When did India-Asia Collide and Make the Himalaya?

Abstract

Critical evaluation and comparison of the available geological and geochronological data from the northern parts of the Himalaya and Trans-Himalaya mountains highlight that these mountains did not initially evolve by the collision of continents of the Indian and Asian plates. Instead, subducted Tethyan oceanic lithosphere in front of the Indian continent melted to produce the calc-alkaline suite of the Shyok-Dras volcanic arc and the Ladakh batholith. Hence, the Indian plate initially subducted beneath and started building up the then existing intra-oceanic island arc. Timing of the first impingement of the Indian and Asia plates has been better constrained at around 57.5 Ma by comparing (i) the bulk ages from the Ladakh batholith (product of partial melting of the Tethyan oceanic lithosphere) with (ii) the subducted continental lithospheric and UHP metamorphosed Indian crust in the Tso Morari, and (iii) biostratigraphy of the youngest marine sedimentation in Zanskar. Thus, the Himalaya witnessed its first rise and emergence from deeply exhumed terrain in the Tso Morari after around 53 Ma, followed by sequential imbrication of the Indian continental lithosphere and associated exhumation during rise of the Himalayan mountains from north to the south since 45 Ma.