The Composition of Earth's Lower Mantle
OPEN ACCESS
Loading...
Author / Producer
Date
2024-07
Publication Type
Review Article
ETH Bibliography
yes
Citations
Altmetric
OPEN ACCESS
Data
Rights / License
Abstract
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.
Permanent link
Publication status
published
Editor
Book title
Journal / series
Volume
52 (1)
Pages / Article No.
605 - 638
Publisher
Annual Reviews
Event
Edition / version
Methods
Software
Geographic location
Date collected
Date created
Subject
lower mantle; chemical composition; Mg/Si ratio; mineralogy; Seismic structure; density; thermal state; mantle convection; dynamical evolution
Organisational unit
09495 - Murakami, Motohiko / Murakami, Motohiko
09784 - Sossi, Paolo Angelo / Sossi, Paolo Angelo
Notes
Funding
203668 - Production of Secondary Atmospheres (SNF)