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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