Prevention of disasters due to the chemical compositions from the magnetite-series granite and zeolite vein in the slope failure area

地震造成的六谷山滑坡很多。边坡失稳主要集中在磁铁矿系列花岗岩和沸石脉分布区。磁铁矿系列花岗岩的强烈破碎和风化是导致边坡失稳集中的主要原因。沸石在滑坡陡崖上呈脉状产出。沸石是沿沿着断层热液蚀变形成的。我们研究了在兵库县南部地震引起的边坡破坏中岩石化学成分与风化程度之间的关系。在风化过程中，Ca、Mg、Fe和Na等元素从岩石中被去除。常见的黑云母和斜长石对化学风化作用相对敏感。黑云母很容易风化，遇水即变成蛭石和高岭石。风化岩中MgO、CaO、FeO含量显著偏低。因此，风化岩石的化学成分与边坡破坏的风化程度有着重要的关系。边坡失稳过程中岩矿化学成分的变化反映了边坡的风化程度，对边坡失稳的防治有一定的参考价值。

Rokko Mountains had many slope failures caused by the Earthquake. The slope failures appear to concentrated in the magnetite-series granite and zeolite vein distribution area. The reason for the slope failure concentration is thought to be heavy crushed and weathering in the magnetite-series granite. Zeolite occur as vein on landslide scarp. Zeolite was formed by hydrothermal alteration along fault. We have been studied the relation between chemical composition of the rocks and grade of weathering in the slope failure caused by the Hyogoken-Nanbu Earthquake. The elements such as Ca, Mg, Fe and Na are removed from the rocks during the weathering process. The common biotite and plagioclase are relatively susceptible to chemical weathering. Biotite is easily weathered and alters in the presence of water to vermiculite and kaolinite. MgO, CaO and FeO contents are remarkable low in the weathered rock. Thus, there is an important relationship between chemical composition of the weathered rocks and grade of weathering in the slope failure. The rock and mineral chemistry in the slope failure reflect to weathering grade and useful for judgment of prevention of the slope failure.