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Noble Gas Partitioning Into The Earth's Outer Core? Ab Initio Calculations On Noble Gas Partitioning Between Silicate and Liquid Iron

惰性气体进入地球外核？

基本信息

批准号：
NE/S01134X/1
负责人：
Lidunka Vocadlo
金额：
$ 56.2万
依托单位：
University College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2019
资助国家：
英国
起止时间：
2019 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FS01134X%2F1
关键词：
Noble Gas Partitioning Into Earth

项目摘要

Rocks from some oceanic islands, such as Iceland and Hawaii, show an unusual geochemical signature with the ratio of isotopes of helium (3He/4He) being very high. Because 3He cannot be produced from radioactive decay, all the 3He must have originated from the accreting solar system. This suggests that the source of these rocks comes from material within a deep isolated primordial reservoir that has been trapped within the Earth throughout its history and has not been affected by subsequent mantle mixing and dynamics. For many years, scientists have been "searching" for these primordial reservoirs and have come up with a number of potential locations, such as regions close to the core-mantle boundary (Large Low Shear Velocity Provinces - LLSVPs, and Ultra Low Velocity Zones - ULVZs) and even isolated zones higher up in the mantle (Bridgmanite Enriched Ancient Mantle Structures - BEAMS). But all these suggestions have their problems. However, one deep reservoir that has received relatively little attention is the Earth's liquid outer core. To establish whether the outer core could, indeed, host noble gases, such as helium, requires knowledge of the partitioning of noble gases between the silicate mantle and the liquid iron alloy outer core. In this proposal we will calculate the necessary partition coefficients in order to determine whether or not the sources of primitive noble gases are consistent with an outer core reservoir. Our results will directly influence our understanding of the origin, scale and survival of mantle heterogeneities, and the intrinsic link to mantle convection and core- mantle exchange. These are some of the biggest issues for understanding the evolution of the Earth from its accretion to present day.

一些海洋岛屿的岩石，如冰岛和夏威夷，显示出一个不寻常的地球化学特征，氦的同位素比率（3He/4He）非常高。因为氦原子不能从放射性衰变中产生，所以所有的氦原子一定都来自于吸积的太阳系。这表明，这些岩石的来源来自一个深隔离的原始储层中的物质，这些储层在地球的整个历史中一直被困在地球内部，没有受到后来的地幔混合和动力学的影响。多年来，科学家们一直在“寻找”这些原始储层，并提出了许多潜在的位置，例如靠近核心-地幔边界的区域（大低剪切速度区- LLSVPs和超低剪切速度区- ULVZs），甚至是地幔中较高的孤立区域（富桥镁石古地幔结构- BEAMS）。但是所有这些建议都有它们的问题。然而，有一个深层储层却很少受到关注，那就是地球的液态外核。要确定外核是否确实可以容纳惰性气体，如氦，需要了解硅酸盐地幔和液态铁合金外核之间的惰性气体分配情况。在这个建议中，我们将计算必要的划分系数，以确定原始稀有气体的来源是否与外岩心储层一致。我们的研究结果将直接影响我们对地幔非均质起源、规模和生存的认识，以及它与地幔对流和核幔交换的内在联系。这些都是理解地球从增生到现在的演变过程中最重要的问题。