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SEMINAR - Prof. Lew Ashwal, Wits University, Johannesburg

Hidden Continents

Prof. Lew Ashwal School of Geosciences Wits University, Johannesburg, South Africa

Date: Friday 1 September

Time: 11:15 - 12:15

Location:  Geoscience, auditorium 1671-137



Inside of a 6 million year old volcanic rock from the plume-related ocean island of Mauritius, we recovered tiny crystals of zircon that give ages of 2500 to 3000 million years. These ages are far older than any rocks that occur in the ocean basins (all are younger than about 200 million years), but are similar to some parts of the continents. Ashwal and his colleagues suggest, therefore, that a fragment of ancient continent must exist beneath the young volcanoes of Mauritius, and that the old zircons were picked up by the magmas 6 million years ago, on their way to their surface eruption sites. This small piece of ancient continent was stranded in the Indian Ocean during the break-up of the Gondwana supercontinent, which started about 200 million years ago, and is still ongoing. Other ancient continental fragments may exist elsewhere in the Indian Ocean, and were once joined together to form a microcontinent that the research team named “Mauritia”. This work allows a better understanding of how continents break apart, and how we can reconstruct the resulting “puzzle pieces” as a function of geologic time.