Thermal budget of hydrothermal systems for the Xianshuihe fault belt in the SE Tibetan Plateau: Insights to the geothermal accumulation processes

The behavior of fault belt is related to temperature, pressure, rock characteristics and fluid activity while the heat transfer processes play crucial role on the dynamic behavior of the fault. However, the thermal characteristic of large strike-slip fault in activity orogenic belt is still unclear. This study constructed a thermal budget model of the Xianshuihe Fault Zone by using four elements model—pure conduction, rainfall infiltration, groundwater discharge, and frictional heating—the different heat fluxes at various depths in the study area were calculated. The spatial characteristics and variations of heat flux with depth were analyzed. The results show that the surface heat flux in the study area is approximately 22 W/m² which is consistent with the soil heat flux measurement. Among the heat flux models, rainfall convection and groundwater discharge are the primary controls of heat transfer which contributing 9.84 W/m² and 8.67 W/m², respectively. These two parts account for over 80 % of the surface heat flux at shallow depths (1–3 km). The pure conduction contributes around 0.16 W/m² approximately 1 % of the total while the frictional heating model provides a surface heat flux of 3.13 W/m², accounting for about 14 % of the total. At depths exceeding 9 km, the frictional heating increasing and contribution exceeds 95 % that is the primary controls of heat transfer in the deeper parts. Our thermal budget results are therefore crucial to understanding the heat accumulation processes and earthquake regime on the fault zone.