黄骅坳陷中区新生代断裂系统及其成因分析

断裂是黄骅坳陷新生代主要构造变形类型,对该区油气成藏有重要影响。本文将黄骅坳陷中区的断裂划分为6个系统,并综合分析了它们之间的关系。每一断裂系统至少有一条主干基底断层,发育在该断层上、下盘的次级断层以不同形式与主干基底断层组合在一起,其剖面上的构造样式和平面上的构造组合显示了该断裂系统在新生代的运动学特征。在系统分析黄骅坳陷中区新生代断裂系统的断层组合、构造样式、主干断层位移方式及生长史的基础上,结合区域构造背景、伸展边界条件及断层间的相互作用,探讨了该区断裂系统的形成机制。分析结果表明:区域构造背景下存在的伸展边界控制了整个黄骅坳陷中区新生代断裂系统总的构造格局,系统中主要断层走向与伸展边界近于平行。这进一步证实了区内右旋走滑作用与伸展作用的相互耦合,致使断层沿走滑构造带出现转向或中断。各断裂系统之间及系统内部断层间的运动学关系表明黄骅坳陷古近纪受两个构造动力控制,一是地幔热作用引起岩石圈北西—南东向引张作用,二是北北东向深断裂带的右旋剪切作用。

Cenozoic fault systems and their genetic analysis in central area of the Huanghua Depression

Fault was a major structure in the Cenozoic Huanghua Depression and an important affect factor for hydrocarbon accumulation.The faults in central area of the Huanghua Depression could be divided into six systems and the interaction among these systems was analyzed in this paper.Every fault system had a major fault at least,which combined the sub-order faults developing in hanging wall or foot wall in various forms.The group features of the faults in section and plane showed the Cenozoic kinematic characters of the fault systems.The mechanism of the fault system in the Cenozoic Huanghua Depression was discussed based on study of the fault groups,structural modes,tectonic backgrounds,boundary directions,the interaction of faults,fault displacement and the history of development of some major faults.The results showed that the regional setting of the fault system was controlled by the extension stress field,so the major faults were parallel to the extensional boundaries.Furthermore,it was proved that the extension tectonics was coupled with the strike-slip structure,which resulted in change of the direction of some faults or suddenly breaking of some faults.The kinematic relation between each fault subsystem and within a fault system showed that the Huanghua Depression was controlled by two dynamic systems:the NW-SE extension caused by mantle heating action,and right-lateral strike-slipping caused by the deep fracture zones.