Crustal thickening and lateral extrusion during the Indo-Asian collision: A 3D viscous flow model

The ∼ 2000 km crustal shortening from the Indo-Asian collision in the past 40–70 million years has been accommodated mainly by crustal thickening in the Himalayan–Tibetan Plateau and lateral extrusion of blocks of Asian continents. However, the spatiotemporal evolution of crustal thickening and lateral extrusion, hence the far-field impact of the Indo-Asian collision on Asian tectonics, remains controversial. Here we present a 3D viscous flow model that simulates the partitioning of crustal material between thickening and lateral extrusion during the Indo-Asian collision. The model assumes conservation of crustal mass, and is constrained by the history of the Indo-Asian plate convergence and by the present-day topography of the Himalayan–Tibetan Plateau. The results show that much of the early collision was absorbed by crustal thickening within the Himalayan–Tibetan plateau. However, lateral extrusion of crustal material has gradually become dominant in the past ∼ 10–20 Myr, indicating increasing influence of the Indo-Asian collision on Asian tectonics.