The rocks were found in Northern Quebec, along the Hudson’s Bay coast, 40 km south of Inukjuak in an area known as the Nuvvuagittuq greenstone belt and they are 4.28 billion years old. These rocks, known as “faux-amphibolites”, may be remnants of a portion of Earth’s primordial crust – the first crust that formed at the surface of our planet.

Until now the world’s oldest rocks were dated back to 3.75 billion years ago. The new rocks were discovered by Jonathan O’Neil, a Ph.D. candidate at McGill’s Department of Earth and Planetary Sciences, Richard W. Carlson, a researcher at the Carnegie Institution for Science in Washington, D.C., Don Francis, a McGill professor in the Department of Earth and Planetary Sciences, and Ross K. Stevenson, a professor at the Université du Québec à Montréal (UQAM).

O’Neil and colleagues estimated the age of the rocks using isotopic dating, which analyzes the decay of the radioactive element neodymium-142 contained within them. This technique can only be used to date rocks roughly 4.1 billion years old or older; this is the first time it has ever been used to date terrestrial rocks, because nothing this old has ever been discovered before.

The data from these findings will give researchers a new window on the early separation of Earth’s mantle from the crust in the Hadean Era, said O’Neil.

"Our discovery not only opens the door to further unlock the secrets of the Earth’s beginnings," he continued. “Geologists now have a new playground to explore how and when life began, what the atmosphere may have looked like, and when the first continent formed.”