Geochemical Atlas – Erzgebirge and Vogtland

Gallium (Ga) concentrations are close to a Gaussian distribution and the log values show a left skew. At 5.6 mg/kg, the arithmetic average is not significantly lower than the median of 5.7 mg/kg. The range between absolute maximum (19.8 mg/kg) and minimum contents (0.9 mg/kg) is comparatively small and the contrast between averages of the different rock units is the weakest among all investigated elements. Maximum concentrations of Ga > 10 mg/kg are detected in the southwestern study area, NW and SW of Oelsnitz in regions of Devonian sediments and volcanics. Areas with lower concentration (Ga > 6 mg/kg) are widespread and little impacted by lithological boundaries or mining districts. Examples are Ordovician to Silurian metasediments of the Lößnitz-Zwönitz Syncline, Ordovician phyllites and mica schists of the northern Erzgebirge rim between Stollberg and Augustusburg, and rock units of the Frankenberg Crystalline Complex. Parts of the Eibenstock Granite, Neoproterozoic gneisses NNE of Seiffen and in the Freiberg mining district show similar concentrations. In contrast, regions with Ga levels below-average (Ga < 4 mg/kg) are more clearly delimited: They relate to the granites of Kirchberg and Bergen, to Cambrian metasediments north of the Fichtelgebirge Pluton, and to Neoproterozoic gneisses between Freiberg and Marienberg. Minima (Ga < 2.5 mg/kg) characterise the Fichtelgebirge Pluton, the Tharandt Volcanic Complex and the Altenberg-Teplice Caldera of the eastern Erzgebirge.