Electron microscopy study of hyalomylonites—evidence for frictional melting in landslides
Abstract
Hyalomylonites, from Langtang (Nepal) and Köfels (Ötz Valley, Austria), were investigated by transmission electron microscopy (TEM). The matrix is glassy at both localities; rarely it is crystallized and devitrified to dendrites and skeletal microlites of plagioclase, alkali feldspar and biotite. The matrix is chemically heterogeneous with schlieren and formed by partial to almost complete melting of host rocks of granitic to granodioritic composition. Locally, glasses with pure quartz, plagioclase and alkalifeldspar composition were found. From SiO 2-glass minimum temperatures of 1520°C are estimated. At both hyalomylonite localities melting appears to be the result of frictional heating on the gliding plane of a large landslide. The host rocks were deformed in a brittle mode. Microstructures typical of plastic deformation at high temperatures are displayed by inclusions and were probably inherited from previous tectonic events.
- Publication:
-
Tectonophysics
- Pub Date:
- May 1985
- DOI:
- 10.1016/0040-1951(85)90103-9
- Bibcode:
- 1985Tectp.115..131M