Siderite concretions in Paleocene series of polish part of the eastern Flysch Carpathians ; Konkrecje syderytowe w warstwach paleoceńskich polskiej części wschodnich Karpat fliszowych

The present paper deals with the results of studies of siderite concretions occurring in black Paleocene shales of the Dukla and Silesian Units. The samples were examined using optical and scanning microscopy, X-ray diffraction and chemical analysis (SEM-EDS, INNA, ICP and estimation of TOC). The main diagenetic minerals of these concretions are iron carbonates close to siderite. Less common are dolomite, ferrous dolomite and calcite. The first phases precipitated from pore solutions were carbonates enriched in manganese. The concretions studied contain up to 49.15 wt.% $Fe_{2}O_{3}$, at most 16.46 wt.% CaO and up to 8.49 wt.% MgO, whereas the content of organic carbon (TOC) is at most 1.42 wt.%. Sideritic concretions of Paleocene beds of the eastern part of the Flysch Carpathians represent, in fact, sideroplesites and manganospherites of early diagenetic origin. They are, in general, impoverished in all trace elements, except Sr, when compared with shales embedding them. The siderite-bearing series in question can be assigned to the siderite-pyrite and siderite geochemical facies.