Sources of Heat and Control Factors in Geothermal Field

Geothermal energy is attracting increasing attention. However, the formation mechanism and the source of heat in geothermal fields are still in dispute. Most scholars believe that the magma pocket can provide direct heating for geothermal fields. In this paper, by means of 2D forward modeling of heat conduction, it is found that the caprock is a necessary condition for forming geothermal fields. When there is a high heat conduction layer in the shallow part, the geothermal profile will display a mirror reflection shape, and the temperature will be divided into high gradient section, low gradient section and low temperature section. The heat dissipation and thermal equilibrium time of the shallow magma pocket (< 10 km) are less than 200 000-500 000 years. Based on the analysis of the temperature data of a large number of geothermal fields, it is concluded that the heat in geothermal fields is from normal basal heat flow instead of the presence of abnormal heat sources, such as magma pocke. When the deep heat is transferred to surface, the temperature field changes due to the difference in the heat conduction ability of the near-surface material:the high heat conduction layer under the geothermal field will rapidly transfer the base heat to the shallow layer and form the abnormal high temperature.