伸展盆地地表热流值的模拟计算—以渤海湾盆地济阳坳陷为例

伸展盆地的大地热流值可以认为是由地幔热流，地壳内部和盆地沉积物生热效应以及岩石圈和沉积物导热性质等多个因素综合叠加的结果。本文根据传热学理论，分析了纯剪切模式条件下伸展盆地内的地表热流值贡献的分布规律及其与伸展因子的理想关系，认为深部热源的能量，伸展因子大小，地壳浅层的生热性质以及盆地构造位置是控制盆地热流高低和展布的关键因素。结合沉积地层的导热性质，放射性元素的生热效应，岩浆区的现今地表热流分布，得到了与正演模拟相接近的结果，验证了该方法思路的有效性。同时对该地区幕式伸展裂陷过程中的地表热流值变化趋势进行了模拟，认为在不同的伸展裂陷幕地表热流值表现为阶段式的升高，在末期达到最大值。

An Inversion Method of the Surface Thermal Flux Distribution in Extensional Basins: A Case Study of Jiyang Depression, Bohai Bay Basin

In an extensional basin, the surface thermal flux could be controlled by several factors such as the thermal flux derived from mantle, radioactive heat generation of the upper crust and sediments, and the thermal conductivities of lithosphere and sedimentary strata. According to the thermal conduction theory, this paper analyzes the surface thermal flux distribution and its ideal relation with the extension factor in the process of basin evolution within the pure-shear model. As a result, the surface thermal flux in an extensional sedimentary basin is always dominated by the energy of deep thermal sources, extension factor, radioactive heat generation in the upper crust and also the structural position in the basin. In combination with the real geologic phenomena during the basin evolution such as thermal conductivity of sedimentary strata, magma underplating and volcanism, this paper improves the traditional pure-shear model. Then the current surface thermal flux distribution in the Jiyang depression in the Bohai Bay basin is inversed. The result is quite similar to that calculated by forward methods. Using an improved pure -shear stretching model, the surface thermal flux variations during multiple episodes of extension in the Jiyang depression are also simulated. This inversion method provides an efficient way to research the basin thermal evolution and evaluate petroleum resources quantitatively, especially is suitable to the area lacking geologic data.