Systematics of metal–silicate partitioning for many siderophile elements applied to Earth’s core formation

Earth’s core is likely the largest reservoir of carbon (C) in the planet, but its C abundance has been poorly constrained because measurements of carbon’s preference for core versus mantle materials at the pressures and temperatures of core formation are lacking. Using metal–silicate partitioning experiments in a laser-heated diamond anvil cell, we show that carbon becomes significantly less siderophile as pressures and temperatures increase to those expected in a deep magma ocean during formation of Earth’s core. Based on a multistage model of core formation, the core likely contains a maximum of 0.09(4) to 0.20(10) wt% C, making carbon a negligible contributor to the core’s composition and density. However, this accounts for ∼80 to 90% of Earth’s overall carbon inventory, which totals 370(150) to 740(370) ppm. The bulk Earth’s carbon/sulfur ratio is best explained by the delivery of most of Earth’s volatiles from carbonaceous chondrite-like precursors.

Download Full-text

Metal–silicate silicon isotope fractionation in enstatite meteorites and constraints on Earth's core formation

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2010.04.030 ◽

2010 ◽

Vol 295 (3-4) ◽

pp. 487-496 ◽

Cited By ~ 67

Author(s):

Karen Ziegler ◽

Edward D. Young ◽

Edwin A. Schauble ◽

John T. Wasson

Keyword(s):

Isotope Fractionation ◽

Silicon Isotope ◽

Core Formation ◽

Earth’S Core ◽

Earth's Core ◽

Metal Silicate

Download Full-text

Experimental evidence for hydrogen incorporation into Earth’s core

Nature Communications ◽

10.1038/s41467-021-22035-0 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Shoh Tagawa ◽

Naoya Sakamoto ◽

Kei Hirose ◽

Shunpei Yokoo ◽

John Hernlund ◽

...

Keyword(s):

Terrestrial Planet ◽

Outer Core ◽

Core Formation ◽

Earth’S Core ◽

Hydrogen Incorporation ◽

Earth's Core ◽

The Core ◽

The Earth ◽

Metal Silicate ◽

Important Constituent

AbstractHydrogen is one of the possible alloying elements in the Earth’s core, but its siderophile (iron-loving) nature is debated. Here we experimentally examined the partitioning of hydrogen between molten iron and silicate melt at 30–60 gigapascals and 3100–4600 kelvin. We find that hydrogen has a metal/silicate partition coefficient DH ≥ 29 and is therefore strongly siderophile at conditions of core formation. Unless water was delivered only in the final stage of accretion, core formation scenarios suggest that 0.3–0.6 wt% H was incorporated into the core, leaving a relatively small residual H2O concentration in silicates. This amount of H explains 30–60% of the density deficit and sound velocity excess of the outer core relative to pure iron. Our results also suggest that hydrogen may be an important constituent in the metallic cores of any terrestrial planet or moon having a mass in excess of ~10% of the Earth.

Download Full-text