九江网状红土中粘土矿物过渡相的矿物学特征及成因
首发时间:2012-04-11
摘要:为研究长江中下游网纹红土中粘土矿物过渡相的矿物学特征及成因,采用X射线粉晶衍射(XRD)、傅里叶红外吸收光谱(FTIR)、以及高分辨透射电子显微分析(HRTEM)等现代测试技术方法,对江西九江红土剖面网纹红土中粘土矿物过渡相开展系统、深入的研究。X射线粉晶衍射及红外吸收光谱分析结果表明,九江剖面网纹红土中粘土矿物组成主要有伊利石和高岭石,少量蒙脱石和伊利石/蒙脱石及微量高岭石/蒙脱石混层矿物过渡相。在高分辨透射电子显微镜下,可观察到蒙脱石晶层向高岭石晶层转化的现象。伊利石/蒙脱石过渡相是伊利石向蒙脱石转化的过渡产物,而高岭石/蒙脱石过渡相则为蒙脱石向高岭石转化的过渡产物,网纹红土中这两种过渡相的出现说明了粘土矿物风化演化的过程,即:伊利石→伊利石/蒙脱石混层矿物→蒙脱石→高岭石/蒙脱石混层矿物→高岭石的演化,同时表明网纹红土形成于风化作用增强的温暖潮湿气候环境。
关键词: 网状红土 九江 早中更新世 粘土矿物过渡相 矿物学特征及成因
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Mineralogy and Genesis of Mixed-layer Clay Minerals in the Jiujiang Net-like laterite
Abstract:Mineralogy and genesis were investigated using X-Ray diffraction (XRD), Fourier infrared absorption spectroscopy (FTIR) and high resolution transmission electron microscopy (HRTEM) to understand the mineralogy and its genesis significance of mixed-layer clay minerals in Jiujiang laterite section. XRD and FTIR results show that the net-like laterite sediments are composed of illite, kaolinite, minor smectite and mixed-layer illite-smectite and minor mixed-layer kaolinite-smectite. HRTEM observation indicates that some smectite layers have transformed into kaolinite layers in net-like laterite. Mixed-layer illite-smectite is a transition phase of illite transforming into smectite, and mixed-layer kaolinite-smectite is a transitional product relative to kaolinite and smectite. The occurrence of two mixed-layer clay species suggests that the weathering sequence of clay minerals in net-like laterite traversed from illite to mixed-layer illite-smectite to smectite to mixed-layer kaolinite-smectite to kaolinite, which indicates that net-like laterite formed under a warm and humid climate with strengthening of weathering.
Keywords: Net-like laterite Jiujiang Early-mid Pleistocene Mixed-layer clay minerals Mineralogy and genesis
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