In a first, researchers discovered a rare mineral that comes directly from Earth's lower mantle

This is "the first time that lower mantle minerals have ever been observed in nature."
Sade Agard

Researchers claim they have discovered a rare mineral that comes directly from Earth's lower mantle- the region between the planet's core and crust - in a new study published in Science.

The finding is a surprise because no one has or expects to retrieve such a high-pressure mineral on the Earth's surface after decades of searching.

However, thanks to a diamond- in which it was entrapped - the new mineral dubbed 'davemaoite,' managed to make the improbable voyage from at least 412 meters within the lower mantle.

The discovery is a step forward in scientists' quest to model the evolution of the Earth's mantle in greater detail.

Davemaoite's radioactive ability drives how heat moves through the deep Earth

Davemaoite makes up mostly 5-7 percent of the material in Earth's lower mantle and is one of three significant minerals there. It is mostly composed of calcium silicate perovskite (CaSiO3)- arguably the most important phase (geochemically) of Earth's lower mantle.

One reason for this is due to davemaoite's unique ability to scavenge radioactive isotopes of uranium, thorium, and potassium.

These isotopes generate a lot of heat in the lower portion of Earth's mantle, making davemaoite an essential player in managing how heat moves through the deep Earth. In turn, this aids in controlling how heat is transferred from the mantle to the crust to power processes like plate tectonics.

Never before has CaSiO3 perovskite been observed in nature since it usually disintegrates when removed from its high-pressure surroundings.

Davemaoite ferried on "the strength of the diamond"

In a first, researchers discovered a rare mineral that comes directly from Earth's lower mantle
The Orapa mine in Botswana where the diamond was found

The CaSiO3-perovskite minerals were unearthed as tiny black specks in a diamond retrieved decades ago from the Orapa mine in Botswana (Southern Africa)- the largest diamond mine in the world by area.

However, a team of U.S. geologists recently acquired the diamond- having little value to jewelers due to its "imperfections"- enabling them to have a closer look.

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"For jewelers and buyers, the size, color, and clarity of a diamond all matter, and inclusions — those black specks that annoy the jeweler — for us, they're a gift," said Oliver Tschauner in a press release from the University of Nevada, Las Vegas, and co-leader of the study.

Regarding davemaoite's unlikely ascent, he commented to Nature, "It's the strength of the diamond that keeps the inclusions at high pressure."

A specialized X-ray technique, known as a synchrotron, revealed the new mineral

Tschauner and collaborators, including geochemist Shichun Huang from the University of Nevada, Las Vegas (UNLV), acquired the diamond before employing a specialized X-ray known as a synchrotron. This enabled them to analyze its internal structure more thoroughly.

They discovered a novel crystalline substance that they termed "davemaoite"-- a name chosen to honor experimental geophysicist Ho-Kwang "Dave" Mao, who created many of the methods Tschauner and his associates employ today.

Davemaoite has since been approved as a brand-new natural mineral by the Commission of New Minerals, Nomenclature, and Classification of the International Mineralogical Association.

Davemaoite can be blasted onto Earth's surface by meteorites

The discovery of davemaoite by Tschauner demonstrates just one of the two ways that highly pressured minerals are discovered in nature: from the interior of meteorites or between 410 and 560 miles beneath the Earth's surface.

Better yet, Tschauder has already made strides in the former path (interior of meteorites) when he discovered the mineral "bridgmanite" back in 2014.

He is optimistic that more mineral discoveries will soon be made, enabling researchers to describe the evolution of the Earth's mantle more accurately.

Abstract:

Calcium silicate perovskite, CaSiO3, is arguably the most geochemically important phase in the lower mantle, because it concentrates elements that are incompatible in the upper mantle, including the heat-generating elements thorium and uranium, which have half-lives longer than the geologic history of Earth. We report CaSiO3-perovskite as an approved mineral (IMA2020-012a) with the name davemaoite. The natural specimen of davemaoite proves the existence of compositional heterogeneity within the lower mantle. Our observations indicate that davemaoite also hosts potassium in addition to uranium and thorium in its structure. Hence, the regional and global abundances of davemaoite influence the heat budget of the deep mantle, where the mineral is thermodynamically stable.

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