Meso‑Cenozoic lithospheric thermal structure and its significance in the evolution of the lithosphere in the Ordos Basin, WNCC, China

Abstract

ABSTRACT The Ordos Basin located in the Western North China Craton (WNCC) has been confirmed to have undergone large-scale lithospheric thinning at the end of the Early Cretaceous (130 ~ 90 Ma), but investigations involving its lithospheric thermal structure in the Mesozoic and Cenozoic are limited. In this study, we employed a 1D, steady-state, heat conduction equation to calculate mantle heat flow and its partitioning, the Moho temperature and the thermal lithospheric thickness of different tectonic units in the Ordos Basin based on an analysis of thermal history reconstruction and crustal layering models. The results suggest that the peak of mantle heat flow at the end of the Early Cretaceous varied between 46.65 mW/m2 and 62.97 mW/m2, far exceeding 50% of surface heat flow, which shows a typical ‘hot mantle and cold crust’ type of lithospheric thermal structure, and the lithospheric thinning reached a minimum thickness of 50 ~ 75 km. This was followed by a thermal decay phase in the Late Cretaceous, and a significant vertical thickening of lithosphere occurred during this period, during which the lithospheric thickness increased to 78 ~ 133 km by the end of the Late Cretaceous. Since the Cenozoic, the ratio of mantle to surface heat flow gradually declined to less than or close to 50%. At present, the average mantle heat flow in the Ordos Basin ranges from 22.10 mW/m2 to 38.76 mW/m2, the lithospheric thickness is between 81 ~ 158 km, and the Moho temperature entirely surpasses 600°C. In addition, we discuss potential factors and uncertainties in the thermal structure calculation. Combined with previous studies, we suggest that the lithosphere in the WNCC has been thinned locally due to asthenosphere upwelling.