Structural & metamorphic evolution of the Zanskar Himalaya in the Suru Valley region(India), from crustal thickening through to melting and exhumation

The Himalaya is one of the best orogenic belts to understand orogenic processes involved in continental collisions because it is the youngest, still ongoing, best exposed and most intensively studied mountain belt on Earth. Unlike the Alps, the Himalaya is relatively simple with profiles across the range from India in the west to Bhutan in the east all remarkably similar. The deepest levels of the crust are exposed in the Greater Himalayan Sequence (GHS) where metamorphism is attributed to a regional Barrovian type event in response to crustal shortening and thickening following continental collision (e.g. Searle 2015). A series of greenschist, staurolite- kyanite- and sillimanite-grade gneisses with a central core of migmatite and crustal melt leucogranites are exposed along the highest peaks. Mapping of metamorphic isograds has characterised the base of the GHS as a zone of inverted metamorphism along the Main Central Thrust zone (Stephenson et al. 2000, 2001) and the top of the slab along the Zanskar Shear zone as a zone of right way up isograds (Honegger 1983; Searle et al. 1999; Walker et al. 1999, 2001). The Suru Valley transect in western Zanskar (NW India) cuts through the entire top section of the GHS - providing a complete profile of regional metamorphism and is almost 75-80% exposed, unlike everywhere in the central and eastern Himalaya where there is far more forest cover). This valley section provides an ideal field transect in which to map out in detail the structures and collect samples over at least 20 km structural profile through the thickened crust of the Himalaya for thermobarometry and geochronology.