黔西南雄武地区铀矿化与有机流体的成因联系  

Genetic Relationship Between Uranium Mineralization and Organic Fluids in the Xiongwu Area,Southwestern Guizhou

作　　者：邱林飞[1] 吴玉[1] 李子颖[1] 蒋宏 徐伟 韩文文 解波 郭建[1] 孙祥[1] 黎丕林 邱锦鸿 QIU Linfei;WU Yu;LI Ziying;JIANG Hong;XU Wei;HAN Wenwen;XIE Bo;GUO Jian;SUN Xiang;LI Pilin;QIU Jinhong(CNNC Key Laboratory of Uranium Resource Exploration and Evaluation Technology,Beijing Research Institute of Uranium Geology,Beijing 100029,China;Research Institute No.280,China National Nuclear Corporation,Guanghan 618300,Sichuan,China;School of Geoscience,Yangtze University,Wuhan 430100,Hubei,China)

机构地区：[1]核工业北京地质研究院中核集团铀资源与评价技术重点实验室,北京100029 [2]核工业二八〇研究所,四川广汉618300 [3]长江大学地球科学学院,湖北武汉430100

出　　处：《大地构造与成矿学》2024年第2期352-367,共16页Geotectonica et Metallogenia

基　　金：国家自然科学重点基金项目(U2167210);中国核工业地质局铀矿地质项目(201922、202143-6、202111);中核集团集中研发项目(2021-143);四川省科学技术厅成果转化示范项目(2021ZHZY0008)联合资助。

摘　　要：在黔西南地区,前人针对构造演化、油气流体、金矿床成矿流体和成矿模式等方面开展了大量的研究,但铀矿床研究方面还十分薄弱,尤其针对有机流体与铀成矿的关系还未开展研究。本次研究在野外地质调查基础上,对黔西南雄武地区大际山铀矿床及大梨树铀矿床中典型的矿石与蚀变围岩样品开展了显微岩相学、扫描电镜‒能谱分析、电子探针、流体包裹体、激光拉曼、稳定同位素等方面研究。宏观上,铀矿体的中心部位往往呈黑色,矿体两侧呈灰色、灰褐色,矿体中心向两侧颜色逐渐变浅。镜下研究发现,铀矿物、黄铁矿等金属矿物与黑色的有机质紧密共生。激光拉曼分析指示,这些有机质经历的最高温度为185~237℃,等效镜质体反射率指示有机质处于高成熟‒过成熟阶段,具有焦沥青的特征。铀矿体外围蚀变带中饱含显示强浅蓝色荧光的轻质油,指示富烃类有机流体与成矿物质可能为同一来源,均为含铀有机流体演化而成。铀矿石中黑色有机质的^(13)C值与其赋矿碳酸盐岩表现出明显的异源特征,且与当地古油藏的C同位素具有相似性,指示焦沥青可能来源于深部侵位的古油藏。铀矿物微区年代学与有机质Re-Os年代学的研究结果在误差范围内基本一致,均为喜山期,进一步指示铀矿物和有机质是同时代地质作用的产物。黔西南雄武地区铀的沉淀应该与油气裂解‒分异作用相关,其铀矿成矿作用既不是以往认为的沉积成岩型,也不是沉积成岩叠加淋积‒热液改造型,而应该是构造作用下、深部渗出含铀富有机质成矿流体形成的渗出碳酸盐岩型铀矿床。成矿过程中,铀钼等多金属可能以微纳米超显微结构的形式随有机流体共同迁移,在温压条件变化的情况下,含矿的富烃类有机流体发生裂解‒分异作用,致使铀、黄铁矿等金属物质与重质组分(沥青)残留于破碎带�Many studies have been conducted on hydrocarbon fluids,tectonic evolution,gold ore-forming fluids,and ore-forming models of gold deposits in Southwestern Guizhou.However,research on uranium deposits is rare,and no study on the relationship between organic fluids and uranium mineralization has yet been reported.After field geological survey,the typical U-ores and altered rocks from the Dajishan and Dalishu uranium deposit in the Xiongwu area of southwestern Guizhou were studied by micropetrography,scanning electron microscopy(SEM),electron microprobes,fluid inclusions,laser Raman,stable isotopes,etc.Uranium minerals and pyrite coexist with the“Black Brown”organic matter under microscope and SEM.The organic matter has typical characteristics of bitumen,and the equivalent vitrinite reflectance values of the bitumen indicate that the organic matter is in the high-mature to over-mature stage with a maximum mature temperature of 185℃to 237℃.The light oil in the alteration zone on the periphery of the uranium ore-body shows strong light blue fluorescence,indicating that the hydrocarbon fluids and uranium minerals may come from the same U-bearing and hydrocarbon rich fluids.The^(13)C values of organic matter in uranium ores and U-bearing carbonate rocks show obvious disparities.The^(13)C values of organic matter are similar to those of the local paleo-reservoir and different from those of the U-bearing carbonate rocks,indicating that the bitumen may originate from the deep intruded paleo-reservoir.The precipitation of uranium is related to the cracking differentiation of the hydrocarbon-bearing organic fluids.The geochronological ages of pitchblende by micro U-Pb method and organic matter by Re-Os method are consistent within the error ranges,indicating that the uranium mineral and organic matter were formed by contemporaneous geological processes in the Himalayan period.The uranium mineralization in the Xiongwu area of Southwestern Guizhou is neither the sedimentary diagenesis type nor the sedimentary diagenesis

关 键 词：烃类流体 裂解‒分异作用 大际山铀矿床 雄武地区 黔西南 

分 类 号：P611[天文地球—矿床学]