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Quartz microchemistry as metallogenetic indicator
Pacák, Karel ; Zachariáš, Jiří (advisor) ; Trubač, Jakub (referee)
Region surrounding the Central Bohemian Plutonic Complex represents one of the most important gold bearing zones in the Czech Republic. Several types of gold deposits dominated by hydrothermal quartz gangue were explored here and distinguished: the Intrusion related gold deposits ("Petráčkova hora" and "Mokrsko") and the orogenic gold deposits ("Jílové u Prahy" and "Kasejovice" ). Deposits "Libčice u Nového Knína" and "Roudný u Vlašimi" are partially similar to the orogenic gold type, but are different from other orogenic type deposits in the region. All together 38 samples from these five deposits were analyzed with laser ablation technique (LA- ICP-MS) to produce 228 measurements. Selected samples were selected to represent both main quartz gangue carrying the Au ore and latter weakly mineralized quartz gangue. Samples representing hydrothermal quartz gangue with no direct relation to Au-ore deposits were also collected in order to compare chemical composition of both quartz types originating from the same area. Main concern of this work was in-situ analysis of chemical composition of different generations of quartz gangue and statistical comparison of differences within individual deposits as well as comparing the examined deposits themselves. Total 65 isotopes were measured, trace element...
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Characteristics of polyphase deformation in quartz microstructure: an example from the Krkonoše-jizera Unit
Očenášková, Eva ; Jeřábek, Petr (advisor) ; Závada, Prokop (referee)
Quartzite samples taken in the east part of Krkonoše-Jizera Massif belong to metasedimentary cover of paraautochtonous unit. Rocks underwent a polyphase deformation which established a strong shape preffered orientation (SPO) of quartz grains. In folded quartz veins, deformation overprint mechanisms and microstructure, CPO and SPO relations were studied. For determination of crystal preffered orientations (CPO) the method of computer integrated polarization microscopy (CIP) was used. Microstructural analysis was focused on grain sizes, aspect ratios, long axis orientations and their relation to the deformation overprint grade. Results implies that dominant mechanism of quartz grain recrystallization is grain boundary migration. Folds were created by simple shear in microscale. The deformation overprint grade is strongest in the top of the fold hinge, where grains achieve highest aspect ratios and sizes. In the lower parts of the fold hinge the original CPO is preserved in small grains and SPO has similar orientation to original CPO. During folding CPO and SPO rotated with shear direction in dependance on deformation overprint grade.
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Sands for the production of foundry moulds and cores
Ostrézí, Filip ; Rusín, Karel (referee) ; Cupák, Petr (advisor)
Bachelor thesis deals with properties of most usable sands in foundries and with their advantages, disadvantages and usability. Most used are silica sands, because of their low prices, but they have a lot of disadvantages like discontinued heat dilatation, acidit reaction and health defect. Mainly described are sands from Czech and Slovak Republic and few sands out of Europe. Non-silica sands don´t have so much disadvantages, but their problem is a big price. Most used non-silica and synthetic sands are described.
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The Effect of Thermal Exposure of the Porosity and Mineralogy of Dense Silica Bricks.
Janek, Ondřej ; Kotouček, Miroslav (referee) ; Nevřivová, Lenka (advisor)
Silica bricks is a refractory building material which contains at least 93 % of silicon dioxide in polymorphic forms, mostly -tridymite, -cristobalite and unreacted -quartz. In glass industry is used for building crowns of glass tanks and in coke industry is used for building coke oven batteries. The advantage is the high refractoriness under load, high resistance to acidic melts. The disadvantage is the low resistance to changes in temperature below 600 °C. The thesis deals with the influence of repeated firing on the silica bricks and to its porous structure and mineralogical composition.
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Study of interactions of organic matter and its components via molecular dynamics
BARVÍKOVÁ, Hana
Humic acids and humates are principal components of humic substances major organic constituents of soil, peat, coal and water around the world. I was involved in research into molecular dynamics simulations of interactions of quartz surfaces with aqueous solutions of ions and small organic molecules representing basic building blocks of larger biomolecules and functional groups of organic matter. We studied interactions of molecules with surfaces for a set of surface charge densities corresponding to the experimentally or environmentally relevant ranges of pH values employing molecular mechanics, molecular dynamics and ab initio techniques. Simulated quartz surfaces covered the range of surface charge densities 0.00, -0.03, -0.06 and -0.12 C-m-2, approximately corresponding to pH values 4.5, 7.5, 9.5 and 11. As model molecules, benzoic acid, phenol, o-salicylic acid and their conjugated bases were chosen. My task was to prepare topologies and parametric models of selected organic matter basic building blocks organic molecules. I focused on studying interactions of these molecules in an aqueous environment with mineral surface quartz. The aim was to process simulation results and analyse conformations of the adsorption complexes and their thermodynamic properties such as interaction energies, free energies and adsorption geometries.
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Computer simulation of interactions of molecules with mineral surfaces
BARVÍKOVÁ, Hana
This thesis is focused on molecular dynamics, modelling interactions and their simulation. One of the tasks was to familiarize with GROMACS, a molecular dynamics simulation software. This work also introduces the basics of molecular dynamics and modelling interactions of organic molecules with mineral surfaces. The aim of the thesis was to solve model tasks in GROMACS and analyze the output results. The thesis describes some of the most important file formats and utilities that are needed for working with GROMACS and the use of both the formats and the utilities. In this program, I built up several systems consisting of combinations of organic molecules such as benzoic acid, phenol, salicylic acid and their conjugate bases with mineral surfaces (quartz crystal) of different surface charge density. Furthermore I analyzed the results of these simulations, behaviour of the structures and adsorption geometries and interaction energies within these systems. The thesis might also serve as a quick introduction and familiarization with GROMACS with emphasis on simulations and analysis of systems with planar interfaces. Within the MetaCentrum Project I worked on the Hermes Computer Cluster belonging to the Faculty of Science at the University of South Bohemia.
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Measurement of the Basic Material Characteristics forTransmission of Chain Filter
Melich, Radek
Observing the Sun with birefringent filters is done mainly with filters tuned constantly on some interesting spectral wavelength. However, a new problem that solves tuning of these filters by a temperature change, meets a problem of a insufficient accuracy of dispersion dependences which are used for calculation of transmission at the exact wavelength and the exact temperature. Designing a filter that reaches an extreme small value in its FWHM (e.g. 0.05 nm) it is then very important to determine birefringent dependency with a sufficient accuracy. The paper shows the technique of getting such dependencies, then it mentions a mathematical process suitable for getting the transmission of Solc filter and finally it compares data got from an experiment with computed data.
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