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Recent allophane coatings from the karst and pseudokarst caves
Melka, Karel ; Cílek, Václav
Allophane is not often present in karst caves. As example of its occurence the Aragonite Cave near Ochtiná (Slovakia) can be set out. It was found there in an asbolane profile forming white earthy intercalations or is present in asbolane Mn ochre positions as the admixture. Allophane often occurs as coatings on the walls of abandoned ore mines. It can be also found in pseudokarst ice caves of the Podyjí National Park (the Ledové sluje Caves) in Moravia. The local aggregates form microcascades and flowstone-like structures in which allophane layers alternate with dark brown Al-Fe phosphates, sometimes with BaSo4 enriched laminate. Allophanes of these two localities were recognised by means of laboratory methods, especially electron microprobe analysis, X-ray powder diffraction and thermal analysis.
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Report on research in the San Salvador Island, Bahamas
Bosák, Pavel ; Hladil, Jindřich ; Slavík, Ladislav ; Melka, Karel ; Venhodová, Daniela ; Chadima, Martin ; Hercman, H. ; Nowicki, T.
Contact of two cycles at shallow carbonate platform shows traces of karstification, formation of soils and important changes of geochemistry (U, Th, K, Fe) and magnetic susceptibility.
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An Environmental Impact of Pyritic Bauxite from the Dajti Mine, Albania
Novák, Jiří Karel ; Minařík, Luděk ; Peza, Luftulla Hasan ; Melka, Karel
The accelerated chemical weathering of bauxite due to acid atmospheric deposition and breakdown of pyrite was simulated using short-termed laboratory acid leaching at 20 o C. Pyrite-bearing gibbsite-boehmitic bauxite giving rise to a number of questions concerning ecology was tested along with oxic boehmitic bauxite from the Dajti mine and that from Mali Korites (Mali Thate Mts., SE Albania). The leachte of pyrite-bearing and sulphate-producing bauxite is enriched in the following risk elements: Cd, Be, Zn, Ni, Co, and much less Cr, Cu, As, and Pb. Toxic soluble hydroxy-alumina ions may be also released into the aquatic environment, because of high concentration in output leachate (563 mg/l). In contrast, the leachates of oxic boehmitic bauxites commonly contain much lower concentrations of toxic elements with exception of Cu (Dajti mine) and Be (new occurence of Mali Korites).
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