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5 th Int. Workshop on Ice Caves (IWIC – V) Barzio (LC), Valsassina, Grigna and Milano, September 16 – 23, 2012 Volume of Abstracts CRYOGENIC MINERALS OF SOME ICE CAVES OF THE URALS Kadebskaya O.I. 1 1 Mining Institute of Ural Branch of Russian Academy of Sciences, Russia (icecave@bk.ru) The aim of this investigation was to characterise cryogenic minerals of the Urals‟ carbonate caves. We selected some caves with the greatest perennial glaciation in the territory of the Northern (Medeo and Eranka (Perm Krai)), Middle (Mariinskaya (Perm Krai) and the Southern Urals (Askinskaya and Pobeda (Bashkortostan)). Minerals were sampled from the surface and body of perennial icing (depth of up to 1 m), walls and clay soils. The mineral component was filtered from the unfrozen water and studied (morphology and chemical composition) with a scanning electronic microscope VEGA 3 LMH with a system of the x-ray energy-dispersive microanalysis INCA Energy 350/X-max 20. The caves have two types of mineral forming conditions: 1) icings where minerals were met both in the massif and on its surface and 2) a plane flowing surface subjacent glaciation zone with peculiar „soft‟ gurs and also accumulations of „moon milk‟ and calcite „fur hair‟ located on vertical and negative wall sections and on clay soil. The main authigenic minerals of icings are calcite and, rarer, ikaite (the Medeo, Eranka, Mariinskaya Caves). We reconstructed their morphological ranks that reflect the degree of solution supersaturation. Ikaite was recognized only in caves of the Northern and Middle Urals, which is connected with lower average annual temperature in these regions. The greatest variety of ikaite‟s morphotypes was noted in the Eranka Cave. The observed morphological variety of mineral phases located both on the surface and in the thickness of icing reflects a sudden change in the degree of solution supersaturation manifested in the formation of both greatly split units (corallites and concretions) and crystals with smooth faces. The latter are typical for large individuals of the regelation nature that are formed in water pellicle at the icing surface through dispersive cryogenic material enlargement. In the framework of this study, large (up to 7 mm) cryogenic concretions were found in the Pobeda Cave (the Southern Urals) for the first time in Russia. Similar formations were recently described in caves of Europe as cryogenic pearl (Ţák, 2008). The described mineral formations enabled us to expand the current cryogenesis conception. Along with previously described minerals formed at shock crystallization during sudden freezing (powder) and at regelation, a new group of minerals can be identified, which were deposited from water undergoing concentration in the course of partial freezing-out. During this process there occurs supersaturation of solutions, which leads to sedimentation of ultradisperse fibrous calcite in the form of „soft‟ gurs at 35
5 th Int. Workshop on Ice Caves (IWIC – V) Barzio (LC), Valsassina, Grigna and Milano, September 16 – 23, 2012 Volume of Abstracts the inclined plane flowing surface and formation of thin lathlike crystal suspension („moon milk‟) on vertical and negative wall sections and calcite „fur hair‟ on clay soil δ 13 C IN CAVE ICE: A NEW PROXY FOR PALAEOPRECIPITATION RECONSTRUCTIONS Perşoiu A. 1 & Bojar A.-V. 2 1 Department of Geography, University of Suceava, Universitatii 13, Suceava 720229, Romania (aurel.persoiu@gmail.com) 2 Salzburg University, Geographie und Geologie, Hellbrunnerstrasse 34, Salzburg , Austria Over the last few years scientific interest in ice caves has been rejuvenated by the possible use of the perennial ice deposits they host in palaeoclimatic and palaeoenvironmental studies. Oxygen and hydrogen stable isotopes, pollen and trace elements in ice, in combination with radiometric and indirect dating methods, have been used to infer past changes in air temperature, moisture sources, vegetation changes and pollution. Although studied in some detailed, the cryogenic cave calcite (CCC) has not been used thus far as a proxy for climatic and environmental elements. In this study we have investigated the palaeoclimatic potential preserved by the stable isotope composition of CCC from Scărişoara Ice Cave (SIC), Bihor Mountains, Romania. A number of 42 calcite samples from impurity-rich layers exposed on the lateral side of the ice block in SIC have been analyzed for their O and C isotope values. Twenty-five samples were recovered from a section of the ice block that formed during the Medieval Warm Period (MWP, prior to 1300 AD), and seventeen samples came from ice that accumulated during the Little Ice Age (LIA, between ca. 1300 and 1700 AD). All calcite samples are composed of CCC with δ 18 O values ranging between -2 and -8 ‰VPDB, and δ 13 C values ranging between 0 and +10 ‰VSMOW. These high δ 13 C values are specific for calcite formed during freezing of water accompanied by rapid degassing of CO2 and strong kinetic fractionation. While the δ 18 O values are evenly distributed through the entire sequence, the δ 13 C values form two distinct groups, with more positive values (with an average of +6 ‰) for samples from the MWP section of the ice block, and less positive values (with an average of +2 ‰) for samples formed during the LIA. We tentatively suggest that, despite strong kinetic fractionation during CCC formation, the heavier δ 13 C values in CCC samples from the MWP are reflecting warmer and/or dryer climates, while during the colder LIA, lower δ 13 C values in soil CO2 led to more depleted δ 13 C values in CCC. Pollen analyses in ice has shown that 36
Page 2 and 3: IWIC - V 5 th INTERNATIONAL WORKSHO
Page 4: President 5 th Int. Workshop on Ice
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Page 13 and 14: Dear Participants, we are very plea
Page 46: POSTER PRESENTATIONS
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