贵阳花溪燕楼剖面下三叠统大冶组地球化学特征与沉积环境分析*
Analysis of geochemistry features and sedimentary environment of the Lower Triassic Daye Formation in Yanlou section of Huaxi, Guiyang

贵阳花溪燕楼剖面下三叠统大冶组微量元素及稀土元素地球化学特征分析表明: U、V、Mo的含量及U/Th、V/Th、Mo/Th的比值,大于澳大利亚后太古代页岩(PAAS)的含量和比值。V/(V+Ni)、V/Cr、Ni/Co、V/Sc以及Mo_EF/U_EF等氧化还原敏感元素的参数特征及其含量显示,大冶组一段处于缺氧-贫氧环境,大冶组二段处于贫氧—氧化环境。研究区经PAAS标准化的稀土配分模式比较平坦,根据大冶组的δCe及Ce/La的参数特征,认为早三叠世整体处于海洋环境;大冶组底部呈现明显Eu正异常,表明受火山热液作用影响明显;可见早三叠世贫氧环境可能与火山作用频发有关。大冶组上部表现微弱Eu正异常,说明火山作用的影响减弱。基于双壳类化石的结构及生活方式分析认为Claraia营外栖足丝固着的生活方式,属于贫氧生物,壳类化石结构只表现棱柱状外壳层和复杂交错纹层状珍珠层,其生活环境应为水动力条件较弱的浅水区。
In this paper,geochemical characteristics of trace elements and rare earth elements of the Daye Formation in Yanlou-Huaxi, Guiyang were analyzed. The enrichment of redox sensitive elements(U,V,Mo)and ratios of U/Th,V/Th,Mo/Th are higher than those of PAAS. Some geochemical parameters of redox sensitive elements such as V/(V+Ni),V/Cr,Ni/Co,V/Sc and Mo^EF/U^EF ratios indicate that the deposit of the Member 1 of the Daye Formation was formed in hypoxia-lean oxygen environment,while the Member 2 of the Daye Formation in the lean oxygen-oxidizing environment. Rare earth element partition type is relatively flat. Hypoxia-lean oxygen environment was instructed by the characteristic parameters of rare earth elements(δCe and Ce/La)in the Early Triassic. The δEu positive anomalies in the Member 1 of the Daye Formation suggest that affected by volcanic hydrothermal process significantly,and weaker influences of volcanism showed slightly positive anomaly in the Member 2 of the Daye Formation. The lean oxygen environment of the Early Triassic is interpreted to be associated with frequent volcanism. Based on analysis of the structure and way of life of bivalves,byssus sessile lifestyle was behaved by Claraia that belongs to lean-oxygen biology. Biological structures of bivalve fossils is divided into the prismatic shell and the complex interleaved laminated pearl layer,which is associated with hypoxia of the ocean environment.The the shallow water with weak hydrodynamic conditions should be the claraia major living environment