Structures in Meso- and Micro-scales in the Sutlej section of the Higher Himalayan Shear Zone, Indian Himalaya

Soumyajit Mukherjee

Abstract


Study of structural geology of the Higher Himalayan Shear Zone (HHSZ) in the Sutlej section reveals S-C fabric, mineral fish, syntectonic growth of porphyroblasts, stretching of clasts, crenulation cleavages, intrafolial folds, duplexes, boudins, and micro-scale hat-shaped minerals and rare sedimentary textures. In migmatites, the S-C fabrics are defined by various thicknesses of leucosomes and melanosomes of various curvatures. In micro-scale, either mineral fish or aligned undeformed grains characterize S-fabrics. Porphyroblasts were either stretched or nucleated syntectonically during the extensional shearing. Hat shaped minerals indicate brittle shear. Intrafolial folds are of various thicknesses and some of their axial traces parallel the shear planes. In the two detachments within the HHSZ, the dominant ductile shear sense is top-to-NE, elsewhere the sense is exclusively top-to-SW. The brittle shear sense in the HHSZ is also top-to-SW. While the brittle shearing postdated the migmatization event in the HHSZ, boudinage was presumably a syn-migmatization process.

Keywords


Higher Himalayan Shear Zone, ductile deformation, brittle deformation, micro-structure

Full Text: PDF