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idw - Informationsdienst
Wissenschaft
Around the Balkan Peninsula, the African plate is sinking beneath the European plate. A piece of deeply submerged African crust resurfaced 40 million years ago far away from the sinking zone. How this phenomenon of so-called vertical extrusion can be explained and whether the Rhodope mountain range in southern Bulgaria was formed in this way is a matter of scientific debate. Dr Iskander Muldashev and Prof Thorsten Nagel from the TU Bergakademie Freiberg have now shown how this process works in a recent publication in the journal Geology. The formation of the Rhodopes was only 40 million years ago - the mountain range is therefore 30-50 million years younger than previously assumed.
Is this the solution to a geological mystery? Huge chunks of African crust plunge deep into the earth and then rise vertically back up again like a lift - despite enormous compressive forces in the overlying European plate. "Our computer models of the formation of the Rhodopes explain the tectonic process of this so-called vertical extrusion. The modelling shows how the Rhodope mountain range was only formed 40 million years ago by the ascent of rocks from the African plate, instead of around 80 million years ago as previously assumed," says lead author Dr Iskander Muldashev.
Investigating the formation of the Rhodopes
Professor Thorsten Nagel knows the mountains well: he has been studying the tectonic history of the Rhodopes for 20 years together with colleagues from various universities. He has reconstructed the sinking and deformation history of rock samples in numerous publications. "Mineralogical investigations show that large parts of the Rhodopes were submerged at depths of up to 100 kilometres. And isotope geochemical data show that this process took place around 40-45 million years ago. The Rhodope Mountains therefore probably originate from the African plate that was submerging at this time."
Until now, it was not clear how this process took place physically. The new models developed by the two Freiberg researchers now show that the buoyancy of the submerged crust is large enough to push the overlying crust apart horizontally despite the forces. "What is special about the Rhodope Mountains is that despite more than 100 kilometres of apparent stretching, the Earth's crust remained particularly thick in this area - a further indication that large amounts of material came up from the depths and penetrated the overlying European crust," adds Nagel.
Models explain Earth's dynamics
The scientists used the large computing capacities at the TU Bergakademie Freiberg's computing centre to calculate the computer models. Using thermomechanical software for so-called parallel computing, complicated deformation processes such as the fracturing and flowing of rocks can be simulated. Such modelling has great potential for the study of tectonic processes, says Muldashev: "We use it to investigate tectonic deformation on a wide variety of scales: from the fracturing of individual minerals to flow patterns in the entire Earth's mantle."
Last September, Thorsten Nagel collected further samples on the northern side of the Rhodope Mountains near Plovdiv. The planned age determinations on the rocks could therefore soon provide further evidence for the accuracy of the computer models - and thus bring us one step closer to solving the geological mystery surrounding the formation of the Rhodopes.
Prof. Thorsten Nagel
Thorsten.Nagel@geo.tu-freiberg.de
The Rhodope Metamorphic Complex as a case for extreme vertical extrusion
Iskander A. Muldashev; Thorsten J. Nagel
https://doi.org/10.1130/G53889.1
Criteria of this press release:
Journalists
Geosciences
transregional, national
Research results, Scientific Publications
English
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