National Repository of Grey Literature 42 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Tectonic and metamorphic evolution of the Tokar-Barka Terrain (East-African Orogeny)
Hořenínová, Marie ; Verner, Kryštof (advisor) ; Peřestý, Vít (referee)
in English This bachelor's thesis summarizes the tectonic and metamorphic evolution of the Tokar-Barka Unit in the southern part of the Arabian-Nubian Shield. The compilation includes an information of regional division, lithological pattern, age, deformation structures and record of metamorphic evolution, mainly in the context of East African orogenic processes. The main episodes of geodynamic evolution are briefly discussed in a regional context. Key words: East-African Orogeny, Arabian-Nubian Shield, Tokar-Barka Unit, Deformation, Tectonics, Metamorphic evolution
Genesis of the eruptive center of rhyolite ignimbrites, the Křivoklát-Rokycany volcanic complex
Ptáček, Jakub ; Tomek, Filip (advisor) ; Verner, Kryštof (referee)
English abstract This bachelor's thesis focuses on the tectonic and volcanological characteristics of the Křivoklát-Rokycany volcanic complex in the Teplá-Barrandian unit. The literature research part emphasizes the broader geological context, where I describe the Neoproterozoic, Cambrian, and lower Ordovician geotectonic development of the Teplá-Barrandian unit within the Avalonian-Cadomian orogenic belt. In the Křivoklát-Rokycany volcanic complex, I focus in detail on the relatively youngest part, which consists of the entire spectrum of facies of rhyolite composition and includes coherent lavas, tuffs, ignimbrites, and dike equivalents. The field research of the practical part of the bachelor's thesis took place in a satellite body of porphyritic rhyolite in the Těškov quarry, about 10 km northeast of Rokycany. The aim of the detailed geological mapping of the investigated quarry was the petrographic description of four distinct rhyolite facies, mapping of their spatial distribution, and possible determination of the eruptive center. Other research methods included analyzes of in-situ magnetic susceptibility and size distribution of rhyolite breccia clasts. The result of the work is a three- dimensional model of the quarry with detailed distribution of rhyolite facies. From the obtained data, I assume...
Structural evolution and U/Pb dating of the Hammar Domain (East-African Orogeny)
Belule, Bezuneh Melka ; Verner, Kryštof (advisor) ; Závada, Prokop (referee)
in English Studied parts of the Hammar Domain and Adola-Moyale Belt is situated at the junction of the Arabian Nubian Shield (ANS) and Mozambique Belt (MB) as a crucial area where to study the overall imprint of the East-African Orogeny in Ethiopia. Based on detailed field geological mapping, morphotectonic analysis of Digital Elevation Model, detailed structural analysis and U/Pb dating results of biotite orthogneiss from the Hammar Domain the overall tectonic evolution associated with the East-African Orogeny is interpreted. The structural evolution of the northern Hammar Domain and northwestern tip of the Adola- Moyale Belt could be defined into four deformation phases D1 to D4 resulted in origin of: (a) Relict compositional banding (S1) of flat-lying orientation defining the primary contacts of high- to medium grade lithologies, (b) superimposed steeply to moderately dipping ~N-S to ~NW-SE trending compressional foliation (S2) due to a regional ~E-W oriented compression and (c) later sub-horizontal to gently NW dipping foliation (S3) associated with well-developed NW plunging lineation. Furthermore, the localized tectonic activity was concentrated in form of narrow brittle-ductile to brittle ~N-S to ~NW-SE trending shear zones, commonly accompanied by hydrothermal mineralization. New...
