Characteristics and origin of the geothermal anomaly in Sijia, Hebei Province

Sijia geothermal anomaly with lot geothermal energy is located in the northwestern part of Qinglong of Hebei Province.In this paper, in order to protect and utilize the geothermal resources scientifically, the geothermal anomaly is studied by means of geothermal field measurement, hydrochemistry and isotope measurement, geophysics measurement, etc. The formation mechanism, occurrence environment and circulation mechanism of geothermal resources in four abnormal geothermal areas are discussed for the first time.According to the study of this area, it is found that the buried depth of geothermal wells in the four geothermal anomalies ranges from -0.94 m to 3.02 m, which is characterized by the shallow depth of the water level.The center of the anomaly in the area is dominated by vertical upward convective heat transfer, and the periphery of the anomaly is dominated by conductive heat transfer.The deep heat flow rises along the fault junction of the anomaly center and generates lateral migration and diffusion.It is stored within a certain range and formed geothermal anomalies in this area.The interpretation results of the CSAMT show that the deep granite body in this area is cut, so that the deep heat flow can rise along the fault, and mixed and heated to the bottom of the Sijia geothermal anomaly areas to form geothermal anomalies in the area.The results of water quality analysis indicated that the hydro-chemical type of the geothermal fluid in this area is mainly SO₄^2--Na⁺ type, F^- and SiO₂ content both have a good positive correlation with water temperature, and those mass concentration are strictly controlled by the ground temperature field.The underground hot water in this area is replenished by atmospheric precipitation, which is the cause of the atmosphere.The value of ³H of the underground hot water in the area is low, ranging from 0.6 T.U to 0.8 T.U, which directive considers that the underground hot water in this area is older than 30 years.The achievement of these results will lead the geothermal resources exploration in eastern Hebei and similar mountainous areas.