准噶尔盆地南缘新生界粘土矿物分布及影响因素

根据粘土矿物的相对含量研究了准噶尔盆地南缘新生界砂岩粘土矿物类型、组合特征及纵、横向分布规律及其主要影响因素。划分出无序伊/蒙混层型、部分有序伊/蒙混层型、伊利石+伊/蒙混层型、蒙皂石型以及含坡缕石型等5类粘土矿物组合。按照伊/蒙混层相对含量的变化,粘土矿物纵向上演化呈正常转化型(伊/蒙混层相对含量降低)、反向转化型(伊/蒙混层相对含量增加)和“S”型(伊/蒙混层相对含量呈曲线变化)3种形式。平面上,伊/蒙混层和伊利石这两类主要粘土矿物从湖盆的边缘向中心分别呈现减少和增多的趋势,湖盆边缘相带以无序伊/蒙混层型、蒙皂石型和含坡缕石型为主,湖盆中心则为部分有序伊/蒙混层型和伊利石+伊/蒙混层型组合等类型。上述分布规律的控制因素主要有沉积环境、构造运动及层序发育等。

CONTROLS ON CLAY MINERAL DISTRIBUTION IN THE CENOZOIC SEDIMENTS OF THE SOUTHERN JUNGGAR BASIN, NW CHINA

Clay mineral distribution and its controls in the Cenozoic sedimentary rocks in the southern Junggar Basin were discussed in this paper. The clay components of the sandstone samples, based mainly on X-ray diffraction (XRD) determinations, carried out in <2 m fraction. The results showed that the clay fraction composition was dominated by illite/smectite mixed layers and illite, although smectite, palygorskite, kaolinite and chlorite were abundant locally. The clay mineral assemblages could be divided into 5 types. According to the content of I/S, three types for modes of the clay minerals' transformation were recognizied, namely, the normal, abnormal and cycle types. The obvious controlling factors of clay mineral distribution included sedimentary environments, tectonic movements and sequence developings. Tectonic movement controlled the sharp breaks of clay mineral distribution, such as the difference between the Cenozoic and Cretaceous, between the Anjihaihe Formation and the Shawan Formation. From the marginal facies to the centeral facies of the basin, the relative content of illite increased obviously, and the relative content of illite/smectite mixed layers had a decreasing tendency.