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Trace element and Re-Os geochemistry of mantle pyroxenites from the Bohemian Massif
Haluzová, Eva ; Ackerman, Lukáš (advisor) ; Jelínek, Emil (referee)
Mantle pyroxenites are important components of mantle rocks, because they provide important insights into bulk composition and heterogeneity of the Earth's upper mantle and therefore, direct evidence of mantle evolution throughout the Earth history. Studied pyroxenites from localities Bečváry (the Kutná Hora Complex), Níhov, Nové Dvory, Mohelno, Horní Kounice, Karlstteten and Meidling (the Gföhl Unit of the Moldanubian Zone) occur as dykes and/or layers within spinel and garnet peridotites from the Bohemian massif. Whole-rock concentrations of rare earth (REE) and other trace elements in studied pyroxenites yield extreme variability, which most likely reflect: 1) variable garnet/clinopyroxene ratios in bulk rocks, 2) different degree of fractionation of parental melts and 3) different concentrations trace elements in the source host material. Pyroxenites from locality Mohelno (LREE-depleted) may be derived from depleted or only slightly enriched suboceanic mantle. In contrast, pyroxenites from Karlstetten, Meidling, Horní Kounice and Nové Dvory (LREE-enriched) crystallized from the melts derived from enriched mantle source with possibly significant contribution of recycled crust. Studied pyroxenites are characterized by extremely variable 187 Os/188 Os ratios. While the pyroxenites from Mohelno and...
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Anisotropie svrchního pláště pod Severními Apeninami z dat mezinárodního experimentu RETREAT (Itálie)
Munzarová, Helena ; Gallovič, František (advisor) ; Novotný, Oldřich (referee)
Title: Anisotropy of the upper mantle under the Northern Apennines based on data from the international experiment RETREAT (Italy) Author: Helena Munzarová Department: Department of Geophysics Supervisor of the master thesis: RNDr. František Gallovič, Ph.D. Department of Geophysics Consultant of the master thesis: RNDr. Jaroslava Plomerová, DrSc. Institute of Geophysics, Czech Academy of Sciences Abstract: In this master thesis, we process data recorded during the passive seismic experiment RETREAT (2003-2006) in the Northern Apennines with the aim to explore the upper mantle structure in the region. Active orogeny in the Northern Apennines relates to the collision of the Tyrrhenian and Adriatic (subducting westward) plates and is accompanied by an eastward retreat of the trench. Directional dependences of P-wave travel-time deviations together with variations of the fast split polarization azimuths of teleseismic SKS waves are derived from data recorded during experiment RETREAT. Both the fossil anisotropic structure in the mantle lithosphere and the anisotropy due to the present-day flow in the sub-lithospheric mantle are sources of the observed velocity-anisotropy patterns. Thick continental Adriatic plate can be divided into at least two sub-regions with their own fossil fabrics. We have also tried to...
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