中国东部中新生代断陷盆地幕式裂陷过程的动力学响应和模拟模型

Episodic Rifting Dynamic Process and Quantitative Model of Mesozoic-Cenozoic Faulted Basins in Eastern China

结合盆地充填和构造演化的整体分析并进行计算机定量模拟 ,揭示了中国东部中新生代断陷盆地的沉降 -充填、构造及热演化等对幕式裂陷过程的动力学响应 .渤海湾和江汉等盆地的整个裂陷期常表现出 3～ 4个裂陷作用幕 ,不同裂陷幕的断裂展布方向、岩浆作用、沉降中心以及沉积体系分布等都发生了明显变化 .如江汉盆地从白垩至新近纪同沉积断裂的展布就显示出从北西向北东向转化的趋势 .幕式裂陷构造沉降速率的变化控制着区域性 (二级 )沉积旋回和层序类型的发育和演化 ,强烈裂陷沉降幕常发育深湖盆型层序 ,而初始和晚期裂陷幕以发育浅湖和河流 -浅湖型层序为特征 .幕式裂陷过程不能用经典的单幕裂谷模型进行正确的描述 ;通过校正每一裂陷幕的初始条件和拉伸系数 ,建立了适用于幕式拉伸裂陷过程的多幕均匀瞬时拉伸模拟模型 .应用这一模型对莺歌海盆地的模拟分析揭示了多幕裂陷过程中岩石圈结构及深部热流等的演化趋势 。

Integrated analysis of basin filling and tectonic evolution, aimed with computer modeling technique, reveals the dynamic process of basin subsidence, sedimentary infill, structure and thermal evolution in response to the multiple rifting processes of the Mesozoic-Cenozoic rift basins in eastern China. The synrift phases of these basins, such as the Bohaiwan and Jianghan basins, usually include 3 to 4 rifting episodes, and the trends of syndepositional faults, the type of volcanic rocks and the distribution of depocenters and depositional systems changed significantly in different rifting stages. The episodic change in tectonic subsidence rate controls the development and evolution of the regional (the second order) sequences. In intensively rifting subsidence episodes, deep lacustrine basin sequences are usually observed, while during the initial and final rifting episodes shallow lacustrine and fluvial basin sequences commonly form. The process of episodic rifting significantly differs from that of the simple rifting in tectonic subsidence and deep heat flow, and can not be accurately described by a simple (one episode) stretching model. Through correction of the initial stretching condition of each rifting episode and stretching index, we have programmed a multiple uniform instantaneous stretching model to simulate the formation of the basins. This model has been applied to reconstruct the lithosphere structure and to evaluate the deep thermal evolution of the Yinggehai basin. The calculated results are in agreement with geophysical data and geological observation in the basin.