## 1 Introduction  
Energy is the material basis for the existence and development of human society. Nowadays the energy problem has gradually become an important factor restricting the global economic and social development, especially the large-scale utilization of fossil fuels, which brings more and more serious environmental pollution problems. The fundamental way out of energy production and consumption revolution lies in renewable and clean energy. Compared with traditional fossil energy (coal, oil, natural gas) and nuclear energy, geothermal energy is an inexhaustible renewable clean energy. And compared with solar energy, wind energy, water energy, and other renewable energies, geothermal energy has the advantages of stability, high utilization rate, safety, low operation cost, comprehensive utilization: stable output without diurnal or dry season change; geothermal power generation can be used as both basic load and peak load regulation load; the average utilization efficiency of geothermal power generation is 73%, which is 5.2 times of the solar photovoltaic power generation, 3.5 times of wind power generation; no explosion, dam break risk and low pollution; low initial investment and long-term income; from high temperature to low temperature, it can be used for power generation, heating, bathing and breeding. It is an ideal and alternative energy.  
At present, geothermal research is very extensive. There were traditional methods for geothermal research and geothermal potential assessment, such as geological analysis [1; 2; 3], geological drilling [4; 5], geophysics [1; 6], geochemistry [1; 2; 3; 5; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16], gravity study [1; 6; 17], and other work methods. Some researches focused on geothermal development and application [18; 19; 20; 21; 22], and many employed new technologies, methods, and perspectives, including numerical simulation [23; 24; 25], remote sensing monitoring [26], isotopic geology [8; 10; 12; 27; 28; 29; 30; 31; 32], biological methods [33], ultra-high temperature geothermal research [34], geothermal database [35], and environmental protection and sustainable development [8; 12].  
Lots of above research results show that geothermal genesis is complex, and there is no universal theory suitable for all geothermal fields [36]. Therefore, in the geothermal exploration, the cause of formation should be determined accurately, which can reduce the uncertainty of technology and geology, reduce the investment risk of geothermal exploration and development, and the uncertainty of geothermal development policy, and create a bright future for geothermal utilization [37; 38; 39].  
Lushan County, China is abundant in geothermal resources. There are five geothermal fields: Shangtang, Zhongtang, Xiatang, Wentang, and Shentang hot spring areas (\"tang,\" the suffix of five place names, means \"hot water\" in ancient Chinese), forming a 50-km geothermal and hotspring belt. Through the means of remote sensing geological interpretation, field geological survey, geophysical exploration, long-term observation, geological drilling, pumping test, and water chemistry test, this study aims to (1) investigate the formation mechanism and control structure of Lushan geothermal springs; (2) find out the distribution range and water sources, water circulation, heat sources, flows of geothermal springs; and (3) assess the amount of geothermal energy.