Hydration weakening and destruction of the North China Craton

Abstract

Cratons are generally considered the most stable parts of the lithosphere. However, recent studies have shown that some cratons have undergone significant thinning and even destruction. The destruction of the eastern part of the North China Craton has been documented through numerous geological, geochemical, and geophysical investigations. Yet, the exact mechanism behind this extensive thinning remains a subject of debate. In this study, we develop two dimensional (2-D) box models in a finite difference code LaMEM to identify the most viable reasons for the destruction of the North China Craton (NCC). We examine the role of slab-induced hydration, high-density lower crust, and weak mid-lithospheric discontinuity in our models. Results indicate that a low angle or flat slab-induced hydration weakening of the eastern part of the NCC can lead to rapid craton destruction if hydration weakening rates are sufficiently fast. This accelerated hydration rate may be attributed to the extensive carbonatite magmatism within the eastern part of the NCC, facilitating a faster pathway for water diffusion throughout the craton. Rapid craton destruction is also contingent upon the craton's density exceeding the surrounding mantle density, and its viscosity decreasing below ${10}^{22}$ Pa s. We observe that the presence of a dense lower crust or a mid-lithospheric discontinuity fail to destroy the NCC unless the craton is sufficiently weakened.