The composition of the Earth

The terrestrial planets of the inner Solar System are believed to be broadly chondritic in composition. Here I suggest that the lithophile element composition of the terrestrial mantle, as approximated by primitive lherzolites having high Al/Si ratios and low Mg/Si ratios, was established by nebular rather than indigenous processes. The implications of this model include: (i) the Mg/Si ratio of the upper mantle is an instrinsic property of the bulk Earth and does not reflect differentiation of a terrestrial magma ocean; (ii) the Moon probably did not form by a giant impact on to the Earth; (iii) refractory lithophile elements should be 2.5-3.0 chondrites in the bulk silicate Earth; and (iv) silicon is not a major constituent of the Earth’s core.

10.1098/rsta.1996.0059

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Citations (7)

The great sulfur depletion of Earth’s mantle is not a signature of mantle–core equilibration

Contributions to Mineralogy and Petrology (2017)

Chris Ballhaus Raúl O. C. Fonseca Carsten Münker Arno Rohrbach T. Nagel

Lithophile

Planetary differentiation

Early Earth

Hotspot (geology)

Primitive mantle

10.1007/s00410-017-1388-3

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Citations (26)

The Lithophile Element Budget of Earth's Core

Geochemistry Geophysics Geosystems (2022)

B. Chidester Simon J. Lock Kellie Swadba Z. Rahman K. Righter

Abstract The relative composition of Earth's core and mantle were set during core formation. By determining how elements partition between metal and silicate at high pressures and temperatures, measurements of the mantle composition and geophysical observations of the core can be used to understand the mechanisms by which Earth formed. Here we present the results of metal‐silicate partitioning experiments for a range of nominally lithophile elements (Al, Ca, K, Mg, O, Si, Th, and U) and S to 85 GPa and up to 5400 K. With our results and a compilation of literature data, we developed a parameterization for partitioning that accounts for compositional dependencies in both the metal and silicate phases. Using this parameterization in a range of planetary growth models, we find that, in general, lithophile element partitioning into the metallic phase is enhanced at high temperatures. The relative abundances of FeO, SiO 2 , and MgO in the mantle vary significantly between planetary growth models, and the mantle abundances of these elements can be used to provide important constraints on Earth's accretion. To match Earth's core mass and mantle composition, Earth's building blocks must have been enriched in Fe and depleted in Si compared with CI chondrites. Finally, too little Mg, Si, and O are partitioned into the core for precipitation of oxides to be a major source of energy for the geodynamo. In contrast, several ppb of U can be partitioned into the core at high temperatures, and this energy source must be accounted for in thermal evolution models.

Lithophile

Planetary differentiation

10.1029/2021gc009986

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Citations (10)

The composition of the Earth

Chemical Geology (1995)

W. F. McDonough Shen‐Su Sun

Enstatite

Volatiles

Lithophile

Planetary differentiation