Acta Musei Moraviae

Provenance of gold in fluvial sediments from the streams situated northwest of the Brno-Žebětín (Moravia, Czech Republic)

The main purpose of this paper was to study the heavy minerals and typomorphic features of placer gold in the central part of the Brno Massif (Brunovistulian Unit, Bohemian Massif). Placer gold occurrences were found in small streams NW from the Brno-Žebětín (NW from Brno city, eastern part of Czech Republic). The Brunovistulian Unit is relatively poor in ore deposits compared with another part of Bohemian Massif. Data obtained from the study of heavy minerals suggest that gold found in fluvial sediments from the righthand tributaries of the Svratka river was derived in close surroundings (from a distance reaching a maximum of the first km). The heavy mineral assemblage is composed of minerals epidote group (16–28 %), magnetite (7–27 %), apatite (7–19 %), titanite and axinite (5–19 %), zircon (6–17 %), amphibole (0–17 %), pyrite (2–15 %), garnet (2–9 %), ilmenite (1–6 %), monazite a xenotime (1–4 %), scheelite (0.0–0.5 %). The petrological character of the clasts and mineral signatures of heavy mineral assemblage each studied samples indicates minimal source area (maximum a few km2). The igneous and metamorphic rocks of the Brno Massif represent the main source of material for clastic sediments within the studied streams. Gold is associated with pyrite and is probably related to hydrothermal quartz veins or alteration zones.