大陆张裂三维有限元的数值模拟

采用纯数值模拟的方法,研究了大陆岩石圈在拉张和底部隆起作用下的张裂现象,编制了三维粘弹性有限元程序,结果表明:(1)单纯拉张或底部隆起时不会造成岩石圈块体层间的相互滑动,不会产生不对称共轭扩张边缘,块体的中间部分总是首先被拉薄而分离,应力应变转移集中到两侧,张裂的不对称性取决于周边的约束或加载条件,张裂共轭边缘的不对称性与周边块体的作用及其它地质改造作用密切相关。(2)拉张与底部隆起同时作用时,将会造成层间的相互滑动,且应力较大。(3)介质的塑性或流变性对张裂及应力有很大的影响,如对位移产生一定影响,同时应力值降低,使层间产生相对运动,张裂以一种渐变的形式出现。

3D finite element numerical simulation of lithosphere rifting

Based on a 3D viscous finite element program written by the authors,the lithosphere rifting caused by extension pulling and bottom rising is numerically simulated.The results of simulation show that pure pulling or rising cannot result in asymmetric conjugate margin,the middle part becomes thinner and separates first,and the stress is accumulated to both loaded sides; the formation of asymmetric conjugate margin depends on the constrains and loadings,so it is deduced that the observed asymmetric conjugate margin might be caused by the interaction between vicinity blocks or by other geological activities;according to simulated results,when lithosphere block is affected by extension pulling and bottom rising together,the relative sliding among different layers that produces the asymmetric conjugate margin is obvious,otherwise it is not obvious;plastic or rheological properties of the practical layers of lithosphere play an important role in the rifting process of lithosphere block.