Evolution of the North China Craton Preserved at Mid-lithospheric Discontinuities

The North China Craton (NCC) exhibits dramatic lithospheric thinning from west (~200 km) to east (~80 km), providing an ideal context to investigate Mid-Lithospheric Discontinuities (MLDs). In this study, we construct a high-resolution 3-D resistivity model using magnetotelluric data from 249 stations across the Western NCC and Trans-North China Orogen (TNCO) to constrain MLD origins.

Our results reveal that the MLD is not a uniform boundary but records diverse thermo-tectonic processes. Along the 36°N profile, the MLD displays strong heterogeneity: beneath the stable Ordos Block, it marks the transition to a conductive 'fossil' root derived from ancient metasomatism; at the suture zone, it preserves a primitive welding signature; and beneath the extending TNCO, it transforms into a dynamic front of modern asthenospheric melting. In the northern Western NCC, the correlation between the MLD and a massive deep conductor along the N-S profile suggests the MLD represents a sharp lithological interface, likely marking the boundary of buried metamorphic residue. These findings support a multi-genetic model for cratonic MLDs. We demonstrate that integrating electrical structures with other geophysical constraints provides critical insights into the evolution and destruction of continental lithosphere.