Experts in diamond research in the Department of Earth and Atmospheric Sciences have made two groundbreaking discoveries this year, thanks to the superdeep sparkling minerals. JEFF W. HARRIS, UNIVERSITY OF GLASGOW
These diamond-encased garnets can form at depths down to 550 kilometres below Earth’s surface.
Iron Five hundred and fifty kilometres below the Earth’s surface, Thomas Stachel discovered highly oxidized iron—similar to the rust we see on our planet’s surface—within garnets found within diamonds. The finding surprised geoscientists around the globe because there is little opportunity for iron to become so highly oxidized deep below the Earth’s surface.
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“On Earth’s surface, where oxygen is plentiful, iron will oxidize to rust,” explains Stachel, professor and diamond expert. “In the Earth’s deep mantle, we should find iron in its less oxidized form, known as ferrous iron, or in its metal form. But what we found was the exact opposite—the deeper we go, the more oxidized iron we found.” The discovery suggests that something oxidized the rocks in which the superdeep diamonds were found. The suspect? Molten carbonate carried to these great depths in sinking slabs of ancient sea floor.
Calcium silicate perovskite In a diamond from 150 kilometres farther down, Canada Excellence Research Chair Laureate Graham Pearson made another surprising diamond discovery. “Nobody has ever managed to keep this mineral stable at the Earth’s surface,” says Pearson. “The only possible way of preserving this mineral at the Earth’s surface is when it’s trapped in an unyielding container like a diamond. Based on our findings, there could be as much as teratonnes of this perovskite in deep Earth. “The discovery of perovskite in this particular diamond very clearly indicates the recycling of oceanic crust into Earth’s lower mantle, giving insight into just what happens after oceanic plates descend into the depths of the Earth.” Diamonds. Just like Shirley Bassey crooned, they’re forever. Romantically symbolic but also scientifically invaluable. The toughest materials on Earth, they also provide a unique window into Earth’s core.
Bright side of the road dust Chemists have discovered that exposure to sunlight causes chemical reactions in the dust found on Edmonton roads. “We found that when you shine light on road dust, it produces a reactive form of oxygen called singlet oxygen,” says Sarah Styler, assistant professor of chemistry. “It acts as an oxidant in the environment and can cause or influence other chemical reactions.” Styler examined road dust collected from Edmonton’s downtown core in September 2016. Just what those chemical reactions are and how they affect us is something Styler is determined to find out. “Unlike tailpipe emissions, which are increasingly heavily regulated, road dust is much more complex and comes from many different sources,” explains Styler. If contaminants in road dust react with singlet oxygen, that means that sunlight could change the lifetime and potency of those contaminants in ways we don’t yet understand. One group of chemicals that could react with singlet oxygen is a set of toxic components of combustion emissions, known as polycyclic aromatic hydrocarbons. Next, Styler and her team will examine road dust from other places around the city, including residential, commercial, and park areas, to better understand if and how the different compositions of road dust will influence reactivity.
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