|
| |
|
| |
|
|
Fluid inclusion study of pegmatites from Skalsko near Jílové and Dolní Bory
Fenclová, Kateřina ; Zachariáš, Jiří (advisor) ; Ackerman, Lukáš (referee)
Fluid inclusions of pegmatites from two localities in the Moldanubina Zone were studied in order to constrain P-T conditions of their crystallization and enstablish composition and properties of fluids associated with pegmatite formation. The first locality Skalsko (near Jílové u Prahy) is located within the Central Bohemian Plutonic Complex (CBPC) of Variscian age.Pegmatitic dykes represent the late stage of magmatic evolution of the CBPC. Pegmatite is hosted by biotite-granodiorite of the "Požáry" and "Sázava" types and probably belongs to the muscovite class of the pegmatites. The other locality, Dolní Bory, is located within the Bory granullite Massif ( metamorphism is dated to about 340 Ma). Following types of pegmatite occur in this district: 1. barren to less evolved pegmatites; 2. more evolved phosphate-bearing pegmatites and 3. Li-complex, the most evolved pegmatites. The studied material comes from an andalusite-diaspore nodule hosted by blocky quartz of the barren pegmatite (pegmatite dike No. 3). Fluid inclusions were studied mostly in quartz (Skalsko, Dolní Bory), andalusite and diaspore (Dolní Bory). Fluids trapped in samples from Skalsko correspond to H2O-CO2 and H2O types. The H2O-CO2 fluid had relatively low salinity (4,1-5,9 wt.% NaCleq), contained from 20 to 5 mol.% CO2 and its...
|
|
| |
|
|
Origin and evolution of silcretes
Kohoutová, Iveta ; Zachariáš, Jiří (advisor) ; Adamovič, Jiří (referee)
Summary: Silcretes are rocks with high content of SiO2 (usually more than 90 wt. %) formed by mobilization of SiO2 during weathering processes. Silcretes formed near the Earth's surface by soil weathering in warm and humid climate are termed as pedogenic silcretes. Another type of silcrete is groundwater silcrete, whose origin is usually associated with the groundwater table and depths of 5-50 m below the surface and arid to semi-arid climate. The third type of silcretes is associated with evaporites. Its genesis is complicated; as well it is difficult to date this silicification. There are four types of silcrete textures: GS-, F-, M-, C- textures; the most common is the F-texture. In the Czech Republic silcretes are more known under the term "sluňáky" or "quartzite". Indeed, in every country where they occur, have their own specific name. Silcretes are essentially composed of SiO2, minor constituents represent heavy minerals and/or feldspar. Cement is mostly α-quartz, chalcedony and opal. Average thickness of silcretes is 1-3 m, rarely 5 meters. Main source of SiO2 is chemical weathering of silicate minerals or quartz dust grains carried by wind and deposited on natural barriers, like blades of grass. There are two models of silcrete formation: lateral and vertical transport model SiO2. Sedimentary...
|
|
| |
|
|
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...
|
|
| |
|
|
Isotope composition of fluids extracted from fluid inclusions
Drahota, Jakub ; Zachariáš, Jiří (advisor) ; Žák, Karel (referee)
Gold-bearing mineralizations and gold deposits in the Bohemian Massif are restricted mainly to Central Bohemian metallogenic zone. In this thesis, the quartz gangue from Mokrsko, Kašperské hory, Jílové u Prahy and Kasejovice deposits was studied, which originated from H2O-CO2±CH4±N2 fluids at temperatures from about 500 to about 300 řC. Quartz was mechanically and chemically purified and CO2 for subsequent isotopic analysis of carbon, was cryogenic separated in a vacuum line for thermal decrepitation of fluid inclusions. Measured value of δ13 C-CO2 varies from -15,7 to -6,5 ‰ PDB. The spread of δ13 C-CO2 data excludes single source of carbon. Up to two different carbon sources can be demonstrated for most of the studied localities. The most likely source appears to be carbon of homogenized upper crust, and organic carbon mobilized during metamorphic processes.
|
|
| |
guest ::
