| Abstract |
In the north-eastern part of China the heat flow values are high in basins but low in mountains and old terrain (Erguna and Jiamusi Terrain). The correspondence among the Moho depth, high conductivity layers with the crust and upper mantle and heat flow can be found from the area. Using Cermark and Rybach's theory, the authors calculated the transformation of P wave velocity to the heat generation density, based on the refraction data. The calculated results can be used to estimate heat flow components of the mantle and crust on the terrains. These results show the differences in mantle heat flow among the terrains in the area. Mantle heat flows vary from west to east as follow: 23 mW/m2 in the Erguna Terrain, 33 mW/m2 in the Hailaer Basin, 33 mW/m2 in the Da Hinggan Mountains, 50 mW/m2 in the Songliao Basin, and 25 mW/m2 in the Jiamusi Terrains. It is a fact that the mantle heat flow values are very low in old Erguna and Jiamusi Terrains, Very high in the Songliao Basin, and middle in the Hailaer Basin and the Da Hinggan Mountains. We may draw the conclusion that the differences in geothermal structure of the crust and upper mantle cause the change in heat flow distribution among the terrains in the area. According to the calculated results, it is a fact that mantle heat flow and the stratum 10km above or below in the crust in every terrain has different contributions to the surface heat flow. Geothermal resources in low-medium temperature geothermal systems of conductive type are mainly occurred in large-scale sedimentary basins, such as Songliao basin is most promising area for development of low-medium temperature geothermal resources. In combination with the known geological and geophysical data the geothermal system structure model of the Changbai hot spring is established. The model shows that during the rising of the hot volcanic gas from a deeper magma in the center of volcanoes. It encounters the water percolated from the crater lakes and their surrounding area. The heated water then flows laterally and passes shallower subsurface. In mountainsides where faults well developed, the hot water rises and appears as surface geothermal occurrence. |