Scientists find the presence of fluids derived from subducted slab in the lower mantle

A team of scientists, led by University College Cork (Ireland) and Bayreuth Geoinstitute (Germany), has found proof of subducted slab fluids in the lower mantle by studying inclusions in diamonds using the ESRF.

In the Juína region, in the west of Brazil, a volcanic eruption brought diamonds from the interior of the Earth to the surface around 93 millions of years ago. Diamonds form perfect capsules so they retain the exact chemistry of material from the part of the Earth where they formed. Scientists are therefore studying these minerals to get information on the composition of the deep upper mantle, the transition zone and lower mantle.

Now a team led by University College Cork (Ireland) and Bayreuth Geoinstitute (Germany) has found that subducted material has penetrated into the sublithosperic mantle (below 250 km) by testing the oxidation state of several diamonds from the Juína region using the ESRF.

The oxidation state of the Earth’s mantle controls important parameters and processes, such as magma generation, speciation and mobility of fluids and melts in the Earth’s interior, deep carbon cycle, recycling of oceanic crust back into the mantle, chemical differentiation of the planet and many others.

It is generally considered that the main three layers of the Earth – its crust, mantle and core, represent profound changes in the oxidation state of iron from ferric (Fe3+) at the surface to mostly Fe2+ in the silicate minerals in the upper mantle, transition zone and the lower mantle and ultimately, to the Fe0 in the core. In short, the surface is very oxidised and the core is metallic so it is very reduced.

Read more on the ESRF website

Image: Georgios Aprilis, ESRF postdoc at ID18 beamline