Pseudotachylites of the Kui-Chitraseni Shear Zones of the Precambrian Aravalli Mountain, Rajasthan

Cataclasites-pseudotachylites are developed along the Kui-Chitraseni shear zone of the Aravalli Mountain. The pseudotachylites are microlitic belonging to three varieties referred to here as patchy-, vein- and fracture- pseudotachylites. The patchy pseudotachylites are the most dominating type that occur in association with cataclasites and show an increase in abundance from the margin of the shear zone towards the center. Vein pseudotachylites owe their origin to the injection of the patchy variety through extensional fractures. Fracture pseudotachylites, the youngest of all, occur along the late stage shear fractures. Presence of vesicles, flow texture, embayed margin of the clasts in addition to power law distribution of coarser clasts and high values of roundness (0.4) support the melt origin of the pseudotachylites. Ultracataclasis followed by frictional melting of the Erinpura granites along the shear zone is ascribed for the development of the cataclasites and pseudotachylites.