DEFORMATION AND FLOW CHARACTER OF THE HIGHER HIMALAYAN CRYSTALLINES (HHC) BELT NEAR TAPOVAN, DHAULIGANGA VALLEY, GARHWAL HIMALAYA

Abstract

The Channel Flow Model proposes that the Higher I limalayan Crystalline (Ill IC) rocks !'orming the anatectic core of' the I limalavas have been extruded out from beneath the Tibetan plateau in fbi-rn of' a channel of weak rnid-crustal rocks. Movement along the Main Central Thrust (MCT) in the south and the South Tibetan Detachment System (S'l'DS) in the north, and exhumation along the I Jimalayan front played an important role in extrusion of' this channel. Quantification of flow in terms otvorticitv is essential to understand the kinematic characterisation of'this crustal scale orogenic channel. Vorlicity analysis of the samples collected from the Main Central Thrust Zone. Dhaiiliganga Valley section in (iarhwal Himalaya, India. has been carried out through the use of' rigid grains rotating in a ductile matrix. The analysis indicates that pure shear provides significant contribution (35% to 55%) to the deformation associated with southward thrusting along the - MCT. This has been combined with detailed field based structural analysis. peirographic analysis and study of' quartz textures which reveal that deformation temperatures increase as one moves at higher structural levels from the MCT. In Vaikrita group defbrrnation temperatures >650°C are indicated by chessboard extinction and amoehoid boundaries of quartz grains, and Vorticity numbers from within the anatectic core have not been reported as most of'thc vorticity gauges fail as deformation temperatures increase towards this region.