玛湖凹陷风城组黏土矿物组成特征及其成因

Clay Mineral Compositions and Its Genesis in Lower Permian Fengcheng Formation of Mahu Sag, Junggar Basin

为明确准噶尔盆地玛湖凹陷下二叠统风城组烃源岩中黏土矿物的特征及其成因,利用X射线衍射和扫描电镜测试,分析了研究区风城组碱湖相烃源岩中黏土矿物组成。结果表明,风城组碱湖相烃源岩黏土矿物具有蒙皂石和伊蒙混层含量高及伊利石含量较低的特点,呈现蒙皂石伊利石化缓慢的现象;结合风城组的沉积背景,蒙皂石异常转化主要受物源区火山岩、气候和成岩流体的共同影响。中基性火山岩和干湿交替的气候,促进了蒙皂石的形成;而以CO_(3)^(2-)为主要阴离子的碱性水体,抑制了蒙皂石的伊利石化。

In this study,X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to analyze the composition characteristics and genesis of clay minerals in the source rocks of the Lower Permian Fengcheng formation of the alkaline lacustrine facies in the Mahu sag,Junggar basin.The results show that the smectite and illite/smectite mixed layer has a higher content,but the illite content is lower,showing slow illitization of smectite.Considering the depositional background of the Fengcheng formation,it is concluded that the abnormal transformation of smectite is mainly affected by the volcanic rock,climate and diagenetic fluids in the source area.The intermediate-basic volcanic rock and the dry/wet alternating climate promoted the formation of smectite,while the alkaline water with CO_(3)^(2-)as the primary anion inhibited the illitization of smectite.