Density structure of the lithosphere beneath North China Craton

Geoscientists all over the world paid a broad attention to the lithosphere of North China Craton (NCC), which was destructed since phanerozoic. A three dimensional P- wave velocity model obtained from seismic tomography was used to construct an initial 3D density model. Then, we got high resolution three dimensional density distributions of the lithosphere in NCC by gravity inversion using bouguer gravity anomaly. In order to improve the inversion speed, Algebraic Reconstruction Technique (ART) was applied for it can avoid the large and sparse matrix inversion of observation equations by using row iterative technique. The results indicate as follows: density distributions of lithosphere beneath North China Craton are inhomogeneous both in horizontal direction and vertical direction. And the density distribution underground is coherent with surfical tectonic. In NCC crust the density anomaly is low, while it is strongly high at 80 similar to 120 km depth. The Ordos block crust exhibit a low density distribution, and high density anomaly with big amplitude exists at 80 similar to 120 km. The high density distribution is conjoint with the high density anomalies of Qinling and Yinshan orogen in the south and north, respectively. That may indicate that Ordos block underwent the deep dynamic process from orogen in the south and north. High density anomaly is visible beneath the mid Taihang Mountain Orogen and eastern basin region at 80 similar to 120 km depth. At the same depth, remarkable high density anomalies exist beneath eastern of NCC with strong lateral heterogeneous in NS direction. It indicates that the upper mantles are inhomogeneous in NS direction beneath this region.