Non-seismic geophysical analysis of potential geothermal resources in the Longgang Block, Northeast China

Although geothermal energy has many clear advantages, including its sustainability and environmentally friendly nature, research into potential geothermal resources across the Longgang Block, Northeast China, has been limited. Here we present the first analysis of the potential geothermal resources in this region that employs joint geological and non-seismic geophysical methods to identify target areas that may be economically viable. We acquire and analyze high-precision gravity, magnetic, and magnetotelluric sounding data, which are constrained using the petrophysical parameters of outcropping rocks across the Longgang Block, to conduct a comprehensive evaluation of the region’s deep geological structures and their geothermal resources potential, with a focus on identifying faults, rock masses, and thermal storage structures. We find that Archean granitic gneiss and Mesozoic rock masses in the deeper section of the Longgang Block possess weak gravity anomalies and high resistivities. We also identify thermal storage structures near these deeper geological units based on their extremely low resistivities. The data are used to infer the dip and depth of known or hidden faults, to constrain the spatial distribution of intrusive rock masses, and to determine the spatial distribution of subsurface thermal storage structures. The potential of the target areas for geothermal resources exploitation is divided into three grades based on contact depths between faults and thermal storage structures, and the scale of their thermal storage structures. Our results suggest that a joint non-seismic geophysical approach can be effective in locating and evaluating geothermal resources in complex geological settings.