Pseudotachylytes of the Bavali Fault Zone, Cannanore District, North Kerala

Abstract

Pseudotachylyte veins occur sporadically within deformed granodiorite-tonalite body and mylonitic gneiss of possible Sargur-equivalent sequence in North Kerala. Pseudotachylyte-bearing zones constitute a part of the wide Bavali fault zone, a continuation of the Moyar shear zone. The second phase of deformation of probable Mid Late Proterozoic age shows a progression in strain regime from mylonite-forming ductile strain through moderate strain rate stage forming ultramylonite to a high strain rate stage forming pseudotachylyte. Pseudotachylyte developed via comminution and frictional melting at different stages within the fault zone. Although it appears to be in place of its origin; pseudotachylyte has not strictly attained 'minimum' melt composition.