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研究人员通过橄榄岩的熔融推断太古代地幔氧化
作者:小柯机器人 发布时间:2023/5/9 16:12:42


2023年5月4日出版的《自然—地球科学》杂志,报道了日本爱媛大学IKuwahara, Hideharu团队的最新成果,在下地幔条件下,通过橄榄岩的熔融推断太古代的地幔氧化事件。

研究团队给出了在28 GPa压力下熔融橄榄岩的实验结果。研究发现,如果岩浆海洋到达下地幔,地球岩浆海洋的Fe3+含量将会被现在的上地幔高一个数量级,这个发现定量的解释了太古代地幔高度氧化的证据。这一巨大的地幔氧化事件应该随着维持一个深岩浆海洋的巨大冲击的停止而结束。随后,上地幔Fe3+含量和氧化态的降低可归因于,较小的碰撞物在晚太古代和早太古代的堆积。

据悉,早期地球的地幔,当它与地核平衡的岩浆海洋中形成时,被认为高度缩小的。相反,一些地质证据表明,古代上地幔的氧化程度与今天相似,甚至可能更高。先前关于安山岩高压熔融的证据,证明了熔体中Fe2+到Fe3+加Fe0的歧化作用,表明随着FeO进入地核,岩浆海洋氧化程度变高。

附:英文原文

Title: Hadean mantle oxidation inferred from melting of peridotite under lower-mantle conditions

Author: Kuwahara, Hideharu, Nakada, Ryoichi, Kadoya, Shintaro, Yoshino, Takashi, Irifune, Tetsuo

Issue&Volume: 2023-05-04

Abstract: The early Earth’s mantle is believed to have been highly reducing when it formed from a magma ocean equilibrating with the core. Conversely, some geological evidence suggests that the Hadean upper mantle was oxidized to a similar degree as or even more than that of today. Previous work on the high-pressure melting of andesite demonstrated the disproportionation of Fe2+ to Fe3+ plus Fe0 in the melt, suggesting the magma ocean became more oxidized as Fe0 was removed into the core. Here we present results of experiments melting peridotite at pressures to 28GPa, that of the uppermost lower mantle. We show the Fe3+ content of Earth’s magma ocean was an order of magnitude greater than that of the present upper mantle if the magma ocean reached the lower mantle, which quantitatively explains the geological evidence for a highly oxidized Hadean mantle. This Hadean great mantle oxidation should have ended with the cessation of the huge impacts that sustained a deep magma ocean. The subsequent reduction in Fe3+ content and oxidation state of the upper mantle may be attributed to the accretion of reduced materials by small impactors in late Hadean and early Archaean eons.

DOI: 10.1038/s41561-023-01169-4

Source: https://www.nature.com/articles/s41561-023-01169-4

期刊信息
Nature Geoscience:《自然—地球科学》,创刊于2008年。隶属于施普林格·自然出版集团,最新IF:21.531