New mineral discovered in a diamond found deep within the Earth

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The calcium silicate found in the lower mantle had never before been found in nature on the earth’s surface.

Scientists have first found a type of calcium silicate called davemaoite that was not previously known to be found naturally on the Earth’s surface. The discovery was made after scientists studied black spots found in a diamond from the depths of the earth.

Named after the Chinese-American geophysicist Ho-Kwang “Dave” Mao, the new mineral davemaoite was found in the diamond formed at high pressure and temperature more than 660 km below the earth’s surface. The study was published in the journal Science today (November 12).

Oliver Tschauner, a researcher at the University of Nevada at Las Vegas who co-directed the study that led to the discovery, said that davemaoite, scientifically called calcium silicate perovskite, or CaSiO3, is one of the most important minerals in the world. Earth in the lower mantle.

Davemaoite concentrates incompatible elements in the upper mantle, including rare earth elements and radioactive isotopes that contribute to the heat of the Earth’s mantle. It can potentially fill in the knowledge gaps in our understanding of the composition of the deep Earth.

Bridge the “knowledge gap”

Yingwei Fei, a geochemist at the Carnegie Institution for Science, said Tschauner and his team “inspire hope” in the discovery of other difficult high-pressure phases in nature, through careful research into deep-origin diamonds or highly shocked meteorites. .

“Such direct sampling of the inaccessible lower mantle would fill our knowledge gap about the chemical composition and heterogeneity of our planet’s entire mantle,” he said. A silicate of this type, formed under high pressure, has never been successfully recovered from the lower mantle of the Earth.

Davemaoite and other similar silicates cannot maintain their original mineralogical structure after being removed from their natural environment under high pressure and high temperature. The only other naturally occurring confirmed silicate mineral, bridgmanite, was found inside a meteorite and is composed of magnesium rather than calcium.

According to Nature, the greenish and octahedral diamond was found in the Orapa mine in Botswana, the largest open pit diamond mine in the world, decades ago. A trader then sold it to George Rossman, a mineralogist at the California Institute of Technology in Pasadena.

Tschauner and Rossman, along with their colleagues, therefore began studying the diamond many years ago. The team used X-ray diffraction to identify and characterize davemaoite in diamond, showing its ability to host potassium, thorium and uranium, the three main heat-producing elements.

“When we broke the diamond, the davemaoite remained intact for about a second, then we saw it expand and swell under the microscope and practically turn into glass,” Tschauner said. New scientist.

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