National Repository of Grey Literature 44 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Record of mechanical processes during emplacement of shallow-level postcaldera intrusions: an example from Cínovec granite, Bohemian Massif
Vitouš, Petr ; Tomek, Filip (advisor) ; Trubač, Jakub (referee)
Collapse calderas are volcanic depressions created by emptying of underlying magma chamber during volcanic eruption and following fall of upper layers. After this the event is often succeeded by resurgence and magma chamber is filled with new magma, which may lead to creation of dike complexes and laccoliths. Inner structure of these resurgent magmatic bodies is defined by many processes like injection of magma, flow and deformation by local and regional stress fields. During crystallization, magma is still vulnerable to deformation, crystals may react to these deformations and orient themselves to it, and the inner structure may become overprinted. So, the creation of magmatic structures happens during final stages of emplacement and records only the last increment of deformation of magma. For studying the existence of inner structures even from macroscopically isotropic rocks, which may show the characteristics of mechanisms of creation of these rocks, I chose the anisotropy of magnetic susceptibility technique (AMS). This work is focused on the Cínovec granite in the Altenberg- Teplice caldera, Krušné hory mountains on the border between Czechia and Germany. Apart from the studied Cínovec granite this caldera is penetrated by series of other granitic bodies. The result of my study is for interpretation...
Formation of mafic granulites as a result of metamorphic and metasomatic processes at the contact of felsic and ultramafic lithologies (Dunkelsteiner Wald granulite massif, Bohemian Massif)
Zelinková, Tereza ; Racek, Martin (advisor) ; Hasalová, Pavlína (referee)
English Abstract The Dunkelsteiner Wald granulite massif in Lower Austria belongs to the Gföhl unit of the Moldanubian zone of the Bohemian Massif. Predominant rocks are felsic granulites which in some places contain garnet pyroxenites and peridotites. There are positions of mafic and intermediate granulites on their intersection. Primary mineral association of mafic granulites is garnet, clinopyroxene rich on Jd and Ca-Tschermack component and kyanite. These rocks probably represent Ca-richer variant of pyroxenites. Contemporary mineral association is make by garnet, clinopyroxene, plagioclase and orthopyroxene. Accessory there is amphibole, spinel, rutile and Ilmenite in the rocks. Sapphire inclusion in garnet cores close to kyanite inclusions has been observed in several cases. Decompression of these rocks creates specific symplectite textures in mafic granulites characterized by plagioclase inclusions. These inclusions are partly or fully surrounded by garnet porphyroblasts on their edges and coarse grain symplectics of plagioclase and pyroxene in matrix. A possible explanation of emergence of this specific texture in rocks on intersection with felsic granulite is an infiltration of melt from felsic lithology. Proof can be the enrichment of K component on edges of plagioclase grains. On the other hand,...
Three-dimensional ambient noise tomography of the Bohemian Massif
Valentová, Ľubica ; Gallovič, František (advisor) ; Burjánek, Jan (referee) ; Kristek, Jozef (referee)
We have performed 3D ambient noise tomography of the Bohemian Massif. We invert adopted inter-station dispersion curves of both Love and Rayleigh waves in periods 4-20 s, which were extracted from ambient noise cross-correlations, using a two-step approach. In the first step, the inter-station dispersion curves are localized for each period into the so-called dispersion maps. To account for finite-frequency effects, gradient method employing Fréchet kernels is used. Assuming membrane wave approximation of the surface wave propagation at each period, the kernels were calculated using the adjoint method. To reduce the effect of data noise, the kernels were regularized by Gaussian smoothing. The proper level of regularization is assessed on synthetic tests. In the second step, the phase-velocity dispersion maps are inverted into a 3D S-wave velocity model using the Bayesian approach. The posterior probability density function describing the solution is sampled by more than one million models obtained by Monte-Carlo approach (parallel tempering). The calculated variance of the model shows that the well resolved part corresponds to the upper crust (i.e., upper 20 km). The mean velocity model contains mainly large scale structures that show good correlation with the main geologic domains of the Bohemian...
