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Conditions of dolomitization at selected localities of the Barrandian
Novotný, Petr ; Zachariáš, Jiří (advisor) ; Suchý, Václav (referee)
Research on dolomitic limestones and dolomites from selected localities of the Barrandian, stratigraphically related to the Scyphocrinites Horizon near the Silurian-Devonian boundary, showed the occurrence of two distinct types of dolomite - diagenetic and epigenetic - differing in petrography and genesis. The diagenetic dolomite is quantitatively predominant. It is finely to moderately coarsely grained with crystal size from 20 μm to 450 μm. Crystals of this dolomite form mostly xenotopic and hypidiotopic textures (occasionally even idiotopic). This type of dolomite formed at low temperature and depth by recrystallization of a carbonate mud during early diagenesis, or during subsequent deeper burial. It is also possible that it originated from recrystallization of previously formed syngenetic dolomite. Fine texture of the diagenetic dolomite is a proof of fast dolomitization and of formation of numerous crystallization centers. Very fine-grained variant of dolomite was also detected (forming aphanotopic texture, size of crystals below 0,002 mm). The epigenetic dolomite, also known as baroque or saddle dolomite, is less common than the former one. It forms white, milky-turbid or clear crystals of large dimensions (0.8 - 3.1 mm). The shapes of these crystals are conspicuous, variously twisted,...
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Variscan fluids of the Barrandian Lower Paleozoic: case study from the Žák's quarry at Velká Chuchle
Stárková, Petra ; Zachariáš, Jiří (advisor) ; Slobodník, Marek (referee)
Hydrothermal veins in the Paleozoic of the Barrrandian testify for fluid migration during diagenesis and/or epigenesis. A more detailed mineralogical and geochemical research of these veins has started since the end of the 20th century. The subject of a research included in this thesis is determination of conditions of formation of syntectonic calcite and quartz-calcite veins in the lokality called Žák's quarry in Velká Chuchle. This thesis is based on field determination of succession of hydrothermal veins and laboratory study of fluid inclusions in minerals as a basic tool for determination of temperatures during formation of veins. In total, there were distinguished four types/generations of calcite and quartz-calcite veins in Žák's quarry (from oldest to youngest): 1) veins of ,,beef calcite", 2) veins with flat crystals of smoky quartz located in joints perpendicular to bedding, 3) shear veins with calcite located in the big fold, 4) a big calcite vein with tectonic striae spatially bound to significant local fault. Veins have thickness aproximatelly from 1 mm to about 15 cm. By the way, veins of ,,beef calcite" are characteristic by orientation of prolonged grains of calcite in the direction orthogonal towards to the plane of vein. The microscopic study of fluid inclusions revealed presence of...
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Gold-bearing quartz veins in peripheral parts of the Jílové ore district and their comparison with the orogenic gold type of mineralization
Žitný, Tomáš ; Zachariáš, Jiří (advisor) ; Strnad, Ladislav (referee)
This thesis discusses gold deposit types, reviews historical approaches to their classification, and focuses in more detail on modern classification approaches. A new classification of gold deposits is presented, and the orogenic deposit type is described in detail. All important characteristics and features of this deposit type are presented. The second part of this thesis discusess the geology and mining history of Jílové u Prahy, which historically has been the most important gold-bearing district in the Czech Republic. A number of other, less important gold-bearing areas are located at periphery of this district, but these areas have yet to be geologicaly studied in detail. The Radlík and Zahořany gold-bearing areas are studied in detail in this thesis. Structural measurements in these areas are presented, some of which are from outcrops, while others come from several adits that have been preserved to the present day. Geological maps of parts of some these adits are presented, focusing on those that could be useful for deposit type identification. The thesis goes on to discuss gangue samples, which were studied microscopically, with fluid inclusions in quartz also subjected to study. The final part of the thesis presents a comparison between the orogenic gold deposit type and measured data. However,...
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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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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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Quartz microchemistry as metallogenetic indicator
Pacák, Karel ; Zachariáš, Jiří (advisor) ; Trubač, Jakub (referee)
Region surrounding the Central Bohemian Plutonic Complex represents one of the most important gold bearing zones in the Czech Republic. Several types of gold deposits dominated by hydrothermal quartz gangue were explored here and distinguished: the Intrusion related gold deposits ("Petráčkova hora" and "Mokrsko") and the orogenic gold deposits ("Jílové u Prahy" and "Kasejovice" ). Deposits "Libčice u Nového Knína" and "Roudný u Vlašimi" are partially similar to the orogenic gold type, but are different from other orogenic type deposits in the region. All together 38 samples from these five deposits were analyzed with laser ablation technique (LA- ICP-MS) to produce 228 measurements. Selected samples were selected to represent both main quartz gangue carrying the Au ore and latter weakly mineralized quartz gangue. Samples representing hydrothermal quartz gangue with no direct relation to Au-ore deposits were also collected in order to compare chemical composition of both quartz types originating from the same area. Main concern of this work was in-situ analysis of chemical composition of different generations of quartz gangue and statistical comparison of differences within individual deposits as well as comparing the examined deposits themselves. Total 65 isotopes were measured, trace element...
