陇南地区大型滑坡滑带土形成与聚集的地球化学研究

Landslide is one kind of harmful geological hazards, and the prediction of landslide action is very important to reduce their damage to human beings life and properties. However, it is difficult to perform correct forecasting of landslide action mainly because there are many unknown factors for a better understanding of landslide development and evolution processes by far. So-called sliding mud here indicates the product of landslide processes from the formation, evolution and till to sliding action of a landslide, owing clear different properties in structural and mineralogical composition and geochemical features from the associated debris rocks and bedrocks on a landslide profile. These specific characteristics are significant to indicate special development and evolution mechanism of the slip zone, and thus attractive to researchers and engineers working on landslide. The major targets in this study will include the Qinyu, Xieliupo, Fenganshan and other landslides in large size and continuously moving in Longnan district, southern Gansu province. The solid samples of debris rocks, sliding mud and bedrocks from typical landslide profiles and also the rocks from surrounding sections will be analyzed for the composition of minerals, major elements, and some isotopes, especially the composition of clay minerals and chemical speciation of some redox sensitive elements including iron, sulfur and manganese. The development history of landslides will be tried by using some cosmogenic isotopes such as 10B and 26Al for suitable rock samples from those landslides. The physical-chemical conditions within the slip zone for the sliding mud formation will be identified based on the composition of clay minerals and chemical speciation of related elements, in order to explain the water-rock interactions within various sites of the slip zone during different periods. The generation mechanism and accumulation processes of sliding mud and their relationship to landslide development and evaluation will be searched. All these study results will provide geochemical evidence for the comprehensive research on landslide development and selection of suitable landslide protection methods.

滑坡地质灾害的准确预报对于防灾减灾至关重要，然而由于其形成和演化的复杂性，导致准确预报受到很多不确定性因素的影响和制约。滑带土是滑坡形成、演化和滑动过程的重要产物，其矿物和元素组成等特征往往有别于相临的滑体和基岩，包含有滑带发展过程与演化机理的信息。本课题将以陇南地区秦峪滑坡、泄流坡滑坡、风安山滑坡等大型持续活动性滑坡为主要对象，选取典型的滑带剖面，对滑坡体、滑带及下伏基岩进行对比研究，重点分析粘土矿物和主微量元素，以及铁、硫、锰等氧化还原敏感性元素赋存状态及其在滑坡剖面上的变化特征，引进宇宙成因核素技术探索滑坡活动历史定年的可能性，综合分析特殊粘土矿物组合及相关元素化学赋存状态与变化规律，反演滑带土形成的物理-化学条件，特别是氧化还原条件，揭示滑坡不同发育阶段和不同部位滑带内特殊的水-岩相互作用，探讨滑带土的形成机理和聚集规律及其对滑坡发展演化过程的指示意义，为滑坡防治提供科学依据。

陇南地区泄流坡滑坡是著名的长期多次活动的大型滑坡，巨大的滑坡体内存在多个相互交错而形态各异的次级滑坡体，滑坡不同部分的差异性滑动导致滑坡堆积体支离破碎，滑坡表面的形态变化多端。滑坡体内被流水冲刷揭露出的多个次级滑体底部的滑动面清晰可见，滑动面可以用来指示滑动方向的擦痕以及由于滑动生热而导致的岩石褪色现象非常清楚，但滑动面上下的滑体和相对的基岩，其岩石学特征没有明显差异，但铁元素化学种的分布特征与日本富山县多个第三系地层型滑坡剖面非常相似，滑带样品的相对还原性特征揭示这个滑动面是在先前存在的破碎带不断发展演化的基础上产生的，伴随还原性粘土矿物的不断形成和聚集，由于粘土矿物遇水容易发生塑性变形从而降低破碎带的阻抗力，当这个破碎带岩石的阻抗力降低到一定程度，在相关地质营力作用下，例如突然的大规模降水等，就很容易引起滑体的向下滑动。这些研究成果已经投稿<Journal of Engineering Geology>。.对于三峡库区巴东县黄土坡滑坡、盐锅峡镇黑方台黄土-基岩复合型滑坡的形成机理和治理方面的建议与中国地质大学（武汉）、兰州大学、三峡大学的同行专家多次交流，并争取联合实施合作研究。