MOSCOW, 19 Jul — RIA Novosti. French and Australian geologists have studied the composition of the rock Islands in the southern Indian ocean and found that there is the formation of “embryonic continent.” The study is published in the journal Terra Nova.
it is believed that the continental crust is built up on the borders of continents and oceans, in the so-called subduction zones, where oceanic lithospheric plates plunge into the mantle under the continent. When they are melted and mixed with the material of the base of the continental plates, granite is formed when magma, rising, forming the upper, the “granite” layer of the continents.
the Results of a study conducted by scientists at the Islands of the Kerguelen archipelago, located in the Indian ocean near Antarctica indicate that the granite 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 emerging new continents.
the Islands of the archipelago is, in fact, rising above the water-capped volcanoes breaking the oceanic crust of the Kerguelen plateau. Slivovitsa of these volcanoes and basalt flows formed the island. However, along with basalts, traditional for the oceans, there is one intrusion of magma introduction — more acidic in composition of rocks of the granite family — syenites are found only on continents. Due to this, the introduction of the earth’s crust in the area of the Kerguelen Islands is abnormally thick on the continents.
after Studying the geometry and internal structure of the intrusions of syenite Intrusive complex South Rale-du-Bati on the Central island of the archipelago, the authors found that the introduction of it was the same as on the continents, in several layers, each of which was gradually raised surrounding rocks. Dating of these layers showed that the total time of formation of the syenite intrusion covers a period of about 3.7 million years between 11.6 and 7.9 million years ago.
In the article they stress that for a final conclusion it is necessary to study in detail the chemical composition of the syenite, in order to understand the origin of its magma and to reconstruct the history of its evolution.
the mountains southern Rale-du-Bati — the only known example of the intrusions of acid composition, located in the center of the oceanic lithospheric plates.