Mantle upwelling induced by slab rollover subduction could explain widespread intraplate volcanism in Tibet

Subduction-induced mantle flow has a considerable geodynamic impact on Earth. It can deflect mantle plumes, transport geochemical signatures and produce upwellings that generate atypical intraplate volcanism. The mantle flow produced by slab rollover subduction, however, remains unstudied, yet it may have a comparable geodynamic significance. Here, we present analogue models of buoyancy-driven subduction in which we image, using a state-of-the-art Particle Image Velocimetry (PIV) technique, the three-dimensional mantle flow induced by two contrasting subduction styles: slab rollback (trench retreat) and slab rollover (trench advance). Our model results show that the advancing subduction mode develops a slab rollover geometry that generates a large-scale upwelling in a broad mantle wedge domain. Based on a comparison between the location of this upwelling and Cenozoic volcanics in Tibet, we propose that slab rollover subduction of the Tethyan and Indian slabs generated a comparably broad mantle upwelling, which drove widespread Cenozoic volcanism in Tibet. Intraplate volcanism inboard of subduction and collision zones, such as in Tibet during the Cenozoic, could be produced by reversed toroidal mantle flow and long-lived upwelling in subduction rollover settings, according to analogue subduction models.