Geochemische Exploration im Breiettal (Schwarzwald, Deutschland)

The Breiet Valley in the Schwarzwald (Germany) was geochemically and geologically evaluated to assess its suitability for a tailing dump. The area is located within the Central-Schwarzwald-Gneiss- Complex near the „Clara“ mine. Paragneiss, granitoids, amphibolites, sandstones (Buntsandstein) and hydrothermal alterations were geologically mapped. Six exploration pits were analysed for antimony, arsenic, cadmium, copper, chromium, nickel, mercury, zinc, lead, cobalt and thallium. Soil samples, stream sediment samples and rock samples were analysed geochemically (XRF, AAS) and mineralogically. There are no heavy metal contaminations, but local anomalies of antimony and chromium. The arsenic content in the soil exceeds the precaution values but is below the geogenic background limits. Higher concentrations of barium were found within sandstones adjacent of an baryte-bearing old open pit. Raised concentrations of barium and strontium within a stream sediment sample south of the old open pit and the old „Clara“ mine were recorded, they are explained by the presence of barite-rich tailings of the old „Clara“ mine or sub-surface barite-rich veins.