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Historical cinnabar deposits in Bohemia - genetic study.
Velebil, Dalibor ; Ackerman, Lukáš (referee) ; Zachariáš, Jiří (advisor)
The study of fluid inclusions proved the metamorphic origin of the cinnabar-pyrite mineralization at the deposit of Horní Luby. In addition, thermal conditions of the mineralization formation were determined. During the deposit forming processes, the primary homogenous H2O-CO2 fluid of the temperature of about 300řC was differentiated to fractions rich in H2O or CO2. The differentiation took place in several stages in the temperature range between 200 to 150řC. Quartz crystallized from the parent fluid at the temperature about 300řC, pyrite at temperatures in the range of 220řC to 210řC and cinnabar at temperatures in the range of 195řC to 160řC. The cinnabar is thus the youngest mineral at the deposit (crystallization succession. quartz - pyrite - cinnabar). At the deposit of Jedová hora, quartz crystallized at the temperature of about 160řC to 150řC, barite at temperature of about 115řC (the fluid boiling point) and cinnabar in the range between these temperatures. The origin of mercury at all Czech historical deposit of cinnabar can be very likely related to Lower Paleozoic submarine volcanism. In all cases, the pre-concentrated mercury was remobilized during the Variscian metamorphosis, followed by precipitation in form of veins with cinnabar or as cinnabar impregnation. Study of tetrahedrite...
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Fluid inclusions in gold-bearing quartz gangue from Padrť and Sobětice localities
Hemalová, Kateřina ; Dobeš, Petr (referee) ; Zachariáš, Jiří (advisor)
Quartz veins with molybdenite and gold from the locality Padrť crosscut metamorphosed Cambrian and Ordovician sediments (quartzite, arcose, cherts) of the Barrandien unit in southwest part of Central Brdy Mts.. Based on fluid inclusion microthermometry we distinguish three main generations of the quartz gangue: Q1 - the oldest quartz, that forms the main portion of gangue; Q2 - xenomorphic crystals growing on Q1, subdivided into Q2a (dark nuclei of crystals with a quantity of primary fluid inclusions) and Q2b (pellucid crystals crystallized to vugs) overgrowing Q2a; Q3 - the youngest quartz (with calcedony-like texture) that overgrowths Q2b crystals. The first generation of quartz (Q1) precipitated from low salinity (~5 wt. % eq. NaCl) aqueous-carbonic fluid with minor methane/nitrogen admixture (~ 5 mol. %). Estimated PT conditions of Q1 formation are >350 řC and ~ 400-500 MPa (depth about 15 km under lithostatic pressure). Formation of quartz Q2 and Q3 is associated with aqueous fluids. Q2 precipitated from low salinity (< 5,9 wt. % eq. NaCl) fluid at 250 to 320 řC and 60 to 120 MPa (depth about 3 - 5 km under hydrostatic pressure). Younger subgeneration Q2b contains quantity of fluid iinclusions with signs of boiling and with wide range of salinity 1,2 to 7 wt. % eq. NaCl. The Q3 was formed from even...
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Isotope composition of fluids extracted from fluid inclusions
Drahota, Jakub ; Žák, Karel (referee) ; Zachariáš, Jiří (advisor)
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.
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