National Repository of Grey Literature 18 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Analogue and numerical simulations of the geodynamical systems - insights from the models of the Earth collision tectonics and Martian mudflows
Krýza, Ondřej ; Lexa, Ondrej (advisor) ; Čížková, Hana (referee) ; Schöpfer, Martin (referee)
Analogue and numerical modelling in geosciences is an excellent tool for studying complex spatio-temporal relationships in mass and energy transfer. Recent developments and advances in the plate tectonics and planetology require a combination of both approaches to simulate processes that cannot be studied directly in-situ. Advanced physical models are complemented by deformation analysis which is based on image velocimetry and photogrammetry, while numerical simulations utilize both modern and traditional methods to solve corresponding equations in complex domains. This work compiles several models that are focused on deformation analysis associated with material and heat transfer in large accretionary systems. The second subject of the thesis represent the investigation of the formation and propagation of large mudflows in martian atmospheric conditions. In the first part of the work we present a general overview of the problems of analogue and numerical modelling including scaling theory, governing equations, individual methods and history. In the second part of the thesis we deal with laboratory and numerical simulations of collision-indentation tectonics associated with the emergence of large accretionary systems on Earth. The last part of the thesis is devoted to experiments designed for the...
High-grade rocks of the Zábřeh Crystalline Complex
Jůzlová, Klára ; Lexa, Ondrej (advisor) ; Buriánek, David (referee)
This Bachelor thesis is focused on the Zábřeh Crystalline Unit and the belt of high-grade rocks in its southern part. The research is aimed to summarize existing knowledge about this unit, to correlate the Zábřeh Crystalline Unit with adjacent units and to confront various opinions on its position within the Bohemian Massif. The practical part of this thesis shows outputs of the initial phase of my ongoing research. Keywords: Zábřeh Crystalline Unit, Teplá-Barrandian Unit, Saxothuringicum, pre-Variscan tectonic evolution
Analogue and numerical simulations of the geodynamical systems - insights from the models of the Earth collision tectonics and Martian mudflows
Krýza, Ondřej ; Lexa, Ondrej (advisor) ; Čížková, Hana (referee) ; Schöpfer, Martin (referee)
Analogue and numerical modelling in geosciences is an excellent tool for studying complex spatio-temporal relationships in mass and energy transfer. Recent developments and advances in the plate tectonics and planetology require a combination of both approaches to simulate processes that cannot be studied directly in-situ. Advanced physical models are complemented by deformation analysis which is based on image velocimetry and photogrammetry, while numerical simulations utilize both modern and traditional methods to solve corresponding equations in complex domains. This work compiles several models that are focused on deformation analysis associated with material and heat transfer in large accretionary systems. The second subject of the thesis represent the investigation of the formation and propagation of large mudflows in martian atmospheric conditions. In the first part of the work we present a general overview of the problems of analogue and numerical modelling including scaling theory, governing equations, individual methods and history. In the second part of the thesis we deal with laboratory and numerical simulations of collision-indentation tectonics associated with the emergence of large accretionary systems on Earth. The last part of the thesis is devoted to experiments designed for the...
The role of deformation partitioning on the tectonic evolution of the superstructure-infrastructure transition in the Teplá-Barrandian domain
Peřestý, Vít ; Lexa, Ondrej (advisor) ; Konopásek, Jiří (referee) ; Grasemann, Bernhard (referee)
Upper part of the orogenic crust (superstructure) significantly differs from the lower part of the crust (infrastructure) by structural and metamorphic record. This fundamental observation is explained by interruption of the mutual evolution due to mechanical decoupling of the hot and ductile infrastructure from the cold and brittle superstructure at certain stages of the orogenic evolution. The superstructure-infrastructure transition zone is a rheologically predisposed domain of sharp deformation and metamorphic gradients with polyphase structural record. Understanding of the deformation partitioning in such a rheologically complex setting is a key aspect in linking of the individual deformation stages between upper and lower crust. The transition zone between unmetamorphosed early-Variscan superstructure (Teplá-Barrandian Domain) and late Variscan high- grade infrastructure (Saxothuringian Domain) crops out at the western margin of the Teplá- Barrandian Domain in the Bohemian Massif. This area is a continuous mid- to lower-crustal section with early-Variscan structural and metamorphic record, which is superposed onto pre-Variscan episode. This thesis aims to decipher individual deformation events, to evaluate their manifes- tations at different crustal levels and to bring new and unifying...
