Terrestrial heat flow measurement and numerical simulation of lithospheric thermal structure in western Sichuan, China

Abstract

The western Sichuan in the eastern Qinghai-Tibet plateau has significant geothermal potential. Heat flow is one of the most important parameters in geothermic, its measurement can help obtain a better understanding of the regional lithospheric thermal structure. In this study, we reported 4 heat flow data based on the continuous steady-state temperature logging and rock thermal conductivity test, including two class-A and two class-D data. Furthermore, we calculated the lithospheric thermal structure by a 2D steady-state thermal conduction equation in COMSOL, analyzing the lateral differences of lithospheric thermal structure in the eastern Qinghai-Tibet plateau. Our study has determined that the heat flow values in the western Sichuan range from 94.7 to 116.2 mW/m2, with a corresponding geothermal gradient of 32.1–37.3 °C/km. Moreover, numerical simulation results indicate significant differences in lithospheric thermal structure between western Sichuan and Sichuan Basin, where the Longmen Shan fault zone is a crucial regional tectonic boundary and a significant temperature gradient zone. Specifically, the Moho temperature in the western Sichuan region ranges from 1000 to 1200 °C with an average temperature of 1060 °C, while the Sichuan Basin ranges from 600 to 700 °C. Besides, the thermal lithosphere thickness in the western Sichuan and the Sichuan Basin is 88–97 km and 105–110 km, respectively. These observations suggest that the western Sichuan region is characterized by high thermal anomaly and provide theoretical evidence for the geodynamic and geothermal development in this area. Finally, we suggest that the high thermal anomaly in western Sichuan is the result of a combination of factors, such as thickened crust, high radioactive heat production, and shear frictional heating from deep fault and so on.