鄂尔多斯盆地中东部马家沟组白云岩地球化学特征研究

1.陕西延长石油(集团)有限责任公司研究院,陕西 西安 710075; 2.中煤科工集团西安研究院,陕西 西安 710077

鄂尔多斯盆地中东部; 稀土元素; 海源流体; 还原环境

Majiagou formation dolomite geochemistry characteristics in the central and eastern part of Ordos Basin
QIANG Juan1,CAO Hong-xia1,ZHANG Xian-xu2,

(1.Research Institute of Yanchang Petroleum Group Co.,Ltd.,Xi'an 710075,China; 2.Xi'an Research Institute of China Coal Technology and Engineering Group Corp,Xi'an 710077,China)

central and eastern part of Ordos Basin; rare earth element; marine fluid; reducing environment

DOI: 10.13800/j.cnki.xakjdxxb.2015.0312

备注

稀土元素分析是一种判别白云岩化流体来源,分析白云岩的形成环境的重要手段。鄂尔多斯盆地中东部白云岩以明显高的Fe含量和低的Na,Sr和Mn含量为特征,白云岩化流体主要为海水或与海水有关,未受或很少受到大气淡水的影响。稀土元素配分图显示所有白云岩样品的曲线形态类似,都呈轻稀土富集和重稀土亏损的右倾模式,且具有Eu负异常和Ce的负异常,δEu平均值为0.45,Ce的平均值为0.35,表明白云岩形成于相对偏碱性还原环境,又受到后期构造热液流体的影响和改造; 三类白云岩的的模式都与泥微晶灰岩相近,也说明白云化流体与海水或海源流体相关; 综合鄂尔多斯盆地中东部马家沟组白云岩地球化学特征可以判断出区内白云岩的形成环境是相对还原的碱性环境。

Rare earth elements as an important mean is used to study the flow dolomitization origin and formation environment analysis of dolomite.The dolomite is characterized by significantly higher Fe content and lower Na,Sr and Mn contents in the central and eastern Erdos Basin.Dolomitization fluid is mainly concerned with sea water or seawater,without or little affected by atmospheric water.The REE distribution map shows all dolomite samples with similar curve shape,are light REE enrichment and heavy REE deficit right mode with a negative anomaly of Eu and Ce,δEu average value is 0.45,the average value of Ce is 0.35,the dolomite formed in relatively alkaline environment,and affected by the late tectonic hydrothermal fluid and transformation; three types of dolomite patterns are similar to the micritic limestons,also shows that dolomitization fluid associated with seawater or marine fluid.Synthesis Formation dolomite geochemistry of Ordos Basin in the central and eastern Majiagou can determine dolomite formed in relatively reduced alkaline environment.