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Volcanic rocks and possibilities of their research using geophysical methods
Votrubcová, Kristýna ; Valenta, Jan (advisor) ; Vlček, Josef (referee)
5 Abstrakt (EN) The research focuses on the application of geophysical methods and subsequent data processing for the prospecting of igneous rocks and the search for volcanic structures. The literature review summarizes the physical and petrological foundations of various physical methods that can be utilized in the search for volcanic rocks, and discusses their most appropriate uses. The greatest emphasis is placed on the method of magnetometry, which is significant in identifying volcanoes. The work also explores the use of geoelectrical and seismic methods, radiometry, and gravimetry. In the practical section, geophysical measurements were conducted in the field to map the extent of the Tertiary volcano and other geological structures in the Elbe Sandstone Mountains. The extent of the volcanic body was successfully mapped using magnetic measurements. The results of the measured Electrical Resistivity Tomography (ERT) profile corresponded to the extent of the volcanite body and showed that the body was significantly fractured. Other findings include the mapping of a fault zone, to which the volcanic body ascend could be linked, and the mapping of another fault zone in a nearby valley, which is assumed to have a fault character. Key words: igneous rocks, volcanism, geophysics, magnetometry, VLF, ERT
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Variscan subduction-related plutonism in the French Massif Central
Usmanova, Diana ; Janoušek, Vojtěch (advisor) ; Špillar, Václav (referee)
The French Massif Central belongs to the Moldanubian Zone, which is an internal part of the Variscan Orogen. The Massif was formed during six tectonic-metamorphic events and has a nappe structure. The Muscovite-bearing Peraluminous Granitoids (MPG), Cordierite-bearing Peraluminous Granitoids (CPG), K-rich Calc-alkaline Granitoids (KCG), and Amphibole-bearing Calc-alkaline Granitoids (ACG) types of granitoids were intruded into the nappe units during the Carboniferous. The formation of FMC granitoid plutons was predominantly linked to continental collision; only the ACG plutonites are older, typical of magmatic arcs. These amphibole-bearing calc-alkaline quartz diorites to tonalites are common in the western French Massif Central (Limousin region), where a 250 km long belt known as the "Limousin tonalite belt" is found. Its linear shape and characteristic geochemical composition suggest a subduction-related origin. Newly obtained geochemical data from the Limousin region indicate an intermediate composition (52-57 wt% SiO2), a metaluminous, subalkaline character, and place the samples in the calc-alkaline series. Furthermore, enrichment of Large Ion Lithophile Elements (LILE), depletion of High Field Strength Elements (HFSE), negative europium anomaly (Eu/Eu* = 0,63-0,92) and relatively low initial...
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Substitution trends in apatites of Cenozoic igneous rocks of the Czech Republic
Mészárosová, Noemi ; Skála, Roman (advisor) ; Ulrych, Jaromír (referee)
This bachelor thesis is focused on studying crystal chemistry of apatites of the Cenozoic igneous rocks of the Czech Republic. The main goal of this thesis is to determine the substitution trends in 23 samples of apatites from selected volcanic rocks of České středohoří Mts., Doupovské hory Mts. and the Labe Tectono-volcanic Zone. It was found that contents of REE (Ce, La, Bd, Sm, as well as Y) and Si correlate mutually. In addition to that this group of elements displays the inverse correlation with Ca and P. These observations confirm the coupled substitution of REE, Y and Si. The second part deals with refinement of crystal structures of studied apatites. The crystal structure of selected samples was refined by Rietveld method. All samples displayed different peak shapes for 00l reflections compared to other reflections. It can be assumed that the change of the shape parameters was caused by different size of crystallites in this direction. During the refinement it was found that the samples A7 and A10 contain two different apatites displaying very similar crystal lattice parameters. In the sample A7 this fact is caused by chemical zoning, in particular, by different concentrations of Ce and La.
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Substitution trends in apatites of Cenozoic igneous rocks of the Czech Republic
Mészárosová, Noemi ; Skála, Roman (advisor) ; Ulrych, Jaromír (referee)
This bachelor thesis is focused on studying crystal chemistry of apatites of the Cenozoic igneous rocks of the Czech Republic. The main goal of this thesis is to determine the substitution trends in 23 samples of apatites from selected volcanic rocks of České středohoří Mts., Doupovské hory Mts. and the Labe Tectono-volcanic Zone. It was found that contents of REE (Ce, La, Bd, Sm, as well as Y) and Si correlate mutually. In addition to that this group of elements displays the inverse correlation with Ca and P. These observations confirm the coupled substitution of REE, Y and Si. The second part deals with refinement of crystal structures of studied apatites. The crystal structure of selected samples was refined by Rietveld method. All samples displayed different peak shapes for 00l reflections compared to other reflections. It can be assumed that the change of the shape parameters was caused by different size of crystallites in this direction. During the refinement it was found that the samples A7 and A10 contain two different apatites displaying very similar crystal lattice parameters. In the sample A7 this fact is caused by chemical zoning, in particular, by different concentrations of Ce and La.
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