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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...
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Mechanisms of granite fracturing and their implications for origin of gold-bearing veins in Mokrsko deposit
Švagera, Ondřej ; Lexa, Ondrej (advisor) ; Franěk, Jan (referee)
The stress concept in geology is widely used for analysis and description of tectonic events. These can be documented directly in the field or by interperetation of results gained by laboratory analysis. The expressions of brittle tectonics and geological events linked with them are often important clues leading to understanding processes giving unique forms to many localities. The origin of gold-bearing veins in Mokrsko deposit is result of long-lasting tectonic processes. During these were created at least 4 generations of brittle structures. The proximity of Variscides is the source of this brittle fracturing. Sázava pluton intruded during the syn- orogenic phase and in the Slapy apophysis of Sázava pluton started the circulation of fluids because of the contact metamorphism. These fluids were using pre-existing EW joint systems. After that, the precipitation of minerals rich in Bi-Te-Cu gave origin to the local gold-bearing mineralization. This mineralisation is partly bound to the quartz-veins localized on Mokrsko- Západ. Their thickness is often in sub-milimeter scale with very regular spacing.
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Chemistry of hydrothermal quartz from the Mokrsko-West gold deposit determined by the LA-ICP-MS method
Štrba, Martin ; Zachariáš, Jiří (advisor) ; Trubač, Jakub (referee)
The Mokrsko-West deposit, situated about 20 km south from Prague, is one of the most important gold deposits in the Bohemian Massif. We can find hydrothermal quartz veins in two types of host rocks: tonalite in the Central Bohemian Plutonic Complex (CBPC) and amphibolite in the Jílové Belt (JB). A several generations of the quartz veins with different mineralization were found in the deposit. This study has several objectives. At first, it determines and compares the chemistry of quartz samples from different generations of hydrothermal veins. In addition, this work describes the distribution of the most important trace elements. Lastly, the work compares the potential differences in the chemistry of samples from the different host rocks (CBPC and JB). With the use of the LA-ICP-MS, 16 quartz samples from the Mokrsko-West deposit were analysed. Finally, 101 analyses were realized. From the analysed trace elements, the most important were Li, Mg, Al, Ca, Fe, Cu, Zn, As, Sb and Pb. Aluminium affects the concentration of the most of analysed trace elements. Positive correlation between Al and the other metals was also found. The samples with high Al content also showed high concentrations of other metals (Fe, Cu, Zn, Pb) and As. Samples with lower Al content showed lower concentration of other metal...
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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...
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Mechanisms of granite fracturing and their implications for origin of gold-bearing veins in Mokrsko deposit
Švagera, Ondřej ; Lexa, Ondrej (advisor) ; Franěk, Jan (referee)
The stress concept in geology is widely used for analysis and description of tectonic events. These can be documented directly in the field or by interperetation of results gained by laboratory analysis. The expressions of brittle tectonics and geological events linked with them are often important clues leading to understanding processes giving unique forms to many localities. The origin of gold-bearing veins in Mokrsko deposit is result of long-lasting tectonic processes. During these were created at least 4 generations of brittle structures. The proximity of Variscides is the source of this brittle fracturing. Sázava pluton intruded during the syn- orogenic phase and in the Slapy apophysis of Sázava pluton started the circulation of fluids because of the contact metamorphism. These fluids were using pre-existing EW joint systems. After that, the precipitation of minerals rich in Bi-Te-Cu gave origin to the local gold-bearing mineralization. This mineralisation is partly bound to the quartz-veins localized on Mokrsko- Západ. Their thickness is often in sub-milimeter scale with very regular spacing.
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