The weathering mechanism of pyroclastic rocks distributed at the landslides in Lembo area, Bana-Bangou district, was investigated from a mineralogical viewpoint. Specimens collected from the landslide profile were composed mainly of kaolinite, illite, chlorite, illite-smectite interstratified mineral, gibbsite, goethite, anatase, maghematite, hematite, quartz and feldspar. The landslide area (pyroclastic rock) was characterized by slow creep movement every raining season. The slip zone was recognized on the landslide profile. Chemical composition of the landslide materials showed the complete leaching of CaO and Na 2 O, whereas a small amount of K 2 O and MgO remained in the whole profile. Detail examinations of the microtexture indicated that the material showed aggregate skeletal matrix with high porosity. This process further caused the decrease of soil strengths and development of micro-texture characteristics that tended to increase the creeping landslide. This displacement rate of the creeping landslide mechanically depended mostly on the pore water pressure in the landslide profile. High pore water pressure always corresponded to the large displacement rate. The mechanism of the creeping landslide was considered from mineralogical characteristics.

Felix Ekodeck

Papers

Clay mineralogy of the landslide in lembo area, bana-bangou district, west province of cameroon