摘要
中国华南地区的华夏地块位于欧亚大陆东南缘,是我国重要的矿产、地热资源区。经历了多期次的构造事件,使得区内广泛分布着不同构造期花岗岩。花岗岩类在地球及其热状态的动力学和演化中发挥着特殊的作用,其放射性衰变产生的热量是地球上的主要热源之一。我国高放射性产热型干热岩资源主要分布于华南地区,以放射性元素的衰变热为主要热源,岩性主要为花岗岩。本文通过对华南地区花岗岩数据统计,分析了华南不同地区、不同花岗岩类型的生热率情况,总结了研究区花岗岩放射性生热特征及其与大地热流之间的关系,对认识研究区地温场主控因素及地热资源分布的宏观背景具有参考价值。本文基于华南地区1933个花岗岩样品的地球化学分析得到如下认识:(1)花岗岩生热率范围0.40~17.45μW/m^(3),平均生热率为4.46±2.66μW/m^(3),同时根据大地热流与生热率分布情况,两者有着较好的对应关系;(2)放射性生热元素U、Th、K的生热贡献率分别为49.45%、40.16%和10.39%,同时,U、Th浓度和Th/U比值变化较大,与年龄无明显相关性;(3)三种类型花岗岩生热率存在差异,I型花岗岩平均生热率明显低于A型和S型花岗岩平均生热率,值为3.86±2.43μW/m^(3),A型和S型花岗岩平均生热率分别为5.55±2.91μW/m^(3)和5.00±2.58μW/m^(3);(4)利用蒙特卡罗方法计算得到华南燕山期花岗岩平均产热量为99.01×10^(5)GJ/a,折合成标准煤为3.38×10^(5)t/a,印支期花岗岩平均产热量为63.13×10^(5)GJ/a,折合成标准煤为2.15×10^(5)t/a;(5)两种地壳模型的计算表明,花岗岩在华南大地热流贡献中有着重要作用,沉积地层覆盖区域,地壳放射性生热对地表热流贡献为29.13 mW/m^(2),占总热流值的41.61%;侵入岩出露区域,地壳放射性生热对地表热流贡献为43.85 mW/m^(2),占总热流值的51.76%。
The South China Cathaysia block is located in the southeast margin of the Eurasian plate,and is an important mineral and geothermal resource area in China.After several tectonic events,granites of different tectonic stages are widely distributed in the area.Granitoids play a special role in the dynamics and evolution of the Earth and its thermal state,and the heat generated by their radioactive decay is one of the main heat sources on Earth.The high radioactive heat-producing hot dry rock resources are mainly distributed in South China,and the decay heat of radioactive elements is the main heat source,and the lithology is mainly granite.Based on the statistics of granite data in South China,this paper analyzes the heat generation rate of different granite types in different areas of South China,and summarizes the radioactive heat generation characteristics of granite in the study area and the relationship between them and terrestrial heat flow,which has reference value for understanding the main controlling factors of the geothermal field and the macro background of geothermal resource distribution in the study area.Based on the geochemical analysis of 1933 granite samples in South China,the following results are obtained:1)The heat generation rate of granite ranges from 0.40 to 17.45μW/m^(3),with an average heat generation rate of 4.56±2.66μW/m^(3),and there is a good correspondence between them according to the distribution of ground heat flow and heat generation rate;2)The contribution rates of radiothermic elements U,Th and K were 49.45%,40.16%and 10.39%,respectively.At the same time,the concentrations of U,Th and Th/U varied greatly,and there was no obvious correlation with age;3)There are differences in the heat generation rate of the three types of granite(Type I、A and S).The average heat generation rate of type I granite(3.86±2.43μW/m^(3))is significantly lower than the average heat generation rate of type A and type S granite,which are 5.55±2.91μW/m^(3) and 5.0±2.58μW/m^(3),respectively;4)A Monte Carlo method is used to calculate that the average heat yield of the Yanshanian granite in South China is 99.01×10^(5) GJ/a(1 GJ/a=109 J/a),which is converted into standard coal 3.38×10^(5) t/a,and that of Indosinian granite is 63.13×10^(5) GJ/a,which is converted into standard coal 2.15×10^(5) t/a;5)The calculation of two crustal models shows that granite plays an important role in the contribution of earth heat flow in South China.In the area covered by sedimentary strata,the contribution of Earth’s radioactive heat generation to surface heat flow is 29.13 mW/m^(2),accounting for 41.61%of the total heat flow value.In the area of intrusive rock exposure,the contribution of crustal radioactive heat generation to surface heat flow is 43.85 mW/m^(2),accounting for 51.76%of the total heat flow value.
作者
李科甫
朱传庆
LI Kefu;ZHU Chuanqing(College of Geosciences,China University of Petroleum-Beijing,Beijing 102249,China;State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum-Beijing,Beijing 102249,China)
出处
《石油科学通报》
CAS
2023年第3期259-289,共31页
Petroleum Science Bulletin
基金
国家重点研发计划课题(2021YFA0716003)资助
关键词
花岗岩
生热率
放射性生热元素
产热量
大地热流
granite
heat generation rate
radioactive heat-generating elements
heat production
heat flow
