鄂尔多斯盆地东南部延长组沉积物稀土元素地球化学特征及其应用

Rare earth elemental characteristics of Yanchang Formantion sediment in Southeast of Ordos Basin

目的确定鄂尔多斯盆地东南部上三叠统延长组沉积体系的分布格局与沉积环境。方法对该区及盆地周缘古陆的岩石样品进行稀土元素地球化学特征的对比研究。结果研究区沉积物的稀土元素分配模式呈"V"字型的"右倾斜"曲线;L/H平均值3.82,轻、重稀土分馏明显,轻稀土富集,重稀土亏损;铈(Ce)微正异常,铕(Eu)呈"谷"状,显示负异常,与盆地北东(阴山)及南部(北秦岭)岩石样品的稀土元素特征相对比具有亲源性。结论研究区沉积物来源于盆地北东及南部;研究区延长组沉积期属于缺氧的还原环境,是良好的生油环境。

Aim To date the distribution of the depositional systems and sedimentary environment of the Yanchang Formation in the southeast of Ordos Basin. Methods The comparison investigation of rare earth elemental （REE） characteristics in rock sample of the research area and around basin is carried out. Results The experimental results demonstrate that the REE distribution is a type which inclines to the right with ＂V＂ shaped. The average of L/H is 3.82. The LREE content of every sample is high and HLREE content is loss. 8Ce is a little positive anomaly and 8Eu is negative anomaly with ＂valley＂ shaped. The REE distribution type of sedimentary rock in the research area is similar to the parent rock in northeast and south of basin. Conclusion This paper supposes the provenance sedimentary rock of the research area is from the northeast and south of Ordos Basin. All of the Ce is greater than - 0. 10, therefore the sedimentary environment is reducing environment during sedimentary period of the Yanchang Formation.