Rocks in Canada's Quebec province found to be the oldest on Earth

TimesLIVE

01-07-2025

The researchers applied two dating methods based on an analysis of the radioactive decay of the elements samarium and neodymium contained in them. They produced the same conclusion, that the rocks were 4.16-billion years old.
Future chemical analyses of the rocks could provide insight into Earth's conditions during the Hadean, a time shrouded in mystery because of the paucity of physical remains.
'The rocks and the Nuvvuagittuq belt being the only rock record from the Hadean, they offer a unique window into our planet's earliest time to better understand how the first crust formed on Earth and what were the geodynamic processes involved,' said University of Ottawa geology professor Jonathan O'Neil, who led the study published on Thursday in the journal Science.
The rocks may have formed when rain fell on molten rock, cooling and solidifying it. The rain would have been composed of water evaporated from Earth's primordial seas.
'Since some of the rocks were also formed from precipitation from ancient seawater, they can shed light on temperatures and the first oceans' composition and help establish the environment where life could have begun on Earth,' O'Neil said.
Until recently, the oldest known rocks were ones dating to about 4.03-billion years ago from Canada's Northwest Territories, O'Neil said. While the Nuvvuagittuq samples are the oldest known rocks, tiny crystals of the mineral zircon from western Australia have been dated to 4.4-billion years old.
The Hadean ran from Earth's formation roughly 4.5-billion years ago until 4.03-billion years ago. Early during this eon, a huge collision occurred that is believed to have resulted in the formation of the moon. However, by the time the Nuvvuagittuq rocks formed, Earth had begun to become a more recognisable place.
'The Earth was not a big ball of molten lava during the entire Hadean eon, as its name would suggest. By nearly 4.4-billion years ago, a rocky crust existed on Earth, likely mostly basaltic and covered with shallow and warmer oceans. An atmosphere was present, but different from the present day atmosphere,' O'Neil said.
There had been some controversy over the age of the Nuvvuagittuq rocks.
As reported in a study published in 2008, previous tests on samples from the volcanic rock layers that contained the intrusions yielded conflicting dates, one giving an age of 4.3-billion years and another giving a younger age of 3.3-billion to 3.8-billion years. O'Neil said the discrepancy may have been because the method that produced the conclusion of a younger age was sensitive to thermal events that have occurred since the rock formed, skewing the finding.
The new study, with two testing methods producing harmonious conclusions on the age of the intrusion rocks, provides a minimum age for the volcanic rocks that contain the intrusions, O'Neil added.
'The intrusion would be 4.16-billion years old, and because the volcanic rocks must be older their best age would be 4.3-billion years old, as supported by the 2008 study.'