Changbaishan Tianchi volcano geothermal system: magma chamber and hidden high-temperature geothermal resources

Changbaishan Tianchi volcano is a late Cenozoic central eruptive composite layered volcano. Since the Holocene, many large-scale eruptions have occurred. So far, the data of tectonic earthquake, surface deformation and hot spring gas composition related to deep magmatic thermal disturbance indicate that volcanoes will still erupt again, which is a potential high-temperature geothermal resource area in eastern China. There are abundant groundwater resources around Changbaishan Tianchi Volcano, and there is sufficient underground heating-sources in magma chamber, which provides the potential advantage of forming high-temperature geothermal resources. In order to study the high temperature geothermal resources hidden in the shallow crust, this paper uses geothermal methods to calculate and analyze the stratigraphic structure, thermal state and volcanic geothermal system in this area based on field invesigation. The results show that the temperature at 2km depth is 66～110℃, and that at 12km depth is 313～417℃. The Curie isotherm surface is shallow, with an average depth of 12.7km and a Curie point temperature of 375 ℃ in this area. The eruption center of Changbaishan Tianchi volcanic and Wangtian'e volcano is the uplift area of Curie isothermal surface. Under the constraint of basement velocity of artificial earthquake, gravity inversion found that, there are density step high pressure zones in the sedimentary strata with a depth of about 3.5～5.5 km. It is a favorable area for forming concealed high-temperature geothermal resources between high pressure zone and magma chamber.