Mantle Heat Flow and Deep Temperature of Jiyang Depression, Shandong, North China

Abstract

The constitution of heat flow and deeper temperature status of different layers in the Jiyang depression plays an important role in analyzing the deep structure of the lithosphere, and interpreting basin formation, evolution and dynamics. According to the latest drilling data and deep geophysical sounding results from the Jiyang depression, two typical crustal structure models which represent depression part and uplift together with margin in this area were determined respectively. This crustal structure is in four layers, composed of sediments, upper, middle and lower crust, respectively. Using the multi-channel spectrum analysis method, the U, Th and ~(40)K content of 43 core samples in the working area were obtained. Statistical results indicate that the average heat production rate of the Jiyang depression is (1.4±0.26) μW/m~3. Based on the terrestrial heat flow distribution of the basin, combined with the heat production of the Jiyang depression deep crust, the mantle heat flow was calculated by means of the “stripping” method, from the shallow to the deep layer of the crust. In addition, the temperature of the upper mantle was calculated using the one-dimensional stable state heat transfer equation. Results indicate that the mantle heat flow for the Jiyang depression is about 38.4-39.2 mW/m~2, which amounts to 58% of the total surface heat flow. This indicates that more than half of the surface heat flow in this area is derived from the mantle. The temperature of the upper mantle is about 602-636 ℃. The Jiyang depression is characterized by a relatively high mantle heat flow value and a high ratio of mantle to surface heat flow. This thermal regime between tectonically active and stable areas is unique in comparison to any other basin in the world.