By examining diamond exploration samples from Baffin Island in northern Canada, diamond expert geologists have accidentally identified a previously unknown remnant of the North Atlantic craton, an ancient part of Earth’s continental crust.
Kimberlite rock samples are a pillar of diamond exploration. Believed to have been created by natural processes several millions of years ago at depths of 150 to 400 kilometers, kimberlites are transported to the surface via geological and chemical forces.
Sometimes igneous rocks have diamonds embedded within them.
“For researchers, kimberlites are underground rockets that pick up passengers on their way to the surface,” explained geologist and lead author of the new study, Maya Kopylova, from the University of British Columbia.
“Passengers are solid chunks of rock in the wall that carry a lot of detail about conditions far below our planet’s surface over time.”
When Kopylova and her colleagues began analyzing samples in southern Baffin Island, on a property of diamond mining firm De Beers, it became clear that the rocks they had come across were extraordinary.
Scientists found that the rocks carried a mineral signature that matched other parts of the North Atlantic craton, an ancient part of Earth’s continental crust that stretches from Scotland to Labrador.
Kopylova explained that the mineral composition of other parts of the North Atlantic craton is so unique that it cannot be confused
It was easy to put the pieces together. The adjacent ancient cratons in northern Canada, northern Quebec, northern Ontario, and Nunavut have completely different mineralogies, Kopylova revealed.
Cratons are stable fragments of the continental crust that are billions of years old, continental nuclei that anchor and bring together other continental blocks surrounding them.
Some of these nuclei are still present in the center of existing continental plates, such as the North American plate, but other ancient continents have broken up into smaller fragments and been rearranged by a long history of tectonic plate movement.
Finding these ‘missing’ pieces is like finding a missing piece of a puzzle, “says Kopylova.”
The scientific puzzle of ancient Earth cannot be complete without all the pieces.
The North Atlantic craton continental plate was broken into fragments 150 million years ago, and currently extends from northern Scotland, through southern Greenland, and continues southwest to Labrador.
The newly identified fragment adds approximately 10 percent to the known expanse of the North Atlantic craton.
This is the first time that geologists have been able to piece the puzzle together at such depth, known as the mantle correlation.
Previous reconstructions of the size and location of Earth’s plates have been based on relatively small rock samples shallow in the crust, formed at depths of one to 10 kilometers.
The new samples allow scientists to better reconstruct the shape of ancient continents based on deeper mantle rocks.
“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-kilometer deep fragments and contrast them based on the details of the deep mineralogy,” revealed Kopylova.
The results of their discovery are published in the Journal of Petrology.