Unveiling Earth’s secrets from super-deep diamonds – EOAS professors in BBC Future

Dr. Evan Smith, Dr. Maya Kopylova

In the BBC Future article on September 22, 2022, Dr. Evan Smith (Research Scientist at Gemological Institute of America, UBC EOAS Adjunct Professor) and Dr. Maya Kopylova (EOAS Professor) talked about their latest findings in diamonds, particularly, the super-deep ones.

Even the most ordinary diamonds are unique as they formed far deeper than any other rocks inside our planet and emerge to the surface. "There are no other materials at the surface coming from a depth of 600km [373 miles], absolutely not," says Dr. Kopylova.

In 2020, Dr. Smith studied a 124-carat super-deep diamond, which was found to form at least 660km (410 miles) below the Earth's surface and within the lower mantle at pressures at least 240,000 times those at sea level (240 times the deepest part of the ocean, the Mariana Trench). 

A lot of secrets about the Earth lie in super-deep diamonds like the 124-carat one, such as ancient carbon. Unlike regular diamonds, which are thought to start life from ancient seawater, super-deep diamonds start life as carbon dissolved within liquid metal, far down in the planet's interior. "It's like molten iron nickel alloy with sulphur and carbon dissolved in that," says Smith. "So it's a totally different kind of fluid, but it's still carbon fluid. It's undergoing whatever chemical or temperature changes, and that's causing carbon to crystallise out."

Most importantly, super-deep diamonds can provide important clues for the process of subduction, as they might be made of subducting tectonic plates that drifted down into the lower mantle in ancient times. "So we've seen diamonds that look like they're essentially pieces of the oceanic crust that have been carried down to the lower mantle," says Smith. "These diamonds are physically telling us that this process is physically true."

BBC Future: https://www.bbc.com/future/article/20220922-the-super-deep-royal-diamond...
Learn more about the UBC EOAS Diamond Exploration Laboratory: https://diamonds.eoas.ubc.ca/