Lateral variation of the strength of lithosphere across the eastern North China Craton: New constraints on lithospheric disruption

The structure and rheology of the lithosphere can provide constraints on our understanding of the geodynamic processes in the Earth's interior. The lateral heterogeneity of the strength and rheological structure of the lithosphere are closely correlated with the lateral variation in the thickness of the seismogenic layer. It is still unclear how geodynamic process(es) are linked with this lateral variation in the geophysical properties of the lithosphere. In order to understand the possible links between geodynamical process and lateral variation of lithosphere strength, we compiled crustal velocity and density structure, the elastic thickness of the lithosphere, and the temperature field, and then construct a northeast–southwest transect of the lithosphere across the eastern part of the North China Craton (NCC) with an overall length of 1660 km. Along the lithosphere-scale transect, we observe that (a) a thinner (80–120 km) Archean lithosphere at the North China Plain (NCP), (b) a lateral variation of the seismogenic brittle layer, which is about 15 km thick beneath the Qinling-Dabie orogenic belt (QDOB) and the Yanshan orogenic belt (YSOB), and about 25 km thick under the NCP. Together, these characteristics represent an excellent illustration of the scale of geodynamic processes necessary to accommodate lateral variations in lithospheric strength and the contribution of these to the mechanism of disruption of the Archean NCC. The thick seismogenic layer beneath the NCP can be formed due to: (1) deeper fault penetration beneath the NCP than beneath the QDOB and the YSOB; (2) the thick brittle layer is preserved after delamination of the lower part of the thickened crust; (3) thickening by changes to brittleness of the brittle/ductile transition layer (BDTL). With constraints of above mentioned geophysical properties of the lithosphere, we propose that (1) only the first and third processes can successfully explain the lateral variation of the thickness of the seismogenic layer across the eastern part of the NCC, and (2) the extensional tectonics and thermal erosion (notwithstanding the delamination of the lithosphere) play their significant roles in the disruption of the NCC.

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► We construct a 1660-km lithosphere-scale transect across the eastern NCC.
► A thickened seismogenic brittle layer is observed under the North China Plain.
► Lithospheric strength was related to its thickness and crustal structure.
► Extensional tectonics or underplating plays roles in lithospheric disruption.