Evolution of magnetic fabric across the Main Central Thrust Zone (MCTZ), Garhwal Himalayas

Abstract

he collisional tectonic setting between the Eurasian and the Indian plate has created the most discussed orogeny called the Himalaya. The Himalayan orogen is one of the most complex and crucial tectonic settings that has maintained to grab much attention for the last few decades. It consists of several thrust bounded tectonic litho-units which have been in collocation since the onset of collision ~ 54 Ma (Yin et al. 2006; Hu et al. 2016; Dutta and Mukherjee 2021) There are many studies that depicts the time of formation, duration, Pressure-Temperature-time (PTt) condition that delineates the movement of Main Central Thrust zone (MCTz) all along the Himalayan Front (Roberts et al.,2020) and also about the exhumation of the crystallines of Higher Himalayan. Here, we majorly focus on the major tectonic unit called “The Main Central Thrust”. The Main Central Thrust is a 2400 km long crustal shear zone which directs how the Himalayan-Tibetan orogeny develops (Heim and Gansser, 1939). High-grade Proterozoic Cambrian rocks of the Greater Himalayan Series are deposited in the form of deep crustal slice by the Main Central Thrust above low-grade Proterozoic rocks of the Lesser Himalayan Sequence (Hodges, 2000; Hunter et al., 2018 Yin and Harrison, 2000). In the Eastern Garhwal Himalaya's Alaknanda Valley, close to the towns of Helang, Joshimath, and Tapoban, the Main Central Thrust manifests itself. The Alaknanda and Dhauliganga River valleys, which typically cut the rocks perpendicular to their strike, provide good exposure of the stratigraphy in this area (Jain et al., 2014). Therefore, the Alaknanda-Dhauliganga valley is chosen to study deformation pattern across the MCT. This study aims to integrate field investigation, microstructural characterization, evaluation of deformation temperature, variation in the rate of stress and strain of basement rocks which will help in inter-relationship between the thrust tectonics, superposed deformation in the basement rocks and to comment on the rapid exhumation of the Himalayan Foreland.