Crustal Thermal Structure and Deep Heat Source Conditions in Songliao Basin, NE China

Abstract

The Songliao Basin is a key geothermal resource area for medium and low temperature geothermal energy in China. Using the latest seismic imaging data, combined with the gravity, geomagnetism and geothermal observation data and the relationship between basin tectonic evolution and mantle heat flow, the heat distribution ratio of deep and shallow strata, the depth of Moho surface and Curie surface, and the heat generation rate structure in Songliao Basin were calculated. The results show that ① the geothermal field of the shallow crust in Songliao Basin is dominated by conductive heat transfer; ② although the Moho surface in the center of the basin is uplifted, the heat flow of the upper mantle is in a state of decay and decline, and the heating of the upper mantle is insufficient, resulting in a relatively low temperature of the Moho surface; ③ the Curie surface in the center of the basin is deeper, which is related to the thermal relaxation of the upper mantle; above the Curie surface, the geothermal gradient is high due to the higher radioactive heat generation rate of granite; under the Curie surface, the geothermal gradient decreases due to the attenuation and fall of the mantle heat flow. It is considered that the upper mantle in the central depression is in the thermal relaxation stage of heat flow attenuation, and its contribution to the surface heat flow is less than that of the radioactive heat generation in the upper crust. The origin of surface thermal anomaly in the central Songliao Basin is mainly the radioactive heat generation of granite in the upper crust.