黔东前寒武纪-寒武纪转换时期微量元素地球化学特征研究  

Trace Element Geochemical Characteristics from the Ediacaran Cambrian Transition Interval in Eastern Guizhou,South China

作　　者：杨兴莲[1] 朱茂炎[2] 赵元龙[1] 张俊明[2] 郭庆军[3] 李丙霞[1] 

机构地区：[1]贵州大学资源与环境工程学院,贵阳550003 [2]中国科学院南京地质古生物研究所现代古生物学和地层学国家重点实验室,南京210008 [3]中国科学院地球化学研究所环境地球化学国家重点实验室,贵阳550002

出　　处：《地质学报》2007年第10期1391-1397,共7页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号40162002);黔科合J字[2007]2151号项目;国家"973"项目(编号2006CB806401);中国科学院知识创新工程重要方向项目(编号KZCX3-SW-141);贵州大学博士启动基金项目资助成果

摘　　要：对黔东丹寨南皋剖面和三都渣拉沟剖面前寒武纪-寒武纪转换时期地层进行了系统的微量元素地球化学研究,结果表明:丹寨南皋剖面的Ba、Pb、Ni、Cu、Zn、Li、V、U等过渡元素和亲硫元素在多金属矿层和牛蹄塘组下部的黑色页岩中明显富集;三都剖面在相同层位也明显富集Cu、Pb、Rb、Ti、Ni、V、Th、Li、Cr、Zr、Sc等微量元素。南皋剖面的δU值和V/(Ni+V)值表明老堡组硅质岩为正常海水的弱氧化环境下沉积物,而牛蹄塘组黑色页岩表现出缺氧环境的特征。三都渣拉沟剖面的δU值和V/(Ni+V)值表明该剖面的还原条件比丹寨南皋剖面强,暗示着水体也较它深,为缺氧环境,其间在老堡组硅质岩中有两个短暂的充氧阶段,进入渣拉沟组缺氧环境较稳定。除丹寨老堡组硅质岩和三都渣拉沟组中上部钙质泥岩U/Th值小于1,表现出水成沉积岩的地球化学特征外,本次研究的两条剖面的其他黑色岩系的U/Th值都大于1,表现出明显的热水沉积岩的地球化学特征。从我们的研究剖面也可看出下寒武统牛蹄塘组底部的Ni-Mo矿多金属的Ni、V等金属的含量是上地壳的9～10倍之高,U高达近百倍,可作地层对比标志层,即梅树村阶的顶界标志。Samples of black rock series collected from the Ediacaran-Cambrian transition interval in eastern Guizhou, South China, were analyzed for trace elements. There is a conspicuous accumulation of Ba, Pb, Ni, Cu, Zn, Li, V, U transitional elements and chalcophile elements in the polymetallic ore layer in the Nangao section, where, except for Sr,Li,and Cr, concentrations of all other elements are extremely high compared with those of the average shales. The elements such as Cu, Pb, Rb, Ti, Ni, V, Th, Li, Cr, Zr, Sc are accumulated at an equivalent level in the Sandu section. The silicastone in the Laobao Formation in the Nangao section formed in a slightly oxidized environment, as indicated by the fact that the δU and V/（Ni＋V）values lie below the critical palaeoredox level. However, the δU and V/（Ni＋V）values indicate an anoxic environment for the black shale of the Niutitang Formation. δU values in the Zhalagou section of Sandu range from 1.75 to 2, with an average value of 1.92, suggesting more strongly reducing conditions and a deeper water environment for this section than for the Nangao section at Danzhai. V/（Ni＋V） values of silicastone in the Laobao Formation and the basal part of the Zhalagou Formation range from 0.8-0.99 （average 0.95）, which is higher than the critical value of 0.83, suggesting anoxic conditions. However, two brief oxic stages have been recorded in the Laobao Formation. The V/（Ni＋V）values of the upper part of the Zhalagou Formation range from 0.59-0.94 （average 0.71）, indicating oxic conditions during these interval. All U/Th values of silicastone of the Laobao Formation in the Nangao section of Danzhai are smaller than 1, showing the geochemical feature of aqueous sediments. However, U/Th values of carbonaceous shale are larger than 1, demonstrating hydrothermal activities. The U/Th values of silicastone of the Laobao Formation and the black shale of the lower part of the Zhalagou Formation in the Zhalagou section of Sandu, are larger than 1 and vary from 6.

关 键 词：黑色岩系 前寒武纪—寒武纪转换时期 微量元素 黔东 

分 类 号：P595[天文地球—地球化学]