There does indeed exist a "Lost Continent" under the island of Mauritius in the Indian Ocean formed after by the break-up of the supercontinent called Gondwana some 200 million years ago.

But before this event, or some 335 million years ago, Gondwana (the southern continent) and Laurasia (the northern continent) joined together to form the supercontinent Pangaea, which existed until 215-175 million years ago. Gondwana then separated from Laurasia and later also broke apart.

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Gondwana included most of the landmasses in today's Southern Hemisphere, including Antarctica, South America, Africa, Madagascar and Australia.

"We are studying the break-up process of the continents, in order to understand the geological history of the planet," said Prof. Lewis Ashwal of the University of Witwatersrand in South Africa and lead author on the paper published in the prestigious journal Nature Communications.

"Archaean zircons in Miocene oceanic hotspot rocks established an ancient continental crust beneath Mauritius."

Archaean refers to the Archean Eon, a geologic eon some 4 billion to 2.5 billion years ago. Zircon is one of the key minerals used by geologists in geochronology, which is the science of determining the age of rocks, fossils and sediments using signatures inherent in the rocks themselves.

Zircons are minerals that occur mainly in granites from the continents. They contain trace amounts of uranium, thorium and lead. Because they survive geological process very well, they contain a rich record of geological processes and can be dated very accurately.

By studying the mineral, zircon found in rocks spewed up by lava during volcanic eruptions, Ashwal and his colleagues (Michael Wiedenbeck from the German Research Center for Geosciences (GFZ) and Trond Torsvik from the University of Oslo) have found that remnants of this mineral were far too old to belong on the island of Mauritius.

"Earth is made up of two parts -- continents, which are old, and oceans, which are "young," said Ashwal.

"On the continents, you find rocks that are over four billion years old, but you find nothing like that in the oceans, as this is where new rocks are formed.

"Mauritius is an island, and there is no rock older than 9 million years old on the island. However, by studying the rocks on the island, we have found zircons that are as old as 3 billion years."

"The fact that we have found zircons of this age proves that there are much older crustal materials under Mauritius that could only have originated from a continent."

Ashwal said their finding ancient zircons in six million-year-old trachyte rocks (an igneous volcanic rock) corroborates a previous study and refutes any suggestion of wind-blown, wave-transported or pumice-rafted zircons for explaining the earlier results.

"According to the new results, this break-up did not involve a simple splitting of the ancient super-continent of Gondwana, but rather, a complex splintering took place with fragments of continental crust of variable sizes left adrift within the evolving Indian Ocean basin."

TagsLost Continent, mauritius, Indian Ocean, Gondwana, Laurasia, Prof. Lewis Ashwal, University of Witwatersrand, Archaean zircons, Zircon