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An eclogitic component in the Pitcairn mantle plume: Evidence from olivine compositions and Fe isotopes of basalts

文献类型：期刊论文

作者Shi, Jin-Hua3; Zeng, Gang2,3; Chen, Li-Hui1,3; Hanyu, Takeshi4; Wang, Xiao-Jun1,3; Zhong, Yuan3; Xie, Lie-Wen5; Xie, Wen-Li3
刊名GEOCHIMICA ET COSMOCHIMICA ACTA
出版日期2022-02-01
卷号318页码:415-427
ISSN号0016-7037
关键词Eclogite Pitcairn EM1 Crustal recycling Fe isotopes Olivines
DOI10.1016/j.gca.2021.12.017
英文摘要Subducted oceanic crust can transform into eclogite in the upper mantle, and generate chemical heterogeneity of mantle plumes, as recorded by elemental and radiogenic isotopic variations in oceanic island basalts (OIBs). The secondary pyroxenite produced by the reaction between eclogite-derived melt and peridotite is increasingly regarded as a major source component of OIBs, as well as peridotite. However, it remains unclear whether eclogite can be a direct source component of OIBs. To test this possibility, we present high-precision whole-rock Fe isotopes and the chemical compositions of olivine phenocrysts from well-characterized EM1-type basalts from Pitcairn Island. The Pitcairn basalts are characterized by moderate Sr-87/Sr-86, low Nd-143/Nd-144 and (206)pb/Pb-204 isotopic ratios, and lowest delta Mg-26 values among OIBs, suggesting a contribution from recycled ancient crustal components (oceanic crust plus sediment). For comparison, we also report the Fe isotope compositions of FOZO-type basalts (with low Sr-87/Sr-86, moderately high Nd-143/Nd-144 and moderate (206)pb/Pb-204 ratios) from the Louisville hot spot track, which were suggested to be a typical peridotite-derived OIB. The Louisville basalts have MORB-like delta Fe-57 values (0.06 parts per thousand-0.15 parts per thousand), whereas the Pitcairn lavas have substantially heavier Fe isotopic compositions (delta Fe-57 = 0.17 parts per thousand-0.31 parts per thousand) than MORBs. Quantitative evaluations suggest that magmatic differentiation, partial melting, and elevated oxygen fugacity in the source are insufficient to generate the heavy Fe isotopic compositions of the Pitcairn basalts. A good correlation between delta Fe-57 and epsilon(Nd(i)) (or delta Mg-26) values in the Pitcairn basalts indicates binary mixing, and the melts derived from the EM1 endmember have unusually heavy Fe and light Mg isotopic compositions. In order to explain the origin of the Fe and Mg isotopic compositions, we calculated the Fe, Mg, and Nd isotopic compositions of partial melts of eclogite, secondary pyroxenite and peridotite, respectively. The results indicate that eclogite is the only suitable candidate to generate melts with both heavy Fe and light Mg isotopes. This inference is strengthened by the major and minor elemental compositions of olivine phenocrysts from the Pitcairn basalts, which show low Fo (73.2-82.5) and Ni contents (620-1949 ppm), and low Mn/Fe (0.011-0.015) and Ni/(Mg/Fe) (524-1041) ratios. These characteristics are markedly different from those of olivines from MORBs and the Koolau lavas from Hawaii, which represent phenocrysts that equilibrated with peridotite-derived and secondary pyroxenite-derived melts, respectively. We therefore argue that eclogite is the source lithology of the EM1 endmember of the Pitcairn basalts. Binary mixing between our modelled eclogite- and peridotite-derived melts produced magmas with relatively low Mg# value, Mg/Fe ratios and moderate Ni contents characteristics, which are preserved in the low-Fo Pitcairn olivines. Our results highlight that, in addition to peridotite and secondary pyroxenite, eclogite may survive in mantle plumes at shallow depths and make a substantial contribution to the source of OIBs. (C) 2021 Elsevier Ltd. All rights reserved.
WOS关键词PARTIAL MELTING EXPERIMENTS ; TRACE-ELEMENT ; HAWAIIAN PLUME ; ISLAND BASALTS ; MAJOR ELEMENTS ; 3 GPA ; IRON ; FRACTIONATION ; SYSTEMATICS ; PYROXENITE
资助项目National Natural Science Foundation of China[42130310] ; Frontiers Science Center for Critical Earth Material Cycling, Nanjing University[DLTD2105] ; Fundamental Research Funds for the Central Universities of China[0206-14380128] ; Fundamental Research Funds for the Central Universities of China[0206-14380114]
WOS研究方向Geochemistry & Geophysics
语种英语
出版者PERGAMON-ELSEVIER SCIENCE LTD
WOS记录号WOS:000744091900013
资助机构National Natural Science Foundation of China ; National Natural Science Foundation of China ; Frontiers Science Center for Critical Earth Material Cycling, Nanjing University ; Frontiers Science Center for Critical Earth Material Cycling, Nanjing University ; Fundamental Research Funds for the Central Universities of China ; Fundamental Research Funds for the Central Universities of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Frontiers Science Center for Critical Earth Material Cycling, Nanjing University ; Frontiers Science Center for Critical Earth Material Cycling, Nanjing University ; Fundamental Research Funds for the Central Universities of China ; Fundamental Research Funds for the Central Universities of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Frontiers Science Center for Critical Earth Material Cycling, Nanjing University ; Frontiers Science Center for Critical Earth Material Cycling, Nanjing University ; Fundamental Research Funds for the Central Universities of China ; Fundamental Research Funds for the Central Universities of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Frontiers Science Center for Critical Earth Material Cycling, Nanjing University ; Frontiers Science Center for Critical Earth Material Cycling, Nanjing University ; Fundamental Research Funds for the Central Universities of China ; Fundamental Research Funds for the Central Universities of China
源URL[http://ir.iggcas.ac.cn/handle/132A11/104024]  
专题地质与地球物理研究所_岩石圈演化国家重点实验室
通讯作者Zeng, Gang
作者单位1.Northwest Univ, Dept Geol, State Key Lab Continental Dynam, Xian 710069, Peoples R China
2.Nanjing Univ, Frontiers Sci Ctr Crit Earth Mat Cycling, Nanjing 210023, Peoples R China
3.Nanjing Univ, Sch Earth Sci & Engn, State Key Lab Mineral Deposits Res, Nanjing 210023, Peoples R China
4.Japan Agcy Marine Earth Sci & Technol, Res Inst Marine Geodynam, Yokosuka, Kanagawa 2370061, Japan
5.Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 100029, Peoples R China
推荐引用方式
GB/T 7714		 Shi, Jin-Hua,Zeng, Gang,Chen, Li-Hui,et al. An eclogitic component in the Pitcairn mantle plume: Evidence from olivine compositions and Fe isotopes of basalts[J]. GEOCHIMICA ET COSMOCHIMICA ACTA,2022,318:415-427.
APA Shi, Jin-Hua.,Zeng, Gang.,Chen, Li-Hui.,Hanyu, Takeshi.,Wang, Xiao-Jun.,...&Xie, Wen-Li.(2022).An eclogitic component in the Pitcairn mantle plume: Evidence from olivine compositions and Fe isotopes of basalts.GEOCHIMICA ET COSMOCHIMICA ACTA,318,415-427.
MLA Shi, Jin-Hua,et al."An eclogitic component in the Pitcairn mantle plume: Evidence from olivine compositions and Fe isotopes of basalts".GEOCHIMICA ET COSMOCHIMICA ACTA 318(2022):415-427.

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来源：地质与地球物理研究所

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