Scientists have discovered a reservoir with three times the volume of all ocean below the surface, according to an international study. Water is found in the transition zone between Earth’s upper and lower mantle. The research team used techniques including Raman spectroscopy and FTIR spectroscopy to analyze the rate diamonds formed 660 meters below the Earth’s surface, ANI reported.
The study confirms what has long been a theory that seawater accompanies the subducting slab into the transition zone. This means that our planet’s water cycle includes the interior of the planet.
“These mineral transitions greatly hinder the movement of rocks in the mantle,” explains Prof. Frank Brenker from the Institute of Geosciences at Goethe University Frankfurt. For example, mantle plumes — plumes of hot rock that rise from deep within the mantle — sometimes stop directly below the transition zone. The movement of the mass in the opposite direction also stops.
“Subducting plates usually have a hard time breaking through the entire transition zone,” Brenker said. “So, in this region below Europe, there’s an entire graveyard of such plates.”
However, the long-term effects of “sucking” material into the transition zone have not been known until now, on its geochemical composition, and whether large amounts of water are present there. “Subducting slabs also carry deep-sea sediments into the Earth’s interior. These sediments can hold large amounts of water and carbon dioxide,” Brenke explained. But until now it was not clear how much entered the transition zone in a more stable form, with hydrous minerals and Carbonates – so it’s not clear if there’s really a lot of water stored there.”
Conditions at the time were certainly favorable for this. The dense minerals wadsleyite and ringwoodite can (unlike olivine at smaller depths) store vast amounts of water—so large, in fact, that the transition zone could theoretically absorb six times the amount of water in our oceans. “So we know that the boundary layer has a huge water storage capacity,” Brenke said. “However, we don’t know if it actually did.”
An international study involving Frankfurt geoscientists now provides the answer. The research team analyzed a diamond from Botswana, Africa. It formed at a depth of 660 kilometers, just at the junction between the transition zone and the lower mantle, where Lynnwoodite is the dominant mineral. Diamonds from this region are very rare, and even among the rare diamonds from ultra-deep origins, they make up only one percent of the diamonds. Analysis showed that the stone contained a significant amount of magnesite inclusions – which were high in water content. In addition, the research team was able to determine the chemical composition of the stone. It’s nearly identical to nearly every piece of mantle rock found in basalt anywhere in the world. This suggests that the diamond must have come from a normal part of the mantle. “In this study, we have shown that the transition zone is not a dry sponge, but contains a lot of water,” Brenke said, adding: “It also brings us closer to Jules Verne’s theory of Earth’s inner oceans. Idea.” The difference is that there is no ocean, but water-bearing rock, which, according to Brenke, neither feels wet nor drips.