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Home > Science and research > Structure, Composition and Evolution of the Earth's Crust > Metamorphic rocks

Metamorphic rocks

Metamorphic rocks underlie more than 40 % of the territory of the Czech Republic and form most of the basement beneath the rocks of the sedimentary cover. They are originally sedimentary or magmatic rocks that have been transformed by high temperatures and pressures (above 150-200° C and c. 1,500 atmospheres) and by tectonic stress. Metamorphism is marked by the growth of new minerals at the expense of the original ones and frequently by the development of preferred orientation in response to tectonic stress that creates foliation planes (“schistosity”). At temperatures above 650°C, partial melting of metamorphic rocks can occur and new bodies of granitoid igneous rock can be formed.

Metamorphic rocks ranging from the lowest grade up to rocks which underwent metamorphism at temperatures higher than 900 °C, and pressures above 25,000 atmospheres (2.5 GPa) are found in the territory of the Czech Republic.. They formed partly during the Upper Proterozoic Cadomian orogeny (650-550 Ma), and particularly during the Upper Palaeozoic Variscan orogeny (390-310 Ma). They have been subjected to numerous stages of plastic and brittle tectonic deformation and older structures are often reactivated during younger tectonic events.

Tectonic model of the Palaeozoic continental collision in the western part of the Czech Massif

Tectonic model of the Palaeozoic continental collision in the western part of the Czech Massif. (Author: J. Franěk)

The investigation of metamorphic rocks covers a wide spectrum of topics ranging from specifically practical questions to research relating to regional geological mapping (e.g. experimental work on the petrology and mineralogy of metabasites and granulites from the Kutná Hora Crystalline Complex and the Moldanubicum, on orthogneisses from the Ore Mountains, and on phyllites from the Železný Brod Crystalline Complex) and the timing and pressure-temperature paths followed by particular units of rock during metamorphism. The results of these different petrological and structural studies are used to interpret the geodynamic setting and rheological development of different lithotectonic units so that geological correlations can be made and the evolution of metamorphic complexes can be better understood. Detailed field and laboratory investigations of selected areas are carried out for specific purposes e.g. the compilation of expert assessments for the Radioactive Waste Repository Authority of the Czech Republic, DIAMO and the national administration.

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Czech Geological Survey
Klárov 131/3
118 21 Praha 1
phone: +420257089463
fax: +420 257 531 376
jaroslava.pertoldova@geologycz