Abstract
The occurrence of pseudotachylyte-ultracataclasite veins at the Main Central Thrust (central Nepal) is reported here for the first time. The veins are planar, mm-thin layers concordant to the main foliation and layering of the wallrock. They contain elongate domains with variable amount of glasses and µm to mm-sized angular to sub-angular fragments. The glasses indicate the presence of pseudotachylyte and its origin by frictional fusion and subsequent rapid cooling. Amoeboid and partly cuspate domain geometries with diffuse contacts result from simultaneous movement and mingling of pseudotachylyte and ultracataclasite materials during injection into opening foliation-parallel cracks. Frequency distributions of fragment sizes, distribution patterns of fragments, and lobate boundaries of mingled materials are quantified by fractal geometry methods. They follow various power laws on various scales and indicate repeated processes of fragmentation, injection of mobile material, flow, mingling, mixing, and solidification. The formation of composite pseudotachylyte-ultracataclasite veins correlates with thrusting along the Main Central Thrust, specifically with the reactivation of the thrust in the Late Miocene to Early Pliocene.
Original language | English |
---|---|
Article number | 105483 |
Journal | Journal of Asian Earth Sciences |
Volume | 241 |
DOIs | |
State | Published - Jan 2023 |
Keywords
- Composite vein
- Fractal geometry
- Frictional fusion
- Main Central Thrust
- Pseudotachylyte
- Ultracataclasite