黔北牛蹄塘组的地球化学特征及形成环境

Geochemical Characteristics and Formation Environment of the Niutitang Formation in the North Guizhou

贵州北部早寒武世的黑色岩系-牛蹄塘组。主要为黑色页岩,含浮游生物,其中产钼、钒等矿床。其具有独特的元素地球化学特征:K、Ti元素在黑色页岩中的含量高于底部硅质岩,而P元素的含量却相反,硅质岩中的含量显著高于其上覆的黑色页岩;岩孔和菜园两地的共同特点是V、Ba、U的含量明显偏高,富集系数在3以上,显著的差别是Ta元素,其在岩孔是亏损的,而在菜园却明显富集;西部岩孔的稀土总量高于东部菜园,稀土配分曲线形态近于水平或略向左倾,具弱的负Eu异常或不显异常。硅质岩较页岩的负Ce异常程度高。地层特征、元素地球化学特征及特征元素和比值,所反映的是下寒武统牛蹄塘组形成于缺氧的还原环境。

Black rock series of the lower Cambrian Niutitang Formation in the north Guizhou as part of deoxidized event in South China is a suit of sediments of transgressive system domain with low ratio deposition, mainly consist of black shale with developed lamination Special geochemical characteristics of the elements that in which produce molybdenum and vanadium deposits. potassium and titanic element contents in black shale are higher than silicalite at base, but phosphor element is contrary in content, which in silicalite is significantly higher than overlying black shale; the common properties at Yankong and Caiyuan two sites show apparently high vanadium, barium and uranium contents, rich coefficient is above 3, distinguished variety is tantalum element loss at Yankong but apparent concentration at Caiyuan; totally, rare earth in western Yankong is higher than in eastern Caiyuan, rare earth distribution pattern is close to horizon or lightly dipping left and take on weak Eu anomaly or no anomaly. Silicalite is higher in negative cerium than shale. Stratigraphic characteristics, elementary geochemical feature and ratio indicate that the Niutitang Formation of lower Cambrian Epoch formed in the deoxidized surroundings lack of oxidation.