Is the Earth's mantle full of diamonds?

Parts of the Earth's mantle could be laden with diamonds, if a new model proved correct. But no, you can not exploit them – they would be almost a hundred kilometers below the surface.

Scientists' models show that sound waves seem to travel too fast through the old stable nuclei of the continents, called "cratons" which extend deep into the mantle at depths of 120 to 150 kilometers (75 to 93 miles). Through observations, experiments and modeling, a team has estimated that the presence of a large number of diamonds, a medium that allows a speed of sound faster than that of other crystals, could explain the 39, anomaly of the speed of sound. "We had all these observations of the speed of sound and we needed something to explain them," concludes Ulrich Faul, a researcher at the Earth Department, Atmosphere of MIT. and the planetary sciences, said to Gizmodo. "We finished with diamonds."

Scientists have modeled the rock under the continents using tomography, which you can imagine as a radiographic image, but using sound waves. But the sound velocities of about 4.7 kilometers per second (about 10.513 mph) are faster than the sound wave speeds in other types of minerals under the crust, according to the journal article Geochemistry, Geophysics, Geosystems

The researchers realized that if the regions had or 3 percent of diamonds by volume or 50 percent of a mineral called eclogite, this would allow the sound velocities that they observed. But these two figures seemed too high, according to the observations of the minerals which are found on the surface of the Earth: rocks containing diamonds, called kimberlites. The researchers compromised and thought that 20 percent eclogist and 2 percent of diamonds could explain the high speeds. The diamonds could be sprinkled like crystals found evenly across the cratons.

In other words, it's nothing like this scene with the geode in The Core.

This research seems clear, but it is still only a hypothesis, explains Faul. There is still some debate about exactly how to measure the speed of sound, as well as how Earth produces the nuclei of continents, or cratons, in the first place.

To say that 2% of these cratons are diamonds is a bit controversial, of course, and would change a lot of what scientists understand on Earth.

"My estimate back of the envelope is that it would almost double the amount of carbon we generally think the Earth's mantle can hold, which would have profound implications for the evolution of the mantle. and Earth's crust, "Wendy Panero, a professor at the Earth Sciences School of the Ohio State University, told Gizmodo. Panero thought the document was interesting, but had some skepticism. "[Two percent volume] is far superior to the amount of diamond found in the kimberlite rock, which is in the karat per ton range." I'm looking forward to seeing more work in the region to see if this hypothesis will withstand for a closer look. "

In other words, diamondiferous rocks on the surface of the Earth have far less diamonds than cratons

In the end, it is difficult to understand the regions Deep Earth, like the mantle, which are inaccessible to direct observation. "They do exactly what seismologists do," Gizmodo Derek Schutt, an badociate professor in the Department of Geosciences at Colorado State University, told Gizmodo. "They saw our best estimates that the diamond seems to work" to explain the mystery, he said. There is still a lot of uncertainty in the speed measurements. The predictions could be accurate, but Schutt says he's not going to hold his breath for the moment

These cratons form some of Earth's oldest rocks, and their study could reveal something about the way the continents move. But there is still a lot of work to be done. "Now we have to do more checks to see if there is something we have forgotten or better measures," said Faul.

[Geochemistry, Geophysics, Geosystems]