Nature

Existence of 3-Billion-Year-Old 'Lost Continent' Beneath Indian Ocean Island of Mauritius Confirmed, Study Says

Previous studies that contended that a 3-billion-year-old "lost continent" is lying beneath the Indian Ocean island of Mauritius have been confirmed, a new study says.

The study, published Tuesday in the journal Nature Communications, backs up a 2013 study that first reported the lost continent by concluding that traces of ancient zircons found in beach sand on Mauritius does indeed point to a continent buried deep below the island.

The mineral zircon is found in sand and rocks in various parts of the world and dates back billions of years to one of the earliest periods of Earth's history, according to the study's authors.

"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," Lewis Ashwal, a geologist at the University of the Witwatersrand, Johannesburg in South Africa, and lead author of the study, said in a news release.

Indian Ocean topography showing the location of Mauritius as part of a chain of progressively older volcanoes extending from the presently active hot-spot of Réunion toward the 65-million-year-old Deccan traps of northwest India.
(Oxford University Press)

The researchers believe a fragment of the ancient supercontinent Gondwana was left behind when it split into Africa, India, Australia and Antarctica, forming the Indian Ocean some 200 million years ago. After that upheaval, the volatile, volcanic birth of Mauritius buried the sliver of the ancient continent under layer upon layer of cooling lava as the island was formed.

"According to the new results, this breakup did not involve a simple splitting of the ancient supercontinent 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," Ashwal said.

(MORE: Ancient Lost Continent Found in Indian Ocean , 2013)

The researchers determined that remnants of the mineral zircon, which spewed from the ancient continent during volcanic eruptions, were far too old to belong on the island of Mauritius.

Lead author Prof. Lewis D. Ashwal studying an outcropping of trachyte rocks in Mauritius. Such samples are about 6 million years old, but surprisingly contain zircon grains as old as 3000 million years.
(Susan J. Webb/University of the Witwatersrand)

"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."

Critics of the previous study contended that zircon could have traveled to the area via trade winds or had been transported in by the tires of a vehicle or on someone's shoes.

The concluding factor, said Ashwal, was that the zircons were found embedded in a 6-million-year-old rock known as trachyte.

"The fact that we found the ancient zircons in rock (6-million-year-old trachyte), corroborates the previous study and refutes any suggestion of wind-blown, wave-transported or pumice-rafted zircons for explaining the earlier results," Ashwal said.

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