'Why this specific part was not destroyed is probably just luck.'

World's oldest known rocks found in Nunavik


The grey rocks at Nuvvuagittuq, 40 kilometres south of Inukjuak, look similar to those in other outcrops along eastern Hudson Bay coast.

But these Nunavik rocks are special. They're the oldest known rocks in the world, with an estimated age of 4.28 billion years.

Nuvvuagittuq's rocks may be remnants of a portion of the first crust that formed on the surface during Earth's early history, according to Jonathan O'Neil, a graduate student at McGill's Department of Earth and Planetary Sciences, and colleagues, whose research findings were published in the Sept. 26 journal Science.

"Most of these very old rocks have been destroyed with time," said O'Neil by telephone from Montreal. "Why this specific part was not destroyed is probably just luck."

O'Neil started looking at the ancient rocks several years ago after Quebec's geological survey of northern Quebec identified rocks 3.8 billion years old in the 10 square km Nuvvuagittuq belt.

"There are very few places on the earth that have rocks this old," O'Neil said.

Geologists have found four-billion-year-old rocks in the Northwest Territories and 3.8 billion years old in southwest Greenland.

Nuvvuagittuq's rocks, of a type known as "greenstone," are also exceptional because they're not green, but beige or grey due to their composition and the temperatures they were subjected to.

The researchers estimated the rocks' age using isotopic dating, which analyzes the decay of a radioactive element contained within the rocks. This dating technique can only be used to date rocks roughly 4.1 billion years old or older. It had previously only been used to date meteorites.

Further analysis of the Nuvvuaqittuq rocks may lead to more understanding about Earth's ancient history, what its atmosphere was like during that era, and when the first continents formed, O'Neil said.

"At that time, the young Earth may have been covered by water with some stable continents," he said. "Probably it was not a really a pleasing place to live on – hotter, for sure."

O'Neil plans to continue his study of the rocks.

As for the people who live in Inukjuak, O'Neil said those who know about the Nuvvuaqittuq rocks' age are impressed and plan to keep a watchful eye over them and curious visitors expected to show up for a look at the world's oldest rocks.

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