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Breccia of Frog Lakes : reconstructing Triassic volcanism and subduction initiation in the east-central Sierra Nevada, CaliforniaRoberts, Sarah Elizabeth 12 March 2014 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / The Antler and Sonoma orogenies occurred along the southwest-trending passive Pacific margin of North America during the Paleozoic concluding with the accretion of the McCloud Arc. A southeast-trending sinistral transform fault truncated the continental margin in the Permian, becoming a locus for initiation of an east-dipping subduction zone creating the Sierran magmatic arc. Constrained in age between two early Triassic tuff layers, the volcanic clasts in the breccia of Frog Lakes represent one of the earliest records of mafic magmatism in the eastern Sierra Nevada. Tholeiitic rock clasts found in the breccia of Frog Lakes in the Saddlebag Lake pendant in the east central Sierra Nevada range in composition from 48% to 63% SiO2. Boninites produced by early volcanism of subduction initiation by spontaneous nucleation at the Izu-Bonin-Mariana arc are more depleted in trace element concentrations than the clasts while andesites from the northern volcanic zone of the Andes produced on crust 50 km thick have similar levels of enrichment and provide a better geochemical modern analogue. Textural analysis of the breccia of Frog Lakes suggest a subaqueous environment of deposition from a mature magmatic arc built on continental crust > 50 km thick during the Triassic. The monzodiorites of Saddlebag and Odell Lakes are temporal intrusive equivalents of the breccia of Frog Lakes and zircon geochemistry indicates a magmatic arc petrogenesis.
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A interação oceano-atmosfera no Atlântico sul e o paleociclo hidrológico na porção leste da América do Sul durante o Holoceno / Air-sea interaction in the South Atlantic and the water paleocycle in eastern South America during the HolocenePrado, Luciana Figueiredo 02 March 2015 (has links)
Este trabalho teve como objetivo investigar processos de interação ar-mar na porção leste da América do Sul e Oceano Atlântico adjacente ao longo do Holoceno (últimos 12.000 anos). Para isso, os efeitos de forçantes naturais sobre a variabilidade climática foram investigados em três escalas temporais: (i) milenar-centenária: efeitos de pulsos de degelo no Oceano Atlântico, e de variações nas forçantes solar e orbital sobre o modo dipolar subtropical do Atlântico sul e consequências sobre a precipitação, durante o Holoceno; (ii) cenário médio: efeitos de diferenças na forçante orbital em relação ao clima presente sobre a precipitação média no continente, durante o Holoceno médio (6.000 anos atrás), por meio de uma compilação de dados paleoclimáticos inédita para esse período, e comparação com resultados de simulações numéricas; (iii) multidecadal: efeitos de variações na forçante vulcânica ao longo do último milênio (850 a 1850 da Era Comum) sobre a variabilidade do modo equatorial do Atlântico e consequências sobre a precipitação na América do Sul. Os resultados mostraram efeitos dos eventos de rápido resfriamento do Hemisfério norte na variabilidade do modo dipolar subtropical do Atlântico sul, com consequências principalmente sobre a precipitação do Nordeste do Brasil. O cenário médio para o Holoceno médio apontou déficit hídrico na porção leste da América do Sul durante esse período, relacionado com menor quantidade de insolação de verão recebida pelo Hemisfério sul. A dificuldade na coleta de testemunhos marinhos foi identificada como um dos principais limitantes em estudos paleoclimáticos. O vulcanismo explosivo observado no último milênio resfriou a região tropical no ano da erupção, e enfraqueceu a relação entre a precipitação na porção leste da América do Sul e o modo equatorial do Atlântico. Finalmente, a presente tese demonstrou, por meio de comparações dados-modelo, a importância do Oceano Atlântico no regimes de chuva da América do Sul em diversas escalas temporais para climas onde a forçante antropogênica era pouco significativa. 195 pp. / This work investigates the air-sea interaction processes in eastern South America and the adjacent Atlantic Ocean for the Holocene (past 12,000 years). The effects of the natural forcings on climate variability were investigated in three time-scales: (i) millennial-to-centennial: effects of Atlantic meltwater pulses and changes in the solar and orbital forcings on the South Atlantic subtropical dipole, and rainfall impacts during the Holocene; (ii) mid-Holocene scenario: effects of changes in the orbital forcing, in comparison to the present-day conditions, on mean precipitation over the continent, during the mid-Holocene (6,000 years ago). This was achieved through an unpublished multiproxy compilation and comparison with numerical experiments; (iii) multidecadal: effects of changes in the volcanic forcing along the past millennium (850 to 1850 Common Era) on the variability of the Atlantic equatorial mode and consequences on precipitation over South America. Results show effects of the Northern Hemisphere cooling events on the variability of the South Atlantic subtropical dipole, with impacts mainly over Northeastern Brazil\'s rainfall. The mid-Holocene scenario results indicate a water deficit in eastern South America during this period related to a decrease in Southern Hemisphere summer insolation. The difficulty in marine cores sampling is identified as one of the main problems in current paleoclimate studies. The explosive volcanism observed during the past millennium cooled the tropical regions at the year of the volcanic eruption, and weakened the relation between the precipitation in eastern South America and the Atlantic equatorial mode. This thesis shows through data-model approaches the importance of the Atlantic Ocean on South America precipitation regimes in the climate timescales where the anthropogenic forcing was not so relevant. 195 pp.
