Joint inversion of the lithospheric structure of the central North China Craton from ambient noise and seismic surface wave

Based on the observation data of the ChinArray Phase Ⅲ deployed in the central North China Craton, the Rayleigh surface wave dispersion with period range of 6 s to 140 s in the studied area is obtained using cross-correlation of ambient noise and seismic surface wave tomography. The high-resolution 3-D S-wave velocity structure of the lithosphere in the central North China Craton is further obtained with the Monte Carlo nonlinear inversion method. The results exhibit significant lateral differences in the lithospheric structure of different blocks of the North China Craton. The central part of the Ordos basin is characterized by high velocity overall, extending below 200 km, but there is a small range of low-velocity anomalies on the southeast margin. The North China basin in the east is characterized by low-velocity with thin crust and lithospheric thickness. Connected low-velocity zones at the northern and southern ends of the central orogenic belt and below the north-south gravity gradient line are observed, which extends below the North China basin. In the lower crust and uppermost mantle, the low-velocity zone in the Datong volcanic group area gradually shifts westward to the northeast corner of the Ordos basin. While in the upper mantle, the low-velocity anomalies in this area gradually fade off as the depth increased. And the low-velocity zone extended below the North China basin in the southeast. Based on the S-wave velocity model obtained in this study, we believe that the heart of the Ordos basin maintains the cratonic characteristics overall, but there is a local lithospheric modification at the southeast margin; the North China basin has experienced strong lithospheric destruction and thinning and crustal extensional deformation; the lithosphere at the northern and southern ends of the central orogenic belt and the north-south gravity gradient line has undergone partial modification and thinning. The mechanism may be the same and due to the upwelling of hot material in the mantle below the North China basin; the upwelling hot material below the Datong volcanic group intrudes into the lower crust below the northeast corner of the Ordos basin. Then it is blocked by the upper crust when rising in the crust and flows eastward to the bottom of the Datong volcanic group, forming the magmatic activity of the Datong volcanic group. The deep source may be related to the stagnant Pacific slab.