基于岩体塑性位错理论的龙门山区域构造系统演化过程

Evolution of regional tectonic system in the Longmenshan mountains based on plastic dislocation theory of rocks

青藏高原对四川盆地的挤压作用导致了龙门山断裂带的形成及其山脉的隆起。本文以龙门山附近区域板块运动以及深部岩体力学特性为背景,采用FLAC3D软件模拟再现了时间跨度为700万年的龙门山区域构造系统演化过程。研究结果表明:在板块运动作用下,F1、F2和F3断层依次形成,贯通的断层对地表的抬升具有较强的控制作用,当断层贯通于地表后,龙门山及其以西的川西高原持续隆起,平均抬升速率约为1.38mm/yr,而龙门山断裂带以东的川西坳陷只有较小的抬升量,从而导致川西高原抬升8996 m,致使该区域产生6000m左右的落差,模拟的地形特征与目前的龙门山地形地貌基本相似。依据模拟结果与实测资料,绘制了龙门山断裂带形成及其附近区域地形地貌的演化过程图,呈现了板块挤压、断层塑性位错、地表侵蚀和沉积作用等因素共同作用对地形地貌的塑造过程。

The compression of the Qinghai-Tibet Plateau andthe Sichuan Basin resulted in the formation of the Longmenshan fault zone and the uplift of its mountains. Based on the regional plate motion characteristics near the Longmenshan Mountain and the mechanical properties of deep rock mass, evolution process of regional tectonic system in the Longmenshan overa time span of 7.0 million years are simulated and reconstructed by FLAC3 D. The results show that faults F1, F2 and F3 wereformed successively under the action of plate movement. The through faults have a strong controlling effect on the uplift of the surface for when they pass through the surface, Longmenshan and the western Sichuan plateau continue to uplift with an average uplift rate of about 1.38 mm/yr. However, while the West Sichuan depression to the east of the Longmenshan fault zone has only a small amount of uplift, the western Sichuan plateau was uplifted about 8996 m, resulting in a height difference of about 6000 m in this area. The simulated topographic characteristics are generallysimilar to the current topographic features. Based on the simulation results and the measured data, the evolutionary process map of the formation of the Longmenshan fault zone and its adjacent regional topography is drawn.Itshows that plate compression, fault plastic dislocation, surface erosion, sedimentation and other factors play an important role in the shaping process of topography and geomorphology.