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Free keywords:
Lithiophorite, Coronadite group, Hollandite, Cryptomelane, 40Ar/39Ar geochronology, Trace elements, Lithium, Manganese, Cobalt, Exploration, Raw materials
Abstract:
Situated in the western Erzgebirge metallogenetic province (Vogtland, Germany), the Eichigt prospect is associated with several quartz-Mn-Fe-oxyhydroxide veins that are exposed at surface. Bulk-rock geochemical assays of vein material yield high concentrations of Li (0.6–4.1 kg/t), Co (0.6–14.7 kg/t), and Ni (0.2–2.8 kg/t), as well as significant quantities of Mn, Cu, and light rare earth elements, a very unusual metal tenor closely resembling the mixture of raw materials needed for Li-ion battery production. This study reports on the results of a first detailed investigation of this rather unique polymetallic mineralization style, including detailed petrographic and mineralogical studies complemented by bulk rock geochemistry, electron microprobe analyses, and laser ablation inductively coupled mass spectrometry. The mineralized material comprises an oxide assemblage of goethite hematite, hollandite, and lithiophorite that together cement angular fragments of vein quartz. Lithiophorite is the predominant host of Li (3.6–11.1 kg/t), Co (2.5–54.5 kg/t), and Ni (0.2–8.9 kg/t); Cu is contained in similar amounts in hollandite and lithiophorite whereas light rare earth elements (LREE) are mainly hosted in microcrystalline rhabdophane and florencite, which are finely intergrown with the Mn-Fe-oxyhydroxides. 40Ar/39Ar ages (~ 40–34 Ma) of coronadite group minerals coincide with tectonic activity related to the Cenozoic Eger Graben rifting. A low-temperature hydrothermal overprint of pre-existing base metal sulfide-quartz mineralization on fault structures that were reactivated during continental rifting is proposed as the most likely origin of the polymetallic oxyhydroxide mineralization at Eichigt. However, tectonically enhanced deep-reaching fracture-controlled supergene weathering cannot be completely ruled out as the origin of the mineralization.