Late Quaternary activity of slow-slip intraplate Mariánské Lázně fault as revealed by trenching and shallow geophysical survey; Bohemian Massif (Czech Republic, central Europe)
Štěpančíková, Petra ; Fischer, T. ; Hartvich, Filip ; Tábořík, Petr ; Rockwell, T. ; Stemberk, Jakub ; Široký, J. ; Sana, Hamid
The NNW-SSE trending Mariánské Lázně Fault (MLF) zone is situated in the western part of the Bohemian Massif (Czech\nRepublic, central Europe) where it intersects NE-trending Cenozoic Eger rift. The northern segment of the MLF controls the\nmorphologically pronounced mountain front of Krušné hory Mts. and eastern limit of Cenozoic Cheb basin, which is famous for\nearthquake swarms (max. ML=4.6) and CO2 emanation. We performed 2D and 3D geophysical survey (electric resistivity\ntomography, ground penetration radar) and 3D trenching to look for large surface-rupturing prehistoric earthquake responsible\nfor pronounced moutain range front. Seven excavated and six hand-dug trenches revealed a complex geology and deformation\nat the study site probably as a result of right-lateral transpression during Late Quaternary. Two Holocene earthquakes 1150-590\nBC and 780-1000 AD were inferred from 14C dating of faulted Holocene colluvium with corresponding magnitudes Mw=6.7-7.0.\nThe latter one is the youngest documented surface-rupturing event in central Europe.\n
New data on the origin of the Fe-Cu-As skarn deposit at Obří důl, West Sudetes, Bohemian Massif
Pašava, J. ; Veselovský, F. ; Dobeš, P. ; Erban, V. ; Pour, O. ; Žák, Karel ; Ackerman, Lukáš ; Haluzová, Eva ; Creaser, R. ; Tásler, R.
The Obří důl Fe-Cu-As sulfide deposit is hosted in metamorphosed lenses of marble, calc-silicate rocks and skarns. The deposit is located up to a few hundred meters away from the contact of the large, late-orogenic Variscan Krkonoše-Jizera Plutonic Complex (KJPC). Mineralogical and fluid inclusion studies of the Gustavská ore lens show that the main sulfide stage, dominated by pyrrhotite, chalcopyrite and arsenopyrite, originated from water-rich hydrothermal fluids with salinities up to 8 wt.% NaCl eq. at temperatures ranging from 324 to 358°C.These fluids replaced mainly the carbonate-rich lithologies. The 34S values indicate a magmatic source of sulfur and Re/Os dating of molybdenite are consistent with simultaneous formation of the main sulfide stage ore and the KJPC.
Determination of the age of secondary uranium minerals using 230Th/234U in selected localities of the Bohemian massif
Roll, Michal ; Goliáš, Viktor (advisor) ; Mizera, Jiří (referee)
This thesis is focused on prominent uranium deposits in Czech Republic and their secondary uranium mineralization. Main goal of this thesis is to analyze collected minerals and to determine their ages. Next step is to prove or disprove hypothesis that this secondary uranium minerals are products of Quaternary glacier weathering. As a suitable analytical method, an alpha spectrometry was used and the age was calculated by 230 Th/234 U ratio. Firstly, chosen methodology was verified with admixture of reference material PU1 (Přibram uraninite) in secular equilibrium and internal standard, both with known activity. Analyzed spectra confirmed that some of the samples lay on the very edge of datability, especially in case of PL1 and GF1, both samples are very young, so they easily could be products of anthropogenic activity (changed environment due to mining works). On the other hand, in case of sample GF3, the age was successfully determined, although it is also quite young phase. In case of samples ME3, ME4 and ME6 was used threshold dating method, because they were considered to be too old for age calculation. The rest of the samples chosen for age determination was analyzed without further complications. Based on the age and geological setting, samples GF3 (3 725 ± 845 years), JE1 (10 655 ± 1 795...
The Origin of Compositional and Textural Zoning of Shallow-Level Granitoid Plutons
Trubač, Jakub ; Janoušek, Vojtěch (advisor) ; Broska, Igor (referee) ; Siebel, Wolfgang (referee)
The principal goal of this Ph.D. Thesis is to contribute to the research on formation of compo- sitional and textural zoning in shallow-level plutons. Processes responsible for emplacement of individual plutons/pulses and the origin of compositional zoning in are addressed in a great detail, from the pluton-scale down to the micro-scale. The main emphasis in the more focused part of this text is on a combination of various quanti- tative data sets from two well-selected plutons (the Říčany Pluton in the Central Bohemian Plu- tonic Complex and the Melechov Pluton in the Moldanubian Batholith). These detailed studies are supported by further research on the Štěnovice, Čistá and Ševětín plutons. In this way we cover the evolution of Variscan magmatism in the heart of Bohemian Massif in its entirety, from Late Devonian till Permian. The thesis is based on combining field and structural studies (including the anisotropy of mag- netic susceptibility, AMS), textural analysis, petrological, geochronological and geochemical methods with geophysical investigations. Mathematical approaches have been designed and applied to the interpretation of geochemical data, with potential applications to other igneous systems. I strongly believe that only such comprehensive studies on well-selected case examples have a...
