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Genesis of the eruptive center of rhyolite ignimbrites, the Křivoklát-Rokycany volcanic complex
Ptáček, Jakub ; Tomek, Filip (advisor) ; Verner, Kryštof (referee)
English abstract This bachelor's thesis focuses on the tectonic and volcanological characteristics of the Křivoklát-Rokycany volcanic complex in the Teplá-Barrandian unit. The literature research part emphasizes the broader geological context, where I describe the Neoproterozoic, Cambrian, and lower Ordovician geotectonic development of the Teplá-Barrandian unit within the Avalonian-Cadomian orogenic belt. In the Křivoklát-Rokycany volcanic complex, I focus in detail on the relatively youngest part, which consists of the entire spectrum of facies of rhyolite composition and includes coherent lavas, tuffs, ignimbrites, and dike equivalents. The field research of the practical part of the bachelor's thesis took place in a satellite body of porphyritic rhyolite in the Těškov quarry, about 10 km northeast of Rokycany. The aim of the detailed geological mapping of the investigated quarry was the petrographic description of four distinct rhyolite facies, mapping of their spatial distribution, and possible determination of the eruptive center. Other research methods included analyzes of in-situ magnetic susceptibility and size distribution of rhyolite breccia clasts. The result of the work is a three- dimensional model of the quarry with detailed distribution of rhyolite facies. From the obtained data, I assume...
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An overview of explosive volcanism on Venus
Baranová, Anna ; Brož, Petr (advisor) ; Tomek, Filip (referee)
An Overview of Explosive Volcanism on Venus - Abstract In this thesis, I aim to provide an overview of explosive volcanism on Venus. The existence of explosive volcanism on Venus is uncertain. Despite unfavorable conditions of high atmospheric density and pressure that hinder explosive volcanic activity, as well as a planetary interior thought to be poor in volatiles that would enable fragmentation, evidence of in the form of putative surface expressions of explosive volcanism on Venus has been proposed - a putative pyroclastic flow deposit, Scathach Fluctus, and a series of locations of radar bright material, interpreted as the deposits of explosive volcanic activity. Numerical modeling of fragmentation and volcanic plume rise has shown that explosive volcanism would only be possible under very specific conditions of vent geometry and location, and magma volatile contents. While H₂O is likely acts as the main volatile on Venus, CO₂ and SO₂ are likely represented in higher percentages in the volatile fraction than on Earth, and hence can lower the required amounts of H₂O to values reasonable under Venusian conditions. If explosive volcanism does occur, it is constrained by the high pressure on the Venusian surface and is believed to exist in the form of pyroclastic density currents, rather than...
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Reconstruction of the geological evolution of the Southern Main Ethiopian Rift
Dvořák, Štěpán ; Verner, Kryštof (advisor) ; Tomek, Filip (referee)
The Main Ethiopian Rift represents a unique insight into process of continental rifting and its comprehensive research can provide partial clarification of open questions such are the causes, mechanisms, and timing of overall tectonic and magmatic evolution. The Main Ethiopian Rift is an intermediary between the Afar triple junction to the north and Kenyan Rift to the south, representing incipient plate boundary between Nubian and Somalian plates. Based on comprehensive geological research of the northern flank of the Southern Main Ethiopian Rift including field geological and structural mapping, petrological and geochemical description of individual lithologies, morphotectonic analysis of Digital Elevation Model, paleostress analysis and gravity pattern assessment including calculation of Linsser indices, some aspects in geodynamic evolution of northern flank of the Southern Main Ethiopian Rift is interpreted. The area recorded typical continental rift-related tectonic and magmatic evolution including "pre-rift" (Eocene to Oligocene) volcanic activity initiated by extensive flood (plateau) alkaline basalt to trachybasalt basalt eruptions due to crustal thinning and mantle plume(s) ascent, followed by fault-dominated "early-rift" (Miocene) bimodal volcanism associated with origin of the rift...
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Magnetic fabric, magma flow and tectonic deformation in volcano-plutonic systems
Tomek, Filip ; Žák, Jiří (advisor) ; Lexa, Jaroslav (referee) ; Petronis, Michael (referee)
Magnetic fabric, magma flow and tectonic deformation in volcano-plutonic systems ABSTRACT This Ph.D. thesis aims to investigate dynamics of emplacement and tectonic history of selected volcano-plutonic complexes in a continental magmatic arc and back arc setting. The thesis presents new data sets from five field areas, presented in separate chapters, which could be viewed as representing a vertical sections through upper part of an intermediate to felsic magmatic system. From top to bottom in this ‛imaginary' vertical system, the examined units are: (1) andesitic lava domes and (2) sub-volcanic magma chambers (<3 km deep) of the Miocene Štiavnica volcano- plutonic complex, Western Carpathians (Slovakia), (3) Shellenbarger pluton (<3 km depth) within the mid-Cretaceous Minarets caldera, Sierra Nevada batholith in California (USA), and ~7-10 km deep granitoids of (4) Lower-Cretaceous Wallowa batholith, Blue Mountains province in Oregon (USA) and (5) Late Devonian Staré Sedlo complex, central Bohemian Massif (Czech Republic). The research incorporates extensive field and structural data, supported by analysis of igneous textures and anisotropy of magnetic susceptibility (AMS). The latter is further accompanied by detailed examination of magnetic mineralogy using thermomagnetic measurements and optical and back...
