Geology, mineralogy and geochemistry of the Sora Ni-Cu-(PGE) sulfide mineralization (Lausitz Block, Germany)

The Sora Ni-Cu-(PGE) sulfide mineralization is associated with a ~400 x 40 m dike-shaped gabbroic intrusion that is exposed in a dimension stone quarry about 5 km SW of Bautzen (Saxony/Germany). The Sora dike is one of several Ni-Cu-(PGE) sulfide-bearing gabbroic intrusions (e.g. Angstberg, Dahrener Berg, Sohland-Rožany, Kunratice) that occur in the Lausitz and Šluknov region on both sides of the German-Czech border. The gabbroic intrusions are part of interconnected magmatic plumbing systems that intruded Cadomian granodiorites of the Lausitz Block (northern Bohemian Massif) in the Middle to Late Devonian (~390–370 Ma). The Sora dike represents a composite intrusion with olivine gabbronorite, gabbro and diorite as major lithologies. The magmatic sulfide mineralization comprises blebby disseminated sulfides in the olivine gabbronorite and variable-shaped massive sulfide patches that locally occur along both contacts of the gabbroic dike to the granodioritic country rock. Subordinately, larger sulfide patches are also hosted by pegmatitic albite-amphibole-enriched schlieren within the olivine gabbronoritic part of the intrusion. The mineralization represents a typical magmatic sulfide mineral paragenesis with dominating pyrrhotite, pentlandite and chalcopyrite, variable amounts of Fe-Ti oxides and trace amounts of PGE-, Au-, Ag- and TABS-bearing minerals. The PGE mineral assemblage is dominated by Pd melonite. The magmatic sulfides are characterized by relatively high Ni tenors (metal content in 100 % sulfide) and variable Cu, Co, Pt, Pd and Au tenors (~0.3–9.0 wt.% Ni, ~0.2–7.0 wt.% Cu, ~0.1–0.4 wt.% Co, ~20–1210 ppb Pt, ~40–1400 ppb Pd and ~20–1230 ppb Au).