Continental Mid-Lithosphere Discontinuity: A Water Collector During Craton Evolution

Abstract

Continental mid-lithosphere discontinuity (MLD) seems to be ubiquitous beneath cratons around the world with the dominant depth of 70–100 km, and is characterized by a shear-wave velocity drop of 2%–7%, according to geophysical observations. The MLD is often considered to be related to a rheologically weak layer; however, the mechanism of MLD formation is widely debated. In this study, we have conducted systematic numerical modeling with a new and simplified deep hydration method to study the dynamics of craton evolution and MLD formation. The results indicate that the MLD may be induced by slow hydration processes within the mantle lithosphere during craton evolution. The top boundary of this hydrated layer is characterized by high water content and low shear-wave velocities, and is consistent with the depth and properties of natural MLD observations. Thus, we propose that the MLD may act as a water collector during craton evolution.