Paleomagnetic study of Paleozoic rocks from SW Mongolia
Joštová, Daniela ; Lexa, Ondrej (advisor) ; Hrouda, František (referee)
English abstract The aim of this thesis is verification of the theory about evolution of the Mongolian orocline in Permo-Triassic by the paleomagnetic analysis of rocks taken from south-west Mongolia and it is the first step to understand the problematics in bigger detail. Basics of magnetism, geomagnetism, paleomagnetism and geology of the studied part of Mongolia are described in first part of this thesis. Second part is dedicated to methodology and my own research with the thermoremanent magnetizations data. Mongolia is situated between three cratons - Siberia, North China and Tarim and it is part of the Central Asian Orogenic Belt (CAOB), which evolution is not well understood and it is still being studied by a lot of researches. Kröner (2010) says, that the area of Mongolia can be divided to 4 tectonic zones (Lake, Trans-Altai, Gobi-Altai and South Gobi), however Badarch et al. (2002) are dividing the area to 44 terranes, which are separated to two parts - North (Caledonian) and South (Variscan) by the Main Mongolian Lineament. Studied part of the Mongolian area lies eastward from north boarder of China and the samples were taken from three parts - Altay, Edrene and Khovd. Sampling techniques and the whole procedure of analysing the measured data is also mentioned. There is also a comparison of the...
Structural and petrological characterization of Melechov massif host-rock migmatites
Zelinková, Tereza ; Lexa, Ondrej (advisor) ; Faryad, Shah Wali (referee)
English abstract This work deals with the structural and petrological characteristics of migmatites surrounding Melechov massif near Humpolec. The aim was to assess the existence of multiple anatectic events that could be caused by intrusion of late granites. The results are based on fieldwork, petrographic observations in thinsections of the collected rocks, study of major minerals chemistry in both melanosome and the leucosome of selected migmatites and a comparison of bulk chemical analyses of selected samples. Studied migmatites are characterized by SSW-NNE oriented migmatitic vertical banding S2, which is intensively transposed into subhorizontal foliation S3 via folding and solid state deformation. Rocks of all studied sites bears common mineral assamblage (Bt + Crd + Sil + Pl + Kfs + Qtz + Ms + Mag). While overall chemical analysis of selected samples do not vary significantly, the chemistry of biotite and cordierite exhibits a significant increase in xMg a slight decrease in Ti from the first to the third locality. Chemistry of other rock-forming minerals do not vary significantly. These differences correlate well with different modal abundance of magnetite, which reaches up to 3% on the locality TM3. Based on the obtained data it can be stated that the studied rocks form a homogeneous domain of the...
Mechanisms of fracturing and origin of veins on Mokrsko deposit
Švagera, Ondřej ; Lexa, Ondrej (advisor) ; Franěk, Jan (referee)
Locality Mokrsko-west is located inside the Josef mining gallery and belongs to the ore district Psí Hory Mountains, known for its high content of micro-granular gold (~ 100 g/t). It is situated within the apophysis of Sázava tonalite, which is a part of Central Bohemian Plutonic Complex, located southerly from Prague. Besides other structural elements, the whole locality contains the network of sheeted quartz veinlets, which is the aim of this thesis. Data from vectorization and image analysis of the photographic documentation from the gallery and electron microscope has been used. The statistical approach has been used to quantify proportions of mineral phases within the quartz veinlets, their cumulative spacing and fractal distribution. Image analysis confirmed the presence of K-feldspathic metasomatism which affects the plagioclase grains. It forms rims on the edges of the quartz veinlets. The proportional relationship of K-feldspar and quartz within the veinlets wasn't confirmed. It's therefore possible that they were two separate processes of the uncertain time relation. Transfer from the lognormal distribution in histograms of vein spacing in drill-cores to the more normal distribution of the veinlets in the gallery walls was observed. Results from the cumulative spacing analysis confirmed...
