The deep geothermal structure of high-temperature hydrothermal activity region in western Sichuan Plateau : a geophysical study

The high-temperature hydrothermal activity region in the Western Sichuan Plateau is located in the northeast margin of the eastern syntaxis of the Tibetan Plateau. This area is the easternmost part of the Mediterranean-Himalayan geothermal belt, and also a notable region of geothermal research. The hot springs in this region are distributed extensively along the Jinshajiang fault, Dege-Xiangcheng fault, Garze-Litang fault and Xianshuihe fault, forming the NW-SE strip-like high-temperature hydrothermal activity area. The geothermal analysis of this high temperature hydrothermal activity area is an important foundation for studying the deep geodynamics process of the eastern syntaxis of the Tibetan Plateau, which also contributes to exploiting and utilizing the geothermal resources in the western Sichuan Plateau. In this paper, we compare the crust-mantle thermal structure acquired from the helium isotopes measurement with geophysical results of the aeromagnetic, gravity data and shear wave data. The Moho and Curie point depth is obtained by inversion. Besides, the deep geothermal structure and geophysical background are discussed in the typical anomaly area of Batang, Litang and Kangding. The result shows that the helium isotope heat flux of the surface is in accord with the geophysical anomalies. The thermal contribution of crust and mantle in the Western Sichuan Plateau is relatively close : the average Q(c)/Q is 51. 38% in Batang, 54. 39% in the Litang area, and 42. 42% in the Kangding area. The thermal structure pattern in this region tends to be a "warm crust-warm mantle" mode. The formation of high surface heat flux in the warm crust background need to be further studied.