Submarine primary Sr-rich Mn-oxide mineralization in the Jurassic Transdanubian Range (Hungary)

摘要

The Transdanubian Range hosts a series of high Sr (up to 1.7 w% Sr) Mn mineralization. The chert and Fe-rich Mn-oxide mineralization occur in association with varicoloured metalliferous clays, in the form of blocks, nodules, wad beds, in close proximity to fracture zones of N-NW-S-SE direction along the NE-SW mountain direction. These Sr-rich Mn-deposits are the marginal parts of black-shale hosted Mn-carbonate ore deposits of Jurassic age which were formed by bacterially mediated diagenetic processes. The Mn mineralogy consists of hollandite, cryptomelane, todorokite, pyrolusite and manganite. The Mn, Fe, (Co+Ni+Cu) ternary diagram of Bonatti et al. (1972) shows hydrothermal origin for the oxide mineralization. Collectively, these deposits can be explained as the fossil documents of a protorift or failed rift system on continental crust in submarine position. The direct connection with igneous activity is not known until now, but the characteristics of oxide mineralization support existence of a hydrothermal vent system.