贝加尔裂谷构造发育的主控因素:基于地球动力学数值模拟

Main Controlling Factors of Structure of Baikal Rift:Based on Geodynamic Numerical Simulation

贝加尔裂谷位于西伯利亚克拉通和萨彦-贝加尔造山带的拼合部位,两侧岩石圈结构及流变性存在明显差异,区域构造演化过程复杂.通过数值模拟方法,正演贝加尔裂谷区岩石圈形变过程,探讨下地壳流变性及先存薄弱缝合带对贝加尔裂谷构造发育的影响.结果显示:裂谷伸展中心两侧岩石圈下地壳流变学性质差异导致应力向造山带一侧传递,裂谷两侧发育不对称的构造样式,其中造山带一侧主要为大区域的铲状断层,而在克拉通一侧主要为小范围的高角度正断层;当岩石圈拼合部位存在先存薄弱缝合带时,会限制应力向造山带一侧传递,导致造山带一侧断裂的发育规模减小,裂谷呈现“窄且深凹陷”的不对称构造特征.

The Baikal rift is located in the convergent zone of the Siberian craton and Sayan-Baikal belt.There are obvious differences in the lithospheric structure and rheological property between the two sides of the rift,and the regional tectonic evolution is complex.Here it investigate the influence of rheological property of the lower crust and preexisting weak zone on the evolution of the Baikal rift using numerical simulation.The results show that the difference in the rheology of the lower crust on both sides of the rift extension center leads to the propagation of stress to the Sayan-Baikal belt,in which large-scale listric faults mainly develop on the Sayan-Baikal belt side,while small-scale high-angle normal faults mainly develop on the cratonic side.If there is a weak zone in the suture zone of lithosphere,the transfer of stress to the side of the Sayan-Baikal belt is limited,resulting in a reduced scale of faulting on the side of Sayan-Baikal belt,and the development of the asymmetric structure of"narrow and deep depression".