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Researchers analyzed rocks with shatter cones at the North Pole Dome in Western Australia and identified mineral signs pointing to an impact that occurred about 3 billion years ago. The result places the structure as the oldest known impact crater on Earth.
The North Pole Dome crater in Western Australia has been identified as the oldest known impact structure on Earth after new analyses indicated that the event occurred about 3 billion years ago.
The discovery helps to clarify a gap regarding the impacts that hit early Earth. While the Moon preserves marks of ancient bombardments, terrestrial records have been modified by heat, pressure, fluids, and geological activity.
Minerals helped date the impact
The study analyzed two rock samples with shatter cones, as well as an impacted quartz vein from the North Pole Dome. The samples included a metadolerite with zircon and a metabasalto with apatite.
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Using advanced mineral dating techniques, the researchers identified signs consistent with an impact that occurred approximately 3 billion years ago. The age resolves an old question about the site, previously associated with different estimates.
The shatter cones already indicated an impact structure. The challenge was to define when this event occurred, especially in ancient mafic rocks, which generally do not preserve ideal minerals for this type of investigation.
Crater preserves rare “mineral clock”
The main evidence came from zircon, a resistant mineral capable of recording geological time for billions of years. At the North Pole Dome, some crystals showed branching and skeletal forms.
The team’s interpretation is that these zircons were modified by the impact. They would have been fragmented, partially recrystallized, and regenerated during the heating caused by the meteorite’s impact.
Apatite confirmed the result. This mineral formed when hot fluids circulated through the damaged rocks. The agreement between zircon and apatite strengthened the conclusion that both record the same event.
Record reaches the Archean Eon
With the new age, the structure of the North Pole Dome becomes the only recognized example of an impact crater from the Archean Eon, a period when Earth’s first continents were forming.
The study, published on June 23 in the journal Geology, pushes the record of terrestrial impacts to a more remote period and offers a rare window into the violent processes of the planet’s early history.
The discovery shows how tiny minerals can preserve decisive clues about extreme events altered by geological time. What did you think of this 3-billion-year-old crater and the role of these minerals in the investigation? Comment.
