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Meteorite bombardment likely to have created the Earth’s oldest rocks

15 Aug 2018, 09:48 UTC
Meteorite bombardment likely to have created the Earth’s oldest rocks
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In the early age of the Solar System, impacts with meteors were more common than modern years. Image credit: CC0 Public Domain
Scientists have found that 4.02 billion year old silica-rich felsic rocks from the Acasta River, Canada – the oldest rock formation known on Earth – probably formed at high temperatures and at a surprisingly shallow depth of the planet’s nascent crust. The high temperatures needed to melt the shallow crust were likely caused by a meteorite bombardment around half a billion years after the planet formed. This melted the iron-rich crust and formed the granites seen today. These results are presented for the first time at the Goldschmidt conference in Boston, United States, on 14 August 2018, following publication in the peer-reviewed journal Nature Geoscience.
The felsic rocks (rocks rich in silica/quartz) found at the Acasta River in Canada, are the Earth’s oldest rocks, although there are older mineral crystals. Scientists have long known that the Acasta rocks are different to the majority of felsic rocks seen today, such as the granites widely used as a building or decorative material. Now a group of scientists from Australia and China have modelled the formation of the oldest Acasta felsic ...

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