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Banská Bystrica, Slovakia

Ferenc S.,Katedra geografie a geologie | Bakos F.,Drnava | Demko R.,Statny Geologicky Ustav D. Stura | Peter Kodera A.,Katedra loziskovej geologie
Bulletin Mineralogicko-Petrologickeho Oddeleni Narodniho Muzea v Praze | Year: 2014

Siderite-quartz-sulphidic veins in the Kohút Zone of Veporic Unit, are best developed at Cinobaňa, Lovinobaňa, and Uderiná villages, in vicinity of the Veporic/Gemeric Units tectonic contact (the Lubeník-Margecany Zone). The mineralization occurs at the small historical deposits, localised within Alpine shear zones (NNE - SSW to W - E directions) in Variscan granitoids, amphibolites and mica schists. Succession of the mineralised structures filling is as follows: relics of host-rock minerals (garnet, xenotime, ilmenite, rutile, magnetite, hematite)→metamorphic mineralization (quartz with CO2-N2 rich fluid inclusions)→Ni-Co sulphidic stage (quartz, pyrite, arsenopyrite, siegenite, polydymite, gersdorffite)→ carbonate stage (siderite, ankerite, Fe dolomite, calcite)→alpine-type paragenesis stage (quartz, apatite, monazite, xenotime, schorl, dravite, foitite, ilmenite, rutile, muscovite, chamosite, calcite)→quartz-sulphidic stage, with two substages: a) Cu sulphidic (pyrite, chalcopyrite, tetrahedrite, galena, sphalerite, stibnite, eugenite?), b) cinnabar (cinnabar, calcite, marcasite)→hematite stage (hematite). Supergene stage is represented by: cinnabar, covellite, chalcocite, limonite and a mixture of Fe, Cu, As, Sb, Ni sulphates/oxides. Quartz with CO2-N2 rich fluid inclusions forms only relics in Fe carbonates and contains a high- salinity aqueous phase (31.9 - 39.8 wt. % NaCleq.) fluid inclusions with CO2 and N2 (up to 41 mol. % N2). Variability in size of gaseous phase and halite crystals, as well as, total homogenization temperatures between 223 - 364°C, suggest a heterogeneous fluid. Bottom of homogenisation temperatures approaching to the real quartz crystallisation temperatures. Two phase, CO2- rich aqueous fluid inclusions in quartz of alpine paragenesis has a salinity 9.6 - 15.2 wt. % NaCl eq., total homogenization temperature ranged from 272 to 347°C. Stable C-O isotope ratios in siderites (δ13C[PDB] -9.6 to -5.6 ‰, δ18O[SMOW] 15.2 - 16.4 ‰) are reminiscent of south Gemeric siderite-polymetallic veins. We assume that quartz with N2- rich inclusions is a product of pre-Upper Cretaceous tectonometamorphic processes, occurring during Lower - Middle Cretaceous (P, T maximum of the Alpine metamorphosis). Siderite was formed during Upper Cretaceous, probably from „Gemeric type“formation brines circulating in the Lubeník - Margecany line and adjacent tectonic structures, after collision of the Gemeric-Veporic Units. Formation of quartz with alpine-type paragenesis was caused by precipitation from SiO2-rich fluids circulating in shear zones after maximum of the Early Cretaceous metamorphism, as a consequence uplift and cooling of the Central Western Carpathians. © 2014, Bull. mineral.-petrolog. Odd. Nár. Muz. (Praha). All rights reserved.

Silhan K.,Katedra Fyzicke Geografie a Geoekologie | Prokesova R.,Institute Vyskumu Krajiny A Regionov | Medvedova A.,Katedra geografie a geologie | Skodova M.,Katedra geografie a geologie | Kardos M.,Technical University In Zvolen
Geoscience Research Reports | Year: 2014

The origin of many recent catastrophic landslides is commonly preceded by some minor movements. On the other hand, it is usual that large landslide events are followed by minor movements as well. Information about these movements is very important for assessment of potential landslide hazards or risks. Unfortunately, data on pre-landslide activity are very scarce (if any). Nevertheless, dendrogeomorphic methods can actually bring good results in this way. In our study the pre- and post-catastrophic activity of the L'ubietová landslide was studied. The landslide is 1200 m long and about 10-20 m deep. Catastrophic reactivation of this landslide occurred during February 1977. Trees with clearly visible signs of the previous landslide activity (tilted or bended stems) were sampled by Pressler increment borer in the area of 1977 source zone and in the position of old landslide blocks lying above the 1977 reactivation. A total of 19 individuals of Picea abies (L.) Karst. were sampled and samples were processed using a standard procedure. Twelve landslide reactivation events were dated (two of them, i.e. 1972 and 1974 were older than the main event in 1977). The activity of the superposed block was at least comparable with 1977 landslide prior to its movement. The question stays, why this area has remained outside the reactivation in1977? Moreover, the comparison of reconstructed chronology with precipitation record shows good conformity with some extremely wet seasons, although some events occurred in exceptionally dry seasons. Based on our results new questions emerged, which should be answered in the future at other localities using larger size of samples.

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