安徽金寨地区花岗岩类放射性地球化学特征及岩石圈热结构研究

Radioactive Geochemical Characteristics of Granitoids and Thermal Structure of Lithosphere in Jinzhai Area,Anhui Province

为研究安徽金寨地区花岗岩类放射性地球化学特征及岩石圈热结构特征,对该地区采集的地表及钻孔花岗岩类样品进行放射性生热元素含量、岩石密度和岩石热导率测试,同时收集前人发表的金寨地区花岗岩类放射性生热元素数据进行分析。研究结果显示:金寨地区花岗岩类U、Th、K2O平均含量分别为10.84×10-6、35.07×10-6和4.82%;岩石放射性生热率的平均值为5.36μW/m3,其主要来自U和Th的放射性衰变热,K的热贡献率相对较低,一般不超过10%,U的热贡献率稍大于Th;岩石热导率的平均值为3.142 W/(m·K),与世界范围内花岗岩类热导率平均值相近。综合已有的地球物理、地球化学及地热学等资料,推断金寨地区地幔热流值略低于地壳热流值,属于“热壳冷幔”型岩石圈热结构。

In order to ascertain the radioactive geochemical characteristics and lithospheric thermal structure characteristics of granitoids in Jinzhai area,Anhui Province,the radioelement content,rock density and rock thermal conductivity of the surface and borehole granitoids samples in Jinzhai area,Anhui Province were measured,and the data of radioelement content of granitoids in Jinzhai area previously published were also collected.The results show that the average contents of U,Th and K2O in granitoids in Jinzhai area are 10.84×10-6,35.07×10-6 and 4.82%,respectively.The average radiogenic heat production is 5.36μW/m3.The main thermal contribution of rocks comes from the radioactive decay heat of U and Th,while that of K is relatively lower,generally less than 10%,and that of U is slightly higher than that of Th.The average thermal conductivity of rocks is 3.142 W/(m·k),which is close to the average thermal conductivity of granitoids in the world.Based on the existing geophysical,geochemical and geothermal data,it is concluded that the contribution of mantle heat flow value in Jinzhai area is slightly lower than that of crust heat flow value,which indicates the lithospheric thermal structure is the type of"hot crust and cold mantle".