Kaolinite-smectite mixed-layer clays in the Jiujiang red soils and their climate significance
Kaolinite-smectite mixed-layer clays in the Jiujiang red soils and their climate significance
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九江红壤高岭石-蒙皂石混层粘土及其气候意义
DOI：
10.1016/j.geoderma.2011.12.006
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发表时间：
2012-03-01
期刊：
影响因子：
6.1
通讯作者：
Wang, Chaowen
中科院分区：
文献类型：
--
作者：
Hong, Hanlie;Churchman, G. Jock;Wang, Chaowen
采用X射线衍射（XRD）、阳离子交换量（CEC）测定和高分辨透射电镜（HRTEM）研究了九江红壤（山顶和坡地）的粘粒矿物学特征。X射线衍射结果表明，土壤中含有高岭石、伊利石、蛭石以及粘土矿物I/S和K/S混合层。在粘土的XRD图谱中，高岭石（001）峰上的低角度肩部分离，在乙醇酸化时移动到类似于8埃，表明土壤中存在混合层K/S粘土。高岭石含量的间层高岭石，蒙脱石估计是类似于95%的样品的中下部土壤剖面和类似于60%的上部，分别。甲酰胺处理后，XRD图谱中10-14 A的宽反射消失，并出现18.7埃的峰。10埃峰在加热到400 ℃时变得更加强烈，表明10-14埃峰是可膨胀的并且容易收缩，因此源自混合层伊利石-蒙皂石（VS）粘土。加热至550 ℃后，7埃峰消失，而10埃峰变得更强，并显示出低角度尾部，表明层间蒙脱石组分是羟基层间的。九江粘粒的CEC值较高（22.2-27.3 cmol/kg），说明土壤中存在蒙皂石。HRTEM分析显示样品中粘土颗粒的不同晶格条纹：绝大多数层间距在10-20埃范围内，少数类似于7和类似于25埃。具有类似于7埃条纹的颗粒显示两个7埃高岭石层合并成一个12埃蒙皂石层的横向过渡。这可以解释为蒙脱石层部分插入高岭石中。K/S层的堆积序列不存在长程有序性，层间互层具有随机性。上部剖面均匀土层中蛭石和伊利石含量较高，I/S和K/S含量较低;中下剖面网状土层中高岭石、I/S和K/S含量较高，蛭石含量较低。K/S粘土的出现证实了九江红土是同沉积成土作用的产物，成土期气候由温暖、季节性干燥向温暖、湿润的转变。(C)2011爱思唯尔有限公司版权所有。
Clay mineralogy of the Jiujiang soils, classified as red earth (on summit and slope), were investigated using X-ray diffraction (XRD), cation exchange capacity (CEC) determination, and high-resolution transmission electron microscopy (HRTEM). The XRD results show that the soils included kaolinite, illite, vermiculite, and mixed-layer I/S and K/S as clay minerals. In XRD patterns of clay separates the low-angle shoulder on the kaolinite (001) peak shifted to similar to 8 angstrom on glycolation, indicating the presence of mixed-layer K/S clays in the soils. Kaolinite content in the interstratified kaolinite-smectites was estimated to be similar to 95% for samples of the middle to lower soil profile and similar to 60% for that of the upper portion, respectively. A broad reflection for 10-14 A disappeared and an 18.7 angstrom peak occurred in the XRD patterns after formamide treatment. The 10 angstrom peak became much more intense on heating to 400 degrees C, indicating that the 10-14 angstrom peak was expandable and easily contractible and thus originated from mixed-layer illite-smectite (VS) clays. After heating to 550 degrees C, the 7 angstrom peak disappeared while the 10 angstrom peak became more intense and showed a low-angle tail, indicating the interstratified smectite component was hydroxy interlayered. The higher CEC values of the Jiujiang clay separates (22.2-27.3 cmol/kg) also pointed to the occurrence of smectite in the soils. HRTEM analysis showed different lattice fringes for clay particles in the samples: a great majority of layer spacings were in the range 10-20 angstrom, with a minority of similar to 7 and similar to 25 angstrom. Particles with similar to 7 angstrom fringes showed a lateral transition of two 7 angstrom kaolinite layers merging into one 12 angstrom smectite layer. This can be interpreted as the partial intercalation of one smectite layer in kaolinite. There was no long-range order in the stacking sequence of K/S layers, and the interstratification was of a random nature. In the uniform soil horizon of the upper profile, there was more vermiculite and illite, but less I/S and K/S, while in the net-like soil horizon of the middle-lower profile there was more kaolinite, I/S, and K/S, with only a trace of vermiculite. The occurrence of K/S clays confirmed that the Jiujiang red earth was derived from syndepositional pedogenesis and the climates changed from warm and seasonally dry to warm and more humid conditions during the soil-forming period. (C) 2011 Elsevier B.V. All rights reserved.