南海北部深水区沉积物稀土元素特征及其物源指示意义  

Ree Geochemical Characteristics of Sediments and Its Implications in the Deepwater Area of the Northern South China Sea

作　　者：吴梦霜[1,2] 邵磊[1] 庞雄 乔培军[1] 向绪洪[1] 赵梦[1] 

机构地区：[1]同济大学海洋地质国家重点实验室,上海200092 [2]中国海洋石油(中国)有限公司深圳分公司研究院,广州510240

出　　处：《沉积学报》2012年第4期672-678,共7页Acta Sedimentologica Sinica

基　　金：国家科技重大专项(编号:2011ZX05025-003);国家重点基础研究发展规划项目(编号:2007CB819501);国家自然科学基金项目(批准号:91128207;40976023)联合资助

摘　　要：对南海北部白云深水区沉积物稀土元素的研究表明,渐新世至中新世的物源发生较大变化。渐新世时期,白云深水区不同区域稀土元素的分布特征差异明显,表明沉积物物源不同。深水区北部沉积物主要来自古珠江物源区,深水区东、西部沉积物中含有较多中基性火山物质,南部则主要包含基性火山物质,说明当时南海北部地区构造活动较强,存在较多火山活动,火山活动由北向南基性成分增多。渐新世末的白云运动使南海北部深水区产生强烈持续沉降,造成陆架坡折带北移,白云深水区从渐新世浅海陆架环境演化为中新世陆坡深水环境,中新世期间沉积物主要来自深水区北部的珠江三角洲物源,深水区东部存在东沙隆起源区,而深水区南部沉积物在中新世仍受到基性火山活动的影响。The Rare Earth Element study of sediments in the Baiyun deepwater area of the northern South China Sea shows three chondrite-normalized REE distribution characteristics in different parts of the deepwater area from Oligocene to Miocene,indicating that different provenances may dominate the deepwater area.From the Oligocene to the Miocene,the sediments of the northern Baiyun deepwater area came from the paleo-Pearl River,featuring relative LREE（light rare earth element） enrichment,even content of HREE（heavy rare earth element） and negative Eu-anomalies,just like the chondrite-normalized REE pattern of PAAS（post-Archean average Australian shale）.This REE characteristic suggested a parent rock type of sedimentary rocks or acid rocks or both.The sediments of the southern part of Baiyun deepwater area showed reduced divergence between LREE and HREE with obvious positive Eu-anomalies,suggesting a supply of basic materials.Well B6 located on a volcanic island in the central part of the Baiyun deepwater area.The Oligocene sediments of Well B6 contained a large amount of intermediate to basic volcanic materials,featuring positive Eu-anomalies.But the chrondrite-normalized REE distribution pattern of the sediments of Well B6 became similar to the REE distribution pattern of the sediments in the north in early Miocene.The sediments of the eastern part of the deepwater area featured no Eu-anomalies or positive Eu-anomalies,indicating that this area was influenced by the volcanic activities on the Dongsha Rise.Negative Eu-anomalies didn＇t occur around this area until 18.5 Ma.The sediments from the northern deepwater area to the location area of W3 was dominated by the paleo-Pearl River from the Oligocene to Miocene.The southern part of the deepwater area was influenced by the basic volcanic materials continuously,and the volcanic activities still happened in the mid-Miocene,much less frequently though.The sediments in the eastern deepwater area mainly came from the Dongsha Rise from the Oligocene to the early Mi

关 键 词：稀土元素 物源 南海北部 白云凹陷 沉积学 

分 类 号：P593[天文地球—地球化学]