Metamorphic densification can account for the missing felsic crust of the Greater Indian continent

Abstract

The long-duration, fast convergence, and imbalance of crustal mass in the India-Asia collisional system challenge the classical rules of continental dynamics. Here, we calculate the mass deficit of felsic crust in Greater India indicating ~20–47% of the felsic crust is missing during collision. Phase equilibria modeling and density calculations demonstrate the pressure-temperature-dependent density of felsic crust is denser than the surrounding mantle at P > 7–8 GPa. Integrated petrological-thermo-mechanical models and analytical studies of the slab-pull forces confirm the Greater Indian continent with its felsic crust can subduct spontaneously under its own negative buoyancy when it is dragged to >170 km by the preceding oceanic slab. The great slab-pull force, induced by the negative buoyancy of subducted crust below 170 km, not only contributes to the long-lasting fast convergence between India and Asia but also explains the crustal mass imbalance during the Himalayan orogeny.