黑色岩系稀土元素地球化学特征及地质意义  

Rare Earth Elements Geochemical Characteristics and Geological Significance of Black Rock Series

作　　者：卢正浩 谢宏[1,2] 白洋 王孟斋 张兰 LU Zheng-hao;XIE Hong;BAI Yang;WANG Meng-zhai;ZHANG Lan(School of Resources and Environmental Engineering,Guizhou University,Guiyang 550000,China;Karst Laboratory of Guizhou University,Guiyang 550000,China)

机构地区：[1]贵州大学资源与环境工程学院,贵州贵阳550000 [2]贵州大学喀斯特实验室,贵州贵阳550000

出　　处：《稀土》2024年第1期63-75,共13页Chinese Rare Earths

基　　金：国家自然科学基金项目(42092009,41662008);贵州省科学技术基金项目(黔科合基[2020]1Y128);贵州大学引进人才科研项目(贵大人基合字[2015]37号)。

摘　　要：贵州铜仁坝黄一带牛蹄塘组底部黑色岩系中蕴藏具有工业价值的富铀磷质岩。为了探讨赋矿岩系源区性质及古海洋的氧化还原环境,本文进行了岩石稀土地球化学研究。结果显示,稀土元素地球化学数据未受到成岩作用和分析方法的明显影响,能够利用该参数进行成岩成矿地质意义的探讨。Ceanom值揭示从陡山沱组过渡到牛蹄塘组时,氧化还原环境总体从还原环境向不断波动的次氧化环境转变,直到牛蹄塘组富含多金属页岩沉积时,环境才逐渐向弱还原转变。Ce异常值表明在新远古代末期到早寒武世水体深度处于动态变化中,并经历过一次明显的海侵-海退过程。LREE/HREE比值、稀土配分模式、Y/Ho与Y图解、Er/Nd比值、(La/Sm)N值等,均说明研究区除磷质岩海水化学沉积特征明显外,(含)硅质白云岩、(灰质)白云岩、黑色页岩、富含多金属页岩、含铁泥质硅质岩以及黏土质磷质岩均受到了不同程度陆源碎屑物质的污染。此外,“帽型”的分配曲线、Ce/La比值、较高的Eu异常以及La/Yb-REE图解指示富含多金属页岩和(黏土质)磷质岩还存在热液的输入,表明早寒武世研究区磷和多金属元素富集时热水喷流作用较强烈而活跃。There is uranium-rich phosphorite with industrial value in the black rock series at the bottom of Niutitang Formation in Bahuang area of Tongren,Guizhou province.In order to explore the nature of source areas of ore-host rock series and the redox environment of ancient oceans,rare earth geochemistry of rocks was studied in this paper.The results showed that the geochemical data of rare earth element(REE)were not obviously affected by diagenesis and analytical methods,which could be used to explore the geological significance of diagenesis and mineralization.Ce_(anom)value revealed that the redox environment changed from reducing environment to fluctuating secondary oxidation environment during the transition from Doushantuo Formation to Niutitang Formation,and the environment gradually changed to weak reduction until Niutitang Formation was rich in polymetallic shale deposits.Abnormal Ce value indicated that the depth of the water body was in a dynamic change from the late Neoproterozoic to the early Cambrian and experienced an obvious transgression-regression process.LREE/HREE ratio,REE partitioning model,Y/Ho and Y diagrams,Er/Nd ratio,(La/Sm)_N value,and others indicated that(bearing)siliceous dolomite,(calcareous)dolomite,black shale,polymetallic-rich shale,iron-bearing argillaceous siliceous rock,and clayey phosphorite were all polluted by terrigenous clastic materials to different degrees except for the obvious seawater chemical sedimentation characteristics of phosphorites in the study area.In addition,the"cap type"distribution curve,Ce/La ratio,highly abnormal Eu value,and La/Yb-REE diagram indicated that there were hydrothermal inputs in polymetallic shale and(clayey)phosphorite,which indicates that hydrothermal exhalation is strong and active when phosphorus and polymetallic elements are enriched in the early Cambrian study area.

关 键 词：稀土元素 富铀型磷矿 黑色岩系 

分 类 号：P595[天文地球—地球化学]