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Application of the laser ablation ICP-MS in the analysis of gem opals
Čimová, Nikoleta ; Strnad, Ladislav (advisor) ; Zachariáš, Jiří (referee)
15 samples of gem opals were analyzed by laser ablation inductively coupled plasma mass spectrometry (LA ICP-MS) and inductively coupled plasma mass spectrometry (ICP-MS). For this study were selected the most representative samples from Slovakia, Australia, Peru, Ethiopia, Mexico, USA and the Czech Republic. These samples were obtained from private collections. The study focuses on the geochemical relationships between various forms of opal originating from igneous and sedimentary environments based on the results from LA ICP-MS and ICP-MS. The major and trace element compositions are unique for each studied opal locality and important for understanding numerous aspects of opal formation. Major element analysis shows that opals are essentially pure SiO2 (77 - 92 wt. %). Al, Fe, Ca, K, Na and Mg are the main elemental impurities. The concentrations of the trace elements vary strongly depending on the opal locality. Differences were found, e.g., in the concentrations of REE and some refractory elements, which might be indicative for determining the provenance of opals. Many studies have been published explaining the origin of luminescence, microstructures and the thermal properties of opals. However, there are very few comprehensive studies comparing gem opals from the most important historical and...
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Application of portable XRF spectrometer for evaluation of the quality of limestone ore and estimation of reserves at the Mořina - východ (Velká Amerika) deposit
Pechar, Tomáš ; Zachariáš, Jiří (advisor) ; Knesl, Ilja (referee)
The present thesis provides assessment potential of the Mořina - Východ deposit (Velká Amerika) as a raw material reserves for the Kozolupy - Čeřinka deposit. The reason for this work is limited lifetime of the Kozolupy - Čeřinka deposit (approx. 11-14 years) that does not allow fulfilling the requirement to ensure the production of limestone for flue gas desulphurization for ČEZ until 2035. Objective of this work is to summarize all the existing knowledge of the deposit and define the expected technological parameters of raw materials and consider the possibility of its use as a raw material for flue gas desulphurization. Special attention was paid to dolomitization of the limestone, namely to its extent and nature, because elevated Mg content lowers the quality of the limestone ore. Finally, ore reserve calculations and mining intentions are presented. On the basis of microscopic research two types of dolomite were distinguish: diagenetic and epigenetic. Diagenetic dolomite originated at shallow burial together with recrystallization of limestone slurry at temperatures up to 50 řC. Homogenization temperatures of primary fluid inclusions in epigenetic dolomite lay in the range 76-92 řC (sample A9) and 63-88 řC (sample A25).The trapping temperature of these inclusions was probably only slightly...
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Mongolian uranium deposits
Tumurkhuu, Gereltsetseg ; Goliáš, Viktor (advisor) ; Zachariáš, Jiří (referee)
Mongolia is a landlocked country, located in northeast Asia between Russia and China. The country has a total area of 1 565 600 kmš and shares a 4 673 km long border with China on its eastern, western and southern sides and a 3 485 km long border with Russia to the north. The mining sector is the single largest industry of Mongolia, accounting for 55 % of industrial output and more than 40 % of export earnings. Prior to 1970, Mongolia was not able to develop its vast mineral resources due to a lack of infrastructure and lack of financing for mineral resource development. However, beginning in 1970, numerous deposits of copper, gold, fluorspar, uranium, and coal were developed by joint ventures formed in partnership with the Soviet Union and its allies. Increased nuclear electricity generation in Asia presents uranium suppliers such as Mongolia with an opportunity to develop its uranium and nuclear industry. This Bachelor thesis "Mongolian uranium deposits" deals with the geology and mineralogy of uranium deposits in Mongolia. It shows a current capacity of uranium reserves and possible resources and also inquiries into the future.
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Genesis of Au-Sb ores at the Krásná Hora deposit
Němec, Matěj ; Zachariáš, Jiří (advisor) ; Dobeš, Petr (referee)
Ore deposits of the Krásná Hora ore district are the main representative of the Sb-Au mineralization in the Czech Republic. It can be classified genetically as epizonal subtype of orogenic gold deposits. Spatially and partly temporally are associated with the intrusion of the Central Bohemian Pluton. The ore bodies are related to quartz veins that follow the course of E-W striking lamprophyre dykes, which are usually heavily crushed and altered. Ore shoots with massive stibnite are located mainly at the intersections of these E-W trending veins with the NW-SE striking tectonic fault zones. Au-Sb ores at Krásná Hora ore district formed in an area of repeatedly activated fault zones. Three generations of hydrothermal quartz were identified on microscopic scale. Earliest quartz (Qtz1), which was considered in the literature auriferous originated from low-salinity H2O - CO2 fluids at ~350 řC and at a depth of about 5 km. The younger quartz (Qtz2) originated at lower temperatures of about 260 řC and lower depth of about 3-4 km from low/saline aqueous fluids. Both older (Qtz1) and younger quartz (Qtz2) are not auriferous. The gold is associated with younger paragenetic formation (Anti + Au + Cc + Qtz3) that fills in intergranular spaces and fractures in Qtz1 and Qtz2 . Due to the partial exhumation of the...
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