Prehliadanie podľa Autor "Majzlan, Juraj"

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    Iron and manganese oxides from the oxidation zone of the Ľubietová-Podlipa deposit
    (Univerzita Komenského v Bratislave, 2025) Majzlan, Juraj; Števko, Martin; Chovan, Martin; Milovská, Stanislava; Jeleň, Stanislav; Mikuš, Tomáš; Biroň, Adrián
    Ľubietová-Podlipa is a small historical Cu deposit in the Veporic unit of the Central Western Carpathians in Slovakia. It is the type locality of libethenite and mrázekite. The oxidation zone of the deposit contains copious pseudomalachite and malachite that attracted the attention of mineralogists and mineral collectors for a long time. Another abundant group of supergene minerals, Fe and Mn oxides and oxyhydroxides (collectively called oxides here), received much less attention and were investigated closely in this work. Bulk analyses of the oxidation zone (channel samples) showed that it is rich in Cu (average 7070 ppm), Mn (430), Zn (650), Ba (640), Bi (235). Concentrations of other elements are low, such as Co (49), Ni (47), Sb (47), W (96), or Ag (1.2). Some of the elements are concentrated by Mn oxides. The Fe and Mn oxides formed mostly by weathering of chalcopyrite and Fe-dolomite. They coat the Cu minerals but may also be the substrate for the growth of the Cu minerals. The Mn oxides are flaky, with individual particles less than 5 mm large and less than 1 mm thick. The particles accumulate in spherical aggregates with size of tens of micrometers. Raman spectroscopy and powder X-ray diffraction indicate that the Mn oxides are most likely mixtures of birnessite and asbolane, with minor amount of tectomanganates (e.g., hollandite). They accumulate CuO (average of electron microprobe analyses 21.8 wt.%), CoO (5.5), BaO (1.0), CaO (0.5), and K2O (0.5) in their structure. Fe oxides occur either as brick-red, massive pseudomorphs after chalcopyrite or as coatings and crusts on fractures. They were identified as hematite or goethite, commonly intergrown. Hematite crystals may be embedded in pseudomalachite and Fe and Mn oxides intergrown in tufts. Fe oxides adsorbed As, Sb, and Bi, when available, but the concentrations of these elements are usually low (< 1.5 wt.%). Fe oxides may be rich in P2O5 (average 2.78 wt.%), SiO2 (1.67), Al2O3 (0.22), and CuO (6.47). Locally elevated Bi concentrations led to precipitation of rare bismutite. Because of their abundance and retention capacity for certain elements, Fe and Mn oxides influenced the composition of the oxidation zone and the environmental mobility of the elements to a great extent.