Variability of chemical composition of apatites from alkaline rocks of the Bohemian Massif
Mészárosová, Noemi ; Skála, Roman (advisor) ; Filippi, Michal (referee)
III Summary This thesis is focused on crystal chemistry and crystal structure of apatites from alkaline rock of the Bohemian Massif. Fifteen samples of volcanic rocks, mostly of the Cenozoic age was selected for the study. Sample No. 5 is of the Silurian age. Sample No. 15 originates from volcanic rock of the Cenozoic age from the Slovak Western Carpathians. This sample was chosen for this study due to its substantially different chemical composition. The contents of major and minor elements in apatites were measured on an electron microprobe, the contents of some minor and trace elements were determined by laser ablation inductively coupled plasma mass spectrometry. Selected samples were investigated by cathodoluminescence (CL) spectrometry. Crystal structure of studied apatites was characterized by X-ray diffraction and Raman spectroscopy. It was found that dominant anion at position X is fluorine. The OH content calculated on the basis of the fully occupied position X is significant in some samples. The amount of Cl is generally low. The exception is the sample No. 15 where Cl reached up to 0.6 apfu (Z = 2). Studied apatites contain many substitutions but they are generally of minor extent. Strontium, iron and REE at position M belong to the most common and most important substituents for calcium in...
Structural evolution of the Královský Hvozd Unit
Vrtiška, Luboš ; Verner, Kryštof (advisor) ; Žák, Jiří (referee)
5 English abstract The introduction of the thesis represents a profound research of current knowledge and survey results to date about the geodynamic tectonic boundary development of the Teplá- Barrandien unit/Moldanubian senzu stricto and the Královský Hvozd unit in the Šumava Mountains. It also describes in detail lithology of the Královský Hvozd unit and historical as well as contemporary opinions of the tectonometamorphic development of the Královský Hvozd unit and adjacent Moldanubian unit and Teplá-Barrandien unit. The research part of the thesis brings results of the analysis of the Královský Hvozd unit tectonic development in relation with the tectonic development of broader surrounding area. The research combines field structural data, detailed microstructure data acquired from collected samples and results of studying deformation mechanisms on orthogneiss samples from the Královský Hvozd unit using the EBSD (Electron Back Scattered Diffraction) performed on partly recrystalised quartz aggregates. The research output is a construction of a tectonic development model of the Královský Hvozd unit and the adjacent area. Four main deformation events (D1-D4) were determined on the basis of structural record and their time sequence in the rocks of the Královský Hvozd unit. On the basis of kinematic...
Genesis of Au-Sb ores at the Krásná Hora deposit
Němec, Matěj ; Zachariáš, Jiří (advisor) ; Dobeš, Petr (referee)
Ore deposits of the Krásná Hora ore district are the main representative of the Sb-Au mineralization in the Czech Republic. It can be classified genetically as epizonal subtype of orogenic gold deposits. Spatially and partly temporally are associated with the intrusion of the Central Bohemian Pluton. The ore bodies are related to quartz veins that follow the course of E-W striking lamprophyre dykes, which are usually heavily crushed and altered. Ore shoots with massive stibnite are located mainly at the intersections of these E-W trending veins with the NW-SE striking tectonic fault zones. Au-Sb ores at Krásná Hora ore district formed in an area of repeatedly activated fault zones. Three generations of hydrothermal quartz were identified on microscopic scale. Earliest quartz (Qtz1), which was considered in the literature auriferous originated from low-salinity H2O - CO2 fluids at ~350 řC and at a depth of about 5 km. The younger quartz (Qtz2) originated at lower temperatures of about 260 řC and lower depth of about 3-4 km from low/saline aqueous fluids. Both older (Qtz1) and younger quartz (Qtz2) are not auriferous. The gold is associated with younger paragenetic formation (Anti + Au + Cc + Qtz3) that fills in intergranular spaces and fractures in Qtz1 and Qtz2 . Due to the partial exhumation of the...

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