Mantle dynamics of the reactivating North China Craton: Constraints from the topographies of the 410-km and 660-km discontinuities

The topographies of the 410-km and 660-km discontinuities have important implications for mantle dynamics. Here we present high-resolution seismic imaging of the 410-km and 660-km discontinuities beneath the North China Craton (NCC) employing the receiver function method. Depth anomalies (deeper or shallower than the global average depths) at both discontinuities were detected by introducing a three-dimensional regional velocity model. The depressions of the 410-km discontinuity are mostly located in the eastern NCC. A local elevation of the 660-km discontinuity appeared in the northwest of the NCC and a significant depression of the 660-km discontinuity is located in the southeast of the NCC. Two dynamic mantle regimes are speculated to explain the formation of the anomalous depth zones in the NCC. One possibility is a complex mantle upwelling linked to edge-derived convection between the stagnant slab and the thick cratonic root. The other potential dynamic regime is slab stagnating, sinking, and induced upwelling at the neighboring slab front. These regimes hint that the mantle flow was possibly dominated by dynamic interactions among the subducting slab, cratonic root, and ambient mantle beneath the NCC.