Acta Musei Moraviae

Epidote-group minerals in quaternary terraces around Brno

Epidote-group minerals are found in various types of Quaternary fluvial sediments near Brno, and their occurrence is linked not only to the alluvial regions of the Svratka and Svitava rivers. For this study, we selected granite and granodiorite boulders that contain hydrothermal veins or tectonic mirrors, with crystals or crystal aggregates of epidote-group minerals. The boulders consist of leucocratic granites with hydrothermal veins primarily composed of epidote, or a combination of epidote and quartz. These characteristics are typical for hydrothermal epidote veins found in granitoids of the Brno Massif. Additionally, accessory minerals such as calcite, palygorskite, and chlorite are present in these veins. Epidote from the granite boulder shows lower Fe³⁺ content (0.61–0.74 apfu) and higher Al content (2.25 to 2.34 apfu) compared to the samples of epidote veins from the Brno Massif, which have Fe³⁺ values ranging from 0.70 to 0.95 apfu and Al values from 2.02 to 2.29 apfu. We attribute this difference to the fact that the studied boulder originates from rocks that are no longer exposed in current erosional sections.