地热田热量来源及形成主控因素

Sources of Heat and Control Factors in Geothermal Field

地热能越来越受到重视,但地热田的形成机制和热量的来源仍存在争议,多数学者认为岩浆囊可以为地热田直接供热.以二维热传导正演模拟为手段得出,盖层是形成地热田的必要条件;在浅部存在高热传导层时,地温剖面会出现镜像倒影形态,温度在垂向上分为高梯度段、低梯度段和低温段,侵位较浅(<10km)的岩浆囊散热和进入热平衡时间小于20~50万a.结合大量地热田温度资料分析认为,地热田的热量不是因为存在异常热源(如岩浆囊),而是来源于正常的基底热流.当深部热量传递到地表时,由于近地表物质的热传导能力的差异引起温度场发生变化,即地热田之下存在高热传导层快速地将基底热量传递到浅层而形成异常高温.

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 kin） 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 mag ma 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.