Science

Davemaoite, the mineral from deep Earth stuck in a diamond observed for the first time

The brief observation of davemaoite offers an unprecedented view of the Earth’s inner layer and opens new areas of research. Thought to make almost 3% of the Earth’s total volume, it could help explain the dynamic of tectonic plates.

diamond from Botswana where davemaoite was found
Davemaoite was found in three microscopic imperfections of this diamond from Botswana | © Aaron Celestian, Natural History Museum of Los Angeles County

On November 12, researchers specialized in mineralogy observed a new mineral made of calcium, silicon and oxygen for the first time time in nature. Trapped inside a rare type of diamond, calcium silicate was only theorized and synthesized in laboratory but never observed before.

One of the reasons that made it so difficult to observe is because it doesn’t exist under atmospheric pressure. In fact, the mineral cannot retain its structure after being removed from its high-pressure environment.

Surprisingly, they have been able to identify it trapped in imperfections of a 4-milliter wide diamond found in Botswana more than 30 years ago.

When we broke open the diamond, the davemaoite stayed intact for about a second, then we saw it expand […] and basically turn into glass“, one of the scientists explained.

Scientists called this compound “davemaoite“.

Diamonds, being the most solid element on Earth, offer a perfect protection to anything stuck inside it. They also prove to be an excellent unalterable time-capsule during their journey from where they were formed millions of years ago up to the surface.

This tiny piece used by the mineralogists could date back between 100 million and 1 billion years ago.

Most of the diamonds usually found are formed at maximum 250 kilometers below the surface but the gem from Botswana belongs to the category or “super-deep diamonds“, from deep Earth, and probably formed between 660 and 900 km below the surface (410 to 560 miles).

The composition showed that the diamond could have only been formed under pressure with conditions similar to the lower mantle, between 240 and 350 million hPa or about 150,000 times as much as the pressure on Earth’s surface.

Almost 3% of Earth’s volume made up of Davemaoite

The lower mantle is a layer of Earth accounting for more than half the volume of Earth, located from 660 to 2900 km below Earth’s surface.

Davemaoite is thought to make 5% to 7% of the lower mantle. As such, the existence of about 3-4% of the total Earth’s volume has just been discovered in nature.

The diamond also contained sodium and potassium, which usually only exists in the Earth’s crust, giving more insights on how material on the surface goes back into the mantle.

Moreover, davemaoite is thought to host radioactive elements, New Scientist explains.

And those radioactive elements like uranium or thorium are an important factor in creating heat as they warm the Earth’s inner layers while they decay. Considered to be responsible for a third of the Earth’s interior heat, scientists found that “heat from radioactive decay contributes about half of Earth’s total heat flux” last July.

And inner places hotter than others, with a different viscosity and fluidity, could explain what drives the movement of tectonic plates.

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