Lithospheric thermal structure in the Dongpu Depression, Bohai Bay Basin, North China

Abstract

The Dongpu Depression is located in the eastern part of the North China Craton, which is the central region of lithospheric destruction and thinning of the North China Craton. The North China Craton is considered an ideal laboratory for studying the thinning and modifications of the ancient lithosphere. Based on rock thermal properties, the present geothermal field, and crustal structure, the thermal lithospheric thickness was calculated using a one-dimensional steady-state heat conduction equation. Assuming that heat is transferred by conduction and that rock thermal conductivity and radiogenic heat production rates are constant, a crustal model is developed. The heat flow generated by radioactive elements is calculated layer by layer through the "back stripping" method, which allows the determination of crustal heat flow, mantle heat flow, and Moho temperature. The results reveal that the thermal lithospheric thickness in the Dongpu Depression varies between 81.9 km and 90.8 km, with mantle heat flow ranging from 37.5 mW/m² to 42.0 mW/m². The ratio of mantle heat flow to surface heat flow is 60.8 %, and the temperature at the Moho interface ranges from 646 °C to 701 °C. These findings suggest a thin thermal lithosphere, a high ratio of mantle to surface heat flow, and elevated Moho temperatures, indicative of a “hot mantle and cold crust” lithospheric thermal structure. The lithospheric thermal structure of the Dongpu Depression indicates that its formation was controlled by extensional tectonics since the Cenozoic, the subduction of the western Pacific Plate, later plate retreat, and deep fault activities including the Lanliao, Yellow River, and Changyuan faults within the basin. This study may offer valuable heat source data for exploring geothermal and oil and gas resources in the Dongpu Depression.