|
|
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...
|
|
| |
|
|
Sulphidic mineralization in the vicinity of the Bílina fault
Markes, Jan ; Zachariáš, Jiří (advisor) ; Goliáš, Viktor (referee)
The neoidic sulphide mineralization located in tertiary sediments of Lom Bílina in Bílina's fault is of hydrothermal origin. The sulphidic mineralization is associated with fault systems of Eger rift and temperature of fluid crystallization was about 50řC. The mineralization of Bílina's fault is rather monotonous, the marcasite and pyrite is mostly found without a trace elements. In the crystals were also registered zones with the contents of trace elements, especially As and Ni. The contents of As enriched precipitation zones were fluctuating from 0,2 to 5,4 wt. %, Ni enriched zones were ranged from 1,6 to 5,9 wt. %. The precipitation zones with increased As and Ni content were very thin, there were very short time intervals of As and Ni enriched fluids precipitation. In the marcasite crystals were also found the porous zones of clay mineral microinclusions. These zones showed higher content of Al and Si. There is high abundance of Fe-disulfides at Bílina's fault-dispersed in coal bed, or bonded to tectonic zone of the Bílina's fault. Pyrite and marcasite are dispersed in the coal bed and genetially aren't related to sulphides bonded to Bílina's fault.
|
|
|
SIlver binding at the polymetallic deposits of Blanice furrow and comparison with similar deposits in the world
Kuchyňová, Markéta ; Zachariáš, Jiří (advisor) ; Goliáš, Viktor (referee)
Blanice Furrow is about 200 km long fault system which extends from Český Brod to basin of Danube in Austria. Ore mineralization is tied to rupture structure of Blanice Furrow. Predominant polymetallic Ag-Pb-Zn±Cu mineralization occurs along entire length of Blanice Furrow. Other important type of mineralization is gold mineralization (Roudný deposit, Dobrá Voda deposit) and uranium mineralization (Okrouhlá Radouň deposit). Historical medieval silver mining districts are Stříbrná Skalice-Střímělice, Ratibořické Hory-Stará Vožice and Rudolfov. This paper describes geology and mineralogy of silver- deposit in Blanice Furrow and comparisom of Blanice Furrow with different types of hydrothermal Ag- deposits such as Ag-Ni-Co-Bi-As deposit or Mississippi Valley type. In Blanice furrow the silver isn't bound to galena and sphalerite as we would expect, but to Ag-tetrahedrite and other silver-bearing minerals. Silver from tetrahedrite is a product of retrograde exchange reaction, which was in progress during cooling in solid state . Ag-values of tetrahedrite and Ag-Sb-S phases can be used it as mineral thermometer. Mineral thermometer can help us to define temperature durinng formation of mineralization, in case of Blanice Furrow the temperature is defined between 200 and 300 řC. Powered by TCPDF (www.tcpdf.org)
|
|
|
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...
|
|
|
Mineralogical and geochemical characteristics of selected hydrothermal mineralizations in the Blanice Furrow
Stehlík, Jan ; Zachariáš, Jiří (advisor) ; Hurai, Vratislav (referee)
Blanice furrow is about 180 km long NNE-SSW trending fault system which extends from Český Brod through České Budějovice to Linz in Austria. Numerous small sized silver bearing Ag-Zn- Pb±Cu deposits and two late-orogenic gold deposits (electrum) are hosted in this tectonic zone. The most important silver-bearing ore regions are Stříbrná Skalice -Střímělice, Ratibořské Hory - Stará Vožice and Rudolfov which were mined in the Middle Ages. The most important gold- bearing deposit is Roudný which was mined in the period 1985-1930. In this thesis, mineralogical characteristics of ore and isotopic composition of carbonates were studied. Galena and sphalerite does not contain silver which has been found in Ag-rich fahlore and other Ag-minerals. δ18 O values of carbonates are 11 - 23 ‰ SMOW and δ13 C values are -8 to -17 ‰ PDB. These isotopoe charakteristics indicates deep methamorphic origin of hydrothermal fluid. Significant variations in δ13 C value suggests more than one source of carbon which is probably of deep crustal origin mixed with carbon of organic origin hosted in moldanubian crystalline units. Isotope fractionation equations have been used to determine the temperatures of carbonate crystallization which are about 100 - 300řC and quite well corresponds to homogenization temperatures of fluid...
|
|
|
Fluid inclusions in gold-bearing quartz gangue from Padrť and Sobětice localities
Hemalová, Kateřina ; Zachariáš, Jiří (advisor) ; Dobeš, Petr (referee)
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...
|
|
| |
|
|
Correlation of tectonic evolution of the Blanice Graben and of late Variscan hydrothermal processes
Hübst, Zdeněk ; Zachariáš, Jiří (advisor) ; Pertold, Zdeněk (referee)
The Blanice graben represents about 200 km long N-S trending tectonic zone with minimal sinistral movement of about 17 km. Large number of hydrothermal ore deposits (eg. the Roudný gold deposit; or numerous small-sized deposits/districts of Ag-Pb-Zn ores - Stará Vožice - Ratibořské Hory or Rudolfov near České Budějovice). This thesis is focused on the northern and central part of the Blanice graben in between the villages Vlašim, Mladá Vožice and Chýnov. Much of the work is focused on the reconstruction of the structural evolution of the Roudný gold deposit. The thesis is aimed in the study of brittle deformation, namely in the study hydrothermal veins, intrusive dikes and in paleostress analysis of fault-slip data. In addition to field data, structural data were also excerpted from unpublished historical documents (reports, maps, underground documentation). At least two phases of brittle deformation were discriminated in the study area. Older phase corresponds to E-W to NW-SE oriented compression. The younger phase represents extension in the E-W to NE-SW direction. During the older phase, the oldest types of quartz veins (Q0 to Q2) formed at the Roudný gold deposit, while type Q3 veins at the same deposit formed during the younger phase. The younger tectonic phase also allowed formation of hydrothermal...
|
|
| |
guest ::
RSS feed.