基于独立成分分析的马里亚纳弧后地幔源区特征研究  

The Signatures of Mantle Sources in the Mariana Trough Indicated by Independent Component Analysis of Basalt Isotopic Compositions

作　　者：于璐瑶 田丽艳 伍锡昌 孙国洪 陈凌轩 YU Lu-yao;TIAN Li-yan;WU Xi-chang;SUN Guo-hong;CHEN Ling-xuan(Institute of Deep-sea Science and Engineering,Chinese Academy of Sciences,Sanya 572000,China;University of Chinese Academy of Sciences,Beijing 100049,China;Laboratory for Marine Geology,Pilot National Laboratory for Marine Science and Technology(Qingdao),Qingdao 266003,China;College of Earth Sciences,Jilin University,Changchun 130012,China;Second Institute of Oceanography,MNR,Hangzhou 310012,China)

机构地区：[1]中国科学院深海科学与工程研究所,海南三亚572000 [2]中国科学院大学,北京100049 [3]青岛海洋科学与技术试点国家实验室海洋地质过程与环境功能实验室,山东青岛266003 [4]吉林大学地球科学学院,吉林长春130012 [5]自然资源部第二海洋研究所,浙江杭州310012

出　　处：《海洋科学进展》2021年第1期73-88,共16页Advances in Marine Science

基　　金：国家自然科学基金项目——南海初始洋壳(IODP1502B钻孔)的Li-Mg-O同位素组成:对洋壳蚀变过程中同位素组成和分馏行为的初步研究(41876044);中国科学院深海与科学工程研究所知识创新工程领域前沿项目——冰岛和雷琼半岛OIB型火山熔岩的地球化学及岩石成因对比研究及其对地球动力学背景的指示(Y570031QY1)。

摘　　要：对采自太平洋洋中脊(277组)、印度洋洋中脊(159组)、马里亚纳海槽(53组)、马里亚纳岛弧(39组)、中南劳海盆(72组)共600组玄武岩数据进行了独立成分分析,从Sr-Nd-Pb五维同位素比值空间提取出占样本方差99%的3个独立成分(IC1,IC2,IC3),并利用这3个独立成分(ICs)与微量元素比值之间的相关性来讨论独立成分的起源。分析结果表明:IC1可以将马里亚纳海槽玄武岩与太平洋洋中脊及马里亚纳岛弧玄武岩区分,并且IC1值与(La/Sm)N比值呈正相关。IC2可以将马里亚纳海槽和马里亚纳岛弧玄武岩区分,而且IC2值与Ba/Th比值呈正相关;IC3可以将弧后盆地和洋中脊玄武岩区分,同时IC3值与Th/Nb呈负相关。分析独立成分的统计特征和微量元素比值特征可知,IC1与印度洋型MORB地幔的富集组分相关,IC2与太平洋板块俯冲产生的含水流体相关,IC3与再循环俯冲沉积物熔体相关。根据ICs地理分布特点,我们认为:1)马里亚纳海槽北部比南部受到更多印度洋型MORB地幔富集组分的影响,表明印度洋型MORB地幔可能从北部置换太平洋型MORB地幔;2)海槽北部地幔源区则是受到再循环沉积物熔体的影响较大,而中部和南部地幔源区可能受到更多俯冲流体的影响。Therefore,the study of back-arc basin basalts in Mariana Trough is important for understanding the structure and geochemical composition of its mantle source,also for revealing the genesis and evolution of the back-arc magma.Here we collected the published geochemical data of basalts from Pacific Mid-Ocean Ridge(277 groups),Indian Mid-Ocean Ridge(159 groups),Mariana Trough(53 groups),Mariana Island Arc(39 groups),and Central-Southern Lau Basin(72 groups),and applied the independent component analysis methods to trace the mantle sources in Mariana back-arc region.We identified three ICs(IC 1,IC 2,IC 3)in the five-dimensional space of Sr-Nd-Pb isotopic ratios,which can account for 99%of the isotopic variance.The correlations between the ICs and the incompatible trace elements ratios were used to examine the origin of these ICs.The results show that IC 1 separates Mariana Trough back-arc basin basalts(BABB)from Pacific Mid-Ocean ridge basalts(MORB)and Mariana Island arc basalts(IAB),and also shows a positive correlation with(La/Sm)N ratio.IC 2 discriminates BABB and IAB from Mariana region from the other three groups,and correlates positively with Ba/Th ratios as well.IC 3 distinguishes BABB and MORBs clearly,and displays a negative correlation with Th/Nb values.The geochemical signatures of trace element ratios and the statistical properties of these ICs further suggest that IC 1 can be related to enriched components of the Indian-type MORB mantle,IC 2 corresponds to a fluid-rich component from the subducting Pacific slab,and IC 3 may represent melt of recycled subducted sediment.The geographic distribution of these ICs supports that the Indian-type MORB mantle might replace the Pacific-type MORB mantle from the northern Mariana Trough.The back-arc magma from the northern Mariana Trough are affected more by recycled subduction sediment melts,and those from the central and southern back-arc basin are influenced more by aqueous fluids released from the subducting Pacific slab.

关 键 词：独立成分分析(ICA) 马里亚纳海槽 Sr-Nd-Pb同位素比值 俯冲作用 印度洋型MORB地幔 

分 类 号：P736[天文地球—海洋地质]