New Study Confirms That The Oldest Rocks On Earth Are Canadians
Iron-rich chert from the Nuvvuagittuq Supracrustal Belt, Québec, Canada, containing tubular and ... More filamentous microfossils.
A team of Canadian and French researchers has confirmed that Nunavik/Quebec in Northern Canada is home to the oldest known rocks on Earth, dating back over 4.16 billion years.
The rocks of the Nuvvuagittuq Greenstone Belt, a rock formation preserved in a fold of the Canada shield, are believed to be over 4.3 billion years old, forming just 200 million years after Earth formed. They include the oldest known examples of sheeted dikes and pillow basalts. Such a succession of volcanic rocks is typically found in a spreading zone of a mid oceanic ridge, forming today Earth's oceanic crust.
However, since first age estimates were published over 20 years ago, Various phases of tectonic deformation and chemical alteration makes it difficult to find pristine rock samples. There are also uncertainties involving the applied methods used at the time to date the rocks.
In a new study, researchers sampled a new section of the greenstone belt, using modern dating methods they confirmed the high age of the entire formation.
Samples were collected in 2017 near the municipality of Inukjuak, Nunavik, as part of Christian Sole's thesis, who completed a master's at the University of Ottawa in 2021. After preliminary analysis, additional work was carried out at the University of Ottawa and Carleton University, to confirm the age of the rocks.
First age estimates were based on volcanic rocks — deposited as lava flows on the bottom of an ancient ocean — chemically altered as they came into contact with water.
The researches focused on magmatic rocks, rocks crystallized before reaching the surface. Radioactive elements are trapped in the forming crystals, slowly decaying providing a natural timer for the rock's formation age.
From left: Christian Sole, Professor Hanika Rizo and Professor Jonathan O'Neil collecting rock ... More samples.
To establish the age of these rocks, the researchers combined petrology and geochemistry and applied two radiometric dating methods using different isotopes of the elements samarium and neodymium. The new dates 'gave exactly the same age,' says study author Jonathan O'Neil, University of Ottawa, in an interview to AP.
The current study shows that dikes of magmatic rocks crossing these volcanic formations are 4.16 billion years old, which confirms that the volcanic rocks must be older, and thus, that this region of the Canadian north is indeed home to the oldest known rocks on Earth.
'Understanding these rocks is going back to the very origins of our planet. This allows us to better understand how the first continents were formed and to reconstruct the environment from which life could have emerged,' concludes O'Neil.
The study,"Evidence for Hadean mafic intrusions in the Nuvvuagittuq Greenstone Belt, Canada," was published in the journal Science.
Additional material and interviews provided by the University of Ottawa.
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