The contribution of magma arose as a result of events following subduction, when one tectonic plate is inserted under another, come from the Earth’s mantle, not from the processing of the earth’s crust, as has been thought so far. This has been experimentally demonstrated by research by the National Museum of Natural Sciences (MNCN), the Andalusian Institute of Geosciences (IACT) – both CSICs – and the University of Salamanca. This discovery, published in Earth and planetary science lettersrepresents an important step forward in knowledge about mechanisms causing the growth of continents and therefore a better understanding of the planet.
The discovery changes the scientific model that explains how new continental crust is created. The Earth’s crust has been slowly but steadily increasing in size since its formation. about 3.5 billion years ago. Until now, the scientific paradigm has attributed this contribution of new material to processes associated with the subsidence of oceanic crust under continental crust or tectonic subduction processes, as occurs in the Andes.
“When this happens, new material is introduced into the earth’s crust, but also the part that sinks into the mantle is lost. This results in a mass deficit because, in the end, about as much crust is gained in subduction zones as is lost. So where does the new bark come from?” asks the MNCN researcher. Daniel Gomez.
how do continents grow
On the other hand, there large granite formations which grow out of magmatism produced millions of years after subduction tectonic movements, after the collision of two continents.
It’s about post-collision magmatism, in which the magma formed at great depths is introduced into the earth’s crust and gradually cools down without coming to the surface, as happens during volcanic eruptions. These events give rise batholithslarge masses of granite that cool slowly become part of the earth’s crust and thus increase the size of the continents.
Gredos mountain range, in Spain, is an example of these formations. “Through petrological experiments, we have shown that these magmas, which were previously attributed to crustal recycling, come from the melting of the mantle. This would imply continental growth during magmatic episodes and would explain the origin of the excess material that is formed and is not associated with subduction movements,” he explains. Antonio CastroMNCN and IACT researcher.
The material formed after the collision of the continents comes directly from the Earth’s mantle.
To prove their hypothesis about the growth of continents, the research team reproduced composition and mineralogy of post-collision batholiths no need to include recycled bark material. “This reproduction of the characteristics of the batholiths indicates that the material formed after the collision of the continents comes directly from the Earth’s mantle,” says Gomez.
“This discovery can bring us closer to understanding the origin of continents and significantly change the models of their origin, which have so far underestimated the role of post-collision magmatism,” he concludes.
This article was first published on SYNCHRONIZATION
Source: Hiper Textual
