Stable equilibrium dynamics explains continental lithosphere deformation

Abstract

Plate tectonics theory postulates the existence of rigid mobile plates, however, what defines and controls their internal deformation, particularly within continents, is not well understood. Using data-driven thermomechanical modelling of the Alpine Himalayan Collision Zone, we hypothesize that deviations from an equilibrium state between mantle dynamics, plate-boundary forces, and the thermochemical configuration of the lithosphere controls continental deformation. The balance between the plate’s internal energy and tectonic forces is quantified by a critical crustal thickness that matches the global average of present-day continental crust. Thicker intraplate domains than the critical crust (orogens) undergo weakening due to their increased internal energy, and dissipate their acquired energy within diffused zone of deformation, unlike the localized deformation seen along plate boundaries. This dissipative evolution is controlled by the feedback between thermal and mechanical relaxation of the out of balance energy in the orogenic lithosphere. Potential runaway instabilities, exponentially growing oscillations, are efficiently dampened by enhanced dissipation from radioactive heat sources. This ultimately drives orogens with their thickened radiogenic crust towards a final equilibrium state. Our results suggest a genetic link between the thermochemical state of the crust and the tectonic evolution of silicate Earth-like planets.