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Genetic relationships between intrusions of porphyry dykes and formation of Au ores at Petrov and Bohuliby
Petrov, Ivan ; Zachariáš, Jiří (advisor) ; Slobodník, Marek (referee)
This master's thesis is focused on genetic relationships between Au-bearing ores and associated granodiorite porphyry dykes in Petrov and Bohuliby area in southwestern part of the Jílové ore district. Subvolcanic rocks with hydrothermally induced alteration and Au/bearing mineralization were characterized by petrography, mineralogy and crystallochemistry. Mutual genetic and textural relationships of studied materials were examined as well and were validated by biotite, arsenopyrite and chlorite empirical geothermometry. First identified generation of sulfide mineralization was formed at 360řC and consist of arsenopyrite, galenite and native gold. At circa 274řC porphyry mineral association was chloritized, and chlorite gangue crystallized. Second generation of sulfide mineralization precipitated at 264řC. Anomalous absence of Bi-Te-S phases and scheelite in hydrothermal paragenesis is important indicator of contrasting conditions of mineralization at the studied areas and main zone of the Jílové ore deposit. Based on acquired data, granodiorite porphyry dikes were categorized to two separate genetic types, which have mutual origin in deep magma chamber of Central Bohemian Plutonic Complex but intruded non-contemporaneously.
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Assembly of the Saxothuringian orogenic wedge: the Variscan P-T-t record of the metasediments of Erzgebirge, Bohemian Massif
Jouvent, Marine ; Lexa, Ondrej (advisor) ; Tichomirowa, Marion (referee) ; Pitra, Pavel (referee)
The formation of collisional orogenic wedges involves complex polyphase deformation and metamorphism. This study reveals the tectonic evolution, internal architecture and the timing of the Variscan orogenic wedge evolution in the Saxothuringian Domain (Bohemian Massif). The studied area is the Erzgebirge Crystalline Complex, characterized by numerous occurrences of the (U)HP rocks. In contrast, the surrounding metasediments have been scarcely studied, although they provide an important link between deep subduction and mid-crustal processes. Using field structural geology, petrology, thermodynamic modelling and geochronology (monazite U-Pb and mica 40 Ar/39 Ar dating), we constrained the P-T conditions and timing of four deformation events (D1-D4) identified by structural analysis. Several transects from the low-grade hanging wall phyllites to the footwall medium-grade micaschists have been investigated. The first M1-D1 event is characterized by HP-LT minerals (garnet, chloritoid, phengite, paragonite, and rutile) defining the S1 foliation with an M1 peak pressure conditions increasing from 13 kbar and 520řC in phyllites to 25 kbar and 560řC in micaschists. The corresponding geothermal gradient of 6-11řC/km is typical for subduction environments. The M2-D2 event corresponds to the deformation and...
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Genetic relationships between intrusions of porphyry dykes and formation of Au ores at Petrov and Bohuliby
Petrov, Ivan ; Zachariáš, Jiří (advisor) ; Slobodník, Marek (referee)
This master's thesis is focused on genetic relationships between Au-bearing ores and associated granodiorite porphyry dykes in Petrov and Bohuliby area in southwestern part of the Jílové ore district. Subvolcanic rocks with hydrothermally induced alteration and Au/bearing mineralization were characterized by petrography, mineralogy and crystallochemistry. Mutual genetic and textural relationships of studied materials were examined as well and were validated by biotite, arsenopyrite and chlorite empirical geothermometry. First identified generation of sulfide mineralization was formed at 360řC and consist of arsenopyrite, galenite and native gold. At circa 274řC porphyry mineral association was chloritized, and chlorite gangue crystallized. Second generation of sulfide mineralization precipitated at 264řC. Based on acquired data, granodiorite porphyry dikes were categorized to two separate genetic types, which have mutual origin in deep magma chamber of Central Bohemian Plutonic Complex but intruded non-contemporaneously.
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Mineralogy and genesis of gold ores hosted by porphyry dykes at Petrov and Bohuliby
Petrov, Ivan ; Zachariáš, Jiří (advisor) ; Strnad, Ladislav (referee)
This bachelor thesis is focused on mineralogy and genesis of Au-bearing ores in southwestern part of the Jílové ore district, in between Petrov and Bohuliby. Crystallization sequence of hydrothermal minerals was identified by textural relationships of mineral phases. Arsenopyrite and chlorite thermometry suggest formation of sulphides and gold at 400-300 řC. Within the scope of this thesis the paragenesis of rock-forming minerals of granodiorite porphyry dikes hosting Au-bearing ores, as well as of late-magmatic to hydrothermal minerals filling in miarolitic cavities in these porphyries, were also interpreted. A hypothesis of granodiorite dikes' origin is suggested as well, involving mixing of magmas with different geochemical signatures.
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Variscan igneous activity at the Bohemicum/moldanubicum boundary
Kubínová, Šárka ; Holub, František (advisor) ; Pertoldová, Jaroslava (referee)
Variscan dike swarms associated with the Central Bohemian Plutonic Complex (CBPC) at the boundary between the Teplá-Barrandian and Moldanubian Units of the Bohemian Massif represent one of the most interesting geological phenomena. Frequency of dykes and their chemical variability do not have any comparable analogy in the whole European Variscides. This work is focused on the study of dyke rocks in the NE periphery of CBPC in geologically very complicated area with intrusions of predominantly deformed granitoids, contact metamorphosed sediments and magmatic rocks of "Islet Zone" with different protolith ages (forming remnants of the original roof of CBPC), deformed basic rocks of uncertain origin and age. The area extends up to the western boundary of the northernmost part of the Moldanubian high-grade metamorphic complex, the boundary itself being also tectonically problematic. Several localities with dyke rocks under study are situated in the area east of Senohraby (SE of Prague), on the northern side (right coast) of the Sázava river, and extend up to the area of Stříbrná Skalice. This area is rich in dykes of gabbro to diorite porphyry accompanied in some places with tonalite (rarely quartz diorite) porphyry and more rarely with amphibole lamprophyres (spessartite). Significantly younger dykes...
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Preservation of HP minerals and textures in felsic and mafic granulites from the Rychleby Mts.
Schlöglová, Kateřina ; Faryad, Shah Wali (advisor) ; Kotková, Jana (referee)
Diploma thesis - Kateřina Schlöglová - 2011 1/2 English abstract Granulites of the Rychleby Mts. represent relics of high-pressure eclogite-facies metamorphic rocks that are scattered in various crustal and mantle segments of the Variscan orogen in central Europe. These rocks may provide important insights into early stages of Variscan plate convergence and burial as well as exhumation mechanisms. We use mineral assemblages and chemistry to reconstruct the pressure-temperature paths, mechanisms of melting, and conditions of mineral preservation of high-pressure granulites, as well as whole- rock geochemistry to aid in interpretation of granulite precursors and their geodynamic setting. The mafic granulites consist of garnet, omphacite, two feldspars, and quartz with accessory rutile and zircon. The peak assemblage was partly replaced by pargasitic amphibole and biotite. Garnet grains are zoned from Grs36Py10Alm54 (core) to Grs20Py38Alm42 (rim), and host inclusions of phengite, omphacite, unmixed feldspars, kyanite, and rutile. Omphacite composition varies from Di44Hd14Jd42 (inclusions in garnet) through Di63Hd20Jd17 (porphyroblasts) and Di63Hd24Jd13 (symplectitic intergrowths with plagioclase). Reintegrated composition of the feldspar porphyroblasts is Or43Ab53An04. The felsic granulite variety is composed...
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