东濮凹陷沙河街组泥岩的稀土元素地球化学特征

REE GEOCHEMICAL CHARACTERISTICS OF MUDSTONES FROM EOGENE SHAHEJIE FORMATION IN DONGPU DEPRESSION

俞惠隆 张金亮 徐伦勋

Yu Huilong Zhang Jinliang Xu Lunxun

本文对东濮凹陷下第三系沙河街组的滨湖水下冲积扇、浅湖、盐湖-半深湖和深湖等四个湖泊亚相中形成的13个泥岩样品,进行了稀土元素组成和模式曲线特征的研究。研究资料表明:本区四个湖泊亚相泥岩的稀土元素组成很相似,均为右倾斜的 Ce 与 Eu 负异常型;稀土高峰元素都是Ce,次高峰元素为 La 或 Y。说明本区泥岩的稀土元素来源相同,且在沉积过程中表现出相似性和继承性。其中盐湖-半深湖相泥岩的稀土含量较其他三个湖泊亚相泥岩低,这是因为干旱蒸发湖盆环境生成的大量硫酸盐或卤化物矿物对稀土元素的富集具有抑制作用。

The total content of REE(ΣREE)from mudstones of the Eogene Shahejie Forma-tion in Dongpu Depression is relatively high,the average value is 215.34 ppm.Ce is thehighest of the REE group,ΣCe is richer than ΣY and ΣCe/ΣY is also high(2.73 on aver-age).These mudstones yield right declined W-shapped curves with negative Ce and Euanomalies,therefore,their REE distribution patterns are parallel to each other.In addi-tion,the REE parameters(Ce/Ce,Eu/Eu,Sm/Nd,ΣCe/ΣY,La/Sm and Ce/Yb) only vary with in a narrow range with small deviations.This indicates that theywere deposited in a lake basin environment.

10.11743/ogg19900206