The Oldest Rock on Earth?

[Astronuc]

A finding in the Arctic could push the formation of Earth’s crust back by 130 million years
by Elena Kazamia, July 23, 2025

When geologist Hanika Rizo goes into the field she spends most of her time looking at her feet. Simply by trekking across the stark Arctic landscape in Northern Quebec, and paying close attention to the ground, she can glean clues about deep time in the color, texture, and arrangement of the solid outcrops of ancient rock that lie exposed here. Large, bauble-like shapes in the magma—“pillow lava”—speak of contact with water. Finding vestiges of water is always exciting, Rizo says, given that it is one of the requirements for the evolution of life. But the ultimate prize lies in the search for Earth’s oldest rock, which can serve as a window into the embryonic stages of Earth’s formation.

In a publication this summer, together with colleagues, Rizo, a scientist at Carleton University in Ottawa, described rocks at one study site, the Nuvvuagittuq Greenstone Belt, as dating to 4.16 billion years ago, making them some of the oldest rocks ever collected on Earth, possibly the oldest ever to have formed on the planet.

“The chemistry of the rocks tells us that they look very similar to the oceanic crust today,” Rizo says. Their surface is hard and crystalline, made of basalt. Rizo calls them the “first rocks” or the “oldest rocks” interchangeably. Geologists believe that to qualify as a “rock,” a piece of the Earth must be taken from the crust, which first formed once our planet’s mantle stabilized, the upper layer of hot, churned-up magma cooling into a solid shell on which continents and oceans rest.

The gold standard for aging rocks is to look at zirconium crystals, which contain traces of radioactive uranium, whose decay sets the rhythm for measuring time. But the rocks that Rizo and O’Neil work with contain no zirconium. Out of necessity, they chose the rare Earth element Neodymium, instead, which is traditionally used to age asteroids. “If you have a zircon age, no one’s going to dispute it,” Rizo says, but other techniques leave room for doubt.

I was reading about geochronology when reading about some current mineral development projects related to HREEs and zirconium-bearing minerals in the southern hemisphere.

https://en.wikipedia.org/wiki/Nuvvuagittuq_Greenstone_Belt
https://iugs-geoheritage.org/geoheritage_sites/the-hadean-to-eoarchean-nuvvuagittuq-greenstone-belt/

“If [the] Nuvvuagittuq rocks are Hadean, that would make them the only terrestrial rocks from this eon that we know of,” says Martin Guitreau of Clermont Auvergne University, who was not involved with the study.

https://cen.acs.org/physical-chemis...ent-rocks-among-worlds-oldest/103/web/2025/07