珠江口盆地多期走滑构造与叠合型拉分盆地:以阳江东凹为例

Superimposition of Strike-slip Faults and Pull-apart Basins in the Pearl River Mouth Basin:A Case Study from the Eastern Yangjiang Sag

珠江口盆地的成盆机制和构造演化过程探讨是该地区烃源岩研究中不可缺少的环节,也是大家广泛关注的焦点问题。本文以阳江东凹为例,通过整体与局部相结合的分析方法,从整体上确定了研究区走滑断裂的发育特征和展布框架,明确了区域构造运动与走滑断裂的成因联系;并将整体划分成局部,聚焦于阳江东凹古近纪盆地构造演化阶段逐步分解与精细检验,对珠江口盆地的成盆机制、发育过程和演化模式进行分阶段解剖和分析。结果表明,研究区的构造演化过程分为三个阶段:文三段沉积期NW-SE向伸展,文二段沉积期南北向区域拉张作用下NE走向断裂右行右阶走滑拉分和文一段-恩平组沉积期NWW向走滑断裂左行左阶拉分。由于三个阶段受到不同的区域构造运动影响,各阶段盆地的打开方式和断裂的分布特征具有一定差异。同时,不同时期的构造演化过程与同时期区域构造应力场的转变一一对应,控制了沉积-沉降中心的分布,据此本文提出珠江口盆地的裂解模式是多期走滑构造控制的"叠合型"拉分盆地的新认识,研究区整体表现为三期构造叠合型盆地,盆地的构造叠合机制与洼陷的生烃排烃具有一定的相关性。

The formation mechanism and tectonic evolution of the Pearl River Mouth Basin,which are critical to understand the development of oil resources in this area,remain controversial.To explore the tectonic evolution and formation mechanism of the eastern Yangjiang Sag,the overall characteristics and directions of strike-slip faults in the area were investigated through comprehensive study of the whole tectonic framework and partial structural analysis.The tectonic evolution of the eastern Yangjiang Sag during the Paleogene can be divided into three stages.During the first stage of the evolution of the Pearl River Mouth Basin,the strike-slip faults were developed under the NW-NE-directed extension.In the second stage,the NE-trending dextral strike-slip faults were developed,which led to the formation of pull-apart basins.During the third stage,the NW sinistral strike-slip faults that control some pull-apart basins were developed.The different tectonic movements of the three stages resulted in the different rift patterns of the basins.Combining the results of this and previous studies,we propose that the extension of the Pearl River Mouth Basin is a pull-apart basin related to multi-stage strike-slip faulting,and is the result of three-stage tectonic superimposition.