## 3 Results and Analysis
### Geological Structure Characteristics of Zhongtang and Wentang Hotsprings
#### 3.2.4 Geological Characteristics of Shentang Geothermal Field  
1. General Situation of Shentang Hotspring  
Shentang hotspring is 10.8 km away from Xiatang hot spring in the west, outcrops on a terrace on the south bank of Sha river, with an elevation of 150 m. The collected data showed that Shentang hotspring outcropped in the form of spring group, with three hotsprings in total, which were generally distributed in the north-east direction (20\({}^{\circ}\)). In this field survey of the study, all hotsprings did not show artesian flow. At present, two geothermal wells were working, from which the No. 2 well was 86 m deep, which was mainly used for bathing and breeding tropical fish, basically long-term working condition. Main parameters: water temperature 53 \({}^{\circ}\)C; water flow 45 m\({}^{3}\)/h; daily flow about 900 m\({}^{3}\)/d; water level 7.30 m; dynamic water level 12.50-13.70 m; water level drawdown about 5.20-6.40 m. The daily production of another well was about 900 m\({}^{3}\)/d, which was mainly used for bathing. Figure 9: Rock core of Xiatang geothermal drilling well: (**a**) Granite, pore developed, fault breccia; (**b**) granite, broken rock core. 2020, 10, 592  
(b) Geological Structure Characteristics of Shentang Hotspring  
Shentang hotspring is about 1400 m away from Checun-Xiatang fault in the north and 750 m away from Shuimozhuang-Licun fault in the south. Shentang geothermal field covers a large area of the quaternary system. According to the drilling data, the thickness of the quaternary system is 13.6-17.0 m, and the underlying bedrock is the andesite porphyrite of Xionger group. 700 m south of Shentang village is Yanshanian granite, in which two NE trending faults F2 are developed, extending to Shentang hotspring. In the southwest of this area, there is an andesite porphyrite of Xionger group, in which the near east-west silicified rock belt is relatively developed. According to the collected geological data, 9 NW and near EW faults were developed along the 2160 m distance of the dam axis of the nearby reservoir, among which the No.9 fault in the south of the dam had the largest scale with a fracture belt width of 200 m, which should be the Checun-Xiatang fault, indicating that the secondary faults of the parallel Checun-Xiatang fault were very developed. It can be inferred that the secondary faults parallel to the Checun-Xiatang fault and faults F1 and F2 are the main thermal control structures of Shentang geothermal field (Figure 10). (c) Geophysical Characteristics of Shentang Hotspring  
(i) Magnetotelluric Sounding (EH-4) Characteristics  
Two magnetotelluric sounding (EH-4) profiles were arranged on the east and west sides of Shentang hotspring, with an azimuth angle of about 30\({}^{\circ}\) (Figure 3). Jc1 profile was 500 m long, with a point distance of 50-100 m, and a total of 9 points were measured. Figure 11 shows that from the beginning of the profile to 350 m, it is a high resistivity geological body. From 350 to 600 m there is a relatively low resistivity depression, which is speculated to be a hot water bearing zone. The zone should be located in the contact zone between the volcanic rocks of the Middle Proterozoic Xionger group and the Yanshanian granite. The primary fracture was developed, and later it was affected by many fault activities. Then the rock among the zone was broken, rich in hot water, and became a deep thermal reservoir. Figure 10: Geological structure of Shentang geothermal field. The JC2 profile is 600 m long, with a point distance 100 m, and a total of 6 points were measured. As shown in Figure 12, there is a 400 m depression of low resistivity from the starting point of the profile. The resistivity increases gradually from the surface to the deep underground, indicating that the upper stratum is relatively broken.