Debate put to rest?
It’s not yet clear whether Nuvvuagittuq outcrops will become widely accepted as Earth’s oldest rocks, according to other scientists who were not involved with the research.
Bernard Bourdon, a geochemist at the Lyon Geology Laboratory in France who had previously taken issue with the earliest dates for Nuvvuagittuq Greenstone Belt published by O’Neil, said he was “more convinced” by the latest work, and it was “well improved” on previous studies.
“What is better, compared to the 2008 paper, is the fact that the two techniques … they give the same age. That’s good. That’s where we criticized the first results,” Bourdon, who is also research director at French scientific research body CNRS, said.
“In the end, I think there’s more credibility to the age,” he said, adding that he had some “small doubts” and would like to investigate the data more in depth.
The age of the rocks “remains an unsolved mystery,” according to Hugo Olierook, a geoscientist and senior research fellow at Curtin University in Australia.
“In the absence of ‘easy’ minerals to date, they have turned to whole-rock, which is fraught with problems as whole-rock samples have multiple minerals,” Olierook said via email.
“It only takes one of these minerals to have been altered and their age ‘reset’ to a younger age for the whole house of cards to fall over,” he added, noting that very high and low temperatures can naturally alter the crystallization age of minerals in rock.
Very little is definitive when dealing with rocks and minerals that have complex geological histories spanning more than 4 billion years, according to Jesse Reimink, the Rudy L. Slingerland Early Career Professor of Geoscience at Penn State University.
“Even if these rocks are ‘only’ 3.8 billion years old, it is quite amazing that they are preserved. This current work presents more compelling data, supporting an age of 4.15 billion years ago, than that which was previously produced, which was already compelling,” Reimink said.
“The timescales are so long, and the history of these rocks and minerals is so tortured, that gleaning any primary information from them at all is pretty amazing.”
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