A team of geophysicists from Germany, South Africa and Norway presented evidence that in ancient times, at the bottom of the Indian Ocean in its central part, there was a microcontinent Mauritius, which united the island of Mauritius, the northeastern coast of Madagascar, the southern coast of the Indian subcontinent and the largest submarine bank, Saya de -Malya of the island of Kargados-Carajos.
Mauritius Island is located in the western Indian Ocean. It belongs to the republic with the same name, which at various times was a colony of the Netherlands, Portugal, Great Britain and France. In terms of area, this land area can be compared with Moscow. The island has a population of around 1.2 million. Scientists are convinced that the formation of Mauritius took place about nine million years ago. The island arose from the cooled lava of underwater volcanoes, which was carried to the surface of the Indian Ocean.
In the same way, the formation of many islands on our planet took place, among them - the Canary Islands, Hawaiian and Kuril Islands. The largest island of volcanic origin is considered to be Iceland, an island that formed at the point where the Eurasian and North American lithospheric plates diverged. At the same time, scientists say that the formation of Mauritius took place in a slightly different way. In this regard, this small island state has attracted great interest of researchers studying the history of the ancient planet over the past two decades.
Location of Mauritius
Image: Ashwal et al. (2016) A mantle-derived origin for Mauritian trachytes. Journal of Petrology, vol. 57, pp. 1645-1675. Oxford University Press
In 1999, zircon was discovered by geophysicists in the sands of Mauritius. Scientists have performed dating using the uranium-lead method, as a result of which they found that the age of the mineral reaches 660 million - two billion years. But how could such an ancient mineral end up on a relatively recent island? Researchers suggest that the samples that were found were part of the part of the land that went under the water, but these mineral particles were carried to the surface by flows of magma released during the eruption of underwater volcanoes.
Scientists published the results of their research in the publication Nature Geoscience. They tried to describe the probable nature of the ancient land to which the discovered minerals belonged. So, in particular, scientists believe that about a few tens of millions of years ago there was a small island of Mauritius - a microcontinent, which in its area could take about a quarter of the modern island of Madagascar. About a billion years ago, it was part of the supercontinent of Rodinia, which also included modern Madagascar and Hindustan.
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The researchers supported the dating of the mineral samples by analyzing the gravimetric data that they had, as well as by reconstructing ancient tectonics and determining the thickness of the earth's crust. All these studies have shown that Mauritius, together with the neighboring Mascarene plateau, could overlap the Precambrian ancient microcontinent Mauritius.
Mass spectrometer used in the work
Photo: Photograph taken by Prof. Michael Wiedenbeck, Deutsches GeoForschungsZentrum (GFZ), Potsdam, Germany
It should be noted that not all scientists accepted the proposed theory. So, according to the French scientist Jerome Diemen, such an ancient mineral zirconium could get into the sand of Mauritius from anywhere, even with ship's ballast. In addition, he noted that relatively close, two hundred kilometers from Mauritius, in the coastal waters of Reunion Island, other groups of geophysicists worked, but they could not find any traces of the existence of the ancient microcontinent. In this regard, the French researcher invited his colleagues to find more convincing evidence that would confirm the existence of Mauritius, for example, to try to find the same zirconium, but not in the sands, but in solid rock.
The most interesting thing is that geophysicists did it. Hard zircons have been found in hard volcanic rocks of trachyte. Uranium-lead dating was also carried out, which showed that the found samples are between 2.5 and 3 billion years old. According to the researchers, these zircons, together with the identification of sand cyclones and data on gravitational anomalies obtained in previous studies, prove that an ancient continental crust existed under Mauritius in antiquity.
The main objective of the new study was to identify ancient trachytic rocks in the rocks of the Miocene period, which existed 5-23 million years ago, found on the island of Mauritius. For the main sample, the scientists took a kilogram of solid rock sent to Germany for analysis. The sample was carefully examined, detailed and cleaned in order to avoid the penetration of foreign inclusions, after which the material was sieved to grains, the diameter of which did not exceed 500 micrometers, and washed with water to remove dust. According to scientists, all these procedures helped to fully exclude the ingress of foreign zircon into the sample under study. A total of 13 mineral grains were dated in this way.
Nude Trachyte Breeds in Mauritius
Photo: Photograph taken by Prof. Susan J. Webb, University of the Witwatersrand
After that, geophysicists proposed a theory of the formation of Mauritius, according to which its crust originates from the central-eastern part of the island of Madagascar. Continental crust from western Hindustan and eastern Madagascar was fragmented and distributed over the western Indian Ocean. This happened 84-92 million years ago, that is, in the Cretaceous period, when the eastern part of the supercontinent Gondwana, the southern part of Rodinia, disintegrated. It was at that time that Hindustan and Madagascar parted, between them a strip of about 200 kilometers wide was formed, which was occupied by the microcontinent Mauritius.
According to scientists, the further fate of the microcontinent is known: Mauritius existed for several tens of millions of years, after which, as Hindustan and Madagascar moved away from each other, went under the water of the Indian Ocean, which at that time began to form.
Ancient rocks and frozen lava that came to the surface of the water formed the modern island of Mauritius about nine million years ago. The most likely remains of Mauritius, according to experts, can be considered the largest underwater bank of the Saya de Malia, which is located north of the island of Mauritius on the Mascarene plateau.
Thanks to the work of researchers, it is possible to carry out a very accurate reconstruction of the geography of the ancient planet Earth, in particular, the early history of Rodinia and Gondwana. Currently, according to scientists, they managed to establish the details of the discrepancy between Hindustan and Madagascar. In the event that geophysicists succeed in creating a detailed map of the location of micro-continents that formed in ancient times in the areas of divergence of supercontinents, this would make it possible to fully reconstruct the formation of modern continents.