zoning. This study proposes the mechanism of sandstone type uranium deposits involved by bacteria and geochemical reactions, and a number of key scientific problems needed to be solved urgently through summarizing metallogenic model of interlayer permeability sandstone type and submerged permeability sandstone type uranium deposits. The exceptional responses of typical sandstone type uranium deposits to geophysical, geochemical, prospecting exploration and remote sensing have great guiding significance to searching for sandstone type uranium deposits.

关 键 词：砂岩型铀矿 氧化-还原分带 成矿机理 微生物成矿 成矿模式 硫酸盐还原菌 

分 类 号：P619.14[天文地球—矿床学]