Sarolta BODOR, János FÖLDESSY, Ferenc KRISTÁLY & Norbert ZAJZON
Institute of Mineralogy and Geology, University of Miskolc, H-3515 Miskolc, Egyetemváros, Hungary, (bodors@gmail.com, foldfj@uni-miskolc.hu, askkf@uni-miskolc.hu, nzajzon@uni-miskolc.hu)

DIAGENESIS AND ORE FORMING PROCESSES IN THE BÓDVASZILAS SANDSTONE OF THE RUDABÁNYA ORE DEPOSIT, NE HUNGARY

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We present the petrographical and geochemical study of the Bódvaszilas Sandstone Formation from the Rudabánya iron ore open pit. The work is linked to the current iron and base metal exploration in Rudabánya. According to our examinations the pore- and vein-filling carbonate cement of the Bódvaszilas Sandstone Formation is presumably early diagenetic. According to the concavo-convex grain contacts and the synthaxial quartz overgrowths on monocrystalline quartz grains, the formation underwent deep burial diagenesis. Base metal sulphides dominantly occur in the cover formations of Bódvaszilas Sandstone, appear only in the fracture zones of the Bódvaszilas Sandstone, as the permeability of the formation was low, therefore the metal bringing solutions were able to move mainly along the fractures. The chemical composition and crystal structure related properties of the „acidic sparry iron ore/cream-spar” from Bódvaszilas Sandstone is described for the first time. These carbonates are intermediate solid solutions between siderite and magnesite. The „cream-spar” was formed simultaneously with the metasomatic „sparry iron ore” by the partial or complete Fe replacement of the diagenetic dolomite cement and carbonate layers of the Bódvaszilas Sandstone Formation. Cassiterite has been detected first time in Rudabánya. According to its crystal habit is not detrital, but formed here, and it is present in a „cream-spar” section in the Bódvaszilas Sandstone.