Scientists Have Discovered A New Continent Emerging In The Indian Ocean
French and Australian geologists have studied the composition of the rocks of Islands in the southern Indian ocean and found that there is the formation of an"embryonic continent," according to the results of the study published in the journal Terra Nova.
It is believed that the continental crust builds up at the borders of continents and oceans, in the so-called subduction zones, where oceanic lithospheric plates sink into the mantle, under the continent. When they are melted and mixed with the base material of continental plates, granite magma is formed, which, rising, forms the upper, "granite" layer of the continents.
From a geological point of view, it is this outer layer that distinguishes continents from oceans: the relatively thin oceanic crust consists mainly of basalts formed as a result of melting mantle material, while the continental crust is thicker and has a granitic composition.
The results of research conducted by scientists on the Islands of the Kerguelen archipelago, located in the Indian Ocean near Antarctica, show that granitic magma, and therefore continental crust can be formed not only in subduction zones but also directly in the center of the oceans. The authors suggest that this is how new continents are born.
The Islands of the archipelago are, in fact, the tops of volcanoes rising above the water, breaking through the oceanic crust of the Kerguelen Plateau. The basalt flows that poured out of these volcanoes formed the Islands. However, along with the basalts that are traditional for the oceans, there is one intrusion (magmatic introduction) of more acidic rocks of the granite family — syenites found only on continents. Due to this introduction, the earth's crust in the Kerguelen region is abnormally thick, as on the continents.
After studying geometry and internal structure of the syenite intrusion of the southern Rallier-du-Baty Intrusive complex on the center island of the archipelago, the authors found that this introduction occurred in the same way as on the continents: in several layers, each of which gradually lifted the surrounding rocks. Dating of the layers showed that the total time of formation of the syenite intrusion covers approximately 3.7 million years — from 11.6 to 7.9 million years ago.
The authors formulated a hypothesis that the syenite massif of Kerguelen island is, in fact, the "embryo of the continent", which is millions of years will become a full-fledged continent. In the article, they emphasize that for a final conclusion, it is necessary to study in detail the chemical composition of syenites in order to understand the origin of its magma and restore the history of its evolution.
The southern Rallier-du-Baty massif is the only known example of an acidic intrusion located in the center of an oceanic lithospheric plate.