Geochemistry and Distribution of Recycled Domains in the Mantle Inferred From Nd and Pb Isotopes in Oceanic Hot Spots: Implications for Storage in the Large Low Shear Wave Velocity Provinces
Geochemistry and Distribution of Recycled Domains in the Mantle Inferred From Nd and Pb Isotopes in Oceanic Hot Spots: Implications for Storage in the Large Low Shear Wave Velocity Provinces
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DOI：
10.1029/2018gc007552
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发表时间：
2018-09-01
影响因子：
3.5
通讯作者：
Konter, J. G.
中科院分区：
文献类型：
--
作者：
Jackson, M. G.;Becker, T. W.;Konter, J. G.
大陆和大洋地壳的俯冲被认为在地幔中产生了地球化学上不同的储层，分别称为EM（富集地幔）和HIMU（高mu = U-238/Pb-204）。然而，EM和HIMU域在地球内部的位置受到很大的限制。我们探讨了极端EM（Nd-143/Nd-144 = 20）地球化学特征的海洋岛屿玄武岩爆发在热点的地理分布，突出三个意见。首先，热点地理上与两个大的低剪切波速度省（LLSVP）有类似的范围内的EM成分。如果这些热点来源于LLSVP通过上升流羽流，这一观察结果是一致的假设，LLSVP形成类似的过程，并有类似的地球动力学历史。第二，EM和HIMU区域呈现不同的纬度分带性：EM组分最极端的海洋热点（Nd-143/Nd-144 < 0.5125）集中在南半球（南纬14度至52度），而HIMU组分的海洋热点主要位于热带附近（北纬38度至29度）。第三，所有13个大洋热点的EM组成（Nd-143/Nd-144 0.512630）的组成。相比之下，HIMU域没有显示出与LLSVP的明确地理关联。因此，地幔中的EM域和HIMU域表现出不同的空间分布。这可能反映了这两个组成部分俯冲输入的差异，或者它们在地球深部分离或积累的差异。
Subduction of continental and oceanic crust is thought to give rise to geochemically distinct reservoirs in the mantle called EM (enriched mantle) and HIMU (high mu = U-238/Pb-204), respectively. However, the locations of EM and HIMU domains in the Earth's interior are poorly constrained. We explore the geographic distribution of extreme EM (Nd-143/Nd-144 = 20) geochemical signatures in ocean island basalts erupted at hot spots, highlighting three observations. First, hot spots geographically associated with the two large low shear wave velocity provinces (LLSVPs) have a similar range of EM compositions. If these hot spots are sourced by the LLSVPs via upwelling plumes, this observation is consistent with the hypothesis that the LLSVPs formed by similar processes and have similar geodynamic histories. Second, the EM and HIMU domains exhibit different latitudinal zonation: oceanic hot spots with the most extreme EM compositions (Nd-143/Nd-144 < 0.5125) are concentrated in the Southern Hemisphere (14 degrees S to 52 degrees S latitude), while oceanic hot spots hosting HIMU compositions are found primarily near the tropical latitudes (38 degrees N to 29 degrees S). Third, all 13 oceanic hot spots with EM compositions (Nd-143/Nd-144 0.512630) compositions. In contrast, the HIMU domains do not show a clear geographic association with the LLSVPs. Therefore, EM and HIMU domains in the Earth's mantle exhibit different spatial distributions. This may reflect differences in subduction inputs of these two components, or differences in how they segregate or accumulate in the deep Earth.