Ongoing craton destruction driven by pre-existing structures in the central North China Craton

It is significant to constrain the anisotropic crustal and lithospheric structures of the North China Craton (NCC) to understand the mechanisms of craton destruction. The NCC consists of the cratonic Ordos block, the Shanxi Rift, and the severely destructed eastern NCC. The Datong volcano zone (DVZ), which is located in the northern Shanxi Rift, suggests active magmatism and volcanism during the Cenozoic. In contrast, the magma-poor southern Shanxi Rift poses a significant challenge in demonstrating the rifting mechanism and processes. Using the database from ChinArray, we obtain anisotropic Rayleigh-wave phase velocity maps by Eikonal tomography and further invert for the 3-D S-wave structure and its azimuthal anisotropy. Strong azimuthal anisotropy with fast polarization directions parallel to the edge of the low-velocity zone is revealed at a depth of 50~60 km to the west of the DVZ, which is the uppermost mantle near Moho. Our results suggest that the magmatic underplating transfers horizontally in the northern NCC and causes ongoing craton destruction by thermal and chemical erosion. We propose that the subduction of the Paleo-Asian Ocean during the Mesozoic, which is a pre-existing structure, may have contributed to lithospheric activation and localized lithospheric thinning in the northern NCC and results in the north-south differential lithospheric deformation. Similar to the Shanxi Rift, other rift systems, such as the Baikal Rift and the Eastern African Rift, may also be the consequence of the lateral motion of an adjacent cratonic block on its margins. The presence of magmatism within the rift zone is mainly dependent on pre-existing structures, such as subduction.