watchers.news/2020/04/02/geologi…of-canada/
Geologists have found a remnant of an ancient lost continent off the coast of Baffin Island in Canada. After studying the samples, the team of scientists identified a fragment of the North Atlantic Craton– an ancient continental crust from millions of years ago that stretched from Labrador to Scotland.
The researchers were investigating pieces of kimberlite– igneous rocks that may contain diamonds– when they noticed that the samples have a mineral signature corresponding to other fragments of the craton. Cratons are billion-year-old, stable blocks of the Earth’s crust commonly found in the middle of tectonic plates, which form the basis of continents.
Study lead author and geologist Maya Kopylova from the University of British Columbia explained that kimberlites are subterranean objects that pick up solid chunks of wall rocks toward the surface. These rocks, on the other hand, hold details about the conditions far beneath the surface of the Earth over time.
In this case, researchers said kimberlite rocks such as their sample, formed at depths below 150 km (93 miles), and were lifted to the surface by both chemical and geological forces.
When the team started analyzing samples from a De Beers Chidliak Kimberlite Province property in southern Baffin Island, they found that the wall rocks were one of a kind.
“The mineral composition of other portions of the North Atlantic craton is so unique there was no mistaking it,” said 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.”
Kopylova added that discovering these lost remnants is like “finding a missing piece of a puzzle.” She continued, “The scientific puzzle of the ancient Earth can’t be complete without all of the pieces.”
150 million years ago, the North Atlantic craton’s continental plate drifted into fragments. The newly-found remnant adds about 10 percent to the known expanse of the craton.
“With these samples, we’re able to reconstruct the shapes of ancient continents based on deeper, mantle rocks,” said 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 km (124 miles) deep fragments and contrast them based on the details of the deep mineralogy.”
The researchers said this is the first time geologists were able to reconstruct the size and location of ancient continents by studying rocks deep down the mantle.