胶莱盆地深部拆离系统及其区域构造意义

Detachment systems in deep of Jiaolai basin and their regional tectonic significance

地震剖面解释结果揭示了胶莱盆地深部两个低角度拆离断裂系统：一个发育于盆地南部诸城凹陷，主拆离面向南缓倾，深度为8—10km；另一个发育于盆地北部高密凹陷和莱阳凹陷深部，由一系列北倾犁式正断层组成，主拆离面向北或北北东缓倾。根据受控凹陷的地层记录分析、剖面复原分析和伸展量估算，并结合地表断裂滑动矢量反演结果，认为盆地南部拆离系统主要形成于早白垩世莱阳组沉积时期，该时期诸城凹陷南北向伸展量达36％-41％，最大伸展方向可能为北西-南东。该拆离系统继承了早期胶南（或苏鲁）造山带深部滑脱构造面，其后期拆离复活主导了胶莱盆地南部不对称伸展构造样式，控制了狭长展布的莱阳期沉积凹陷发育。北部拆离系统主要形成于晚白垩世盆地伸展阶段，伸展作用可能延续到古新世时期。控制了盆地王氏组沉积。这个时期横穿莱阳凹陷和高密凹陷南北向伸展量估计为20％-25％，最大的伸展方向近南北向。该拆离系统调节了胶莱盆地近南北向拉分伸展，其形成与盆地东、西两侧北北东向边界断裂带右旋剪切作用有关。胶莱盆地深部两个深部拆离系统的时空复合或叠合造就了盆地内部复杂的伸展构造样式。识别这两个拆离系统不仅对盆地形成机理和动力学背景提供了重要的深部构造制约，对盆地油气勘探也具有重要的指导意义。

Seismic interpretations reveal two low angle detachment systems in the Jiaolai basin： one, developed 8 - 10 km beneath the Zhueheng depression in the southern part of the basin, has a detachment surface gently dipping to the south; the other, developed in the north Gaomi and Laiyang depressions, consists of a series of N-dipping listric normal faults and has a major detachment surface gently dipping to the north or NNE. Based on the sedimentary records analysis, profile retro-deformation, and estimated stretch properties of the above-mentioned depressions, in combination with the fault slip data analyses at the surface, the southern detachment system is considered to be formed during the early Cretaceous Laiyang stage when the Zhucheng depression had a N-S stretching rate of 36%- 41% and a possible NW-SE maximum stretching. This detachment system inherited an early deep decollement zone in the Jiaonan （or Su-Lu） orogenic belt; its late reactivation dominated the asymmetric extension pattern and controlled the development of the narrow, elongate sedimentary depression in the Jiaolai basin in Laiyang stage. The northern detachment system had taken shape during the stretching stage in the late Cretaceous. It is possible that the stretching process continued until the Paleocene and controlled the deposition of the Wangshi Formations. The N-S extension across the Laiyang and Gaomi depressions during the stage is estimated to be at 20% -25%, the maximum stretching direction being nearly N-S. This detachment system accommodated the N-S pull-apart stretching of Jiaolai basin and its formation was related to the fight-lateral shear along the NNE-trending boundary fault zones on the eastern and western sides of the basin. The spatial and temporal superimposition of these two detachment systems resulted in the complex extensional structural styles in the Jiaolai basin. The identification of these two deep detachment systems not only provides structural constraints on the mechanisms and dynamic setting of the basin formation, but also is of great significance for petroleum exploration in the basin.