Microstructures in landslides in northwest China – Implications for creeping displacements?
Microstructures in landslides in northwest China – Implications for creeping displacements?
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DOI：
10.1016/j.jsg.2017.11.009
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发表时间：
2018
影响因子：
3.1
通讯作者：
M. Schäbitz;C. Janssen;H. Wenk;R. Wirth;B. Schuck;H. Wetzel;Xing-min Meng;G. Dresen
中科院分区：
文献类型：
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作者：
M. Schäbitz;C. Janssen;H. Wenk;R. Wirth;B. Schuck;H. Wetzel;Xing-min Meng;G. Dresen
用光学显微镜、透射电子显微镜、X射线衍射仪和同步辐射X射线衍射仪对甘肃省南部(中国)三个滑坡样品的显微结构、矿物成分和结构进行了研究。常见的片状硅酸盐有绿泥石、伊利石、白云母、高岭石、叶蜡石和地开石。其他矿物有石英、方解石、白云石和钠长石。在其中一个样品中，通过TEM-EDX分析和TEM大角度环形暗场图像检测到了石墨和无定形碳。索尔头滑坡体和斜流坡滑坡体中存在摩擦系数极低的石墨和叶蜡石，对降低滑坡体的摩擦强度具有特别重要的意义。认为该滑坡经历了与断裂带相似的变形过程。较低的摩擦系数提供了强有力的证据，表明缓慢移动的滑坡是由弱矿物的存在控制的。此外，透射电子显微镜观察表明，粘土滑移带材料中的颗粒尺寸减小主要是由机械磨损造成的。方解石和石英的粒度减小是压力溶解和碎裂作用共同作用的结果。因此，除了滑坡成分外，超细粒滑带物质的存在也可能有助于滑坡的弱化过程。滑带样品的透射电子显微镜图像显示了局部排列的粘土颗粒，以及广泛分布在整个基质中的扭曲和褶皱的片状硅酸盐。新形成的小粘土颗粒具有随机的方向。同步辐射X-射线衍射仪测定表明，苏头滑带和段河-巴兰滑带局部剪切带中硅酸盐成分的择优取向程度较强。这项工作是首次报道在滑坡中观察到定向良好的粘土组构。
Microstructures, mineralogical composition and texture of selected landslide samples from three landslides in the southern part of the Gansu Province (China) were examined with optical microscopy, transmission electron microscopy (TEM), x-ray diffraction (XRD) and synchrotron x-ray diffraction measurements. Common sheet silicates are chlorite, illite, muscovite, kaolinite, pyrophyllite and dickite. Other minerals are quartz, calcite, dolomite and albite. In one sample, graphite and amorphous carbon were detected by TEM-EDX analyses and TEM high-angle annular dark-field images. The occurrence of graphite and pyrophyllite with very low friction coefficients in the gouge material of theSuoertouandXieliupolandslides is particularly significant for reducing the frictional strength of the landslides. It is proposed that the landslides underwent comparable deformation processes as fault zones. The low friction coefficients provide strong evidence that slow-moving landsliding is controlled by the presence of weak minerals. In addition, TEM observations document that grain size reduction in clayey slip zone material was produced mainly by mechanical abrasion. For calcite and quartz, grain size reduction was attributed to both pressure solution and cataclasis. Therefore, besides landslide composition, the occurrence of ultrafine-grained slip zone material may also contribute to weakening processes of landslides. TEM images of slip-zone samples show both locally aligned clay particles, as well as kinked and folded sheet silicates, which are widely disseminated in the whole matrix. Small, newly formed clay particles have random orientations. Based on synchrotron x-ray diffraction measurements, the degree of preferred orientation of constituent sheet silicates in local shear zones of theSuoertouandDuang-He-Balandslide is strong. This work is the first reported observation of well-oriented clay fabrics in landslides.