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A interação oceano-atmosfera no Atlântico sul e o paleociclo hidrológico na porção leste da América do Sul durante o Holoceno / Air-sea interaction in the South Atlantic and the water paleocycle in eastern South America during the HoloceneLuciana Figueiredo Prado 02 March 2015 (has links)
Este trabalho teve como objetivo investigar processos de interação ar-mar na porção leste da América do Sul e Oceano Atlântico adjacente ao longo do Holoceno (últimos 12.000 anos). Para isso, os efeitos de forçantes naturais sobre a variabilidade climática foram investigados em três escalas temporais: (i) milenar-centenária: efeitos de pulsos de degelo no Oceano Atlântico, e de variações nas forçantes solar e orbital sobre o modo dipolar subtropical do Atlântico sul e consequências sobre a precipitação, durante o Holoceno; (ii) cenário médio: efeitos de diferenças na forçante orbital em relação ao clima presente sobre a precipitação média no continente, durante o Holoceno médio (6.000 anos atrás), por meio de uma compilação de dados paleoclimáticos inédita para esse período, e comparação com resultados de simulações numéricas; (iii) multidecadal: efeitos de variações na forçante vulcânica ao longo do último milênio (850 a 1850 da Era Comum) sobre a variabilidade do modo equatorial do Atlântico e consequências sobre a precipitação na América do Sul. Os resultados mostraram efeitos dos eventos de rápido resfriamento do Hemisfério norte na variabilidade do modo dipolar subtropical do Atlântico sul, com consequências principalmente sobre a precipitação do Nordeste do Brasil. O cenário médio para o Holoceno médio apontou déficit hídrico na porção leste da América do Sul durante esse período, relacionado com menor quantidade de insolação de verão recebida pelo Hemisfério sul. A dificuldade na coleta de testemunhos marinhos foi identificada como um dos principais limitantes em estudos paleoclimáticos. O vulcanismo explosivo observado no último milênio resfriou a região tropical no ano da erupção, e enfraqueceu a relação entre a precipitação na porção leste da América do Sul e o modo equatorial do Atlântico. Finalmente, a presente tese demonstrou, por meio de comparações dados-modelo, a importância do Oceano Atlântico no regimes de chuva da América do Sul em diversas escalas temporais para climas onde a forçante antropogênica era pouco significativa. 195 pp. / This work investigates the air-sea interaction processes in eastern South America and the adjacent Atlantic Ocean for the Holocene (past 12,000 years). The effects of the natural forcings on climate variability were investigated in three time-scales: (i) millennial-to-centennial: effects of Atlantic meltwater pulses and changes in the solar and orbital forcings on the South Atlantic subtropical dipole, and rainfall impacts during the Holocene; (ii) mid-Holocene scenario: effects of changes in the orbital forcing, in comparison to the present-day conditions, on mean precipitation over the continent, during the mid-Holocene (6,000 years ago). This was achieved through an unpublished multiproxy compilation and comparison with numerical experiments; (iii) multidecadal: effects of changes in the volcanic forcing along the past millennium (850 to 1850 Common Era) on the variability of the Atlantic equatorial mode and consequences on precipitation over South America. Results show effects of the Northern Hemisphere cooling events on the variability of the South Atlantic subtropical dipole, with impacts mainly over Northeastern Brazil\'s rainfall. The mid-Holocene scenario results indicate a water deficit in eastern South America during this period related to a decrease in Southern Hemisphere summer insolation. The difficulty in marine cores sampling is identified as one of the main problems in current paleoclimate studies. The explosive volcanism observed during the past millennium cooled the tropical regions at the year of the volcanic eruption, and weakened the relation between the precipitation in eastern South America and the Atlantic equatorial mode. This thesis shows through data-model approaches the importance of the Atlantic Ocean on South America precipitation regimes in the climate timescales where the anthropogenic forcing was not so relevant. 195 pp.
