南海西南次海盆陆缘演化与幕式扩张的岩浆-构造-地层记录  

Rift Evolution and Magmatic-Tectonic-Stratigraphic Records of Episodic Seafloor Spreading at Southwest Sub-Basin of South China Sea

作　　者：杨天一 唐勇 任建业[1,5] 巢鹏 Yang Tianyi;Tang Yong;Ren Jianye;Chao Peng(College of Marine Science and Technology,China University of Geosciences,Wuhan 430074,China;Second Institute of Oceanography,Ministry of Natural Resources,Hangzhou 310012,China;Key Laboratory of Submarine Geosciences,Ministry of Natural Resources,Hangzhou 310012,China;School of Oceanography,Shanghai Jiao Tong University,Shanghai 201620,China;Hubei Key Laboratory of Marine Geological Resources,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]中国地质大学海洋学院,湖北武汉430074 [2]自然资源部第二海洋研究所,浙江杭州310012 [3]自然资源部海底科学重点实验室,浙江杭州310012 [4]上海交通大学海洋学院,上海201620 [5]中国地质大学海洋地质资源湖北省重点实验室,湖北武汉430074

出　　处：《地球科学》2025年第1期195-216,共22页Earth Science

基　　金：国家重点研发计划项目(Nos.2023YFC2808803,2023YFE0126100);国家自然科学基金项目(Nos.41830537,42206074);浙江省科技创新领军人才项目(No.2021R52058)。

摘　　要：目前对于边缘海背景下被动大陆边缘的形成演化机制仍存在争议,特别是对洋陆转换带的构造特征与形成过程的认识存在明显不足.为了深入探索边缘海背景下南海陆缘与洋陆转换带构造结构与形成演化特征,通过对横跨西南次海盆V型尖端地震剖面的解释与研究,识别出莫霍面(Moho)、基底和海底3个一级陆缘界面,划分出细颈化域、超伸展域、原洋域等构造单元;进一步精细解释了共轭陆缘盆地充填层序和多期断裂系统,识别出破裂不整合界面Bi,将陆缘盆地同裂陷期层序(Tg-Bi)划分为S1-S5五个层序,建立了西南次海盆V型尖端区域共轭陆缘的构造-地层格架.构造-地层格架中S3/S4层序之间的界面CBi、S4/S5之间的界面POBi分别与陆壳破裂和原洋洋壳Ⅰ的破裂对应,记录了西南次海盆共轭陆缘岩石圈伸展破裂过程中发生的重要构造事件.结合断裂活动性和盆地原型的分析,将西南次海盆共轭陆缘同裂陷期的演化划分为伸展、细颈化、超伸展和原洋洋壳四个阶段,建立了西南次海盆共轭陆缘演化模式.还建立了西南次海盆V型尖端共轭陆缘地壳的“鳄鱼嘴”结构,识别出总宽度达231 km的两期原洋洋壳.结合外缘高地和同破裂层序(S4-S5)研究,提出两期原洋洋壳的发育与西南次海盆的两幕扩张过程相对应,由原洋洋壳构成了同期洋盆的洋陆转换带.揭示了西南次海盆张开过程中岩石圈的伸展破裂机制与洋脊传播过程中幕式扩张作用对陆缘构造、地层和岩浆作用的影响,对于深入研究南海岩石圈的伸展破裂过程、洋陆转换带的成因以及南海被动陆缘形成的动力学机制具有重要意义.The formation and evolution mechanism of the passive rift margin under the marginal sea background is still controversial,especially existing studies on the structural characteristics and formation process of the oceanic and continental transition zone are insufficient.In order to deeply explore the tectonic structure and evolution characteristics of the rift margin and oceanic transition zone of the South China Sea(SCS)under the background of marginal sea,this study presents an investigation of the seismic profiles across theⅤ-shaped tip of the Southwest Sub-basin of the SCS,identifying three first order rift margin interfaces including the Moho,Top of basement,and seafloor.The tectonic units of the conjugate margin are subdivided into the necking domain,the hyper-extended domain,and the proto-oceanic domain.The study further refines the interpretation of the stratigraphic sequences and multi-phase fault systems at the conjugate margin as well as identifies the breakup unconformity surface Bi.We divide the syn-rift sequence(between Tg and Bi)into five sequence units(S1-S5),establishing a tectono-stratigraphic framework for the conjugate margin of the SW sub-basin of the SCS.The study indicates that the interface CBi between S3 and S4,as well as the interface POBi between S4 and S5,corresponds to the break-up of continental crust and proto-oceanic crustⅠ,respectively,recording important tectonic events during the rifting.Based on the analysis of fault activity and basin prototyping,we divide the evolution of the conjugate margin into four stages:stretching,necking,hyper-extending,and proto-oceanic crust developing,establishing the rift margin evolution model for the conjugate rift margin of the SW sub-basin of the SCS.This study also identifies a"crocodile-jaw"structure in the crust of the conjugate margin of theⅤ-shaped tip at the SW sub-basin of the SCS,recognizing two phases of proto-oceanic crust with total width of 231 km.Based on the investigation of the outer high and syn-breakup sequence(S4 and S5),

关 键 词：南海 西南次海盆 陆缘演化模式 幕式扩张 原洋洋壳 洋陆转换带 岩浆-构造-地层记录 海洋地质学 

分 类 号：P736[天文地球—海洋地质]