How and when was carbon distributed in the Earth?

It is generally accepted that planetary surfaces were covered with molten silicate, a "magma ocean", during the formation of terrestrial planets. In a deep magma ocean, iron would separate from silicate, sink, and eventually form a metallic core. In this stage, elemental partitioning between a metallic core and a magma ocean would have occurred and siderophile elements would be removed from the magma ocean.

Such a chemically differentiated magma ocean formed the present-day Earth's mantle. Previous studies have experimentally investigated carbon partitioning between iron liquid and silicate melt under high-pressure conditions and found that a terrestrial magma ocean should be more depleted in carbon than the present day.

Thus, how and when the carbon abundance in the Earth's mantle has been established is still poorly understood.

All previous studies have used a graphite capsule, and therefore, the sample was saturated with carbon. However, the bulk Earth is unlikely to be saturated with carbon given the carbon abundance in chondrites which are believed to be the building blocks of the Earth.

Moreover, it is known that the partition coefficient varies with the bulk concentration of the element of interest even if experimental conditions are identical.

In order to investigate the effect of bulk carbon concentration on its liquid metal-silicate partitioning behavior, researchers at Ehime University, Kyoto University, and JAMSTEC have conducted new carbon partitioning experiments at carbon-undersaturated conditions using a boron nitride capsule.

The new experimental result shows that the partition coefficient of carbon between iron liquid and silicate melt at carbon-undersaturated conditions is several times lower than previous studies using a graphite capsule. This suggests that carbon in a magma ocean may not have been as depleted as previously thought and requiring re-investigation of the core-mantle partitioning of carbon.

Research paper

Related Links
Ehime University
Carbon Worlds - where graphite, diamond, amorphous, fullerenes meet

Tweet

Thanks for being there;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Monthly Supporter
$5+ Billed Monthly

paypal only

SpaceDaily Contributor
$5 Billed Once

credit card or paypal

Humanity's emissions '100-times greater' than volcanoes
Paris (AFP) Oct 1, 2019
Human activity churns out up to 100 times more planet-warming carbon each year as all the volcanoes on Earth, says a decade-long study released Tuesday. The Deep Carbon Observatory (DCO), a 500-strong international team of scientists, released a series of papers outlining how carbon is stored, emitted and reabsorbed by natural and manmade processes. They found that manmade carbon dioxide emissions drastically outstrip the contribution of volcanoes - which belch out gas and are often fingered as ... read more