Recent allophane coatings from the karst and pseudokarst caves
K. MELKA and V. CÍLEK
Institute of Geology, Academy of Sciences of the Czech Republic, Rozvojová 135, 165 02 Praha 6, Czech Republic
Key words: allophane, pseudokarst systém, Podyjí National Park, karst caves, Ochtiná Aragonite Ceve, asbolane, X-ray powder diffraction, thermal analysis, electron-microprobe analysis
Allophane is not often present in karst caves. As an example of its occurrence 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 the 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 laminae.
Allophanes of these two localities were recognised by means of laboratory methods. Especially, electron microprobe analysis, X-ray powder diffraction and thermal determination were used.