On preparatory causal factors, initiating the prehistoric Tsergo Ri landslide (Langthang Himal, Nepal)

摘要: Abstract The most probable series of causal factors and their complexity make analysis synthesis the Tsergo Ri landslide (Langthang Himal, central-north Nepal) restricted, especially in this case a prehistoric event with spread age data. Interpreting morphologic, lithologic, structural engineering-geologic aspects relation to preparatory subsequent processes will therefore be only an approach. solid basement broken crest landslide, as well surrounding areas upper section Langthang valley, are included High Himalayan Crystalline: leucogranitic dikes (dipping towards southwest) intruded gneisses migmatites (primary foliation northeast). Formation these caused one many or preexisting structures, leading development landslide. In addition, tectonic movements related seismicity forced specific deformation metamorphic rocks: ultramylonites, two generations faults striated slickensides, pseudotachylites degraded substantial horizons weakness. spatial orientation enabled predetermination morphologic (e.g., slope destabilising forces, trend dip sliding). association intrusions, disseminated mineralized, extensive sulphidic ore structure outcrops at Due brittle rheologic behaviour poor weathering resistance ore-bearing horizon (parallel main sliding plane) also made slopes susceptible sliding. Material displaced from scarp by landsliding, was mixed up rocks undisturbed ground subsequently cemented secondary mineralization, thus forming ore-breccias top surface rupture. Neotectonic stress release associated erosional similarly oriented existing zones weakness, may have acted and/or triggering factor for destabilisation too. Hyalomylonite primary surfaces, gneiss analysed means scanning electron microscopy energy-dispersive X-ray analysis, indicate deformational patterns attributed tectonics mechanisms. feature is distinguished clearly those created shock-wave events (i.e. impact-triggered Kofels Tyrolean Alps, Austria). Thus, seismic activity might been event.