南海东北部大陆坡地震反射异常体的属性分析与岩性识别  

Property analysis and lithology identification of seismic reflection anomalies on the continental slope of northeastern South China Sea

作　　者：李博安 胡善政 阎贫[1,2] 于俊辉 王潇 唐群署 LI Bo’an;HU Shanzheng;YAN Pin;YU Junhui;WANG Xiao;TANG Qunshu(Key Laboratory of Ocean and Marginal Sea Geology,South China Sea Institute of Oceanology,Innovation Academy of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences,Guangzhou 510301,China;Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou 511458,China;University of Chinese Academy of Sciences,Beijing 100049,China;Bureau of Geophysical Prospecting INC.,China National Petroleum Corporation,Chengdu 610213,China;Hainan Branch Company of CNOOC(China)Ltd,Haikou 570311,China)

机构地区：[1]中国科学院边缘海与大洋地质重点实验室,南海海洋研究所,南海生态环境工程创新研究院,广东广州510301 [2]南方海洋科学与工程广东省实验室(广州),广东广州511458 [3]中国科学院大学,北京100049 [4]东方地球物理公司西南物探分公司,四川成都610213 [5]中海石油(中国)有限公司海南分公司,海南海口570311

出　　处：《热带海洋学报》2022年第1期204-214,共11页Journal of Tropical Oceanography

基　　金：中国科学院青年创新促进会(Y202076);南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项(GML2019ZD0204、GML2019ZD0104);中国科学院南海海洋研究所“南海新星”Ⅰ类(NHXX2019DZ0101);广东省特支计划(2019BT02H594);国家自然科学基金(U1901217、91855101、41876052)。

摘　　要：南海北缘属于非火山型大陆边缘。过去的研究在洋陆转换带北部的地震剖面上曾观测到一些疑似岩席和火山体的高振幅异常体,但对这些高振幅异常体的属性却缺乏进一步的研究。本文在南海东北部大陆坡上的两个多道地震剖面(SO1E和SOY)中也发现了一个长度超过15km、厚度约为1.2km的巨大高振幅异常体,它为研究者提供了一个探究洋陆转换带北部是否存在岩浆活动的机会。本研究对该高振幅异常体进行了速度分析与AVO(amplitude variation with offset)分析。结果表明,与周围岩层相比,该高振幅异常体内部有较高的P波速度和泊松比。结合区域地质背景和异常体内部的反射特征及大小形状,推测该高振幅异常体为火成侵入岩,并将其进一步归类为岩盖,揭示了中新世以后南海北部洋陆转换带北部曾发生过多期次的岩浆活动。The northern margin of the South China Sea(SCS)is often regarded as a magma-poor passive continental margin.Many high amplitude anomalies were observed in previous studies on seismic profiles at the northern part of the Continent-Ocean Transition(COT)in the northern SCS,and were interpreted as sills and volcanos.However,further investigation on the properties of these high amplitude anomalies was lacking.In this study,we observed a large anomaly with a thickness of~1.2 km in two multi-channel seismic profiles(SO1E and SOY)on the northeastern continental slope of the SCS.This provides an opportunity to determine the presence of magmatic activities north of the COT.Velocity analysis and AVO(amplitude variation with offset)analysis were performed for the large-amplitude anomaly.Results show that the high-amplitude anomaly has a higher P wave velocity and Poisson’s ratio than the host strata above.Considering the regional geologic background,the internal reflection characteristics,spatial size and shape of this high-amplitude anomaly,we suggest that the high-amplitude anomaly can be characterized as an igneous rock and further classified as a laccolith.This also indicates that multi-phase magmatism occurred north of the COT since the Miocene.

关 键 词：南海东北部 岩盖 速度分析 AVO分析 

分 类 号：P738.4[天文地球—海洋地质] P736.12[天文地球—海洋科学]