Crustal Structure and Geothermal Mechanism of the Gonghe-Guide Basin Based on EIGEN-6C4 Satellite Gravity and Aeromagnetic Data

Abstract

The Gonghe-Guide Basin is situated in the northeastern edge of the Tibetan Plateau, one of China’s main targets for geothermal research and exploitation. We present a new crustal structure of the entire basin by using EIGEN-6C4 satellite gravity and aeromagnetic data aimed to further recognize the geothermal mechanisms. The data are processed using the wavelet multi-scale decomposition method and the iterative compact depth from extreme points imaging method. The gravity inversion results reveal distinct low-density regions in the middle-upper crust at 15–35 km depth, which is most likely caused by partial melting. The magnetic inversion results show negative or no magnetism within a similar depth range. But at shallow depths of the same horizontal positions, there is high positive magnetism, which can be interpreted as granite. The results correspond well with the magnetotelluric and seismic results and can be an effective supplement. To confirm and validate this conclusion, a 2D geological model of a profile from a typical area is created to show the detailed tectonic. Based on the new crustal structure results, the suggested geothermal target is the low/negative density corresponding to low/negative magnetism located at deep depths and high/positive magnetism located at shallow depths. Then we established a geological conceptual model to illustrate this process. This indicates that tectonic movement is taking place in the deep part of the earth in the Gonghe-Guide Basin. The research on the geological structure and geothermal heat source mechanism in the Gonghe-Guide Basin can provide a primary reference for research on geothermal resources in other areas with similar geological structures.