The discovery of three-billion-year-old minerals from under the island of Mauritius is presented in a study published in Nature Communications this week. This finding provides evidence for the presence of ancient continental crust beneath Mauritius, which would have been part of the continent ‘Mauritia’ and formed part of the ancient nucleus of Madagascar and India.

There is growing evidence that old continental crust may be present beneath young ocean-island volcanoes, when previously it was believed there was only oceanic crust. In oceanic settings, young geological hotspots that form ocean-island volcanoes may interact with old continental crustal plates and this may result in micro-continental fragments being brought to the surface, but physical evidence to support this theory has been limited.

Now, Lewis Ashwal and colleagues report the discovery of zircon crystals ranging from 2.5 to 3.0 billion years old within lavas brought up to the surface in Mauritius. They propose that these old zircons may be fragments of ancient Archaean continental crust. These findings shed new light on the mechanisms of plate tectonics in these young oceanic hotspots.