| Title | Classification of Geothermal Systems in China |
|---|---|
| Authors | Zhonghe PANG Ji LUO Jumei PANG |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | resourc calssification, China, heat source, mantle plume, deep faulting, crustal magmatism |
| Abstract | Classification of geothermal systems provides good basis for exploration and assessment of geothermal resources. China is rich in geothermal resources. There have been different classification schemes developed and used in the country in the past. These are currently classified according to their temperature ranges that result in a high-inter medium-low scale. This has been quite useful in geothermal development and utilization. However, with the evolving trends in utilizing more and more geothermal heat in other forms, the limitation of this kind of classification scheme is encountered with problems. There is a need to set up new schemes of classification. The search for geothermal resources is governed by the general laws of heat accumulation in the earth’s crust at reasonable depth. In this paper we propose a new classification which is based on the type of heat source, followed by mechanism of heat transfer. Five types of tectono-genic heat sources are identified and two types of heat transfer mechanisms have been used for the classification. The dominant factor in determining the uneven distribution or accumulation of heat energy in the crust is emphasized. Other influencing factors are used to further classify the resources into subcategories. Geothermal prospects or plays in the Himalayas are considered to be supplied with crustal magmatism/partial crustal melting, caused by collision-induced heat conversion from mechanical energy. Geothermal resources in the hot and warm basins in east and central China are fed by elevated heat flux from mantle upwelling in a rifting tectonic background, typical examples are the Bohaibay and Songliao Basins. Mantle heat is also dominating those geothermal resources found in regions with recent volcanic activities or where Cenozoic mantle plumes are found to exist. Good examples are Tengchong geothermal field in SW China and Changbaishan geothermal play in NE China. Deep faulting also induces heat accumulation in the crust that serves as an additional heat source that is found in major fault zones. Tanlu fault zone in eastern China is a typical example of this, so are those in SE China, including Zhangzhou, Fuzhou geothermal fields. Geothermal resources with dominant radiogenic heat contribution from radio nuclides have not been confirmed but maybe a new type to be discovered in China. The search for hot dry rock geothermal resources should also be based on this fundamental understanding. This classification scheme is believed to be more effective in guiding geothermal exploration and assessment of resources, which will also be briefly described in the paper. |