Lithospheric thermal structure of the North China Craton and its geodynamic implications

Abstract

We conduct 2-D numerical modeling of the lithospheric thermal structure of the North China Craton (NCC) on basis of twenty-four crustal velocity structure profiles. About five hundred heat flow data constitute the principal constraints for our modeling. The modeling results demonstrate marked lateral variations in thermal regime of the crust-lithosphere system in the NCC. The average mantle heat flow decreases from 38±5mWm−2 under the Bohai Bay Basin in the eastern NCC to 27±4mWm−2 under the Ordos Basin in the western NCC, characterized by a ‘cold crust but hot mantle’ structure and a ‘hot crust but cold mantle’ structure, respectively. Thermal lithospheric thickness varies from ∼65km beneath the Tan-Lu Fault zone to ∼160km beneath the western and northern Ordos Basin, with similar trend to the seismic lithosphere. However, the disparities in thickness between the thermal and seismic lithosphere are within 20km beneath the Bohai Bay Basin, but 30–90km beneath the Shanxi-Weihe Graben and 50–120km beneath the Ordos Basin. This may imply a westward thickening trend of the rheological boundary layer, which might be attributed to the reducing of asthenosphere viscosity due to hydrous fluid released by dehydration of the subducting Pacific Plate under the eastern NCC. Combined with other pieces of evidence, we suggest that vigorous mantle processes may occur beneath the eastern NCC, whereas the western NCC is relatively stable.