Primitive noble gases sampled from ocean island basalts cannot be from the Earth's core.
Primitive noble gases sampled from ocean island basalts cannot be from the Earth's core.
复制标题
从海洋岛屿玄武岩中采集的原始惰性气体不可能来自地核。
DOI：
10.1038/s41467-022-31588-7
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发表时间：
2022-06-30
影响因子：
16.6
通讯作者：
Brodholt, John P. P.
中科院分区：
文献类型：
--
作者：
Li, Yunguo;Vocadlo, Lidunka;Ballentine, Chris;Brodholt, John P. P.
羽流中的稀有气体同位素需要原始挥发物的来源，这些挥发物在地球中大部分被隔离了4.5 Gyrs。在提议的储层中，由于缺乏关于地幔来源的强有力的地球化学和地球物理证据，岩心越来越受到关注。这是支持分区数据显示，足够的氦和氖可以被纳入核心源羽今天。在这里，我们进行从头计算的He，Ne，Ar，Kr和NH3在铁和硅酸盐熔体成核条件下的分配。对于他，我们的结果与以前的研究一致，允许大量的他在核心。相比之下，Ne的分配系数比He低三个数量级。这个非常低的分配系数将导致核心中的3 He/22 Ne比约为103，远高于在洋岛玄武岩（OIB）中观察到的。我们的结论是，核心是不是在OIB的惰性气体的来源。Li等人建立的基于从头计算的液-液分配模型揭示了He和Ne在核幔分离过程中的强烈分馏作用，从而得出热点区的原始挥发分不可能来自核幔的结论。
Noble gas isotopes in plumes require a source of primitive volatiles largely isolated in the Earth for 4.5 Gyrs. Among the proposed reservoirs, the core is gaining interest in the absence of robust geochemical and geophysical evidence for a mantle source. This is supported by partitioning data showing that sufficient He and Ne could have been incorporated into the core to source plumes today. Here we perform ab initio calculations on the partitioning of He, Ne, Ar, Kr and Xe between liquid iron and silicate melt under core forming conditions. For He our results are consistent with previous studies allowing for substantial amounts of He in the core. In contrast, the partition coefficient for Ne is three orders of magnitude lower than He. This very low partition coefficient would result in a 3He/22Ne ratio of ~103 in the core, far higher than observed in ocean island basalts (OIBs). We conclude that the core is not the source of noble gases in OIBs. Li et al. established a liquid-liquid partition model based on ab initio calculations to reveal that He and Ne strongly fractionate during core-mantle separation, which concludes the primitive volatiles seen in hotspots cannot be from the core.
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