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National Repository of Grey Literature 2 records found  Search took 0.01 seconds. 
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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