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利用化学全分析、薄片鉴定及扫描电镜等测试、观察手段,分析了头寨滑坡发生的岩体玄武岩及其腐岩玄武岩腐岩的岩石化学和矿物学特征。化学全分析结果表明新鲜玄武岩与核心石在除Fe外,其它组分无明显的改变;核心石在转变为腐岩过程中Si、Ca、Na、Mg等元素逐渐流失,Fe、Al等逐渐富集,同时烧失量LOI和化学蚀变指数CIA显著增加,硅铝比逐渐减少。薄片鉴定表明主要矿物化学风化作用顺序为玻璃质、辉石、斜长石,与造岩矿物风化稳定性序列一致,腐岩中主要的次生矿物为蒙皂石及绿泥石。在扫描电镜下观察到风化前锋形态曲折,风化前锋附近矿物呈现物理裂痕,沿着解理面更易出现,风化前锋两侧的岩石矿物形态差异显著。岩体的化学-物理耦合风化作用不仅表现在宏观尺度上,而且在细观-微观的尺度上更为明显。铁元素的价态变化存在于玄武岩腐岩形成的整个过程之中并导致岩石体积增大,从而产生物理裂纹。
The petrochemical and mineralogical characteristics of rock basalt and its saprolite basaltic rock occurring in Tauzhai Landslide were analyzed by means of full chemical analysis, thin slice identification and scanning electron microscopy. The results of chemical analysis show that there is no obvious change in the fresh basalt and core rock except for Fe, while the core rock gradually lost Si, Ca, Na, Mg and other elements during the transition to saprolite, while the Fe and Al are gradually enriched At the same time, LOI and chemical alteration index (CIA) increased significantly, and the Si / Al ratio decreased gradually. Flake identification shows that the order of the main mineralized chemical weathering is vitreous, pyroxene and plagioclase, consistent with the sequence of weathering stability of rock-forming minerals. The main secondary minerals in the rock are smectite and chlorite. The morphology of the weathering front was observed under the scanning electron microscope. The minerals near the weathering front showed physical cracks along the cleavage planes. The rock mineral forms on both sides of the weathering striking strikingly differed significantly. The chemical-physical coupling of rock mass weathering is not only on the macroscopic scale, but also on the meso-micro scale. Variations in the valence of iron occur throughout the formation of basaltic rock and lead to an increase in the volume of the rock, creating a physical crack.