Zinc-lead ore deposit in Lower Triassic (Roethian) dolomites at Bolesław (Olkusz region, Poland)

Abstract

At the Bolesław mine the Zn-Pb ore bodies occur within the Middle Triassic ("ore-bearing") and the Lower Triassic dolomites. It is an exceptional feature in the Silesian-Cracow ore district. The Roethian ore bodies are small and irregular, formed of rich ore surrounded by the aureole of dispersed sulfides, monheimite and barite. They lie preferably in synsedimentary breccias, solution breccias (often superimposed on the previous ones) and collapse breccias. Mineralogical composition of the arc is simple: sphaleritc-galena-marcasite with abundant colloidal varieties (mostly brunckite) precipitated during four stages of mineralization at 95-115ºC. The ore bodies were formed partly by the replacement, partly by the open space filling, formed due to hydrothermal karstification of the host dolomites