The crustal heat production rate and crustal and mantle heat flow distribution in the land areas of China

The crustal and mantle heat flow distribution reflects the deep heat sources and the most fundamental geothermal background of a region and provides the most basic constraint on geothermal resources in a certain region. Based on data from Crust 1.0 and other geological data, this study divided the land areas of China into 19 horizontal tectonic zones and set the distribution ranges and thicknesses of strata between the Quaternary and the upper mantle in the structural zones vertically. This study measured 664 sets of data on radioactive heat production rates nationwide, obtained approximately 1000 sets of crustal U, Th, and K contents and A data, and systematically confirmed the radioactive heat production rate of each stratumin the tectonic zones. The statistical results show that the upper, middle, and lower crusts in the land area of China have an average heat production rate of 1.31 mu W center dot m(-3), 0.57 mu W center dot m(-3), and 0.22 mu W center dot m(-3), respectively. Based on the map, the above data as well as the latest measured data of national terrestrial heat flow (1503 sets), this study analysed the distribution of the crustal and mantle heat flow in the land areas of China, obtaining the following results. The land areas of China with a ratio of the crustal heat-flow value to the mantle heat-flow value (q(c)/q(m)) greater than 1 and 1.2 cover an area of 80.1% and 65.8% of the total area of the land areas, respectively. The crust serves as the major heat source of terrestrial heat flow in the land areas of China except some basins in eastern and central China. Among crustal heat sources, bedrock and the upper and middle crusts contribute a vast majority of terrestrial heat flow (roughly 50%). The crustal heat flow in the land area of China has an area-weighted average of approximately 39.1 mW center dot m(-2), which is the highest in the Qinghai-Tibet Plateau and the second in the southeast coastal areas due to the large crustal thickness and the high heat production rate of bedrock strata, respectively. The mantle heat flow in the land area of China has an area-weighted average of 29.7 mW center dot m(-2) which is close to the global average value of mantle heat flow. The eastern coastal area, areas around Ordos, and the Tibetan-Yunnan junction have higher mantle heat flow than the other zones. The areas with high crustal and mantle heat flow are highly consistent with main distribution areas of geothermal resources in China.