中国东部地热异常区深层高温分布特征与动力学背景

High-temperature characteristics and geodynamic background at depth of geothermal anomaly areas in eastern China

中国东部的东北地热异常区、华北及华东地热异常区、东南丘陵-沿海地热异常区是中国重要的地热资源区,研究其深部地温分布特征与动力学背景对合理开发、高效利用地热资源具有重要的科学意义。中国东部自北向南,地热地质条件及热源成因各不相同。东北地区地热资源主要分布在长白山、松辽盆地、二连盆地以及依兰-伊通裂谷地堑,是火山、裂谷地堑、深断裂活动区,其深部热源与地温分布主要与西太平洋现代俯冲板片的岩浆活动有关。华北及华东地区地热资源主要分布在渤海湾盆地、南华北盆地群、郯庐断裂带的临沂-郯城段以及苏北盆地,是裂谷地堑、活动深断裂、岩溶热储发育区,其深部热源及地温分布主要与青藏高原东向挤出、太平洋俯冲后撤导致的盆地伸展、断陷以及深大断裂带走滑活动有关。东南丘陵-沿海地区地热资源主要分布在广东中西部、江西中南部以及福建东北部,是火山、岩体放射性高值区,其深部热源及地温分布主要与南海张裂、岩石圈减薄的岩浆活动有关。深部地温及居里面计算结果表明:中国东部地热异常区热流值≥80 mW/m^(2)的点在10 km深度的地温分别为,东北260~360℃,华北及华东270~400℃,东南丘陵-沿海地区260~340℃。在居里温度统一取475℃的条件下,居里面深度分别为:东北14.7~23.7 km,平均20.5 km;华北及华东18.4~26.5 km,平均22.1 km;东南丘陵-沿海地区16.9~24.9 km,平均21.9 km。综合分析认为,中国东部存在3种不同特征的地热资源区:长白山、东营等地,浅层地温高,居里面浅,地幔热源浅;松辽盆地中部的大安-大庆之间、渤中坳陷北侧的唐山等地,浅层地温高,但居里面深,地幔热源深;泉州-漳州之间浅层地温低,但居里面浅,地幔热源浅。

There are many geothermal resource areas in eastern China, such as the Dongbei(northeastern China), Huabei-Huadong(northern and eastern China) and Southeast Hilly Coast geothermal anomaly areas. In order to rationally exploit and efficiently utilize geothermal resources, it is necessary to study the geothermal distribution and geodynamic background at depth of these geothermal anomaly areas. Different geothermal anomaly areas in eastern China have different geothermal geological conditions and heat source genesis. The Dongbei geothermal anomaly area-with geothermal resources mainly distributed in the Changbai Mountain, Songliao Basin, Erlian Basin and Yilan-Yitong fault graben-is an active area of volcanos, rifts and deep faults, and its deep heat-source and high-temperature anomaly are mainly related to magmatism caused by the western Pacific subduction. The Huabei-Huadong geothermal anomaly area-where geothermal resources are mainly distributed in the Bohai Bay Basin, South Huabei Basin Group, Linyi-Tancheng section of the Tanlu fault zone as well as Subei Basin-is a development area of rift valleys, active deep faults and karst thermal reservoirs;the deep heat-source and high-temperature anomaly in this area are mainly related to basin extension, fault depression and deep fault sliding caused by eastward compression of the Qinghai-Tibet Plateau and subduction-retreat of the Pacific plate. The Southeast Hilly Coast geothermal anomaly area-where geothermal resources are mainly distributed in central and western Guangdong, central and southern Jiangxi and northeast Fujian-is an area with volcanic belts and rock masses that have high radioactive element contents, and its deep heat-source and high-temperature anomalies are mainly related to magmatism caused by lithospheric tension thinning in the South China Sea. According to our calculation, in areas with heat flow greater than 80 mW/m^(2), ground temperatures at 10 km depth can range between 260-360 ℃ in Dongbei, 270-400 ℃ in Huabei-Huadong, and 260-340 ℃ in Southeast Hilly Coast area. When the Curie temperature is taken as 475 ℃, the Curie depths can range between 14.7-23.7 km in Dongbei, 18.4-26.5 km in Huabei-Huadong, and 16.9-24.9 km in Southeast Hilly Coast area. Through comprehensive analysis we found that there are three types of high-quality geothermal resource areas in eastern China, with different thermal structures: 1) high shallow-ground temperature, deep Curie depth and shallow mantle heat-source in the Changbai Mountain and Dongying area;2) high shallow-ground temperature, deep Curie depth and deep mantle heat-source in the central Songliao Basin and northeastern Bohai Bay Basin;and 3) low shallow-ground temperature, shallow Curie depth and shallow mantle heat-source in the area between Quanzhou and Zhangzhou.