A new study, published in the Journal of Petrology, presents new discoveries about the North Atlantic Craton.
A craton is a part of continental crust that is considered stable and consists of old crystalline bedrock probably covered by layers of sediments. Sometimes cratons still exist as whole entities at the center of continental plates while others have split into smaller parts over millions of years.
The North Atlantic Craton belongs to the second category as it was split into fragments about 150 million years ago. Currently, it stretches from northern Canada to northern Fennoscandia (the peninsula comprising the Scandinavian and Kola Peninsulas) though Greenland and Scotland.
Canadian geologists were studying diamond samples from Baffin Island (located between Greenland and the mainland of Canada) when they made an accidental discovery. More specifically, the researchers were examining Kimberlite samples that frequently contain diamonds. Kimberlites are formed deep beneath the earth's crust but they advance to the surface of the ground as a result of geological and chemical processes. During these processes, they carry with them parts of wall rocks, that also exist deep within the earth, while preserving these parts in good condition. “For researchers, kimberlites are subterranean rockets that pick up passengers on their way to the surface,” Maya Kopylova, lead author of the study and Professor at the Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, stated.
Researchers examined 120 rock samples utilizing mineralogy, thermobarometry and petrography techniques.
What scientists found is that the wall rocks that were carried by the kimberlites were unique. They discovered a "mineral signature" that was not anticipated and that showed a clear connection to the North Atlantic craton revealing one of its missing pieces. "The mineral composition of other portions of the North Atlantic craton is so unique there was no mistaking it. 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,” Prof. Kopylova, said.
It is the first time that such a correlation was made based on evidence from deep earth materials. Current models about the size and location of the tectonic plates are based on data from shallow investigations (about 10 km below the surface).
According to the new findings, the ancient geologic structure is 10% larger than previously known.
Sources: University of British Columbia, Sciencealert
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