Structure, stratigraphy and magnetic susceptibility of Bomdila Gneiss, Western Arunachal Himalaya, India

Abstract

Bomdila Gneiss (BG) of Western Arunachal Himalaya (WAH), a suite of felsic magmatic rocks of different components of Palaeoproterozoic age is hosted within the Lesser Himalayan Sedimentary Sequence (LHSS) and placed between the two notable thrust systems- MCT at the top of the structural level to the north and MBT at the lower structural level to the south. Both MCT and MBT are highly sheared ductile zone of high strain and the felsic batholith around Bomdila signatures the protolithic history as porphyritic granite. The BG is highly sheared, strained and displays a number of shear sense indicators like σ, δ, mica fish, stretch ribbon, S-C fabric, dislocation fabric and effect of mylonitisation. Stratigraphic status, magnetic susceptibility and whole rock geochemistry of BG have been studied to evaluate the tectonostratigraphy and nature of granite as ilmanite series (reduced type) and the related data sets are correlated as supplements with the redox state (moderately reduced type).