【摘要】 本文根据对华北平原盆地内大地电磁测深资料反演得到的最新结果,结合分析地震测深得到的地震波速度结构,研究了区域内深部热场分布特征及剩余重力异常演绎规律,得出了关于华北平原盆地区在构造上和动力学过程中表现出的四个明显的特点。最后对华北新生代盆地形成和演化过程中热和重力作用进行了初步分析。更多还原

【Abstract】 Geophysical data, obtained from the Cenozoic North China Plain Basin and adjacent regions, has been synthetically analysed. New information about the electrical structure of the crust and the upper mantle are obtained by using the inversion method of continuous resistivity variation. On the basis of these results, the temperature distribution and the volume fraction of the melt phase of rocks in the uppermost mantle are determined. The electrical structure is compared with the seismic wave velocity structure of the crust and upper mantle beneath these regions. The rapid gravity computation method for two-dimensional bodies is used for calculating the gravitational anomaly of each sediment layer and the residual anomalies corresponding to the relevant stripped layers. These results suggest the following tectonic and dynamic characters in the regions:1. Characteristic subsidence and extension occur in the basin region whereas compression and rising appear in the shoulders. Within the basin region, depressions and uplifts appear one after another in succession.2. The crust and lithosphere beneath the basin are thinner than those beneath the adjacent regions, those beneath the depressions are thinner than those beneath the uplifts within the basin.3. The velocity value of the lower crust is greater and the Bouguer gravity anomalies are higher in the basin than those in the adjacent mountains.4. There are intermediate low resistivity-low velocity zones in the crust and higher heat flow in the basin. A higher deep temperature field exists beneath the depressions.The mantle’s upwelling model with subconvections can reproduce the above mentioned characters and trace the formation process of the North China Plain Basin. This model includes three stages. The first stage is a deep temperature increase with a material permeating upward. This stage corresponds to the processes occurring from the later Cretaceous period to the Paleocene epoch. The second stage represents upwelling with connected smaller branch comvections corresponding to the processes occurring from the Eocene to the Oligocene epoch. Since the later Tertiary period the basin has been in the last stage of thermal contraction and subsidence.更多还原