用物理模拟实验研究走滑断裂和拉分盆地

PHYSICAL EXPERIMENTAS ON STRIKE-SLIP FAULT AND PULL-APART BASIN

本文按照下地壳和岩石圈地幔塑性流动控制上地壳构造变形的思想,采用脆延性双层模型,在考虑模型相似性的条件下,通过延性层流动驱动脆性层进行走滑断裂和拉分盆地模拟实验。实验结果表明,在左行走滑阶段发育两条"S"型左行右阶断裂带;在右行走滑改造阶段,早期左行右阶断裂带被改造为"Z"型右行右阶断裂带。走滑断裂发育过程中共有三种类型的拉张伸展:(1)"S"型破裂逐渐伸展,形成多个菱形盆地;(2)几个相邻的斜列"S"型断裂在剪切作用下端部被错断连通,形成"地堑—地垒"构造;(3)在右行走滑阶段,沿右行右阶断裂拉张形成拉分盆地。先存的上隆拱张断裂限制了走滑断裂的位置和方向。脆性层强度对走滑断裂的形成和发展具有约束作用,脆性层结构对脆延性的层间耦合作用和走滑断裂特征具有显著影响。

According to the theory that plastic flow of the lower layer(including lower crust and upper mantle lithosphere)controls upper layer (upper crust)deformation in the multilayer lithosphere,the paper studies the physical experiments of strikeslip fault and pullapart basin adopted ductile/brittle doublelayers model. The experiment results show that strikeslip model developed sinistral rightstep fault zone which consisted of a lot of \!S\'type faults during sinistral strikeslip stage. The early fault zone was reconstructed and became dextral rightstep \!Z\'type fault during dextral strikeslip stage.There are threetype extensions in the strikeslip fault zone:(1)a lot of diamond basins formed with stretching of 'S'type fault;(2)the 'grabenhorst' structure appeared when the ends of adjacent 'S'faults were sheared and connecting;(3)the pullapart basins formed along right steps of dextral faults during the second strikeslip stage. The stretching faults formed in the stage of uplifting limit the location and the direction of strikeslip faults.Strength of brittlelayer restricts the forming and the development of strikeslip faults,and the texture of brittlelayer influences coupling of brittleplastic layers and characters of strikealip faults.