Lithology, geochemistry and metamorphic evolution of northern Hammar Domain (East-African Orogeny)
Gashe, Negessa Gonfa ; Verner, Kryštof (advisor) ; Racek, Martin (referee)
in English The studied part of the Hammar Domain is composed of the Neoproterozoic basement rocks belonging to the Southern Ethiopian Shield (SES), partly covered by volcanic and volcanosedimentary deposits of the Main Ethiopian Rift (MER). The high-grade migmatite to migmatized biotite paragneiss and amphibolites were intruded by numerous peraluminous granite and granodiorite bodies and gabbros of metaluminous composition. The results of U/Pb zircon dating of granodiorite yielded at 507.7 ± 3.2 Ma, which is interpreted as the age of magma emplacement and crystallization. The P-T estimation reveal the peak P-T conditions at ca. 1.21 to 0.88 GPa and ca. 842 to 700 řC which were followed by retrograde part P-T path (from ca. 0.84 to 0.12 GPa) with decrease of temperature from ca. 700 to 464 řC. The emplacement of gabbro in syn-tectonic settings took place at P = ca. 0.87 to 0.93 GPa and T ca. 650 řC reflecting magma emplacement to ca. 30 km in depth. Next, the syn- to post- tectonic emplacement and crystallization of biotite and amphibole-bioitite granodiorite reveal P = 0.27-0.52 GPa and T ca. 720-836. The events described above were associated with the latter period of the East-African Orogeny, which resulted in overall consolidation of the Gondwana continent.
Reconstruction of the geological evolution of the Southern Main Ethiopian Rift
Dvořák, Štěpán ; Verner, Kryštof (advisor) ; Tomek, Filip (referee)
The Main Ethiopian Rift represents a unique insight into process of continental rifting and its comprehensive research can provide partial clarification of open questions such are the causes, mechanisms, and timing of overall tectonic and magmatic evolution. The Main Ethiopian Rift is an intermediary between the Afar triple junction to the north and Kenyan Rift to the south, representing incipient plate boundary between Nubian and Somalian plates. Based on comprehensive geological research of the northern flank of the Southern Main Ethiopian Rift including field geological and structural mapping, petrological and geochemical description of individual lithologies, morphotectonic analysis of Digital Elevation Model, paleostress analysis and gravity pattern assessment including calculation of Linsser indices, some aspects in geodynamic evolution of northern flank of the Southern Main Ethiopian Rift is interpreted. The area recorded typical continental rift-related tectonic and magmatic evolution including "pre-rift" (Eocene to Oligocene) volcanic activity initiated by extensive flood (plateau) alkaline basalt to trachybasalt basalt eruptions due to crustal thinning and mantle plume(s) ascent, followed by fault-dominated "early-rift" (Miocene) bimodal volcanism associated with origin of the rift...
Fabrics and geodynamic evolution of orthogneisses in the Moldanubian Zone
Kryl, Jakub ; Verner, Kryštof (advisor) ; Venera, Zdeněk (referee)
Fabrics and geodynamic evolution of Moldanubian orthogneisses English abstract The aim of this paper is a structural analysis of selected mostly Cambro-Ordovician orthogneisses cropping out in a part of high-grade rocks of western Moldanubian Zone. These rocks have been affected by HT-MP/LP metamorphism and the polyphase deformation during the Variscan orogeny. In the blaník orthogneisses, (Qtz + Kfs + Plg + Bt ± Ms ± Sill ± Ky) an early deformation banding dips steeply to SSE to ESE. These fabrics were overprinted by NW to N gently dipping foliation with well developed stretching lineations plunging to W. Rare kinematic indicators (e. g. fold and pressure shadows asymmetry) reveal a strong subvertical contraction and stretching in the ~N-S direction. Based on the microstructural analysis this contractional event was connected with the activity of "Grain Boundary Migration Recrystallization" (GBM). Ductile shear zones dipping to E, locally ESE or ENE were identified. Bechyně orthogneisses (Qtz + Kfs + Plg + Bt ± Ms) is a N-S elongated body with the presence of regional pervasive metamorphic foliation dipping homogenously under low angles from SSW to WNW . These foliations bear well developed mineral or stretching lineation of quartz, biotite and feldspar aggregates plunging to ~SW. In the blaník orthogneiss...

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