松辽盆地长岭断陷构造演化及其动力学背景

Structure evolution and its kinetic setting of Changling fault depression in Songliao basin

通过大量高精度二维地震剖面的构造解析与平衡地质剖面构造演化史定量恢复,探讨了松辽盆地长岭断陷的构造演化及其地球动力学背景。长岭断陷发育NNE、NNW、SN等多个方向的低角度铲式正断层,它们可能是在晚侏罗世—早白垩世郯庐断裂系左行走滑派生的次级破裂的基础上受断陷期强烈地壳伸展拆离作用形成的。断陷期可分为早晚两个脉冲式伸展事件,每个伸展脉冲均由一个快速伸展期和其后的缓慢伸展期组成,前者与火山活动高峰期相对应,后者则是构造转换期。早期伸展是以热穹窿式多向拉伸为标志,可能是侏罗纪岩石圈加厚后根部发生拆沉作用导致地壳弹性回调和岩浆底侵的结果。而晚期伸展则以NWW—SEE向区域伸展为标志,是对中国东部广泛的地壳伸展拆离和岩石圈减薄事件的响应,可能是伊则纳崎板块俯冲产生的弧后扩张效应。

The structure evolution and its dynamics during the rifling stage in the Changling faut depression in northeast China are discussed in Songliao basin according to the structural analysis of precise 2D seismic profiles and their quantitative structure evolution restoration. Multi-directional low-angle listric faults, e.g. NNE, NNW and SN developed in the Changling fault depression, which probably formed basing on the secondary fractures induced by the sinistral strike-slip movement of the Tanlu fault zone during the Late Jurassic to Early Cretaceous and influenced by the intensive crustal detachment during the rifling stage. The faulted phase can be divided into two episodic extensional extents. Each extension episode is composed of a relatively rapid extension age coeval with the peak of volcanism and a subsequent slow extension age coherent with structural transition. The early extension episode is marked by the dominglike multi-directional extension which was probably resulted from the crustal elastic rebound and magma underplating induced by the delamination of the thickened lithosphere during the late Jurassic. The late extension episode was characterized by the NWW-SEE regional stretching corresponding to the vast crustal detachment and lithosphere thinning in eastern China, which was probably caused by the back-arc extension effect of the subduction of Izanagi Plate.