我国陆区地壳生热率分布与壳幔热流特征研究

The crustal heat production rate and crustal and mantle heat flow distribution in the land areas of China

壳幔热流配分代表了一个地区的深部热量来源与最基础的地热背景,为区域地热资源的形成提供了重要的约束条件.本文依托CRUST1.0模型与地质资料,将中国陆区在平面上划分为19个构造区,在垂向上将这些区域从第四系沉积物至上地幔的地层划分为8个圈层,确定了这些圈层的分布范围和厚度.在全国范围内实测放射性生热率数据664组,收集地壳放射性生热率及U、Th、K元素含量数据约1000组,系统地完成了上述区域各圈层的放射性生热率填图,统计得出我国陆区上、中、下地壳生热率的平均值分别为1.31μW·m^(-3)、0.57μW·m^(-3)与0.22μW·m^(-3).在此基础上,结合最新的全国大地热流测量数据(1503组)完成了我国陆区地壳-地幔热流分布的研究.研究结果表明,我国陆区qc/qm>1的面积占80.1%、qc/qm>1.2的面积占65.8%.除我国东部、中部的一些盆地之外,在我国陆区大部分地区,地壳均为大地热流的最主要热源.地壳各圈层中,基底层至中地壳为地壳的主要的产热区域,贡献了平均约50%的大地热流值.本文以面积加权计算得我国陆区地壳热流平均值为39.1 mW·m^(-2),其中青藏高原最高、东南沿海次之,两者分别得益于较大的地壳厚度与较高的基岩地层生热率.我国陆区地幔热流平均值为29.7 mW·m^(-2),与全球地幔热流平均值接近,其中东部沿海地区、环鄂尔多斯地区、藏滇地热带分布区较高.地壳热流、地幔热流的高值区与我国的主要地热资源分布区均具有较好的一致性.

The crustal and mantle heat flow distribution reflects the deep heat sources and the most fundamental geothermal background of a region and provides the most basic constraint on geothermal resources in a certain region.Based on data from Crust 1.0 and other geological data,this study divided the land areas of China into 19 horizontal tectonic zones and set the distribution ranges and thicknesses of strata between the Quaternary and the upper mantle in the structural zones vertically.This study measured 664 sets of data on radioactive heat production rates nationwide,obtained approximately 1000 sets of crustal U,Th,and K contents and A data,and systematically confirmed the radioactive heat production rate of each stratumin the tectonic zones.The statistical results show that the upper,middle,and lower crusts in the land area of China have an average heat production rate of 1.31μW·m^(-3),0.57μW·m^(-3),and 0.22μW·m^(-3),respectively.Based on the map,the above data as well as the latest measured data of national terrestrial heat flow(1503 sets),this study analysed the distribution of the crustal and mantle heat flow in the land areas of China,obtaining the following results.The land areas of China with a ratio of the crustal heat-flow value to the mantle heat-flow value(qc/qm)greater than 1 and 1.2 cover an area of 80.1% and 65.8% of the total area of the land areas,respectively.The crust serves as the major heat source of terrestrial heat flow in the land areas of China except some basins in eastern and central China.Among crustal heat sources,bedrock and the upper and middle crusts contribute a vast majority of terrestrial heat flow(roughly 50%).The crustal heat flow in the land area of China has an area-weighted average of approximately 39.1 mW·m-2,which is the highest in the Qinghai-Tibet Plateau and the second in the southeast coastal areas due to the large crustal thickness and the high heat production rate of bedrock strata,respectively.The mantle heat flow in the land area of China has an area-weighted average of 29.7 mW·m^(-2),which is close to the global average value of mantle heat flow.The eastern coastal area,areas around Ordos,and the Tibetan-Yunnan junction have higher mantle heat flow than the other zones.The areas with high crustal and mantle heat flow are highly consistent with main distribution areas of geothermal resources in China.