In a recent study that was published in Science, scientists claim to have found a rare mineral that originates directly from the lower mantle of the planet, which is the layer between the planet’s core & crust.
After decades of searching, no one expected to find such a high-pressure mineral on the Earth’s surface, therefore the discovery came as a surprise.
Thanks to a diamond in which it was trapped, however, the new mineral, dubbed “Davemaoite,” made the unlikely voyage from at least 412 meters down into the lower mantle.
The discovery advances scientists’ efforts to understand the evolution of the Earth’s mantle in more detail.
The radioactivity of Davemaoite determines how heat is transported down the deep Earth
One of three important minerals found in the lower mantle of the Earth, davemaoite makes up mostly 5-7% of the material. It is mostly made of calcium silicate perovskite (CaSiO3), which is likely the most significant lower mantle phase in terms of geochemically.
One reason for this is Davemaoite’s unique ability to remove radioactive isotopes of uranium, thorium & potassium.
Davemaoite is a crucial component in controlling how heat goes through the deep Earth since these isotopes produce a lot of heat in the lower part of the Earth’s mantle. As a result, it is easier to manage how heat is transmitted from the mantle to the crust to power processes such as plate tectonics.
CaSiO3 perovskite has never been seen in nature previously since it normally disintegrates when taken out of its high-pressure environment.
Davemaoite ferried on “the strength of the diamond”
The CaSiO3-perovskite minerals were discovered as tiny black specks in a diamond recovered decades ago from the Orapa mine in Botswana (Southern Africa), which is the world’s largest diamond mine by area.
However, a team of geologists from the United States recently bought the diamond, which had little value to jewellers due to its “imperfections,” allowing them to take a closer look.
“For jewellers and consumers, the size, colour, and clarity of a diamond all matter, and inclusions — those black specks that irritate the jeweller — for us, they’re a gift,” said Oliver Tschauner, co-leader of the study, in a press release from the University of Nevada, Las Vegas.
Regarding the unlikely rise of davemaoite, he commented to Nature, “It is the diamond’s strength that keeps the inclusions under high pressure.”
A specialized X-ray technique, known as a synchrotron, revealed the new mineral
Before using a specialised X-ray known as a synchrotron, Tschauner and colleagues, including geochemist Shichun Huang from the University of Nevada, Las Vegas (UNLV), acquired the diamond. They were able to thoroughly investigate its internal structure.
They found a new crystalline material that they named “davemaoite” in honour of experimental geophysicist Ho-Kwang “Dave” Mao, who developed many of the techniques Tschauner and his colleagues still use today.
Davemaoite has since been approved as an entirely new natural mineral by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association.
Davemaoite can be blasted onto Earth’s surface by meteorites
Tschauner’s discovery of davemaoite shows only one of two ways high-pressure minerals are discovered in nature: from inside of meteorites or b/w 410 to 560 miles below the earth surface.
Tschauder has already achieved progress in the former path (inside of meteorites) by discovering the mineral “bridgmanite” in 2014.
He is optimistic that more mineral discoveries will be made shortly, allowing researchers to more correctly describe the evolution of the Earth’s mantle.