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Mineralogical and geochemical characteristics of ore for possible iron production in Podravina region, NE Croatia

The main goal of this study was to determine mineralogical and geochemical characteristics of possible bog iron ore samples found during geological investigations in vicinity of Molve area. Based on numerous iron processing smelting workshops found throughout Podravina region, and on similar case studies in various archeological sites in southern Hungary, it is believed that this type of ore was used for iron production from late antiquity up to Middle Ages in NE part of Croatia. Samples were found on surface and several meters below surface, with largest sample weighing over 2 kilograms. In order to better understand bog iron ore and its formation mechanism, several laboratory methods have been performed. X-ray powder diffraction (XRD) was used to determine mineralogical composition of samples. Detail geochemical characterization of two samples was performed using inductively coupled plasma mass spectroscopy (ICP-MS). Scanning electron microscopy with adjoining energy-dispersive X-ray spectroscopy (SEM-EDS) was used in order to better understand the distribution of mineral phases and geochemical components. The main mineralogical components of analyzed samples were quartz, goethite, feldspars and amorphic matter. Samples showed variable concentrations of Fe2O3 (37.86–39.06 wt%) and MnO (19.17–27.42 wt%). SEM-EDS analysis enabled characterization on micromorphological scale, providing information on iron and manganese elemental distribution and possible formation mechanisms. Two different phases were detected, one being crystallized phase composed of iron and manganese minerals and second, amorphous phase, showing slightly different chemical composition with elevated concentration of barium in manganese phase. Based on mineralogical and geochemical characteristics, studied ore samples indicate possibility of bog iron ore formation in Podravina region and its use for iron smelting and production.

Bog iron ore, Podravina region, mineralogy, geochemistry

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