THE EFFECT OF MID-LITHOSPHERIC DISCONTINUITY ON THE STABILITY OF CRATON

The long-term survival of craton has always been an important research topic of geodynamics. Although in a few cases, cratons might have been destroyed (e.g., North China craton), most of cratons remain stable through long-time plate tectonics. Recent studies found a gradient zone with significantly reduced velocity in the mantle lithosphere beneath craton, named mid-lithospheric discontinuity (MLD). Some studies suggest that MLD is a weak-coupling layer, which may accommodate some displacements between the upper and lower lithosphere. In this study, we construct 2-D numerical models to investigate the influence of the MLD’s viscosity and plate velocity on the stability of craton. The results show that the viscosity of MLD in stable craton is greater than 5´10²⁰ Pa s. When MLD’s viscosity is less than 5´10¹⁹ Pa s, no/little craton root can survive through plate tectonics. Our results show that the mechanical properties of MLD may play a fundamental role in craton stability. Even seismic velcosities reduce in MLD, the visocisty of MLD may be still higher than 5´10²⁰ Pa s.