(ORDO NEWS) — Scientists from the University of Arizona have found that diamonds are forming at the boundary between the core and the mantle of the Earth, and a process similar to the formation of rust is going on. The study is published in Geophysical Research Letters.
The Earth’s core contains approximately 90% of the planet’s carbon. It is surrounded by a mantle, and it was previously thought that there was almost no carbon in it.
Scientists have found that the mantle contains much more carbon than expected – all because of its leakage from the core.
At the same time, it passes into the form that is most stable under the conditions at the boundary of the core and mantle, becoming a diamond.
The mantle also contains iron, upon interaction with which at high temperatures an iron-carbon alloy is formed at the boundary between the core and the mantle.
The oceanic crust of the Earth, containing minerals, can sometimes sink to this boundary (the phenomenon of subduction).
Here, due to the high temperature, water can be released from the minerals. When it interacts with an alloy of iron and carbon, a reaction occurs similar to the rusting of steel.
The authors performed experiments on an advanced photon source at the Argonne National Laboratory, where they compressed an iron-carbon alloy and water to the pressure and temperature expected at the core-mantle interface.
The water and metal then reacted to form oxides and hydroxides of iron, just as happens when rusting on the surface of the Earth.
Scientists believe that the formation of diamonds at the boundary between the core and the mantle could have taken place over billions of years since the start of subduction in the bowels of the planet.
Seismic surveys can discover diamond deposits in the future.
The authors of the work plan to investigate the behavior of other light elements in the core, such as silicon, sulfur and oxygen, and how such changes can affect the mineralogy of the deep mantle.
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