Dynamics of hidden hotspot tracks beneath the continental lithosphere

Abstract

The presence of mantle plumes beneath old continental regions may have been underestimated due to the lack of surface expressions. New seismic results reveal a corridor-like low seismic velocity zone at the bottom of the continental lithosphere beneath the eastern United States, interpreted as the erosion of the moving continental lithosphere by a plume conduit. Here we study the dynamics of the interaction between a mantle plume conduit and a moving depleted continental lithosphere. With thermochemical numerical models in 3-D Cartesian geometry, we show that a plume conduit can erode the bottom of the continental lithosphere, generating a corridor-like low seismic velocity zone downstream the plate motion direction. This low seismic velocity corridor is typically ∼300 km in width and ∼50 km in height, with several percent of P-wave velocity reduction within it. It can survive more than 100 Myr and extend thousands of kilometers. The surface swell topography of this corridor is much smaller than those beneath the oceanic lithosphere, forming ‘hidden tracks’. We propose that other ‘hidden tracks’, with little surface expression, may exist beneath old continental regions. Such ‘hidden tracks’, once found, may provide additional constraints on plate motion history.