湘西北北部地区黑色岩系铀多金属成矿环境研究  

Study on the Metallogenic Environment of Uraniferous-Polymetallic Black Rock Series in the Northern Part of Northwestern Hunan

作　　者：王健[1] 王文全[1] 杨帆 王振云[1] 李治兴[1] WANG Jian;WANG Wenquan;YANG Fan;WANG Zhenyun;LI Zhixing(CNNC Key Laboratory of Uranium Resources Exploration and Evaluation Technology,Beijing Research Institute of Uranium Geology,Beijing 100029,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

出　　处：《铀矿地质》2024年第2期250-259,共10页Uranium Geology

基　　金：中国核工业地质局地勘费项目“全国低品位大矿量易开发铀资源远景评价”(编号:地D202346-4)资助。

摘　　要：湘西北北部地区主要包括晓坪坳陷、慈利断陷盆地等区域,是湘西北成矿带上有用元素种类和矿物类型最为丰富的地区。文章通过对湘西北北部地区开展系统的地质调查评价和取样分析,研究表明区内铀多金属矿化形成环境主要为深水环境向浅水环境的过渡区域,海洋中的边缘浅海环境具有更佳的铀成矿条件。微量元素特征参数表明,研究区从震旦纪到寒武纪海洋环境是由相对富氧向缺氧环境的转变,寒武纪在海水缺氧的大背景下,发生过一到两次短时间小规模的充氧事件。对U、Th、稀土等元素的研究表明湘西北北部地区从震旦纪晚期到寒武纪早期U的富集速率明显加快,而后U富集速率逐渐降低,指示研究区在寒武纪早期海洋中的热水作用最为强烈,而后逐步减弱,且成矿作用过程中有深部物质的参与,矿化越好,受深部热水影响越强。对Ce的研究结果表明,研究区震旦纪到寒武纪在大的海退背景下存在3个较为明显的海平面“升-降”转化界面,可以将这段地质历史划分为4个海平面升降变化阶段,在海平面升高阶段,沉积物中Ce异常减小,海洋中还原性增强,有利于有机质和铀多金属元素的富集。研究区矿物学方面的发现与通过地球化学方法得出的结论具有较好的一致性,晶质铀矿、铀石等矿物的晶型、共生关系和所包含的Y、Se等元素指示寒武纪时期研究区黑色岩系成矿处于较高温度、强还原的条件下,且海底热流喷涌过程中携带有深源物质参与成矿。The northern part of northwestern Hunan mainly includes Xiaoping depression and Ciligraben basin,which is the most abundant area of useful elements and minerals in the whole metallogenic belt.Based on the systematic geological evaluation and sampling analysis in the northern part of northwestern Hunan,the results show that the environment of uranium polymetallic mineralization in the study area was mainly a transition from deep-water to shallow-water environment,and that the marginal shallow-sea environment in the ocean is better for uranium mineralization.The characteristic parameters of trace elements indicated that the marine environment in the study area changed from relatively oxygen-rich to anoxic environment from Sinian to Cambrian period,in the context of seawater hypoxia,there were one or two short,small-scale oxygenation events in the Cambrian period.The study of elements such as U,Th,and rare earths have shown that the enrichment of U in the northern part of northwestern Hunan accelerated significantly from Late Sinian period to Early Cambrian period,and then gradually decreased,indicating that the hydrothermal process in the ocean in the study area was the strongest in Early Cambrian period,and then gradually weakened,and deep materials involvement the process of mineralization,the better mineralization was the result of the stronger influence of hydrothermal process.The study results of Ce showed that there were three obvious sea level"rise-fall"transition in the study area from Sinian to Cambrian in the context of the large sea regression,and this geological history can be divided into four stages of sea level rise and fall changes.Anomalous reduction of Ce in sediments and the reducibility in the ocean increased during the sea level rise phase favor enrichment of organic matter and uranium polymetallic.The findings of mineralogy in the study area are in good agreement with the conclusions obtained by geochemical methods.The crystal type,symbiosis and Y,Se and other elements of uraninite ore and cof

关 键 词：铀多金属 黑色岩系 成矿环境 湘西北 

分 类 号：P619.14[天文地球—矿床学]