摘要
济阳坳陷深部地热状况对于分析岩石圈深部结构特征、探索该盆地形成和演化的地球动力学过程具有重要意义 .依据济阳坳陷最新的钻探资料和深部地球物理探测结果 ,按沉积盖层、上、中、下地壳 4层结构 ,建立了分别代表该区凹陷部位和凸起及斜坡带上的 2种地壳结构模型 .通过多道能谱分析 ,测试了区内 4 3块岩心样品的放射性元素U、Th、40 K含量 ,统计得出了济阳坳陷沉积盖层的平均生热率为 ( 1.4 0± 0 .2 6 ) μW/m3.在研究大地热流分布的基础上 ,结合济阳坳陷地壳各岩层放射性生热率 ,采用“剥层”法 ,从地表开始 ,由浅到深逐步扣除各层段所提供的热量 ,得到了济阳坳陷的地幔热流 .并且采用相似的方法 ,利用一维稳态热传导方程 ,分析了地壳上地幔顶部的温度状况 .结果表明 ,济阳坳陷的地幔热流约为 3 8.4~3 9 .2mW/m2 ,占整个地表总热流量的 5 8% ;地幔顶部温度约为 6 0 2~ 6 3 6℃ .与世界上其他各类地质构造单元相比 ,济阳坳陷无论是地幔热流值或其与地表热流之比值都是比较高的 ,其深部地热状态具有介于稳定地区和构造活动区之间的特点
The constitution of heat flow and deeper temperature status of different layers in the Jiyang depression plays an important role in analyzing the deep structure of the lithosphere, and interpreting basin formation, evolution and dynamics. According to the latest drilling data and deep geophysical sounding results from the Jiyang depression, two typical crustal structure models which represent depression part and uplift together with margin in this area were determined respectively. This crustal structure is in four layers, composed of sediments, upper, middle and lower crust, respectively. Using the multi-channel spectrum analysis method, the U, Th and ~(40)K content of 43 core samples in the working area were obtained. Statistical results indicate that the average heat production rate of the Jiyang depression is (1.4±0.26) μW/m~3. Based on the terrestrial heat flow distribution of the basin, combined with the heat production of the Jiyang depression deep crust, the mantle heat flow was calculated by means of the “stripping” method, from the shallow to the deep layer of the crust. In addition, the temperature of the upper mantle was calculated using the one-dimensional stable state heat transfer equation. Results indicate that the mantle heat flow for the Jiyang depression is about 38.4-39.2 mW/m~2, which amounts to 58% of the total surface heat flow. This indicates that more than half of the surface heat flow in this area is derived from the mantle. The temperature of the upper mantle is about 602-636 ℃. The Jiyang depression is characterized by a relatively high mantle heat flow value and a high ratio of mantle to surface heat flow. This thermal regime between tectonically active and stable areas is unique in comparison to any other basin in the world.