Kinematics and geodynamics of the India-Eurasia collision

The collision between the Indian and Eurasian continents produced the world's most pronounced mountain range, impacted long-term global climate and oceanic circulation, and deformed vast swathes of Southeast Asia. However, the collision chronology remains controversial largely due to uncertain pre-collision margin geometries. We embed two end-member scenarios of pre-collision geometries within a global plate motion model in our plate reconstruction software, GPlates. A scenario that implies long-lived Andean-style subduction along southern Eurasia was chosen to represent conventional models of convergence that require a very large Greater India. An alternative scenario, based on interpretations of ophiolite emplacements, present-day mantle structure, volcanogenic episodes, convergence rate trends and deformation events, suggests the existence of long-lived Tethyan intra-oceanic subduction. In this scenario, a smaller Greater India collides with an intra-oceanic island arc at ~60 Ma at equatorial latitudes, coinciding with a convergence rate drop, ophiolite emplacement and the onset of back-arc subduction. A final continent-continent collision occurs at ~40 Ma to consume the back-arc basin and induce extreme crustal deformation and lateral expulsion of Southeast Asian continental blocks. Plate velocities were sampled using a 50 km global mesh on the surface and were applied as the kinematic surface boundary layer to drive subduction from 200 Ma to the present using the mantle convection code CitcomS. The predicted mantle structure from end-member scenarios was validated using P- and S- wave seismic tomographic models, where long-term Andean-style subduction failed to reproduce the discrete slab volumes and the large latitudinal range of mid-mantle Tethyan slabs. The alternative scenario better reproduces the present-day mantle structure and the evidence for a multi-stage collision, volcanogenic episodes and characteristics of long-lived intra-oceanic Tethyan subduction.