The Structure and Stability of Cratons

Cratons, the ancient cores of continental plates, have remained stable for billions of years. The high strength of the cratonic root has long been considered vital for its survival in the dynamic mantle. However, recent high-resolution seismic studies have unveiled widespread velocity discontinuities within the middle of the continental mantle lithosphere in nearly all cratons. These discontinuities, known as mid-lithospheric discontinuities (MLDs), are characterized by a sharp reduction in seismic velocity of 2-7% over 10-20 km, primarily at depths of 80-120 km. They are typically less than 30-40 km thick and are globally distributed. Many researchers propose that MLDs are likely weaker than the melt-depleted lithospheric mantle of cratons, providing a possible explanation for the phenomenon of lithosphere destruction and thinning in various cratonic areas. Despite these regions of lithosphere destruction, many cratons remain stable and possess thick roots even after prolonged plate motion. This study reviews the structure of cratons and the distribution of MLDs, as well as investigates the dynamics of cratonic root in the presence of MLDs using numerical models.