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Rare Mineral Discovery Identifies Ancient Meteorite Impact

Western Australian geologists have discovered a rare mineral that only forms in nature during meteorite impact events. At 1.2 billion years old, the discovery of reidite in shocked zircon from impact ejecta at Stac Fada in Scotland is more than double the age of the previous oldest known occurrence at 450 million years.

“The discovery of this Precambrian occurrence indicates the potential for using the presence of reidite to indicate and record very ancient impact events,” said Prof Steven Reddy of Curtin University. “It is a breakthrough discovery that will help determine terrestrial impact events which have had a profound influence on Earth’s geological, geochemical and biological evolution.”

All natural occurrences of reidite are associated with the transformation of the mineral zircon during the high pressures and temperatures associated with meteorite impact events. However, the record of Precambrian impacts is poorly constrained due to the dynamic nature of plate tectonics, erosion and deposition of younger rocks, which may destroy or cover the evidence of ancient impacts.

The reidite was discovered using advanced mineral characterisation technologies housed at Curtin University. Reddy used a technique called electron backscatter diffraction to effectively discriminate between reidite and its compositionally identical host zircon.

The discovery paves the way for developing reidite as a proxy for meteorite impact events that can be extended back in geological time to provide insights into the Earth’s early impact record.

The discovery has been published in Geology.