Publication details

Neuspořádaný uhlík v tektonických zónách paleozoických sedimentů (devon moravskoslezského paleozoika)

Title in English Disodered carbon in tectonic zones of the Palaeozoic sediments (Devonian of the Moravosilesian Palaeozoic)


Year of publication 2021
Type Article in Periodical
Magazine / Source Geologické výzkumy na Moravě a ve Slezsku
MU Faculty or unit

Faculty of Science

Web Text článku
Keywords Moravo-Silesian Palaeozoic; carbonate strata; black carbonaceous matter; deformation structures; Raman spectra; disordered carbon; organic matter; temperatures
Description Dark carbonaceous matter staining tectonic zones and deformed carbonate strata of the Moravo-Silesian Palaeozoic were studied by several methods. Samples were taken from tectonic structures in the quarry in Čebín and in the middle quarry in Mokrá near Brno. The grey-black-coloured rocks are clearly macroscopically and microscopically deformed, show traces of brittle ductile shear deformation and with foliation developed. The dark colour is caused by the presence of black carbon matter, which is documented by methods of optical and electron (BSE) microscopy and Raman spectra. The mineral assemblage has the character of hydrothermal mineralization migrating along tectonic structures. Mineralization consists mainly of quartz, carbonates (calcite, dolomite), phyllosilicates (mica, chlorite, kaolinite), pyrite and it also includes black carbon. Apatite is one of the interesting and unusual components. The content of organic and elemental carbon determined by the thermo-optical method in intensively mineralized zones is around 2.5 mass %. The carbonaceous matter was more accurately identified using Raman spectra. The spectra at the two studied localities have a very similar shape and are very close to the spectra of black carbon in low-grade carbon coal matter, very disordered carbon and/or amorphous carbon (coal, kerogen). The spectra show the presence of peaks in the D, G and 2D regions and are different from the spectra of ordered and disordered graphite. The presence of a small peak G in the analysed spectra (Lorentzian function) also indicates the possible presence of a small amount of more ordered carbon in the studied black carbon matter. The components of the black mineralized zones were most likely mobilized from the surrounding rock formations during the Variscan tectono-metamorphic events. The similarity with the spectra of poorly ordered carbon matter from low metamorphic conditions shows transformation temperatures of 150–280 °C, which is in accordance with other thermometric methods in the region of the southern edge of the Moravo-Silesian Palaeozoic.

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