Investigating the Heat Source of Yangbajing Geothermal Field, South Tibet, with Magnetotelluric Data

The Yangbajing geothermal field, located in the south part of the Tibetan plateau is the largest high-temperature geothermal system of the whole plateau. Numerous hydrological, geological, and geothermal studies have been conducted to gain insights into the heat source of the geothermal system. Geothermal studies show that heat flow in this area is extremely high. However, heat flow contributed by the crustal radiogenic heating together with mantle heating still can not explain the anomalously high heat flow (~116 mW/m²) here. In this study, we use the high-resolution 3D electrical resistivity models, generated from magnetotelluric data in the Yangbajing region of southern Tibet, that image zones of enhanced conductivity in the middle crust. Such features may relate to partial melts (or magma chambers) with a melt fraction of more than 19%. Here, with the help of other available data, primarily hydrothermal and geochemical data, we estimated the heat flow generated by the partial melts in this area. Furthermore, we performed a set of simulations to reproduce the thermal evolution of the magma chambers in this region. our results indicate that the magma chambers below the study region may provide sufficient heat flow to fill the relatively large heat flow gap (~20.25 mW/m² ), apart from the mantle heat conduction and radiogenic heating for the geothermal system. In addition, the thermal evolution simulations show that the magma chambers beneath the Yangbajing geothermal system may remain relatively warm, after the long cooling procedure. Our results highlight the possible contribution of the magmatic heat generation to the Yangbajing geothermal system, and reveal that crust contributes a significant proportion of the total surface heat flow (~70.75 mW/m²) in the Yangbajing geothermal field, which is much higher when compared with the typical rift basins in China.