Mineralogy of Fe-Mn Nodules in Fragiudalfs of the Carpathian Foothills, SE Poland.

Mineralogy of Fe-Mn nodules in Fragiudalfs of the Carpathian Foothills, SE Poland

Wojciech Szymanski a, Michal Skiba b, Artur Blachowski c

a Jagiellonian University, Institute of Geography and Spatial Management, Department of Pedology and Soil Geography, Gronostajowa St. 7, 30-387 Cracow, Poland; E-mail: w.szymanski@uj.edu.pl
b Jagiellonian University, Institute of Geological Sciences, Department of Mineralogy, Petrology and Geochemistry, Oleandry St. 2a, 30-063 Cracow, Poland; E-mail: michal.skiba@uj.edu.pl
c Pedagogical University, Institute of Physics, Department of Mössbauer Spectroscopy, Podchorążych St. 2, 30-084 Cracow, Poland; E-mail: sfblacho@cyf-kr.edu.pl

Fe-Mn nodules are common features occurring in various soils, especially in soils exhibiting imperfect drainage. The main aim of the present study was to determine mineral composition of the Fe-Mn nodules in Fragiudalfs of the Carpathian Foothills in Poland using quantitative X-ray diffraction (QXRD), Fourier transform infrared spectroscopy (FTIR) and Mössbauer spectroscopy (MS). The obtained results show that the Fe-Mn nodules from Fragiudalfs of the Carpathian Foothills in Poland are composed mainly of silicates (quartz, K-feldspars, plagioclases) and phyllosilicates (dioctahedral mica, smectite, chlorite, and kaolinite), which are impregnated with iron and manganese oxides and hydroxides. Iron minerals are represented by goethite and lepidocrocite. Both the iron minerals are characterized by very small particles. Goethite occurring in all of the studied Fe-Mn nodules clearly prevails over lepidocrocite. Lepidocrocite show higher concentration only in nodules from lower part (fragipan horizon) of the soil profile located on a footslope and showing the strongest stagnic color pattern. Manganite and todorokite represent manganese minerals, however todorokite is observed only in nodules from illuvial horizons (Btx, Btg) of the studied Fragiudalfs. The Fe-Mn nodules from eluvial horizons (Eg) show higher concentrations of silicates (quartz, K-feldspars, plagioclases) than the nodules from illuvial horizons. Fe-Mn nodules from the illuvial horizons (fragipan and argillic) exhibit higher concentrations of phyllosilicates (i.e. clay minerals) relative to eluvial horizons. The differences in quantitative mineral composition of the Fe-Mn nodules between eluvial and illuvial horizons are related to translocation of clay minerals from upper soil horizons into the lower part of the soil profiles. Similar mineral composition of the Fe-Mn nodules and bulk soil material indicates that the nodules were formed in situ due to cyclic reduction and oxidation of Fe- and Mn-oxides.