Two islands located east off Madagascar — Réunion and Mauritius — have recently revealed they are hiding a micro-continent that was once a part of what is now Madagascar and India.
The micro-continent — or continent fragment — known as Mauritia detached approximately 60 million years ago as Madagascar and India drifted apart from one another, but has been hidden underneath huge masses of lava ever since.
In fact, the discovery of Mauritia appears to point to a much greater frequency of micro-continents such as this than previously thought, according to a study published in the latest issue of the journal Nature Geosciences.
According to the Helmholtz Centre Potsdam, “the break-up of continents is often associated with mantle plumes:
These giant bubbles of hot rock rise from the deep mantle and soften the tectonic plates from below, until the plates break apart at the hotspots. This is how Eastern Gondwana broke apart about 170 million years ago. At first, one part was separated, which in turn fragmented into Madagascar, India, Australia and Antarctica, which then migrated to their present position.
The geoscientists studying the region — collected from Norway, South Africa, Britain, and Germany — believe that the plumes currently underneath the islands Marion and Réunion may have played a part in the emergence of the Indian Ocean.
The research published in Nature Geosciences looked at sand grains from the beach of Mauritius and found that they contained semi-precious zircons aged between 660 and 1970 million years. The age of these zircons is explaiend by the fact that zircons were carried by the lava as it was pushed through the subjacent continent crust.
The dating method to date the zircons was supplemented by a recalculation of plate tectonics which explains just how and where the fragments ended up in the Indian Ocean.
“On the one hand, it shows the position of the plates relative to the two hotspots at the time of the rupture, which points towards a causal relation,” said Dr. Bernhard Steinberger of the GFZ German Research Centre for Geosciences, who along with Dr. Pavel Doubrovine of Oslo University calculated the hotspot trail. “On the other hand, we were able to show that the continent fragments continued to wander almost exactly over the Reunion plume, which explains how they were covered by volcanic rock.”
The conclusion of the study is that the trail of the Réunion hotspot is actually continental fragments which were previously unheeded, covered as they were by the volcanic rocks of the Réunion plume.