珠江口盆地构造演化旋回及其新生代沉积环境变迁

Tectonic Evolution Cycles and Cenozoic Sedimentary Environment Changes in Pearl River Mouth Basin

目前对珠江口盆地中生代以来的演化过程及其与沉积环境演变的响应关系尚缺乏系统性认识.基于珠江口盆地中-新生代岩浆活动、断陷结构样式及其改造、典型构造变形样式、沉积中心的转换等特征的对比分析,将盆地中-新生代的构造演化划分为4个阶段、7个期次:(1)中侏罗世-晚白垩世早期(~170~90 Ma)为古太平洋板块俯冲主控的陆缘岩浆弧-弧前盆地演化阶段;(2)晚白垩世-始新世中期(~90~43 Ma)为太平洋板块俯冲后撤背景下弧后周缘前陆/造山后塌陷-主动裂谷演化阶段;(3)始新世中期-中中新世(~43~10 Ma)为华南挤出-古南海俯冲拖曳主导的被动陆缘演化阶段;(4)晚中新世以来(~10~0 Ma)为菲律宾板块NWW向仰冲主导的挤压张扭演化阶段.~90 Ma、~43 Ma、~10 Ma分别实现了由安第斯型俯冲向西太平洋型俯冲、由主动裂谷向被动陆缘伸展、由被动陆缘伸展向挤压张扭的转换.在此过程中,伴随着古南海和南海的发育-消亡,新生代裂陷期沉积环境由东向西、由南向北逐渐海侵,裂后期由南向北阶段性差异沉降,由陆架浅水向陆坡深水转换,这使得珠一/三、珠二、珠四坳陷的石油地质条件具有显著的分带差异性.

There is still a lack of systematic understanding of the evolution process of the Pearl River Mouth Basin since the Mesozoic and its response to the evolution of sedimentary environment.Based on the comparative analysis of the magmatic activity,architectural style of depression and its modification,typical structural deformation style and migration of sedimentary centers,the tectonic evolution of the Pearl River Mouth Basin in Meso-Cenozoic can be divided into 4 stages and 7 periods:(1)the evolution stage of the continental-margin magmatic arc and forearc basin,dominated by paleo-Pacific plate subduction,from Middle Jurassic to early Late Cretaceous(~170-90 Ma);(2) the evolution stage of peripheral foreland basin/post-orogenic collapse to active rift basin in back-arc area,dominated by the subduction retreat of Pacific plate,from Late Cretaceous to Middle Eocene(~90-43 Ma);(3) the evolution stage of passive continental margin,dominated by South China block’s extrusion and proto-South China Sea subduction,from Middle Eocene to Middle Miocene(~43-10 Ma);(4) the evolution stage of compression and tensional-shear faults,dominated by NWW upward thrust of the Philippine Sea Plate,since the Late Miocene(~10-0 Ma).~90 Ma,~43 Ma and ~10 Ma are three important periods of tectonic transformation.The subduction of the West Pacific transformed from Andean-type subduction to West Pacific-type subduction in ~90 Ma,and the rifting transformed from active rift to passive continental margin extension in ~43 Ma,and the tectonic environment transformed from passive continental margin extension to compression and wrench in ~10 Ma.In this process,with the development and extinction of the proto-South China Sea and the South China Sea,the sedimentary environment in the Cenozoic rifting period gradually transgressed from east to west and from south to north.In the post-rifting period,under the control of phased differential subsidence from south to north,depositional environment transformed from shallow water to deep water,which resulted in significant zoning differences of the petroleum geological conditions in Zhu Ⅰ/Ⅲ,Zhu Ⅱ and Zhu Ⅳ depressions.