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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
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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...
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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.
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Geodynamic evolution and post-collisional magmatic activity in the Arabian-Nubian Shield (East African Orogeny) and southwestern Moldanubian Zone (Central European Variscides)
Megerssa, Leta Alemayehu ; Verner, Kryštof (advisor) ; Závada, Prokop (referee) ; Johnson, Kenneth (referee)
The Variscan orogenic belt along the exhumed root domain, known as the Moldanubian Zone as well as the Arabian-Nubian Shield (ANS) in the East African Orogeny (EAO) of Ethiopia, are considered as typical areas for studying late-orogenic (post-collisional) processes and magmatism. Based on a wider range of field and analytical methods: field structural mapping, anisotropy of magnetic susceptibility (AMS) analysis, thermobarometric calculation and P-T evolution, conventional U/Pb dating, a reconstruction of geodynamic evolution and magmatism in the southwestern part of Moldanubian Zone (Bohemian Massif) and Tokar-Barka Terrain (southern part of Arabian-Nubian Shield is undertaken. The Variscan case portrays the peculiar overprint by the Late Orogenic tectonothermal event which is absent in the case of the Arabian-Nubian Shield (ANS) hence offering a compelling contrast to investigate the possible underlying mechanism involved for the different processes in the post-orogenic phase. In the southern ANS a post-collisional intrusive Chewo pluton composed of monzodiorite and quartz monzonite marks the late tectonic overprint which intruded into a low-grade Neoproterozoic juvenile crustal Tokar-Barka terrane. Thermobarometric estimations indicate its emplacement to be c. 10-13 Km depth, idealized from AMS...
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