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Tertiary limestones and sedimentary dykes on Chatham Islands, southwest Pacific Ocean, New ZealandTitjen, Jeremy Quentin January 2007 (has links)
The Chatham Islands are located in the SW Pacific Ocean, approximately 850 km to the east of the South Island of New Zealand. This small group of islands is situated near the eastern margin of the Chatham Rise, an elongated section of submerged continental crust that represents part of the Late Paleozoic-Mesozoic Gondwana accretionary margin. The location and much of the geology of the Chatham Islands are attributed to intra-plate basaltic volcanism, initiated during the Late Cretaceous, in association with development of a failed rifting system to the south of the Chatham Rise. Despite the volcanic nature of much of the geology, the majority of the Cenozoic sedimentary stratigraphic record on the islands comprises non-tropical skeletal carbonate deposits whose deposition was often coeval with submarine volcanics and volcaniclastic deposits. This has resulted in complex stratigraphic relationships, with the volcanic geology exerting a strong influence on the geometry and distribution of the carbonate deposits. These limestones, despite some general field descriptions, have been little studied and are especially poorly understood from a petrographic and diagenetic perspective. The carbonate geology in detail comprises eleven discrete limestone units of Late Cretaceous through to Pleistocene age which were studied during two consecutive field expeditions over the summers of 2005 and 2006. These limestone occurrences are best exposed in scattered coastal outcrops where they form prominent rugged bluffs. While many of the younger (Oligocene to Pliocene) outcrops comprise of poorly exposed, thin and eroded limestone remnants (it;5 m thick), older (Late Paleocene to Early Oligocene) exposures can be up to 100 m in thickness. The character of these limestones is highly variable. In outcrop they display a broad range of textures and skeletal compositions, often exhibit cross-bedding, display differing degrees of porosity occlusion by cementation, and may include rare silicified horizons and evidence of hardground formation. Petrographically the limestones are skeletal grainstones and packstones with a typical compositional makeup of about 70% skeletal material, 10% siliciclasts, and 20% cement/matrix. Localised increases in siliciclastics occur where the carbonates are diluted by locally-derived volcaniclastics. The spectrum of skeletal assemblages identified within the Chatham Island limestones is diverse and appears in many cases to be comparable to the bryozoan dominant types common in mainland New Zealand and mid-latitude Australian cool-water carbonates in general. However, some key departures from the expected cool-water carbonate skeletal makeup have been identified in this study. The occurrence of stromatolitic algal mats in Late Cretaceous and Early Eocene carbonate deposits indicates not cool-temperate, but certainly warm-temperate paleoclimatic conditions. A change to cool-temperate conditions is recorded in the limestone flora/fauna from the mid-Late Miocene times following the development and later northward movement of the Subtropical Front. An uncharacteristic mix of shallow-shelf (bryozoans) and deeper water fauna (planktic foraminifera), together with their highly fragmented and abraded nature, is indicative of the likely remobilisation and redistribution of carbonate, primarily during episodic storm events. The Chatham Islands limestones formed within the relative tectonic stability of an oceanic island setting, which was conducive to ongoing carbonate accumulation throughout much of the Cenozoic. This contrasts markedly with other mainland New Zealand shelf carbonates which formed over sporadic and short-lived geological periods, experiencing greater degrees of burial cementation controlled by a relatively more active tectonic setting. As a consequence of the tectonically stable setting, the Chatham Islands limestones have experienced little burial and exhibit a paucity of burial cementation effects. They remain commonly soft and friable. Detailed petrographic investigations have shown the limestones are variably cemented by rare uneven acicular spar fringes, poorly to well-developed syntaxial rim cements about echinoderm fragments, and equant/blocky microsparite. Staining of thin sections and cathodoluminescence petrography show these spar cement generations are non-ferroan and their very dull- to non-luminescent nature supports precipitation from Mn-poor oxygenated waters, likely of an either meteoric or combined marine/shallow burial origin. Micrite is the dominant intra- and inter-particle pore fill and occurs both as a microbioclastic matrix and as precipitated homogenous and/or micropeloidal cement. The rare fringing cements often seen in association with homogenous and/or micropeloidal micrite may be indicative of true early marine (seafloor) cement precipitation and localised hardground development. An interesting feature of the geology of the Chatham Islands is the occurrence of carbonate material within sedimentary dykes. The locations of the dykes are in association with volcanic and volcaniclastic deposits. Similarities between dyke characteristics at Red Bluff on Chatham Island with mainland