A Study of Inverted Metamorphism in the Higher Himalayan Yamuna Valley, Uttarkashi District, Uttar Pradesh

The distinctive feature of the Higher Himalaya of Yamuna Valley is that with in the hanging wall greenschist metapellitic nappe, quartzite and marble of footwall are exposed both with inverted disposition of isograds in the eyelid windows. These Barrovian type syn- to post-tectonic events of metamorphism are recorded in the rocks. Chlorite to garnet zone paragenesis in metapelitic rocks and chlorite-biotite zone paragenesis in quartzite and marble are developed by stronger earlier event of metamorphism (M1). The second event of metamorphism (M2) is mild, followed by another feeble retrogressive event (M3). While inversion of isograds in metapelites is attributed to hot slab thrust over the cold, in quartzite and marble, evidences suggest additional role of shear heating and contact effect by a sub-surface cooling igneous body.