地球下地幔的成分

IF 11.3 1区 地球科学 Q1 ASTRONOMY & ASTROPHYSICS Annual Review of Earth and Planetary Sciences Pub Date : 2024-07-23 DOI:10.1146/annurev-earth-031621-075657
Motohiko Murakami, Amir Khan, Paolo A. Sossi, Maxim D. Ballmer, Pinku Saha
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引用次数: 0

摘要

一个多世纪以来,确定占地球总体积近一半的地球下地幔的成分一直是地球科学的核心目标,因为它对地球的起源和演化具有制约作用。然而,下地幔的主要元素化学性质(如 Mg/Si 比率)与上地幔是相似还是不同,仍然存在争议。在此,我们采用多学科方法,通过考虑地球化学、地球物理学、矿物物理学和地球动力学提供的证据,来探讨地球下地幔的组成问题,进而探讨硅酸盐体地球(地壳和地幔)的组成问题。地球化学和地球动力学证据基本一致,表明下地幔摩尔 Mg/Si≥1.12(硅酸盐体地球≥1.15),与岩石记录和全地幔搅拌的累积证据一致。然而,与径向地震参考模型相比,以桥粒岩和铁闪长岩构成的下地幔为基础的矿物物理信息地震属性剖面表明 Mg/Si ∼ 0.9-1.0。这突出了考虑其他矿物(如钙闪长岩和钙闪长岩)存在的重要性,并可能表明下地幔的成分随深度而变化。最后,我们将讨论如何提高我们对地球下地幔和硅酸盐体成分的认识,包括其对地核轻元素预算的影响。从矿物物理、地球物理、地球化学和地球动力学的综合角度对地球的下地幔成分进行了回顾。
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The Composition of Earth's Lower Mantle
Determining the composition of Earth's lower mantle, which constitutes almost half of its total volume, has been a central goal in the Earth sciences for more than a century given the constraints it places on Earth's origin and evolution. However, whether the major element chemistry of the lower mantle, in the form of, e.g., Mg/Si ratio, is similar to or different from the upper mantle remains debated. Here we use a multidisciplinary approach to address the question of the composition of Earth's lower mantle and, in turn, that of bulk silicate Earth (crust and mantle) by considering the evidence provided by geochemistry, geophysics, mineral physics, and geodynamics. Geochemical and geodynamical evidence largely agrees, indicating a lower-mantle molar Mg/Si of ≥1.12 (≥1.15 for bulk silicate Earth), consistent with the rock record and accumulating evidence for whole-mantle stirring. However, mineral physics–informed profiles of seismic properties, based on a lower mantle made of bridgmanite and ferropericlase, point to Mg/Si ∼ 0.9–1.0 when compared with radial seismic reference models. This highlights the importance of considering the presence of additional minerals (e.g., calcium-perovskite and stishovite) and possibly suggests a lower mantle varying compositionally with depth. In closing, we discuss how we can improve our understanding of lower-mantle and bulk silicate Earth composition, including its impact on the light element budget of the core. ▪The chemical composition of Earth's lower mantle is indispensable for understanding its origin and evolution.▪Earth's lower-mantle composition is reviewed from an integrated mineral physics, geophysical, geochemical, and geodynamical perspective.▪A lower-mantle molar Mg/Si of ≥1.12 is favored but not unique.▪New experiments investigating compositional effects of bridgmanite and ferropericlase elasticity are needed to further our insight.
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来源期刊
Annual Review of Earth and Planetary Sciences
Annual Review of Earth and Planetary Sciences 地学天文-地球科学综合
CiteScore
25.10
自引率
0.00%
发文量
25
期刊介绍: Since its establishment in 1973, the Annual Review of Earth and Planetary Sciences has been dedicated to providing comprehensive coverage of advancements in the field. This esteemed publication examines various aspects of earth and planetary sciences, encompassing climate, environment, geological hazards, planet formation, and the evolution of life. To ensure wider accessibility, the latest volume of the journal has transitioned from a gated model to open access through the Subscribe to Open program by Annual Reviews. Consequently, all articles published in this volume are now available under the Creative Commons Attribution (CC BY) license.
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