Ancient continental lithosphere dislocated beneath ocean basins along the mid-lithosphere discontinuity: a hypothesis
Zhensheng Wang1, Timothy M. Kusky1, 2, *, Fabio A. Capitanio1, 3
1. State Key Lab of Geological Processes and Mineral Resources, Center for Global Tectonics, School of Earth Sciences, China University of Geosciences, Wuhan, China
2. Three Gorges Research Center for Geohazards, China University of Geosciences, Wuhan, China
3. School of Earth, Atmosphere and Environment, Monash University, Clayton, 3800 VIC, Australia
The documented occurrence of ancient continental cratonic roots beneath several oceanic basins remains poorly explained by the plate tectonic paradigm. These roots are found beneath some ocean-continent boundaries, on the trailing sides of some continents, extending for hundreds of km or farther into oceanic basins. We postulate that these cratonic roots were left behind during plate motion, by differential shearing along the seismically imaged mid-lithosphere discontinuity (MLD), and then emplaced beneath the ocean-continent boundary. Here, we use numerical models of cratons with realistic crustal rheologies drifting at observed plate velocities to support the idea that the mid-lithosphere weak layer fostered the decoupling and offset of the African continent’s buoyant cratonic root, which was left behind during Meso-Cenozoic continental drift and emplaced beneath the Atlantic Ocean. We show that in some cratonic areas, the MLD plays a similar role as the lithosphere-asthenosphere boundary for accommodating lateral plate tectonic displacements.