Zircon crystals and impact-altered minerals reveal that a colossal asteroid impacted Western Australia’s Pilbara region approximately 3 billion years ago.
Arctic Dome Crater: (A) Simplified map of the Eastern Pilbara Terrain (EPT, Western Australia). Key geological features include Paleoarchean granite domes (pink) and greenstone belts (green and blue), with the North Pole Dome (NPD) at the center. (B) Geological map featuring NPD and shutter cone fields (yellow stars). (C) Quartz (Qtz) carbonate vein intersecting the shutter cone line. Image credit: Kirkland et al., doi: 10.1130/G54866.1.
According to Professor Chris Kirkland from Curtin University and his research team, “While evidence of heavy bombardment exists for the Moon during the Hadean and early Archean eras, the impact history on Earth remains largely unclear.”
“Identifying meteorite impact structures can be challenging, especially when impacts occur within Archean upper crustal rocks, which often lack quartz or zircon—minerals that preserve impact signatures.”
“Recently identified dense shutter cone fields in the Arctic Dome provide tangible evidence of impact on these weakly metamorphosed mafic rocks.”
“Shatter cones were once thought to have formed around 3.47 billion years ago.”
However, new findings reveal two fracture cones that suggest an impact event between 2.7 billion and 400 million years ago linked to the Neoarchean Low Basalt Mountains.
In their latest study, researchers analyzed two rock samples containing shattered cones (zircon-bearing metadolerite and apatite-bearing metabasalt), along with shocked quartz veins from the Arctic Dome.
Using advanced mineral dating techniques, they uncovered the most compelling evidence yet that the impact occurred roughly 3 billion years ago.
Professor Kirkland stated, “This discovery addresses long-standing questions regarding the timing of this impact event.”
Previously identified as an ancient impact structure, the exact age was unknown until now.
“The impact left behind a ‘mineral clock.’ By dating the minerals that have either regenerated or newly formed in these damaged rocks, we can determine the occurrence of this unusual event,” he explained.
“Key to this research are zircon minerals, renowned for their ability to retain geological timelines spanning billions of years.”
“Some of the zircons from the Arctic Dome exhibit unique branched skeletal shapes, interpreted as shock-altered crystals formed by heat and pressure during intense impact.”
“These zircon crystals provide a record of events that transpired about 3 billion years ago, marking the best estimate of the impact time.”
To further validate their findings, apatite was analyzed—this mineral forms as hot fluids move through impact-altered rocks, confirming similar dating results.
The correlation between these two mineral systems enhances our confidence that we are observing signs of a singular significant event: a meteorite impact.
This latest research positions the Arctic Dome structure as Earth’s oldest known impact crater and the sole recognized example from the Archean Era, a period when Earth’s earliest continents were forming.
Professor Kirkland highlighted, “Dating ancient impact craters poses challenges due to geological alterations such as heat, pressure, and fluid movements over billions of years, which may obscure original impact signals.”
“Our study successfully separates the moment of impact from its extensive geological history.”
This groundbreaking discovery extends Earth’s impact record deeper into geological history than any previously dated crater, offering an invaluable insight into the violent processes that shaped the early Earth.
For more details, refer to the team’s paper published in the June 23 edition of Geology.
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C.L. Kirkland et al. “How old is the Arctic Dome impact in Western Australia?” Geology, published online June 23, 2026. doi: 10.1130/G54866.1
Source: www.sci.news
