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Differentiation and crystallization of evolved granitic melts, the Říčany pluton, central Bohemian Massif
Jandová, Tereza ; Dolejš, David (advisor) ; René, Miloš (referee)
Evolved silicic rocks display a variety of igneous textures, which can provide important information on crystallization kinetics and rheology in natural magma chambers. Individual kinetic effects such as diffusion rate, nucleation rate, growth rate and post-solidification modifications are likely to be reflected in the modal and textural appearance of the resulting rock. This work focuses on characterization and interpretation of solidification textures in a 600 m wide and 5 km long body of highly evolved, boron-rich aplites and pegmatites at the southern endocontact of the Říčany granite pluton (Central Bohemian Plutonic Complex). This rock suite is associated with biotite Říčany granite, hosting microgranite and aplite dyke swarm, and it is built up by massive tourmaline aplites, layered aplites with tourmaline-rich or locally garnet-rich bands, pegmatite pockets, pegmatite layers with unidirectional solidification textures (comb layers), megacryst zones (analogous to stockscheider), and late pegmatite dykes discordant to layering. Textural as well as modal variations are usually sharp and observable megascopically as well as on the microscale. All aplites and pegmatites usually contain similar proportions of quartz, albite-rich plagioclase, K-feldspar, various proportions of tourmaline (up to...
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Numerical model for the origin of magmatic textures and its application to the Fichtelgebirge/Smrčiny granite batholith
Špillar, Václav ; Dolejš, David (advisor) ; Ježek, Josef (referee) ; Žák, Jiří (referee)
Magmatic processes are major agents responsible for the formation and differentiation of the Earth's crust. In contrast to extensive efforts to improve understanding and utility of igneous geochemistry, physical processes of magma differentiation and solidification remain largely unclear. Large variability of igneous textures provides record of these processes and intensive parameters governing the crystallization. In this thesis, we develop quantitative methods, which allow us to better interpret igneous textures in the framework of physics of solidification. We have developed a new three-dimensional model of crystallization from one- component melt driven by homogeneous and heterogeneous nucleation and crystal growth. The predicted textures are quantitatively characterized by crystal size distributions, spatial distribution functions and parameters representing grain contact relationships. The model employs high resolution in a large volume simulation domain in order to produce statistically stable results. Our simulations, performed for various functional forms of nucleation and growth rates with respect to time, imply that (i) crystals are ordered (anti-clustered) on short length scales. This reflects that other crystals already have a finite size at the time of nucleation of younger crystal,...
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Hydrodynamic and thermal mode ling of reactive flow in the surroundings of intrusions
Jandová, Tereza ; Dolejš, David (advisor) ; Bruthans, Jiří (referee)
English Summary Intrusion of magma into the Earth's crust is associated with significant thermal perturbations, release of aqeuous fluids and formation of hydrothermal system. In order to better understand the feedback relationships between fluid flow, thermal evolution and permeability variations, we have modeled conductive and advective cooling of a shallow- crustal pluton using the SHEMAT software. Our model represents a two-dimensional cross section through the lithosphere with homogeneous material properties, whebery the heat and mass conservation equations are solved by finite difference method. We first calculate the stable lithospheric geotherm by emplying constant basal thermal flow of 40 mW m-2 and a constant surface temperature. Subsequently, we consider a rectangular magmatic intrusion emplaced at 5-10 km depth, which forms a contact aureole by conductive cooling. With time, a mushroom-like shape of the contact aureole is predicted. Inclusion of aqueous fluid flow into the model causes only a small alteration of thermal evolution mainly because the permeability is low and the fluid mass is negligible due to very low density under hydrothermal conditions. In addition to thermal effects, we have explored variations in hydraulic head in order to address the ensuing effects on the flow velocity. The...
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Volumetric and electrostatic properties of water and their application to aqueous thermodynamics and mineral solubility at high temperatures and pressures
Hanková, Barbora ; Dolejš, David (advisor) ; Zachariáš, Jiří (referee)
Hydrothermal fluids are important mass and heat transfer agents in the Earth's crust and mantle. Aside from their transport role, the aqueous fluids act as reactants or products in rock environment during diverse processes ranging from partial melting, magmatic and metamorphic devolatilization. This study evaluates the effect of equations of state and thermodynamic data for aqueous species on prediction of mineral solubility in aqueous fluids at high temperatures and pressures employing the Helgeson-Kirkham-Flowers model (HKF). These calculations require: (i) volumetric properties of water; (ii) dielectric properties of water; (iii) aqueous species thermodynamic properties. A comparison of ten equations of state against the IAPWS scientific standard reveals that volumetric properties of water up to 1200 řC and 50 kbar are predicted within 5 %, except at low pressure (below 2 kbar), temperatures higher than 1000 řC, and the liquid-vapor equilibrium curve, particularly in the proximity of the critical point of water. The deviations of volumetric and electrostatic properties of water propagate into the mineral solubility calculations. For quartz and corundum these deviations lead to discrepancy in mineral solubility of up to half an order of magnitude for molal concentrations. These discrepancies...
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Reactive fluid flow and origin of the fracture-controlled greisens in the Horní Blatná granite pluton, Krušné hory Mts.
