曼达岬海盆渐新世‒中新世沉积物的稀土元素组成及其物源指示意义  

Rare Earth Element Compositions for Oligocene-Miocene Sediments in Mentalle Basin of Southeastern Indian Ocean:Characteristics and Provenance Implications

作　　者：孙天琪 徐兆凯[1,2,4,5] 万世明 李铁刚[2,3,6] 常凤鸣 Sun Tianqi;Xu Zhaokai;Wan Shiming;Li Tiegang;Chang Fengming(Key Laboratory of Marine Geology and Environment,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China;Laboratory for Marine Geology,Laoshan Laboratory,Qingdao 266061,China;University of Chinese Academy of Sciences,Beijing 100049,China;Center for Excellence in Quaternary Science and Global Change,Chinese Academy of Sciences,Xi’an 710061,China;Center for Ocean Mega-Science,Chinese Academy of Sciences,Qingdao 266071,China;Key Laboratory of Marine Sedimentology and Metallogeny,First Institute of Oceanography,Ministy of Natural Resources,Qingdao 266061,China)

机构地区：[1]中国科学院海洋研究所海洋地质与环境重点实验室,山东青岛266071 [2]崂山实验室海洋地质过程与环境功能实验室,山东青岛266061 [3]中国科学院大学,北京100049 [4]中国科学院第四纪科学与全球变化卓越创新中心,陕西西安710061 [5]中国科学院海洋大科学研究中心,山东青岛266071 [6]自然资源部第一海洋研究所海洋地质与成矿作用重点实验室,山东青岛266061

出　　处：《地球科学》2023年第7期2764-2777,共14页Earth Science

基　　金：中国科学院战略性先导科技专项(Nos.XDB42000000,XDB40010100);国家自然科学基金项目(Nos.41876034,41676038).

摘　　要：为了探究东南印度洋曼达岬海盆(Mentelle Basin)内沉积物的源‒汇过程,利用国际大洋发现计划(IODP)369航次在该海盆内获取的渐新世‒中新世岩心沉积物,进行了稀土元素(REE)组成特征及其控制因素和物源指示意义的研究.结果显示,与球粒陨石、上地壳(UCC)和澳大利亚后太古代页岩(PAAS)这三种标准物质相比,所研究沉积物的稀土元素含量(ΣREE)与轻/重稀土含量比值(ΣLREE/ΣHREE)等总体特征与UCC最为相近,其UCC标准化后的稀土元素配分模式则呈现出轻稀土稍富集的整体平缓特征.样品的ΣREE与稀土分馏指标(La/Yb)_(UCC)和(Gd/Yb)_(UCC)明显受控于粒度效应与风化作用,而ΣLREE/ΣHREE、δEu、(La/Sm)_(UCC)和(Sm/Nd)_(UCC)则基本不受上述两种作用的影响.UCC标准化后的稀土元素配分模式、基于稀土元素组成的物源判别函数以及Zr-Th-Sc物源判别三角图均表明伊尔冈克拉通是所研究沉积物最可能的物源区,并且该物源区的主要源岩在13 Ma时由中基性岩向酸性岩转变.上述物源研究结果有望为东南印度洋地区渐新世‒中新世时期的古气候与古环境重建工作奠定坚实的基础.In order to study the sedimentary source-to-sink processes for marine sediments deposited in the Mentalle Basin of Southeast Indian Ocean from the Oligocene to Miocene,here it conducts the rare earth element(REE)composition analysis on these sediments derived during the International Ocean Discovery Program(IODP)Expedition 369.It characterizes the REE compositions and then analyzes their controlling factors and provenance significance.Among the three standard materials of the chondrite,the post Archean Australian shale(PAAS)and the Upper Continental Crust(UCC),the overall REE compositions of the sample sediment,including the REE contents(ΣREE)and the light REE/heavy REE ratio(ΣLREE/ΣHREE)is close to the characteristics of UCC.The variations ofΣREE,(La/Yb)_(UCC) and(Gd/Yb)_(UCC) are obviously affected by grain size and weathering processes,whileΣLREE/ΣHREE,δEu,(La/Sm)_(UCC) and(Sm/Nd)_(UCC) have no correlation with grain size and weathering proxy.The UCC-normalized REE patterns,discriminant function based on REE composition,and the triangular diagram of Zr-Th-Sc indicate that the Yilgarn Craton is the most likely provenance of Oligocene-Miocene terrestrial sediments from the Mentalle Basin.And the main weathering parent rocks of the Yilgarn Craton change from intermediate-mafic rocks to acidic rocks at 13 Ma.The above provenance research results will lay a solid foundation for the reconstruction of paleoclimate and paleoenvironment in the Southeast Indian Ocean from the Oligocene to Miocene.

关 键 词：曼达岬盆地 渐新世‒中新世 稀土元素组成 沉积物来源 海洋地质学. 

分 类 号：P736[天文地球—海洋地质]