Acta Musei Moraviae

Cathodoluminescence study, Petrography and Lithology of Marble in Moravicum (Bílý Potok Unit, Svratka Dome, Bohemian Massif)

The contact of the Bílý Potok and Bíteš Units (Svratka Dome, Moravo-Silesian Zone) is characterized by presence of marble in the highest lithostratigraphic part of the phyllite complex of the Bílý Potok Unit. The marble contains a mineral assemblage calcite + quartz + albite + muscovite + biotite + titanite ± dolomite ± chlorite, with accessory rutile, tourmaline, and scarce LREE-fluorocarbonates; the assemblage is stable under LP-LT metamorphic conditions, at T < 520 °C. The prevailing rock type is a gray fine-grained silicaterich marble, whereas a white medium-grained silicate-poor marble is less frequent; both types sometimes contain partially deformed carbonate veins, locally with ptygmatic folding. The marble is a metamorphic equivalent of limestone with elevated contents of quartz, clay minerals, and organic matter; its sedimentation took place in partially euxenic environment. Using cathodoluminescence microscopy, four calcite types were distinguished: dark orange calcite I and orange calcite II form the marble matrix, whereas pale orange calcite III and rare orange-yellow calcite IV are recrystallization products. Marble from the northern part of the Bílý Potok unit is typically strongly deformed, whereas marble in the southern part is characterized by coarser grain size and intense recrystallization. The studied marble occurrences typically contain postmetamorphic hydrothermal veins (calcite + Fe dolomite ± fluorite). The mineral assemblages and petrographic-lithological contents of the studied marble are equivalent to the marble occurrences in the Upper Lukov Unit in the Dyje Dome of the Moravo-Silesian Zone.