黔北凤冈地区牛蹄塘组黑色岩系及方解石脉地化特征及环境意义

Localization characteristics and environmental significance of black rock system and calcite veins of Niutitang Formation in Fenggang Area, Northern Guizhou

利用电感耦合等离子体质谱仪,对黔北凤冈地区YF1井牛蹄塘组黑色岩系及方解石脉体的12件岩心样品,进行微量元素和稀土元素测试,分析牛蹄塘组微量元素和稀土元素特征,研究黑色岩系及方解石脉形成的氧化还原环境。结果表明:黑色岩系和方解石脉的微量元素分布特征形态相似,方解石脉中Sr元素较黑色岩系的富集;牛蹄塘组沉积过程中不仅存在海水沉积,还有热液流体的参与;微量元素指标及稀土元素Eu和Ce异常同步,指示牛蹄塘组沉积环境为缺氧—厌氧的还原环境;方解石脉的Eu和Ce异常指示形成环境为弱氧化性质。该结果揭示早寒武世牛蹄塘组黑色岩系的沉积环境特征,以及当时古海洋环境的化学条件及演化过程。

By means of inductively coupled plasma mass spectrometer,trace and rare earth elements were tested on 12 core samples of black rock series and calcite vein in YF1 well in Fenggang Area,Northern Guizhou Province.By analyzing the characteristics of trace elements and rare earth elements in Niutitang Formation,the oxidation-deoxidation environment of black rock series and calcite veins was studied.The results show that the distribution of trace elements in the black rock series and the calcite veins are similar,and Sr elements in the calcite veins are more abundant than that in the black rock series.During the deposition of Niutitang Formation,there was not only seawater deposition but also hydrothermal fluid participation.The abnormal synchronization of trace element indexes and rare earth elements Eu and Ce indicated that the sedimentary environment of Niutitang Formation was hypoxia-anaerobic reduction environment.Abnormal Eu and Ce of calcite veins indicate weak oxidation in the formation environment.The results reveal the sedimentary environment characteristics of the black rock series in the Early Cambrian Niutitang Formation,as well as the chemical conditions and evolution process of the paleo-marine environment at that time.