Written in SCIENCE he
A team of geologists has used computer models to analyze with so much precision the white shales of the Alps that question a previous theory about the plate movement. The geoscientists examine the rocks in the mountain belts to explain how they moved towards the depths before returning to the surface. This story of burial and exhumation reveals how the mountains and the tectonics of plates.
Under the enormous pressure that reigns within the Land, some rocks that sink together with plates transform into different types. For example, the silica (SiO2) of the rock becomes coesitaalso known as the UHP polymorph of SiO2, during this metamorphosis UHP (UHP: Ultra High Pressure). The crystal lattices are denser and more compact despite still being chemically silica. The rocks UHPs also come to the surface when plates rise again from the depths and can be found in specific locations in the mountains.
To date, the researchers they had the hypothesis that hydroxide rocks iron were buried at a depth of 120 kilometers. From there, they returned to the surface with the plates. The ambient pressure decreased at a static rate during the process.
However, recent research carried out by the Goethe University Frankfurt and the universities of Heidelberg and Rennes (France) questions the idea of long and constant progress. The research team examined white shale from the Dora Maira in the western Alps of Italy. The findings were published in Nature Communications.
“White schists are rocks that formed as a result of the UHP metamorphosis of a hydrothermally altered granite during the formation of the Alps,” stated Thibault Duretz, head of the Geodynamic Modeling Working Group at the Department of Geosciences at the University of Heidelberg.
Together with the team, he analyzed it first by cutting a slice very thin about 50 micrometers thick and then gluing it on glass. In this way, the minerals could be identified under the microscope. The next step was computational modeling of particular and particularly fascinating fields.
Due to the rapid decompressionthe assumption that the rock UHP can reach a depth of 120 kilometers seems less likely, according to Duretz, since the ascent from that depth would take place over a long period of time, which is not equivalent to a high decompression rate. He geoscientist He states that they assume that the white shale is still found at a depth of between 60 and 80 kilometers.
Our hypothesis is that, instead, rapid processes occurred tectonic which caused minimal vertical displacements of the plates. Suddenly, the plates shook upward a little in the Earth’s interior and, as a result, the pressure surrounding the UHP rock decreased in a relatively short time