A frozen fjord on Baffin Island, Canada’s largest water-bound landmass and the world’s fifth-largest island.
Looking through the diamond exploration samples from the island, scientists from the University of British Columbia have identified a new remnant of the North Atlantic craton, which stretched from present-day Scotland to North America, before it broke apart 150 million years ago. The samples suggest that the craton was 10 percent larger than previous believed.
Craton are old and stable parts of the continental lithosphere, which consists of the Earth’s two topmost layers, the crust and the uppermost mantle. Surviving cycles of merging and rifting of continents, they are characteristically composed of ancient crystalline basement rock, and covered younger sedimentary rock. They extend as much as several hundred kilometers into the Earth’s mantle.
Geologists find that diamonds, and more specifically their kimberlite host rock, provide valuable insights into the cratons’ geological history. Since diamonds they were formed millions of years ago at depths of 150 to 400 kilometers below the earth’s surface, and were brought to the surface by geological and chemical forces, they enable researchers to reconstruct the shapes of ancient continents based on deeper, mantle rocks.
“For researchers, kimberlites are subterranean rockets that pick up passengers on their way to the surface,” said University of British Columbia geologist Maya Kopylova, in an article published by the institiution. “The passengers are solid chunks of wall rocks that carry a wealth of details on conditions far beneath the surface of our planet over time.”
SAMPLES FOR STUDY PROVIDED BY DIAMOND MINING COMPANIES
Kopylova and the team from the University of British Columbia were analyzing samples extracted from De Beers Chidliak Kimberlite Province property, which is located in the south of Baffin Island. They soon realized that it had a mineral signature that matched other portions of the North Atlantic craton.
The samples were initially provided by Peregrine Diamonds, a junior exploration company that was acquired by De Beers in 2018.
“The mineral composition of other portions of the North Atlantic craton is so unique there was no mistaking it,” says Kopylova. “It was easy to tie the pieces together. Adjacent ancient cratons in Northern Canada—in Northern Quebec, Northern Ontario and in Nunavut—have completely different mineralogies.”
PIECING TOGETHER PIECES OF A GEOLOGICAL PUZZLE
The newly identified fragment of the North Atlantic craton adds roughly 10 percent to the known expanse of geological mass, and it is the first time geologists have been able to piece parts of the puzzle together at such depth. All previous reconstructions of the size and location of Earth’s plates have been based on relatively shallow rock samples.
Highlighted in purple, the North Atlantic craton, which stretched from present-day Scotland, across Greenland to North America, before it broke apart 150 million years ago.
The Chidliak Kimberlite Province mining site on Baffin Island.
“With these samples we’re able to reconstruct the shapes of ancient continents based on deeper, mantle rocks,” stated Kopylova. “We can now understand and map not only the uppermost skinny layer of Earth that makes up one percent of the planet’s volume, but our knowledge is literally and symbolically deeper. We can put together 200-kilometre deep fragments and contrast them based on the details of the deep mineralogy.”
Finding these ‘lost’ pieces is like finding a missing piece of a puzzle,” commented Kopylova. “The scientific puzzle of the ancient Earth can’t be complete without all of the pieces.”