Occurrence of pseudotachylites in the vicinity of South Almora Thrust zone, Kumaun Lesser Himalaya.

Thin veins of pseudotachylites are observed within the South Almora Thrust (SAT) zone of the Almora crystallines, Kumaun Lesser Himalaya. The SAT zone presents a relatively wide variety of mylonite types. Within this zone thin, dark-coloured veins of pseudotachylites are found. Folded veins of irregular thickness are also observed. The pseudotachylites are formed by rapid crystallization of melts. Intense deformation and friction-related heating is generated during the thrust sheet movement, which is responsible for producing the melts. Small amount of melts generated during the frictional heating cool rapidly in association of the wall rock and form thin veins, which have sharp boundaries (or folded) within the wall rock. Quartz, K-feldspar and plagioclase occur as porphyroclasts in the host rocks. [ABSTRACT FROM AUTHOR]