Magnetically stratified continental lower crust preserved in the North China Craton

The magnetic properties of lower crustal xenoliths, and outcropping granulites suggest that magnetically stratified lower crust is preserved in the northern North China Craton. The upper layer (~24-33km) is represented by strongly magnetic granulite-facies terrains, in which the mafic granulites have the highest susceptibility (κ, mean 67.92×10^-3SI) and natural remanent magnetization (NRM, mean 0.59Am^-1). In contrast, the lowermost layer (~33-42km) is mainly composed of mafic granulites and pyroxenites sampled as xenoliths, which are weakly magnetic with κ and NRM of 0.9-1.5×10^-3SI and 0.04-0.1Am^-1, respectively. The formation of the weakly magnetized lowermost crustal layer is associated with continuous underplating of mantle-derived basaltic magmas at the pre-existing crust-mantle boundary from the late Mesozoic to Cenozoic. We suggest that this magnetically stratified lower crust may be widespread beneath the North China Craton.