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AKIPRESS.COM - Scientists have tracked the "family history" of a rock back to some of the earliest times on Earth, reports BBC.
Researchers analysed the concentration and distribution of particular types of atoms in the granite to show it must have been recycled from something that existed 4.2 billion years ago.
This "parent rock" was very probably basalt of the sort produced on the ocean floor, they say.
The team reports its work in this week's Science Magazine.
With most rock on Earth being broken down by weathering or taken back into the planet's interior just a few hundred million years after production, there is very little, truly ancient material to look at.
Geological genealogy offers a very useful alternative in the circumstances, says Dr Jonathan O'Neil from the University of Ottawa, Canada.
"To put everything into perspective, the Earth is about 4.6 billion years old, and I would say that rocks that are 3.8 billion years and older - we can count them on the fingers of our hands.
"We have very limited places to learn something about the first billion years of Earth history. That's our challenge," he told the Science in Action programme on the BBC World Service.
Dr O'Neil and colleagues examined samples of rock from the "Canadian Shield", a swathe of territory moving east of Hudson Bay in Canada.