珠江口盆地构造-地层格架及成因机制探讨  

A discussion on the tectonic-stratigraphic framework and its origin mechanism in Pearl River Mouth basin

作　　者：钟志洪 施和生 朱明 庞雄 何敏 赵中贤[2] 刘思青[2] 王菲 

机构地区：[1]中海石油(中国)有限公司深圳分公司 [2]中国科学院南海海洋研究所

出　　处：《中国海上油气》2014年第5期20-29,共10页China Offshore Oil and Gas

基　　金：NSFC-广东省联合基金重点项目"南海共轭陆缘穿时破裂过程对深水盆地构造发育及油气成藏的影响(编号:U1301233)";国家自然科学基金重点项目"南海早期构造演化的沉积记录(编号:91128207)";"十二五"国家科技重大专项"南海北部深水区储层识别技术与评价(编号:2011ZX05025-003)";"十二五"国家科技重大专项"近海大中型油气田形成条件与分布(编号:2011ZX05023-006)"部分研究成果

摘　　要：珠江口盆地位于南海北部大陆边缘东部,是新生代形成的被动陆缘伸展盆地。该盆地自下而上划分为中生代基底构造层、古新世—早渐新世裂谷构造层和晚渐新世以来的漂移构造层,各个构造层均代表了该盆地在被动大陆边缘演化过程中的一个特定成因阶段。分析认为,该盆地裂谷阶段的构造格架具有东西分段、南北分带特征。两幕不同区域构造背景下的伸展作用是控制盆地东西分段格局形成的主要原因:古新世—中始新世的伸展作用主要是在太平洋板块俯冲作用下发生,而晚始新世—早渐新世的伸展作用是在印支半岛旋转挤出及古南海向南俯冲的背景下发生。盆地南北分带的构造特点受岩石圈伸展机制差异的控制:古新世—中始新世裂陷幕在厚地壳和薄岩石圈背景下以宽裂谷方式伸展,形成盆-岭式结构;晚始新世—早渐新世裂陷幕在正常岩石圈背景下发生窄裂谷方式伸展,裂陷作用集中在现今的南海北部大陆边缘。物理模拟实验表明:北部裂谷带经历加厚型地壳-正常地壳-减薄型地壳的伸展过程,而南部裂谷带则主要经历减薄型地壳-超减薄型地壳的演化过程,由此导致南、北裂谷带构造-沉积格局的显著差异。盆地漂移阶段的沉降过程与南海海底扩张期间地幔上升流向南迁移有关。Located in the east part of the continental margin along the northern South China Sea,Pearl River Mouth basin is a Cenozoic passive-margin-extension basin.From the bottom to the surface,there are three tectonic levels in the basin,i.e.the Mesozoic basement,the Paleocene-Lower Oligocene rift and the drift since Upper Oligocene,and each level represents a special episode of basin origin during the passive margin evolution.The tectonic framework during rifting in the basin is characterized by the west east segmentation and north south zonation.The west-east segmentation was mainly controlled by two extension episodes in different regional structures：Paleocene-Middle Eocene extension occurred mainly due to Pacific subduction; and Late Eocene-Early Oligocene extension was caused by Indochina rotation-extrusion and the southward subduction of proto-South China Sea.The north-south zonation was controlled by different mechanisms of lithosphere extension：Paleocene-Middle Eocene rifting episode occurred as an extension with wide-rift style in the setting of thick crust and thin lithosphere,resulting in a basin-range structure; and Late Paleocene-Early Oligocene rifting episode occurred as an extension with narrow-rift style in the setting of normal lithosphere,with the rifting concentrated on the margin in the northern South China Sea.An experiment of physical simulation has suggested that there is an extension of thickened-normal-thinned crust and an evolution from thinned to ultra-thinned crust respectively in the north and south rift zone,resulting in the significant differences in structural-sedimenta ry framework between the two rift zones.The subsidence during drifting in the basin was related to the southward migration of mantle upwelling during sea floor spreading in South China Sea.

关 键 词：珠江口盆地 构造-地层格架 成因机制 裂谷构造层 漂移构造层 被动大陆边缘 岩石圈伸展 

分 类 号：P542.3[天文地球—构造地质学]