Heřmanská, Matylda ; Dolejš, David (advisor) ; Štemprok, Miroslav (referee)
Magmatic intrusions emplaced in the shallow continental crust are often associated with hydrothermal alteration and mineralization systems. Alteration zones and their assemblages can be described by means of reaction progress and this variable then used to calculate the time-integrated fluid fluxes, responsible for the mineral formation, if gradients in fluid composition, temperature and pressure are known or estimated. Two limiting cases of this approach have been applied in previous numerical models: (i) infiltration of aqueous fluid that is out of equilibrium with the host rocks, thus producing an alteration sequence as the fluid flux increases, and (ii) fluid flow in local equilibrium with host rocks, where mineral changes are induced by pressure and temperature gradients along the flow path. These two models generally yield results that differ by several orders of magnitude but are both in use for estimating fluid fluxes and transport properties in the lithosphere. We propose a combined model that evaluates the disequilibrium fluid infiltration and the pressure-temperature gradients simultaneously, and apply it to the interpretation of fracture-controled greisen alteration in the Horní Blatná granite pluton in the Krušné hory Mts. (Czech Republic). The Horní Blatná pluton is a composite...
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Volumetric and electrostatic properties of water and their application to aqueous thermodynamics and mineral solubility at high temperatures and pressures
Hanková, Barbora ; Dolejš, David (advisor) ; Zachariáš, Jiří (referee)
Hydrothermal fluids are important mass and heat transfer agents in the Earth's crust and mantle. Aside from their transport role, the aqueous fluids act as reactants or products in rock environment during diverse processes ranging from partial melting, magmatic and metamorphic devolatilization. This study evaluates the effect of equations of state and thermodynamic data for aqueous species on prediction of mineral solubility in aqueous fluids at high temperatures and pressures employing the Helgeson-Kirkham-Flowers model (HKF). These calculations require: (i) volumetric properties of water; (ii) dielectric properties of water; (iii) aqueous species thermodynamic properties. A comparison of ten equations of state against the IAPWS scientific standard reveals that volumetric properties of water up to 1200 řC and 50 kbar are predicted within 5 %, except at low pressure (below 2 kbar), temperatures higher than 1000 řC, and the liquid-vapor equilibrium curve, particularly in the proximity of the critical point of water. The deviations of volumetric and electrostatic properties of water propagate into the mineral solubility calculations. For quartz and corundum these deviations lead to discrepancy in mineral solubility of up to half an order of magnitude for molal concentrations. These discrepancies...
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Thermokinetic model and quantitative description of magmatic textures
Špillar, Václav ; Dolejš, David (advisor) ; Marsh, Bruce D. (referee) ; Higgins, Michael D. (referee)
Variability of magmatic textures records a wide array of physicochemical and mechanical processes that have operated in a magma chamber during its crystallization. Here I investigate how the final textural record can quantitatively be used to decipher the magma crystallization history and internal dynamics of magma chambers. The thesis is based on a formulation of numerical models of texture formation under the activity of various crystallization processes. Numerical results are then compared to the new quantitative textural datasets derived from four distinct magmatic systems in the Bohemian Massif: (i) Fichtelgebirge-Smrčiny granite batholith; (ii) Krkonoše-Jizera plutonic complex; (iii) Kdyně mafic intrusion; (iv) České středohoří volcanic complex. Combination of the field textural studies with their interpretation via numerical crystallization models provides new implications regarding magmatic crystallization and internal dynamics of magma chamber. The most important results of this Ph.D. thesis are as follows: (i) a new method has been developed that allows the rates of nucleation and growth of crystals to be derived from quantitative textural data. The method requires using the crystallinity evolution in time as an independent constraint in order to provide unique solution. In case of the...
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Small-scale volcanoes on Mars: image analysis, numerical modeling and comparison with terrestrial analogs
Brož, Petr ; Dolejš, David (advisor) ; Rothery, David (referee) ; Baratoux, David (referee)
Small-scale volcanoes represent diverse group of landforms which vary in morphology, morphometry, and mechanisms of their formation. They are the most common volcanic form on Earth, and their existence and basic characteristics were also predicted for Mars. Availability of high-resolution image data now allows to search, identify and interpret such small volcanic features on the martian surface. This thesis extends our knowledge about the small-scale volcanoes with the following objectives: (a) to document the existence of martian analogues to some of the terrestrial volcanoes, in particular scoria cones, tuff cones, tuff rings and lava domes; (b) to establish their morphological and morphometrical parameters; and (c) to examine the effect of environmental factors, which differ on Earth and Mars, on the mechanisms of formation of the scoria cones. Interpretation of remote sensing images and digital elevation models reveals that scoria cones, tuff rings and cones, and lava domes exist on different parts of the martian surface and, in some cases, far away from previously well-known volcanic provinces. Scoria cones have been identified in the volcanic field Ulysses Colles situated within the Tharsis volcanic province; tuff cones and tuff rings have been found in the Nephenthes/Amenthes region at the...
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Volcanic-hosted massive sulfide deposits: structure, origin and examples from the Iberian Pyrite Belt
Krátký, Ondřej ; Dolejš, David (advisor) ; Zachariáš, Jiří (referee)
English abstract The volcanic-hosted massive sulfide deposits (VHMS) represent one of the key deposit types in the modern world. Due to their polymetallic composition (Zn, Pb, Cu, Ag, Au and Sn in some cases) they are important source of the base metals as well as the precious metals. They have been forming through the Earth's history and are actively forming even now on a modern sea- floor through emanations of hot metal-bearing fluids. Extensive study of the volcanic-hosted massive sulfide deposit began in 1960s after discovery of active seafloor vents on the bottom of the Red Sea (e.g. Miller et al., 1966) in form of black smokers. They represent channels and are results of emanation of the hydrothermal fluids into the water column and actual evidence of the hydrothermal processes. Hydrothermal fluids were enriched in various elements, including base and precious metals. Certain elements (specifically metals) were leached from the host rock (volcanic and sedimentary) by the percolating seawater. This seawater was heated and modified into hydrothermal fluid by a heat from a magmatic intrusion, which represents the driving force of the whole hydrothermal system. This intrusion can be of variable composition - from basic to felsic. Sometimes fluids that are produced by this intrusion are also enriched in...
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