湘赣边界鹿井地区下寒武统斑点板岩是铀矿化重要围岩之一,为研究斑点板岩的地球化学特征、原岩形成构造环境以及对铀矿化的贡献,采集了钻孔中10个新鲜斑点板岩样品进行了镜下观察和主微量元素分析.研究表明,斑点板岩重结晶作用明显,岩石几乎由绢云母、绿泥石、石英等新生矿物组成,其原岩属泥质类岩石.与中国东部泥质岩和华南碳质页岩对比,斑点板岩的CaO、P2O5和烧失量较低,在变质过程中,原岩的有机质成分及多种微量元素、成矿元素已发生了变化或迁出.斑点板岩铀含量为8.12×10-6,而Th/U值(2.67)明显高于华南碳质页岩(0.15),斑点板岩铀元素在变质过程中已发生了活化迁移,成为鹿井地区铀源的可能性大大降低.斑点板岩的SiO2/Al2O3、Th/Sc值以及SiO2-(K2O/Na2O)和Th/Sc-Zr/Sc图解指示其原岩具有被动陆缘沉积物源区的特征,形成的构造环境较稳定;V/(Ni+V)值及Ce负异常指示原岩的沉积环境为还原容量较大的边缘海环境.
The spotted slate of the lower Cambrian in the Lujing area,in the border of Hunan and Jiangxi prov-ince,is an important wall rock for uranium mineralization.To study its geochemical characteristics,tectonic set-ting and the contribution to uranium mineralization,ten fresh samples of spotted slate are collected from the bore-hole for microscopic observation and major and trace elements analyses.The research shows that the spotted slate has obvious recrystallization,and the rock is almost composed of new minerals such as sericite,chlorite group,quartz and so on.Its original rock is argillaceous rock.Compared with the muddy rocks in eastern China and the carbonaceous shale in southern China,the spotted slate has lower content of CaO,P2O5,and loss on ignition.During the metamorphic process,the organic matter composition,various trace elements,and ore-forming ele-ments of the original rock have been changed or migrated out.Uranium content of the spotted slate is 8.12 × 10-6,while the Th/U value(2.67)is higher than that of the carbonaceous shale in southern China(0.15).The uranium element of the spotted slate has undergone activation and migration during the metamorphic process,thus greatly reduce the possibility of being a uranium source for uranium mineralization in the Lujing area.The SiO2/Al2O3,Th/Sc ratios,SiO2-(K2O/Na2O)and Th/Sc-Zr/Sc diagrams indicate that the original rocks possess the affinity of passive continental margin sediments,and formed in a relatively stable tectonic setting.The ratio of V/(Ni+V)and Ce negative anomalies indicate that the sedimentary environment of the original rock is a marginal sea environment with a large reduction capacity.