The geochemical signature of rare-metal pegmatites in the Central Africa Region: Soils, plants, water and stream sediments in the Gatumba tin–tantalum mining district, Rwanda

• The environmental impact of coltan mining in the Gatumba area is harmless.
• Trace element contents of soils and most plant materials are below guideline values.
• Water and stream sediment samples meet internationally accepted standards.

We studied trace elements in soils, plants, water and stream sediments in the Gisuma–Kibilira catchment of the Gatumba area of western Rwanda which has a long tradition of artisanal to small-scale tin–tantalum mining from rare-metal pegmatites. The geochemical fingerprint of soil, plant, water (springs and surface water in dry and rainy seasons) and stream sediment samples reveals elevated concentrations of Li, Rb, Cr, and Cs, but low As and U abundances at or below the global average. Trace element contents of soils and most plant materials are below internationally accepted guideline values. All water samples analyzed meet the World Health Organization (WHO) drinking water guidelines, and the stream sediments are below critical values of Dutch environmental standards. These data provide a baseline for environmental impact studies for rare-metal mining projects in the Central Africa Region.