二连盆地中生代构造变形主控因素:物理模拟与讨论

二连盆地是中国东北部中生代含油气盆地,与中国东部中生代裂陷盆地之间存在显著的几何学与运动学相似性,根据盆内构造线走向和典型地震剖面构造样式可划分为中央正向裂陷带和周缘斜向裂陷带。尽管前人对盆地中生代构造变形开展了大量研究,但有关同期构造控制因素的认识尚不清晰。为此,研究以二连盆地为原型,设计了3组分别改变伸展速率、伸展方向及同沉积作用的平面沙箱模型。实验结果表明伸展方向控制裂陷内部断层特征;南东向的伸展速率改变深层构造薄弱带的扩展和断裂发育规模;同沉积作用促进基底滑脱层的活动强度,且进一步抑制边界断裂的生长。模拟结果还揭示了伸展方向是该盆地构造变形的主要控制因素;同沉积作用和伸展速率为次要控制因素。同时根据中国东部及邻区典型中生代裂陷盆地的几何学与运动学相似性,认为"南东向伸展"可以提供较好的运动学解释。

Major Controlling Factors of the Mesozoic Tectonic Deformation in the Erlian Basin: Physical Simulation and Discussion

The Erlian Basin is a Mesozoic oil-and gas-bearing basin in northeastern China. There are significant geometric and kinematic similarities between the Erlian Basin and other Mesozoic rift basins in eastern China. According to the tectonic line of the basin and the structure observed from the typical seismic profiles, the Erlian Basin consists of a central forward rift zone and peripheral diagonal rift zones. Although a considerable amount of research has been carried out on the pre-tectonic control of the Mesozoic deformation of the basin, the contemporaneous tectonic controlling factors remain unclear. In this study, three planar sandbox models were designed to determine the major controlling factors by changing the extension rate, the extension direction, and the syn-sedimentation. The results showed that the extensional direction controlled the internal fault characteristics of the rift. The ability of the extension direction to control the fault characteristics increased with distance from the rift boundary. The rate of extension changed the expansion of the weak tectonic zone and the scale of fracture development. Larger extension rates could lead to a largerand more complex fracture system. The syn-sedimentary action promoted the activity of the underlying slip-off layer, inhibited the growth of the boundary fault, and thereby reversely promoted the development of internal secondary fractures. The experimental results also showed that the extension direction was the major controlling factor of the tectonic deformation of the basin. The syn-sedimentation and extension rate were the secondary controlling factors. Additionally, according to the geometric and kinematic similarity of typical Mesozoic rift basins in eastern and adjacent areas of China, the study suggested a “southeastward extension” as a possible kinematic mechanism for the basin.