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Deformation and petrological record of polyphase quartzo-feldspathic rocks in Erzgebirge, Bohemian Massif
Kryl, Jakub ; Lexa, Ondrej (advisor) ; Závada, Prokop (referee) ; Hasalová, Pavlína (referee)
The Erzgebirge dome, exposing Proterozoic - Early Palaeozoic metagranitoids and metasedimentary rocks of the Saxothuringian domain in the Bohemian Massif, is formed by a tectonic stack of several UHP-HP and HT units exhumed during the Variscan continental subduction-collision process. A systematic study of orthogneiss deformation microstructures carried out on a regional scale has been done to evaluate these units' extent and relative structural position in the subduction complex. Five different microstructural types have been distinguished, revealing two overprinting sequences with 1) coarse-grained microstructures in the parautochthonous Kateřina-Reitzenhain Dome and 2) fine- grained microstructures in the allochthonous HP-HT Gneiss Eclogite Unit I. P-T conditions of the individual overprinting microstructures calculated by conventional thermobarometry suggest continuous deformation during exhumation along two contrasting P-T paths. The warmer one in the parautochthonous unit showed exhumation from ~13.5 kbar and ~820 ◦C to ~3 kbar and ~500 ◦C, while the colder one in the allochthonous unit showed exhumation from ~16 kbar and ~740 ◦C to ~3 kbar and ~400 ◦C. The overprinting microstructures are associated with vertical shortening interpreted as ductile thinning. This deformation started at depths...
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Crystal chemistry of pyralspite garnets
Soumar, Jan ; Skála, Roman (advisor) ; Ulrych, Jaromír (referee)
Bohemian garnets have been known as a jewellery stone for many centuries. There is still a lot of interest in them, however, the reserves in traditional locations are getting smaller. That is why search for alternative source of similar garnets in gem quality started. Shavaryn Tsaram deposit in Mongolia is considered as one of the potential sources. Pyrope samples from eight Bohemian localities of two areas (České středohoří [The Central Bohemian Uplands] and Podkrkonoší [The Giant Mountains]) and from Shavaryn Tsaram deposit in Mongolia were analysed using electron microprobe, LA-ICP-MS, ICP-OES, Mössbauer spectroscopy and x-ray powder diffraction. The data were compared with the conclusion that the Mongolian garnets from Shavaryn Tsaram deposit are so different from the Bohemian ones that it will not be possible to use them as a gem material of similar qualities. Bohemian garnet can be characterised as a red garnet with refraction index 1.747 (+/- 0.001) with dominant pyrope component of the average composition Py78Alm17Gr5 and Cr2O3 content above 1 wt.%. The data were also evaluated from two classification schemes point of view. The schemes by Schulze (2003) and Grütter (2004) are used in determining source materials and in diamond prospection. According to them source rocks of Bohemian garnets...
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Properties and characteristics of recycled garnet abrasives for AWJ
Martinec, Petr ; Hlaváček, Petr ; Ruppenthalová, Lucie ; Sitek, Libor
The use of recycled garnet abrasive from sludge after cutting materials is a current\nproblem. The behavior of individual garnet abrasives in the AWJ process depends\non the geological origin of the garnets, which also affects all the material\ncharacteristics of the garnet recyclate. The parameters of the BARTON HPX80 and\nGMA 80 abrasive inputs and their recycled products were compared: mineralogical\ntype, apparent density, granularity, grain shape and mineralogical purity,\nmicrohardness data and the degree of damage to the garnet grains. All individual\nparameters of abrasives and their recyclates are reflected in the index of cutting\nefficiency of abrasive. The effect of abrasive material properties on cuttability of\nabrasives is synergistic. The new parameters in the evaluation of abrasives are\nmicro-hardness (brittleness criterion), specific surface and pore size distribution\n(internal grain damage criterion).
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Crystal chemistry of pyralspite garnets
Soumar, Jan ; Skála, Roman (advisor) ; Ulrych, Jaromír (referee)
Bohemian garnets have been known as a jewellery stone for many centuries. There is still a lot of interest in them, however, the reserves in traditional locations are getting smaller. That is why search for alternative source of similar garnets in gem quality started. Shavaryn Tsaram deposit in Mongolia is considered as one of the potential sources. Pyrope samples from eight Bohemian localities of two areas (České středohoří [The Central Bohemian Uplands] and Podkrkonoší [The Giant Mountains]) and from Shavaryn Tsaram deposit in Mongolia were analysed using electron microprobe, LA-ICP-MS, ICP-OES, Mössbauer spectroscopy and x-ray powder diffraction. The data were compared with the conclusion that the Mongolian garnets from Shavaryn Tsaram deposit are so different from the Bohemian ones that it will not be possible to use them as a gem material of similar qualities. Bohemian garnet can be characterised as a red garnet with refraction index 1.747 (+/- 0.001) with dominant pyrope component of the average composition Py78Alm17Gr5 and Cr2O3 content above 1 wt.%. The data were also evaluated from two classification schemes point of view. The schemes by Schulze (2003) and Grütter (2004) are used in determining source materials and in diamond prospection. According to them source rocks of Bohemian garnets...
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Abrasives and possibilities of increase in efficiency of abrasive waterjets
Martinec, Petr ; Sitek, Libor
The contribution focuses on the research into abrasive materials and possibilities of adjustment of their properties in order to increase the efficiency of the processes of machining and cutting with abrasive waterjets. Cutting ability of commonly available garnet concentrates and nontraditional products which are starting to access to the Czech market were tested and compared. In addition, entirely new garnet products which are not commercially available yet, recycled abrasives, abrasives with various sizes of grains and heat-affected abrasives or abrasives coated with a thin plastic layer were studied.
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Highly luminescent nanophosphors - new physics, technologies and applications
Nikl, Martin ; Čuba, V. ; Bárta, J. ; Jarý, Vítězslav
The application of radiation synthesis in the manufacturing nanopowders of binary and ternary oxide nanophosphors is reviewed. Technological routes are described: irradiation of specific solutions containing soluble metal salts and OH radical scavenger by UV or ionizing radiation results in the formation of finely dispersed solid phase which is separated from the solution and subsequently converted by further thermal treatment into crystalline nanopowders with typical dimension of grains of several tens of nanometers. Doped ZnO, Y2O3, Y3Al5O12, Lu3Al5O12 and Gd3(Ga,Al)5O12 nanophosphors were prepared and their luminescence and scintillation characteristics were measured. In the photoluminescence decay of doped garnets the distinct effect of nanosized grains was found consisting in the slowing-down of the decay due to the change of effective refractive index.
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