Application of multivariate statistical methods for analysis of 2D thermo-mechanical numerical models of diapirism
Krýza, Ondřej ; Lexa, Ondrej (advisor) ; Ježek, Josef (referee)
Application of multivariate statistical methods for analysis of thermomechanical numerical models of diapirism Most of the thermo-mechanical processes, that are associated with the geodynamic evolution of the lithosphere, can be derived from the laws of conservation of mass, momentum and energy in a continuous conception of space. The study of such dynamical systems reveals their strong sensitivity to variation of the initial conditions. For testing the applicability of multivariate statistics in analyzing the influence of the initial conditions, two independent 2D thermo-mechanical multilayer numerical models of crustal diapirism of the Moldanubiam zone were created. The diapirism in central part of Moldanubian zone is characterized by exhumation of HP-HT granulites during the Variscan orogeny (Lexa et al., 2011) which is influenced by density contrast of the middle mafic and lower felsic crust, the ratio of the amount mafic and felsic material, radiogenic heat productivity of the felsic lower crust and shape of the interface of this two layers. The initial setup of this models reflects the situation in future central part of the Bohemian Massif after subduction of the Saxothuringian continental crust and after redistribution of felsic material beneath a base of a lower-crustal area of the...
Structural and Petrophysical Characterisation of Granite Intended for Radioactive Waste Stocking
Staněk, Martin ; Lexa, Ondrej (advisor) ; Žák, Jiří (referee) ; David, Christian (referee)
Structural and petrophysical analysis have been conducted within the Melechov massif with focus on structures controlling the porosity, permeability and thermal conductivity of the rock. The structure of the massif has been constrained based on extensive dataset including AMS and field structural measurements of ductile and brittle structures. Maps and stereograms have been constructed to display the magnetic fabrics and the fracture system of the studied massif. The fracture system of the massif has been described by two principal and two supplementary sets of joints and by faults formed mainly by joint reactivation or less frequently formed as shear fractures. The measured petrophysical data have been used to characterize the effect of fracturing and alteration on pore space geometry and in turn on permeability, thermal conductivity and elastic properties of the studied granite. Distinct petrophysical properties have been identified for pristine granite, for fractured fresh granite as well as for fractured granite altered by Fe-oxide, chlorite and clay minerals. Relations between the measured petrophysical properties have been explained in terms of evolution of the rock pore space. A detailed microstructural study combined with multidirectional P-wave velocity measurements at high confining pressure and...
Numerical simulations of geodynamic processes
Krýza, Ondřej ; Lexa, Ondrej (advisor) ; Ježek, Josef (referee)
ENGLISH ABSTRACT The aim of this work is to provide a basic overview in numerical modeling of geodynamic processes. Therefore, work is divided into two main parts that almost independently describe its main topic. Both parts are designed to allow reader easily locate sources for more detailed and deeper description of the problem. The first part deals with the mathematical and physical apparatus, which is used to describe the geodynamic processes and their formalization due to the application for the construction of mathematical models. This section is mainly based on the description of conservation laws and related equations (continuity equation, Navier-Stokes equations, heat transfer equation) and also gives an overview of relations describing the force interactions in solids and rheology. The second aspect of this work is explanation of the principle of numerical methods (finite differences, finite volumes, finite elements and spectral methods) and their brief overview. In this part, the work is focused on finite differences, a description of which is the main topic of this part. In last chapter of this work, an example of the implementation of finite difference method for modeling of the thermal evolution of fold structures is given. We elaborate simple kinematic and thermal model to simulate time and...

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