Mantle geochemistry: Insights from ocean island basalts

查看全文 作　　者：HUANG [1]ShiChun;ZHENG [2]YongFei

机构地区：[1]Department of Geoscience, University of Nevada;[2]CAS Key Laboratory of Crust-Mantle Material and Environment, School of Earth and Space Sciences, University of Science and Technology of China

出　　处：《Science China Earth Sciences》索引2017年第60卷第11期,共25页

基　　金：supported by the National Science Foundation (Grant No. NSF EAR-1524387);National Natural Science Foundation of China (Grant No. 41590620) 摘　　要：The geochemical study of the Earth's mantle provides important constraints on our understanding of the formation and evolution of Earth, its internal structure, and the mantle dynamics. The bulk Earth composition is inferred by comparing terrestrial mantle rocks with chondrites, which leads to the chondritic Earth model. That is, Earth has the same relative proportions of refractory elements as that in chondrites, but it is depleted in volatiles. Ocean island basalts(OIB) may be produced by mantle plumes with possible deep origins; consequently, they provide unique opportunity to study the deep Earth. Isotopic variations within OIB can be described using a limited number of mantle endmembers, such as EM1, EM2 and HIMU, and they have been used to decipher important mantle processes. Introduction of crustal material into the deep mantle via subduction and delamination is important in generating mantle heterogeneity; however, there is active debate on how they were sampled by mantle melting, i.e.,the role of olivine-poor lithologies in the OIB petrogenesis. The origin and location of high 3He/4He mantle remain controversial,ranging from unprocessed(or less processed) primitive material in the lower mantle to highly processed materials with shallow origins, including ancient melting residues, mafic cumulates under arcs, and recycled hydrous minerals. Possible core-mantle interaction was hypothesized to introduce distinctive geochemical signatures such as radiogenic 186 Os and Fe and Ni enrichment in the OIB. Small but important variations in some short-lived nuclides, including 142 Nd, 182 W and several Xe isotopes, have been reported in ancient and modern terrestrial rocks, implying that the Earth's mantle must have been differentiated within the first 100 Myr of its formation, and the mantle is not efficiently homogenized by mantle convection. 关键词：地球化学特征地幔动力学洋岛玄武岩球粒陨石地幔不均一性地幔熔融原始材料氙同位素

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Mantle geochemistry: Insights from ocean island basalts

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