Destruction of the North China Craton due to hydration weakening

The North China Craton is an important example of extensive craton thinning and partial destruction. While the significant thinning of the eastern part of the craton is well-documented, the underlying mechanism driving this process remains a subject of considerable debate. Proposed explanations include mantle perturbation and thinning linked to multiple subduction zones, eclogitization of the lower crust followed by lithospheric foundering, a weak mid-lithospheric discontinuity (MLD) induced delamination, and hydration weakening caused by slab dehydration or water transport from the mantle transition zone. A common limitation among these hypotheses is their inability to account for the partial nature of the craton's destruction, where the eastern half experienced extensive thinning and magmatic activity, while the western part remained largely stable.

To investigate the evolution and potential mechanisms of craton destruction, we developed two-dimensional Cartesian box models in a finite difference code LaMEM. These models explore the effects of hydration weakening via low-angle slab dehydration, the role of the MLD, and the influence of lower crustal eclogitization. Our findings indicate that the eastern half of the craton has to be significantly weakened and denser than the underlying mantle to undergo destruction. This partial weakening may result from hydration, facilitated by a low-angle or flat subducting slab which could act as a primary source of water. To align with the observed geological timescale of craton destruction (20–30 million years), the hydration process must outpace the diffusive timescale of water in the upper mantle. Accelerated hydration may have been driven by magmatic infiltration, particularly carbonatite volcanism, which could provide rapid pathways for water diffusion within the craton. Our models suggest that without sufficient weakening, neither the presence of an MLD nor a dense lower crust alone can lead to the craton's destruction.