Scientists from the Australian National University in Canberra studying ancient minerals have filled in some gaps in our picture of Earth in the Hadean eon, 4.4. billion years ago.
The Jack Hills, in mid-west Western Australia, are home to the world’s oldest known mineral samples, called detrital zircon grains. These small zircon grains are the only known geological record of the Earth’s crust from the Hadean eon. No other rocks remain from that period to provide us with clues about how Earth’s first crust was formed.
Scientists from the Australian National University in Canberra studied the elements present in younger zircons, of known origin, to create a geological ‘Rosetta Stone’ to determine how the Jack Hills’ zircons formed. They reported their findings in Nature Geoscience.
The team discovered that the elements present in the 4.4 billion-year-old zircon minerals suggested that the Earth’s earliest crust was made from the melting of igneous rock. The results clarify some ambiguity surrounding Earth’s earliest history and help to understand how Earth’s crust has changed over time.
Based on the elemental analysis, the scientists think that the surface of Earth in the Hadean eon was barren, mountainless and almost entirely under water except for a few small islands.
Lead researcher and Earth scientist, Dr Antony Burnham said, “We’ve improved the focus on the image of the world at that time but there are still plenty of questions unanswered.”
In today’s world, the research may also have some industrial benefit. “Zircons may be useful for finding ore bodies and understanding the processes behind economic mineralisation,” Burnham added.
Andrew Stapleton is a scientist, science writer and podcaster based in Adelaide.
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