Microstructures of the Higher and Lesser Himalayan sequences near Taliha, Arunachal Himalaya, India

Abstract

In the upper Subansiri District of Arunachal Pradesh, India, Higher Himalayan Crystallines are exposed in and around Taliha and the outcrop of MCT in the immediate south of Taliha is recognizable with the development of tourmaline bearing leucogranite dykes representing melting of the crustal rocks. The gneisses of the Taliha area consist of mainly quartz, mica, K-feldspar and garnet. The Quartz clasts of the Taliha gneiss are internally fractured and deflected the foliation defined by mica. Mica and feldspar fish are seen in the quartz-mica schist with right lateral sense of shear in the Lesser Himalayan sequences in the south of Taliha. The gneisses represent two generations of schistocity. The leucogranite of Taliha area bears tourmaline and shows alignment of mica. The leucogranite dykes are boudinaged at places indicating an extension in the NW direction. The micro scale structures in the gneisses and schists thus represent ductile deformation. A top - to - ENE sense of shear is displayed by asymmetric trapezoid shaped minerals and the mineral fish can act as reliable shear sense indicators.