THE SURFACE TECTONICS OF LITHOSPHERIC DELAMINATION FOLLOWING OCEAN PLATE SUBDUCTION: INSIGHTS FROM LABORATORY AND NUMERICAL EXPERIMENTS

In various geological instances, continental delamination is associated with preceding ocean plate subduction, however the relationship between the two processes has not been recognized. In this work, we present a series of lithosphere scale two-dimensional (2-D) and three dimensional (3-D) laboratory and numerical experiments to investigate the evolution from ocean lithosphere subduction to collision and possible delamination of the mantle lithosphere from the crust. We test how varying the magnitude of plate convergence alters the behavior of the subduction-delamination model. Our experiments show that a converging and retreating plate can develop to continental mantle lithosphere delamination. A negative surface topography is supported at the delamination hinge and this migrates back with the peeling lithosphere. With a high plate convergence, the crust and mantle lithosphere separate at the collision zone in a form of chisel tectonics as oncoming pro-crust is accreted on top of the overriding plate and the converging mantle lithosphere subducts below. Localized high topography develops at this zone of crustal accretion and thickening. The results suggest that delamination may be simply a continental continuation of plate retreat and that lithospheric removal is triggered by the transition from one process to another. Our modeling results can contribute to geological interpretations of the Alpine tectonics particularly in the Mediterranean region and Tibetan plateau where both delamination and flake tectonics is proposed.