In diamonds found deep below the Earth's surface, researchers found the first example of an unprecedented mineral. Researchers think the mineral is unlikely to be found on Earth's surface.
The mineral is called davemaoite, after the eminent geophysicist Ho-kwang (Dave) Mao. Davemaoite was the first example of a high-pressure calcium silicate perovskite (CaSiO3) found on Earth.
Quoted from Live Science, another form of CaSiO3, known as wollastonite, is commonly found throughout the world, but davemaoite has a crystalline structure that forms only under high pressure and high temperatures in Earth's mantle, a dense layer of Earth trapped between the outer core and the Earth's outer core. crust.
Davemaoite has long been thought to be an abundant and geochemically important mineral in the Earth's mantle. But scientists have never found direct evidence of its existence because it breaks down into other minerals as it moves to the surface and the pressure is reduced.
However, analysis of diamonds from Botswana, which form in the mantle about 660 kilometers below Earth's surface, has revealed intact davemaoite samples trapped within. Therefore, the International Mineralogical Association has now confirmed davemaoite as a new mineral type.
"The discovery of davemaoite was a surprise," said study lead author Oliver Tschauner, a mineralogist at the University of Nevada, Las Vegas, United States.
Tschauner and his colleagues discovered davemaoite samples with a technique known as synchrotron X-ray diffraction, which focuses high-energy X-ray beams at specific points within the diamond with microscopic precision.
By measuring the angle and intensity of the reflected light, researchers can decipher what's inside. Samples of davemaoite in diamonds are only a few micrometers (millionths of a meter) across, so less robust sampling techniques will miss the content.
Davemaoite is believed to play an important geochemical role in the Earth's mantle. Scientists theorize that the mineral may also contain other trace elements, including uranium and thorium, which release heat through radioactive decay. Therefore, davemaoite can help generate a large amount of heat in the mantle.
In a 2014 study published in the journal Science, researchers described another theoretical high-pressure mineral from the mantle, known as bridgmanite. However, the bridgmanite samples did not come from the mantle but from inside meteorites.
"The discovery of davemaoite indicates that diamonds can form further in the mantle than previously thought, and this suggests that they may be the best place to look for more new minerals from the mantle," Tschauner said.
"The work of Tschauner et al. inspires hope in the discovery of other difficult high-pressure phases in nature," said Yingwei Fe, a geophysicist at the Carnegie Institution for Science in Washington, DC, who was not involved in the study, in a related Science article.
"Direct sampling of such an inaccessible lower mantle will fill a gap in our knowledge in the chemical composition of our entire planetary mantle."