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The Late Devonian to early Carboniferous kinematic evolution of the Teplá-Barrandian/Moldanubian boundary
Tomek, Filip ; Žák, Jiří (advisor) ; Babuška, Vladislav (referee)
ENGLISH ABSTRACT The Late Devonian to Early Carboniferous kinematic evolution of the Teplá-Barrandian/Moldanubian boundary The Staré Sedlo complex (SSC) is a relic of meta-igneous arc-related pluton in the southern part of the Sedlčany-Krásná Hora roof pendant, intruded by granitoids of the Central Bohemian Plutonic Complex along the boundary of Teplá-Barrandian (TBU) and Moldanubian units (MU), Bohemian Massif. The SSC mainly comprises deformed orthogneisses of calc-alkaline granodiorite to tonalite protoliths of Late Devonian age (380−365 Ma; Košler et al., 1993) that were commonly mingled with minor basic magmas. Locally preserved subhorizontal intrusive contacts of the orthogneisses against their meta-sedimentary host rock indicate that these magmas intruded as a sill complex. The SSC preserves a rather unusual flat-lying subsolidus foliation (dip <40ř) associated with subhorizontal ~NE-SW-trending mineral lineation. Mesoscopic structures, anisotropy of magnetic susceptibility (AMS), and deformational microstructures indicate prolate shape of the strain ellipsoid with dominant coaxial pure shear regime. The solid state microstructures record cooling of the orthogneiss protolith down to the ambient greenschist facies conditions followed by its static recrystallization due to the intrusion of the younger...
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From deposition to caldera resurgence: pyroclastic density current dynamics as revealed by magnetic anisotropy of the Teplice rhyolite, Bohemian Massif
Vitouš, Petr ; Tomek, Filip (advisor) ; Mlčoch, Bedřich (referee)
Better understanding of pyroclastic density current (PDC) dynamics is one of the key volcanological focuses, as PDCs represent one of the most life-threatening volcanic hazards. PDCs associated with explosive collapse calderas are difficult to observe and examine directly, and thus research of internal architecture of calderas and their PDC deposits is focused on extinct and partly eroded volcano-plutonic systems. Such a case is the Late-Carboniferous Altenberg-Teplice caldera in NW Bohemian Massif, which exposes a large body of ignimbrites (deposits of the PDC) called Teplice rhyolite (an intra-caldera fill). This body is well exposed on the southern flank of the Krušné hory/Erzgebirge Mts., mainly its members: Teichweg, Lugstein-Pramenáč, Vlčí kámen-Medvědí vrch and Přední Cínovec. As these ignimbrites appear macroscopically isotropic, I employed the Anisotropy of magnetic susceptibility (AMS) in order to quantify their internal structure. A total of 1232 specimens from 63 sampling stations were analyzed for the AMS, complemented by susceptibility vs. temperature variations and petrographic observations. Obtained AMS data, carried by a mixture of paramagnetic ferrosilicates and low-Ti titanomagnetite, indicate various processes recorded in ignimbrites. The relatively oldest and moderately welded Teichweg...
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From deposition to caldera resurgence: pyroclastic density current dynamics as revealed by magnetic anisotropy of the Teplice rhyolite, Bohemian Massif
Vitouš, Petr ; Tomek, Filip (advisor) ; Mlčoch, Bedřich (referee)
Better understanding of pyroclastic density current (PDC) dynamics is one of the key volcanological focuses, as PDCs represent one of the most life-threatening volcanic hazards. PDCs associated with explosive collapse calderas are difficult to observe and examine directly, and thus research of internal architecture of calderas and their PDC deposits is focused on extinct and partly eroded volcano-plutonic systems. Such a case is the Late-Carboniferous Altenberg-Teplice caldera in NW Bohemian Massif, which exposes a large body of ignimbrites (deposits of the PDC) called Teplice rhyolite (an intra-caldera fill). This body is well exposed on the southern flank of the Krušné hory/Erzgebirge Mts., mainly its members: Teichweg, Lugstein-Pramenáč, Vlčí kámen-Medvědí vrch and Přední Cínovec. As these ignimbrites appear macroscopically isotropic, I employed the Anisotropy of magnetic susceptibility (AMS) in order to quantify their internal structure. A total of 1232 specimens from 63 sampling stations were analyzed for the AMS, complemented by susceptibility vs. temperature variations and petrographic observations. Obtained AMS data, carried by a mixture of paramagnetic ferrosilicates and low-Ti titanomagnetite, indicate various processes recorded in ignimbrites. The relatively oldest and moderately welded Teichweg...
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Scoria cones on the Moon: morphologies, distribution, and mechanism of their formation
Novotný, Radek ; Brož, Petr (advisor) ; Tomek, Filip (referee)
The recent observations of the Moon show, that there was long-lasting volcanic activity on the lunar surface, that left many volcanic features behind. These features are in the form of lunar seas, which are covering thousands of kilometers wide impact basins, or small volcanic bodies of various shapes. Some of these bodies are relatively small, up to 170 meters high conical bodies occurring on the near side and far side of the Moon. Based on research about the Marius Hills and South Pole-Aitken locations, it was suggested, that these bodies could be a lunar equivalent of terrestrial cinder cones. Cinder cones are created by degassing and fragmentation of magma with subsequent deposition of pyroclastic material into the surroundings. This shape similarity of the lunar cones to the terrestrial cones is surprising, as there is less gravitational acceleration on the Moon's surface and the atmosphere is missing. This means, that particles are able to flow further, and this should also affect the appearance of the volcanic bodies. The aim of this work is to review available literature mentioning lunar cones, to map their frequencies on the surface of the Moon, to determine their basic shapes and explain possible differences or concordances in their shapes with terrestrial cinder cones. On the basis of the...
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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...
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