我国发现的伊利石-蒙皂石规则混层(ISⅡ型)的研究

ORDERED 3∶1 MIXED-LAYER ILLITE-SMECTITE FROM SANGZHI COUNTY, HUNAN PROVINCE: A XRD, DTA AND INFRARED ABSORPTION STUDY

本文对湖南桑植地区三叠系/二叠系界线粘土进行了X射线粉末衍射、差热,红外等分析。结果表明:这些粘土主要为伊利石-蒙皂石规则混层,属ISII型。据X射线粉末衍射测定了混层的组成、有序化程度和内部结构。文中还讨论了伊利石-蒙皂石的差热分析和红外吸收光谱结果。

X-ray powder diffraction (XRD) analysis, differential thermal analysis(DTA) and infrared absorption analysis have been done of the clays near the Permian/ Triassic boundary at Sangzhi County, Hunan Province. The results show that the clays are mainly represented by ordered mixed-layer illite-smectite, belonging to the ISII type i. e., three illite layers intercalated with a smectite layer. The composition, degree of ordering and crystal structure of the mixed layer have been determined on the basis of the X-ray powder diffraction data. The smectite content ranges from 8.65 to 20.05％. The differential thermal analysis and infrared absorption spectrum of the illite-smectite are also discussed. The differential thermal curves of the ISII type are different from those of illite or smectite, or the mechanical mixture of the two. Their DTA data show that there is a not very sharp endothermal valley between 500℃ and 600℃ and that the endothermal valley caused by the dehydroxylation reaction is not pronounced either and is asymmetrical, being steeper at the high-temperature side. The infrared absorption profiles are similar to those of the mixture ot illite and smectite, i. e. showing the features of both illite and smectite.