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DOI | 10.1073/pnas.2007982117 |
The niobium and tantalum concentration in the mantle constrains the composition of Earth’s primordial magma ocean | |
Dongyang Huang; James Badro; Julien Siebert | |
2020-10-26 | |
发表期刊 | Proceedings of the National Academy of Science
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出版年 | 2020 |
英文摘要 | The bulk silicate Earth (BSE), and all its sampleable reservoirs, have a subchondritic niobium-to-tantalum ratio (Nb/Ta). Because both elements are refractory, and Nb/Ta is fairly constant across chondrite groups, this can only be explained by a preferential sequestration of Nb relative to Ta in a hidden (unsampled) reservoir. Experiments have shown that Nb becomes more siderophile than Ta under very reducing conditions, leading the way for the accepted hypothesis that Earth’s core could have stripped sufficient amounts of Nb during its formation to account for the subchondritic signature of the BSE. Consequently, this suggestion has been used as an argument that Earth accreted and differentiated, for most of its history, under very reducing conditions. Here, we present a series of metal–silicate partitioning experiments of Nb and Ta in a laser-heated diamond anvil cell, at pressure and temperature conditions directly comparable to those of core formation; we find that Nb is more siderophile than Ta under any conditions relevant to a deep magma ocean, confirming that BSE’s missing Nb is in the core. However, multistage core formation modeling only allows for moderately reducing or oxidizing accretionary conditions, ruling out the need for very reducing conditions, which lead to an overdepletion of Nb from the mantle (and a low Nb/Ta ratio) that is incompatible with geochemical observations. Earth’s primordial magma ocean cannot have contained less than 2% or more than 18% FeO since the onset of core formation. |
领域 | 地球科学 |
URL | 查看原文 |
引用统计 | |
文献类型 | 期刊论文 |
条目标识符 | http://119.78.100.173/C666/handle/2XK7JSWQ/301945 |
专题 | 地球科学 |
推荐引用方式 GB/T 7714 | Dongyang Huang,James Badro,Julien Siebert. The niobium and tantalum concentration in the mantle constrains the composition of Earth’s primordial magma ocean[J]. Proceedings of the National Academy of Science,2020. |
APA | Dongyang Huang,James Badro,&Julien Siebert.(2020).The niobium and tantalum concentration in the mantle constrains the composition of Earth’s primordial magma ocean.Proceedings of the National Academy of Science. |
MLA | Dongyang Huang,et al."The niobium and tantalum concentration in the mantle constrains the composition of Earth’s primordial magma ocean".Proceedings of the National Academy of Science (2020). |
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