摘要
基于沉积物AMS14 C定年,研究了近千年来台湾以东黑潮主流区沉积物的稀土元素组成变化特征及赋存形态,探讨了该区近千年来稀土来源。台湾东黑潮主流区近千年来沉积物中稀土元素总量平均为119.82μg/g,低于上陆壳和中国黄土的稀土元素平均含量,与冲绳海槽较为接近;轻重稀土元素比值平均为11.30,明显富集轻稀土,具有明显的陆源属性。研究区沉积物稀土元素对球粒陨石和上地壳标准化配分模式均表现为轻稀土富集重稀土相对亏损,且具有弱的Ce正异常。根据定年结果及稀土元素变化特征趋势将柱状沉积物分为3层:0～8.5、8.5～21.5和21.5～30cm,随深度增加稀土元素总量的平均值逐渐增大,轻重稀土元素比值逐渐减小,Ce正异常程度逐渐减弱。稀土元素赋存形态分析表明,La、Ce、Pr、Nd 4种轻稀土元素主要为天然陆源,其他稀土元素受氧化还原环境影响相对较大。稀土元素主要存在于残渣态中,其次为铁锰氧化物结合态,残渣态对台湾以东黑潮主流区沉积物中总稀土元素的配分模式起决定性作用,也是造成Ce正异常的关键赋存形态。近千年来沉积物中稀土元素变化与沉积物粒度关系不大,物质来源较为稳定,台湾东部河流输入是研究区沉积物中稀土元素的最重要来源,亚洲大陆风尘输送对稀土元素的贡献较小。
Rare earth elements(REE)and their fractions in the sediments of Kuroshio mainstream off eastern Taiwan were determined to reveal the REE geochemical characteristics and provenances of the sediments for the past millennium.AMS14 C is used for dating.The average ratio of light REE to heavy REE(LREE/HREE)is 11.30 in the sediments of research core,obviously enriched in light REE.The average total REE content is 119.82 ppm,which was under the REE abundance of upper continental crust(UCC)and China loess,and close to the figure of Okinawa Trough.The chondrite-normalized REE patterns and the UCC-normalized REE patterns show a similar trend:light REE enriched with slightly positive Ce anomalies.The research core may be subdivided into three layers according to the chronohorizon and variation trend of REE:0~8.5 cm,8.5~21.5 cm,21.5~30 cm respectively.The average REE contents increase with depth,while the LREE/HREEratio decrease and the extent of positive Ce anomalies weaken with depth.The results of REE fractionation show that La,Ce,Pr and Nd come from terrigenous sources,as the other REEs are susceptible to the oxidation-deoxidation conditions.The residual fractions of the sediments of the research area are mainly the uppermost fractions of REE,and followed by the Fe/Mn-oxides fractions as the second.Facts show that the residual fraction of REE play a decisive role in the total REE patterns of the Kuroshio mainstream sediments,as well as the key factor of positive Ce anomalies in the total REE.The REE features show no obvious relations with grain size,and the provenance of REE was relatively stable over the past millennium.It is inferred that the rivers input from eastern Taiwan was the most important source of REE in the sediments of the research area,and input from East Asian monsoon subordinates.
作者
王越奇
宋金明
袁华茂
李学刚
李宁
王启栋
WANG Yueqi;SONG Jinming;YUAN Huamao;LI Xuegang;LI Ning;WANG Qidong(CAS Key Laboratory of Ecology and Environmental Sciences. Insiiiuie of Oceanology. Chinese Academy of Sciences. Qingdao 266071,China;University of Chinese Academy of Sciences,Beijing 100049 , China;Function Laboratory of Marine Ecology and Environmental ScienceQingdao National Laboratory for Marine Science and Technology,Qingdao 266237, China;Center for Ocean Mega-Science , Chinese Academy of Sciences. Qingdao 266071, China)
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
2019年第2期104-113,共10页
Marine Geology & Quaternary Geology
基金
深海专项(预研)"深海典型生境生物多样性与生态系统"(2016ASKJ14)
山东省-国家基金委联合基金"海洋生态环境变化的生物地球化学机制"(U1606404)
中国科学院创新先导专项项目"黑潮向近海生源要素的输送"(XDA11020102)
