Géza SZENDREI¹, Péter KOVÁCS-PÁLFFY², Mária FÖLDVÁRI² & Kamilla GÁL-SÓLYMOS^3
1Hungarian Natural History Museum, H-1431 Budapest, Pf.: 137, Hungary, e-mail: szendrei@min.nhmus.hu
²Geological Institute of Hungary, H-1143 Budapest, Stefánia út 14, Hungary, e-mail: kovacs@mafi.hu,
foldvari@mafi.hu
³Eötvös Loránd University, H-1111 Budapest, Pázmány P. st. 1/c, Hungary, e-mail: kamillasolymos@yahoo.com

MINERALOGICAL STUDY OF FERRUGINOUS AND MANGANIFEROUS NODULES SEPARATED FROM CHARACTERISTIC PROFILES OF HYDROMORPHIC SOILS IN HUNGARY

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Only a few studies have been carried out on the mineralogy of ferruginous and manganiferous nodules in Hungarian hydromorphic soils. Therefore it was decided to enrich the data on these nodules and to make an attempt to interpret them with respect to hydromorphic influences. The brown and black nodules separated from 9 characteristic soil profiles were analysed by X-ray diffraction, thermal analysis, selective dissolution methods and SEM combined with microanalysis. This study confirmed that nodules were formed during the impregnation of the groundmass by iron and manganese compounds. Goethite was common in hydromorphic soils, while lepidocrocite was determined in nodules from horizons with enhanced hydromorphic impacts. Manganese minerals were extremely rare. The nodules contained a con-siderable amount of amorphous and poorly crystalline compounds; in this context the black nodules con-tained more of these compounds than the brown ones. The data for selected dissolutions of iron and man-ganese compounds showed those horizons having different hydromorphic influences. Black nodules with brown coatings were observed in various soil types and in localities which were a considerable distance from each other, and this indicated after accumulation a depletion or inhibited immobilization stage of manganese compounds in the formation processes of the nodules. The mineralogical study of the ferrugi-nous and manganiferous nodules from Hungarian soils contributed to a deeper knowledge of iron and manganese accumulations in the hydromorphic soils of the European prairie ecodivison, as well.

amorphous compounds, ferrihydrite, goethite, hydromorphism, lepidocrocite, manganese minerals, nodules, selective dissolutions.