Normal versus Metal-rich Black Shales in the Barrandian Neoproterozoic of the Teplá-Barrandian Unit: a Summary with New Data


Authors: Pašava J

Published in: Bulletin of Geosciences, volume 75, issue 3; pages: 229 - 239;

Keywords: Barrandian Neoproterozoic Formation, Teplá-Barrandian Unit, Normal black shale, Metal-rich black shale, Geology, Geochemistry, Mineralogy, Stable Isotopes, Radiogenic Isotopes, Fluid Inclusions, Environmental impacts,

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Normal and metal-rich black shales can be recognized in the Barrandian Neoproterozoic of the Teplá-Barrandian Unit. Normal black shales form, together with greywackes, thick flyschoid sequences. They have been deposited mostly under normal marine conditions. They are generally poor in trace elements, with concentrations very close to other world normal black shales. Conversely, metal-rich black shales mostly occur in close association with basic volcanogenic rocks (similar to recent MORB) and were formed in lower energy environment - semiisolated or isolated basins. They bear anomalously high metal concentrations derived mostly from occasional volcanogenic-hydrothermal vents. These outcropping facies together with numerous waste dumps and pit lakes which resulted from their past mining represent a serious danger for human living especially through the generation of acid waters.