CHARACTERISTICS OF CHINESE CONTINENT CURIE POINT ISOTHERM

Based on the latest compiled 1/100 million aeromagnetic map data, the Curie point depth was estimated by power spectrum method. The calculation obtained 8004 Curie point depth values in Chinese continent. Eventually, we completely compiled the Chinese continental Curie point isotherm map. This map first fully shows the characteristics of Chinese continental Curie point depth. The study shows that Curie point isotherm is characterized by depression inside the stable blocks with the depth of 28∼45 km, such as the Tarim Basin, Junggar Basin, Qaidam Basin, Hoh Xil-Bayan Har Depression area, the Yangtze Basin area, North China basin area, Songliao Basin, Erlian Basin, Bayan-Wuwei-Chaoshui basin, Pearl River Estuary-southeast Hainan basin. The Curie depth of North China basin area is shallower than Tarim continent block and Yangtze continent block, which may be related to the fact that North China block suffered a complex post-transformation which resulted in the asthenosphere upwelling and lithospheric thinning. Hoh Xil-Bayan Har block is a NWW trending Curie point isotherm depression area in northern Tibetan Plateau, where developed a large area of Triassic sedimentary strata and experienced less magmatism. The stable blocks all have uplifted Moho and depressed Curie point isotherm. Conversely, the Curie point isotherm of active orogenic belt is characterized by uplift at the depth of 18∼26 km, such as the Mountain (Mtn.) area of northeast and northwest China, Qinling-Dabie area, West Kunlun-Tibet-Sanjiang-Kangdian area, the southeast coastal areas and so on. The uplift reflects the geothermal gradient difference caused by tectonic and magmatic activities. A collection of 816 heat flow data from published literatures are used to study the relationship between Curie point isotherm and heat flow. The results show that there is not a simply linear relationship between the depth and heat flow. When the depth is greater than 30 km, the heat flow values are less than 100 mW·m⁻². While the Curie point depth is less than 30 km, the heat flow values vary in a wide range. The high heat flow values are mostly found in the east coast of China, southern Tibet-Sanjiang area, Qinling-Dabie area, and the east of Liaoning province, which are all characterized by uplift of Curie point isotherm. These areas are important for future geothermal exploration.