论文部分内容阅读
利用稀土元素和微量元素 ,分析鄂尔多斯盆地中部上三叠统延长组母岩类型和物源方向。研究表明盆地中部延长组砂岩和泥岩的稀土元素地球化学特征、REE分配模式及微量元素蜘蛛图解相同 ,表现为轻稀土富集 ,重稀土亏损 ,铕、铈元素亏损 ;REE分配模式均呈“右倾斜、LREE富集、HREE平坦”型 ;微量元素蜘蛛图解具“四峰三谷一平坦”型 ,曲线呈阶梯状分布 ;砂岩和泥岩的地球化学特征、REE分配模式及微量元素蜘蛛图解与盆地东北缘的太古代、元古代变质岩相一致 ,而与火成岩的重稀土富集、轻稀土亏损、“V”字型REE分配模式和“三峰两谷”型、曲线呈“W”字型分布的蜘蛛图解的特征有显著的差别。说明延长组母岩是盆地东北缘的太古代、元古代变质岩 ,主要物源方向为北东向。依据物源方向、沉积环境、砂岩岩石学特征、砂岩稀土元素和微量元素的特征 ,将鄂尔多斯盆地中部上三叠统延长组沉积划分为两大三角洲沉积体系 ,即北东向的安塞三角洲沉积体系、志靖三角洲沉积体系、安边三角洲沉积体系和北西向的盐定三角洲沉积体系。在三角洲沉积体系划分的基础上 ,详细阐述了不同三角洲沉积体系的岩石学特征、稀土元素和微量元素的特征及延长组长 6—长 2段沉积时期三角洲沉积体系的演化过程
Using rare earth elements and trace elements, the authors analyze the source rocks and types of the Yanchang Formation in the Upper Triassic of Ordos Basin. The REE distribution patterns and trace element spiders are the same, showing the light rare earth enrichment, heavy rare earth loss, depletion of europium and cerium, and the distribution pattern of REE shows “right Inclination, LREE enrichment, HREE flat ”type; trace element spider diagram with a“ four peaks and three valleys flat ”type, the curve was ladder-like distribution; geochemical characteristics of sandstone and mudstone, REE distribution patterns and trace elements spider diagram and basin northeast The Archean and Proterozoic metamorphic rocks are consistent with the REE distribution pattern of “V” REE and the pattern of “three peaks and two valleys” There are significant differences in the characteristics of spider diagrams. The results show that the Yanchang Formation parent rock is Archean and Proterozoic metamorphic rocks in the northeastern margin of the basin and the main source direction is NE direction. According to the provenance direction, sedimentary environment, petrological characteristics of sandstone, rare earth elements and trace elements in sandstone, the sedimentary facies of the Upper Triassic Yanchang Formation in the central Ordos Basin are divided into two major deltaic sedimentary systems, ie, the northeastern Ansai delta sediments System, the depositional system of the Zhijing delta, the depositional system of the An delta and the depositional system of the Yanding delta northwestward. Based on the division of sedimentary system in the delta, the petrological characteristics, characteristics of rare earth elements and trace elements in different deltaic sedimentary systems and the evolution process of deltaic sedimentary system during the sedimentary period of Member 2 and Member 2 are extended.