Theoretical model for Jurassic manganese mineralization in Central Europe, Úrkút, Hungary


Authors: Polgári M, Szabó-Drubina M, Szabó Z

Published in: Bulletin of Geosciences, volume 79, issue 1; pages: 53 - 61; Received 28 March 2003; Accepted in revised form 19 September 2003;

Keywords: bacterial, hydrothermal, manganese, black shale, Jurassic, Europe,

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The Transdanubian Range hosts a series of Mn carbonate, and cherty Fe- and Sr-rich Mn oxide mineralizations associated with varicoloured metalliferous clays near fracture zones of a N-NW-S-SE direction along the NE-SW trending mountain range. The Mn oxide deposits occur along the margins of black shale-hosted Mn carbonate mineralizations formed by bacterially mediated diagenetic processes.
Here we show a provisional model of the ore formation of the shale-hosted Mn carbonate deposits. According to this model, the role of prokaryotic bacteria in obtaining elements from solutions is of particular importance. Some, if not all, shale-hosted Mn carbonate deposits are of a biogenic sedimentary origin, such as the 'Mn ore stromatolites' for which a hydrothermal/exhalative source for the metals has been demonstrated. Though the function of bacteria is not visible in these masked systems, it nonetheless completely changes the primary characteristics of the inorganic system. The deposits considered in this study can be explained as the remnants of a protorift or failed rift system that formed within submerged continental crust.