Diamond Found in Deep Earth May Hold New Mineral

                 Deep-Earth Diamond Contains a New Mineral

The unexpected discovery of calcium silicate perovskite, a mineral never before seen in nature, has opened a window into the mysteries of the Earth's mantle. Found at depths of 660 to 900 kilometres below the planet's surface, the mineral can only form under extreme pressure. This finding has the potential to revolutionize geologists' understanding of the mantle's influence on plate tectonics.

Though the mineral had been created in the laboratory at a pressure of 20 gigapascals, it reverted to a different form when removed from the artificial environment. This led researchers to believe that discovering naturally occurring calcium silicate perovskite from the mantle would be nearly impossible. As Oliver Tschauner of the University of Nevada, Las Vegas, explains, "We believed the chances of discovering it were so slim that we never actively sought for it." However, this remarkable discovery has now revealed a wealth of new information about the Earth's deep mantle.

The tiny gray blobs of mineral embedded in this slice of clear diamond are the first samples of newly named davemaoite, a calcium silicate perovskite mineral that only forms in the lower mantle.

The unexpected discovery of a diamond created deep in the Earth's mantle has revealed a material that has never been seen before in nature. This finding provides a unique insight into the planet's deep mantle and may help to uncover new information about the planet's structure at depths of more than 660 kilometres. This could potentially help geologists to better understand how the mantle influences plate tectonics on Earth.

When scientists investigated flaws in a diamond from Orapa, Botswana, they were surprised to find three small particles of calcium silicate perovskite. This variant had a distinct cubic crystal structure that distinguished it from other varieties of the mineral. The researchers named the new mineral davemaoite after geologist Ho-Kwang Dave Mao, who pioneered the use of diamonds as a way to produce mantle-like pressures on the Earth's surface.

Geoscientists can gain a better understanding of the composition of the Earth's mantle by studying what is present in the crust. Rocks and minerals are transported up and down between the layers over millions of years, but the minerals morph and alter as they leave the lower mantle's intense pressure and blistering temperatures. Diamonds, however, are the only direct window into this region as they do not morph and can lock in microscopic inclusions under their extreme hardness. Diamonds form at least 150 km below the surface, with some starting as deep as 1,000 km below the surface under extreme pressure—even when the diamond ascends to the crust and is plucked by a miner."The diamond doesn't allow anything in or out," says Oded Navon, a geologist at the Hebrew University of Jerusalem who studies diamonds and the deep mantle but was not involved in the davemaoite finding. "It's a near-perfect closed box."

The unexpected discovery of davemaoite, a calcium silicate perovskite mineral, has captivated scientists around the world. Found embedded in a diamond from Orapa, Botswana, the mineral had never been seen before in nature and provides a unique glimpse into the planet's deep mantle. This discovery could help geologists better understand how the mantle influences plate tectonics on Earth.

The davemaoite particles were incredibly small, measuring only five to ten micrometres across. To analyze the inclusions, the researchers used x-rays and then drilled into two of them with a laser, vaporizing the material and passing it through a mass spectrometer to identify the elements. Surprisingly, the davemaoite contained an unusually high level of potassium, which may have helped preserve the mineral during its time on the Earth's surface.

The findings, published in Science, have opened up a new realm of possibilities for scientists to explore the mysteries of the Earth's mantle. With further research, the discovery of davemaoite could help unlock the secrets of the planet's deep interior and provide invaluable insight into the processes that shape our world. 

 

According to Yingwei Fei, a geochemist at the Carnegie Institution for Science who wrote an editorial accompanying the new study in Science but was not involved in the research, the high potassium level also suggests a global "conveyor belt" that circulates elements between the crust and deep mantle.Although potassium is not abundant in the deep mantle, it is believed to get there in slabs of crust at subduction zones, when one tectonic plate is forced beneath another.

 

According to Tschauner, one type of potassium, davemaoite, is radioactive and contains trace quantities of radioactive elements such as thorium and uranium, which are not easily absorbed by the other minerals that make up the lower mantle. This is significant, as the decay of these elements accounts for almost one-third of the heat generated in the Earth's core. Geoscientists believe davemaoite makes up roughly 5 to 7 percent of the lower mantle based on mineral concentrations closer to the Earth's surface. However, Tschauner notes that the mineral may not be evenly distributed. As a result, pockets of uranium- and thorium-rich davemaoite may predominate in some areas, which could explain why some portions of the mantle are hotter than others. These hotspots help to drive circulation in the mantle, which in turn drives plate tectonics, so slight fluctuations in mineral concentrations could have a major impact on the planet's surface. Such changes could also provide insight into the relationship between the Earth's crust and lower mantle, aiding in the understanding of how materials migrate between them. According to Tschauner, this is a field of study that is only now becoming possible. Having access to genuine minerals from the lower mantle is a relatively new avenue for this type of research, he says.

 

  

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