No abstract available

[en] I-type tonalites and granodiorites represent important rock types building the Variscan basement of the Tatric and Veporic units. A characteristic accessory mineral assemblage of this granitoid rock, magnetite + titanite + allanite, indicates oxidation conditions during late- to post-magmatic stages. However, titanite population is not uniform, and at least two types of this mineral can be distinguished in different textural positions. In this contribution I present new interpretation of both titanite types and discuss their petrogenetic significance on the example of Tribec tonalite (Tatric unit) and Sihla tonalite (Veporic unit). (authors)

No abstract available

[en] Eight samples from different petrographic types of granitic rocks typical of the Strazovske vrchy Mts. crystalline complex show a considerable dispersion in the ⁸⁷Sr/⁸⁶Sr vs. ⁸⁷Rb/⁸⁶Sr graph. The isochron slope constructed from 5 samples indicates an age of 393±6 m.y. of whole rocks and an initial ratio of ⁸⁷Sr/⁸⁶Sr=0.7060±0.0002. The dispersion of samples is probably caused by removal of alkalis in an acid environment or by Sr contamination from the surrounding metamorphic rocks. (author). 3 figs., 1 tab., 20 refs

[en] Nanoscale composite materials based on titanium dioxide, sulphur, and carbons were obtained. The samples were characterized using X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, Brunauer–Emmett–Teller and Barret–Joiner–Halenda methods, electron paramagnetic resonance spectroscopy, and ultraviolet–visible and infrared spectroscopy. X-ray powder diffraction revealed the phase of anatase in all composites and appearance of rutile phase for samples with high sulphur content. It was established that composites consist of nanoparticles ca. 6–10 nm. Analysis of nitrogen adsorption–desorption isotherms for the synthesized samples showed the presence of a hysteresis loop which is the evidence for mesoporous structure of the powders. Absorption spectra of nanocomposites showed a bathochromic shift compared with the absorption band of pure TiO₂. It was found that modification of titanium dioxide with sulphur and carbons leads to bandgap narrowing of composites. Nanocomposite samples showed higher photocatalytic activity in the destruction of safranin T under ultraviolet and visible irradiation compared to pure titanium dioxide. It can be connected with the participation of additives in the inhibition of electron–hole recombination, prolongation of charges lifetime, increasing of efficiency of interfacial charge separation, and formation of doping electronic states.

[en] This paper presents geochronological data for the volcanic dykes located in the northern Povazsky Inovec Mts. The dykes are up to 5 m thick and tens to hundreds of metres long. They comprise variously inclined and oriented lenses, composed of strongly altered grey-green alkali basalts. Their age was variously interpreted and discussed in the past. Dykes were emplaced into the Tatricum metamorphic rocks, mostly consisting of mica schists and gneisses of the Variscan (early Carboniferous) age. Two different methods, zircon SHRIMP and monazite chemical dating, were applied to determine the age of these dykes. U-Pb SHRIMP dating of magmatic zircons yielded the concordia age of 260.2 ± 1.4 Ma. The Th-U-Pb monazite dating of the same dyke gave the CHIME age of 259 ± 3 Ma. Both ages confirm the magmatic crystallization at the boundary of the latest Middle Permian to the Late Permian. Dyke emplacement was coeval with development of the Late Paleozoic sedimentary basin known in the northern Povazsky Inovec Mts. and could be correlated with other pre-Mesozoic Tethyan regions especially in the Southern Alps. (authors)

[en] The northern extent of the Scandinavian Caledonides includes the Skibotn Nappe Complex of still debated structural position. This paper is focused on part of this complex and presents new U-Th-total Pb monazite dating results for the migmatitic gneiss of the Kaafjord Nappe. The rocks show mineral assemblage of garnet + plagioclase + biotite + white mica + kyanite + rutile ± K-feldspar ± sillimanite. Thermodynamic modelling suggests that garnet was stable at P-T conditions of ca. 680-720 grad C and 8-10 kbars in the stability field of kyanite and the rocks underwent partial melting during exhumation following a clockwise P-T path. This episode is dated to 444 ± 12 Ma using chemical Th-U-total Pb dating of the Y-depleted monazite core. Second episode highlighted by growth of secondary white mica resulted from subsequent overprint in amphibolite and greenschist facies. Fluid assisted growth of the Y-enriched monazite rim at 419 ± 8 Ma marks the timing of the nappe emplacement. Age of migmatization and thrusting in the Kaafjord Nappe is similar to the Kalak Nappe Complex, and other units of the Middle Allochthon to the south. Nevertheless, the obtained results do not allow for unambiguous definition of the tectonostratigraphic position of the Skibotn Nappe Complex. (authors)