engleski

Evidence for the formation of bog iron ore in soils of the Podravina region, NE Croatia: Geochemical and mineralogical study

This study brings evidence for possible bog iron ore formation in soils of the Podravina region, NE Croatia. During decades of archaeological investigations in the region, numerous sites with iron smelting workshops, furnaces and iron slag materials were found in the region. As archaeological evidence indicates the presence of near-by bog iron excavation sites, a total of 44 soil profiles were drilled in the vicinity of the archaeological sites. Six soil profiles, consisting of five Gleysols and one Fluvisol, were selected for further mineralogical, geochemical and textural analyses due to their visible redoximorphic features. The X-ray diffraction (XRD) analyses confirmed goethite, quartz, clay minerals, plagioclase, feldspars and dolomite. Chemical analyses indicate Fe content above median values for the Podravina region. The Kalinovac-Hrastova Greda profile showed the highest content of Fe2O3, (31.52 wt. %) at 60–80 cm depth, while the other investigated profiles show Fe2O3 contents between 3.97 and 10.90 wt. %. Contents of As (1.8–563.6 ppm) and P (484–4513 ppm) indicate high accumulations of these elements in the soils. Textural analyses indicate a high amount of silt and, sporadically, sand in all profiles, while showing a relatively small amount of clay. The enrichment factor of Fe2O3 shows significant enrichment in the Kalinovac- Hrastova Greda profile, indicating a possible ore formation. Based on the microelement distribution of Ce, Cs, Hf, La, P and Zr, all soils show a common parent material, but significant differences in contents of Fe and other major oxides indicate different formation processes. This is attributed to differences in the soil texture of the selected soil profiles, oscillations of the groundwater table and changes between oxidative and reductive conditions. The results of this study indicate that the Podravina region is a suitable area for the formation of bog iron ore, although recent conditions inhibit the formation of bog iron ore due to changes in agriculture and melioration which are altering groundwater levels.

bog iron ore ; geochemistry ; soils ; Drava river ; Podravina region

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