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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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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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Mineral and chemical changes of magma crystallization during formation of post-Variscan intrusions and veins in the Moldanubian Zone of the Bohemian Massif
Kubínová, Šárka ; Faryad, Shah Wali (advisor) ; Rapprich, Vladislav (referee) ; Moyen, Jean-François (referee)
- 1 - English abstract The late-Variscan magnesium-rich potassic to ultrapotassic igneous rocks create numerous dykes, dyke swarms and several plutonic bodies at the boundary between the Moldanubian Zone and the Teplá-Barrandian Block of the Bohemian Massif. They represent a volumetrically smaller group of igneous rock but they are the key to understand generation of melt and processes of mantle metasomatism and shallow-level magma differentiation. In addition, they are considered as an indicator of the tectonic evolution of this part of the Bohemian Massif during the final stages of the Variscan orogenesis. Currently, they are the subject of discussion by several authors in terms of their genesis, emplacement time and geodynamic significance. The presented thesis is a compilation of four scientific publications that are aimed at the petrological study of selected (ultra)-potassic dyke rocks from several localities at the western border of the Moldanubian Zone. The study of mineral textures, mineral chemistry and whole-rock geochemistry together with magnetic fabrics, structural field relations and age determinations allowed us to describe the crystallization history of these rocks, discuss their evolution from melt generation to magma ascent and emplacement, and form the model of sequence of Variscan...
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Emplacement and magnetic fabrics in dikes of syenite porphyries (Western Moldanubian Zone)
Orságová, Lucie ; Verner, Kryštof (advisor) ; Žák, Jiří (referee)
ENGLISH ABSTRACT We present new results of structural and magnetic (AMS) analyses of selected dikes of melasyenite, quartz melasyenite to melagranite porphyries accompanied by lamprophyres (minettes). The studied dike from the locality Nihošovice were dated by U-Pb method on zircons at 338 Ma. The asymmetric structural pattern of the studied dikes gives an excellent evidence for their emplacement and orientation of magmatic flow. The studied dikes were emplaced into: (i) Prevailing parts of the Central Bohemian Plutonic Complex (locality Malčice) and (ii) host high-grade metamorphic rocks of western part of the Moldanubian Zone (locality Nihošovice). Despite of the extensive area of occurrence, compositional variations and age of emplacement of these dikes are relatively narrow. Their geochemical and petrological compositions broadly correspond to ultrapotassic plutonic rocks (durbachites). The dikes are steeply dipping in trend ~NNW-SSE to ~W-E, with range in width between ~20 and ~25 meters. In general, our results show: (i) A relatively low degree of magnetic anisotropy (P= 1.012 - 1.152); (ii) Mostly oblate (planar) fabric, especially in marginal parts of the intrusive bodies (T= -0.091 - 0.941); (iii) Evidence for subhorizontal magmatic flow trajectory defined for a newtonian magma with typical...
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