渤海湾盆地中、新生代岩石圈热结构研究

Meso-Cenozoic Lithospheric Thermal Structure in the Bohai Bay Basin

本文以浅部沉积盆地热历史恢复结果为基础,结合地热学的有关理论计算得到渤海湾盆地中生代以来不同地质时期壳幔热流配分及莫霍面温度。结果显示,渤海湾盆地在早白垩世晚期和古近纪中晚期达到两次地幔热流与地表热流之比高峰,其两期地幔热流占地表热流比例都超过65%。莫霍面温度在早白垩世晚期、古近纪中晚期及新近纪早期(仅在临清坳陷、沧县隆起和冀中坳陷)出现3次高峰,其温度分别为900～1100℃、820～900℃和770～810℃。本文的研究不仅揭示出白垩纪是渤海湾盆地岩石圈热结构的重要转型期,即由三叠纪和侏罗纪的"冷幔热壳"型转变为白垩纪以来的"热幔冷壳"型的岩石圈热结构,还揭示出渤海湾盆地在早白垩世晚期和古近纪中晚期发生两期强烈的构造裂陷作用。因此,本文的研究可以为中国东部大陆岩石圈地球动力学的研究提供地热学参数。

In this paper, the distribution of the mantle heat flow, crust heat flow and the Moho surface temperatures in the different geologic periods were calculated on the basis of results of the thermal history of shallow sedimentary basin in combination with the theory of the geothermics. The results show that the ratio of the mantle heat flow and surface heat flow reached high peaks twice in the late period of the Early Cretaceous and the mid-late period of the Paleogene, respectively, and the corresponding mantle heat flows were more than 65 % of the surface heat flows. The Moho surface temperatures reached high peaks three times, 900～1100℃, 820～900℃ and 770～810℃, in the late period of the Early Cretaceous, the mid-late period of the Paleogene and the early period of the Neogene（only Linqing depression, Cangxian uplift and Jizhong depression）, respectively. The studies not only revealed the Cretaceous was an important period of significant change during the geologic history in the Bohai Bay Basin： the lithospheric thermal structure began to transform from ＂cold mantle and hot crust＂ type before the Cretaceous to ＂hot mantle and cold crust＂ type since the Cretaceous, but also revealed that the basin has experienced two large-scale tectonic rifting. Therefore, this paper may provide the thermal parameters for the studies of the geodynamic evolution of the eastern China.