Celadonite and smectite formation in the Úrkút Mn-carbonate ore deposit (Hungary)

Synsedimentary and early diagenetic oxygen levels are estimated by evaluating celadonite-smectite formation in Jurassic marine black shale-hosted manganese carbonates. Celadonite formed under suboxic-dysaerobic conditions, Al-rich Fe-smectite formed under suboxic-anaerobic conditions, and nontronite formed under anoxic-anaerobic conditions during sedimentary burial. A genetic pathway by direct precipitation from solution is proposed for the enormous mass of celadonite based on mineral and textural evidence. Lamination of the manganese ore is independent of clay-mineral composition and was created by a series of mineralized Fe-rich biomats.