Privileged Planet: more on early zircons (Introduction)

by David Turell , Friday, July 12, 2024, 19:12 (66 days ago) @ David Turell

Another study of early zircons:

https://www.sciencemagazinedigital.org/sciencemagazine/library/item/12_july_2024/420649...

"By using a form of artificial intelligence (AI) to analyze some of the oldest crystals on the planet, researchers have concluded that plate tectonics—the planet-scale geological machinery that floats giant slabs of crust across and sometimes into Earth’s mantle—began much earlier than many scientists had assumed.

"The researchers find evidence for a start more than 4 billion years ago, during the Hadean eon—just a few hundred million years after the planet’s formation. The work suggests tectonics might have had an early hand in creating the first land and helping life begin, says Ross Mitchell, a geophysicist at the Chinese Academy of Sciences who coauthored the new study, which was published this week in the Proceedings of the National Academy of Sciences. “Hadean Earth would have been habitable, permitting the origin of life not only at hydrothermal vents, but also in Darwin’s ‘warm pools’ at Earth’s surface,” he says.

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"The oldest zircons, discovered in Australia’s Jack Hills, date back to 4.3 billion years ago. Zircons can crystallize out of fresh magma from the mantle, much like the ocean crust of today, but they can also form from sedimentary rocks on land that wash into the ocean, sink back into the mantle, and re-emerge in later bursts of igneous activity as granites. These resurfaced “S-type” zircons provide evidence of the existence of both continents and the subduction process, Mitchell says.

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'Mitchell and colleagues then applied the trained algorithms to 971 ancient Jack Hills zircons with uncertain origins. Overall, they found that more than one-third were S-type, including a few that were up to 4.2 billion years old. Mitchell and his team have “something that looks like it could be a really useful tool,” says Beth Ann Bell, a geochemist at the University of California, Los Angeles. “This is significant not only for the early Earth, but for going throughout the geological record.”

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"...evidence for early plate tectonics is growing—at least based on the stories preserved in the Jack Hills zircons. In April, researchers reported that freshwater was involved in the formation of 4-billion-yearold zircons—another sign that continents, and presumably, plate tectonics, existed at the time (Science, 3 May, p. 497).

"What is needed now are additional ancient zircons from places other than Australia, Fu says. The Jack Hills zircons could record events from one exceptional region that’s not representative of the globe. Still, it may be time to assume plate tectonics is nearly as old as the crust itself, Fu says—at least until it can be disproved."

Comment: it is like fine tuning evidence for design. Plate tectonics create life and appear in just 300 million years after the Earth formed. More evidence for design.