occurrences from East Coast and Canterbury Basins (North and South Islands, respectively) on mainland New Zealand have been recognised. They show complex structures including sidewall striations, internal flow structures as revealed by grain sorting, and extra-clast inclusions of previous fill lithologies which are characteristic of carbonate injection. This is in contrast to other dykes which are known to be of a passive fill origin. Multiple phases of carbonate sediment injection can be recognised by crosscutting relationships enabling the determination of a parasequence of events. Possible injection mechanisms are most likely associated with sediment overloading or hydrothermal pressurisation associated with emplacement of submarine volcanics. The Chatham Islands provide an exciting example of a geologically unique and complex non-tropical carbonate depositional setting. The production of carbonates is controlled by volcanic and volcaniclastic sediment input with the types of carbonate deposits and water depth variations related to thermal uplift/subsidence in association with global eustatic sealevel and temperature changes associated with development of Southern Ocean water fronts from the Late Cretaceous-Cenozoic. Carbonate deposition on the Chatham Islands is considered to relate to a rather variable and small scale oceanic, high energy, cool-water carbonate ramp setting whose geometry was continually evolving/changing as a consequence of periodic volcanic episodes.
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Experimentelle und numerische Untersuchungen zur Ausbreitung von Volumenstörungen in thermischen Plumes. / Experimental and numerical studies of the propagation of volume disturbances in thermal plumes.Laudenbach, Nils 14 December 2001 (has links)
No description available.
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Analysis of microbial diversity in an extreme environment: White Island, New ZealandIbáñez-Peral, Raquel January 2009 (has links)
"June, 2008". / Thesis (PhD)--Macquarie University, Division of Environmental & Life Sciences, Dept. of Chemistry & Biomolecular Sciences, 2009. / Bibliography: p. 227-259. / Literature review -- Materials and methods -- Sampling sites and sampling material -- Enrichment cultures and molecular analyses -- Optical and binding characterisation of the QDs -- Applications of the QDs -- Concluding remarks. / White island, the most active volcano in New Zealand, is a poorly studied environment that represents an ideal site for the investigation of acidophilic thermophiles. The microorganisms present on here are continually exposed to extreme environmental conditions as they are surrounded by steamy sulphurous fumaroles and acidic streams. The sediment temperature ranges from 38°C to 104°C whilst maintaining pH values below 3. A survey of the volcanic hydrothermal system of White Island was undertaken in order to gain insights onto the microbial diversity using culture-dependant techniques and molecular and phylogenetic analyses. A novel liquid medium based on "soil-extract" was designed which supported growth of bacterial and archaeal mixed cultures. Molecular analyses revealed that the dominant culturable bacterial species belong to the Bacteroidetes, Firmicutes and α-Proteobacteria groups. Several previously uncultured archaeal species were also present in the mixed cultures. The knowledge gained from these studies was intended to help in the development of a novel microbial detection technique suitable for community analysis. -- Conventional molecular techniques used to study microbial biodiversity in environmental samples are both time-consuming and expensive. A novel bead-based assay employing Quantum dots (QDs) was considered to have many advantages over standard molecular techniques. These include high detection speeds, sensitivity, specificity, flexibility and the capability for multiplexed analysis. QDs are inorganic semiconductor nanoparticles made up of crystals about the size of proteins. It has been claimed that the physical and chemical properties of the QDs have significant advantages compared to organic dyes, including brighter fluorescence and resistance to photo-bleaching. Their optical properties facilitate the simultaneous imaging of multiple colours due to their flexible excitation and narrow band emission. Functionalised QDs are able to bind to different biological targets such as DNA, allowing high-throughput analysis for rapid detection and quantification of genes and cells. -- The optical and physical characteristics of the QDs as well their interaction with biomolecules are shown to be suitable for the development of a novel bead-based technique able to target the key microbial species and identify them by flow cytometric measurements (FCM). The broad absorption and narrow emission spectra of the QDs, as well as their fluorescence intensity and specify to target biomolecules, was compared to other organic fluorophores. The potential advantages and limitations of QDs as a fluorophores for biological applications are discussed. -- The data acquired during this study provides a broad overview of the microbial diversity and ecology of the volcanically-active hydrothermal systems of White Island and constitutes the baseline for the development of a novel bead-based technique based on QDs. / Mode of access: World Wide Web. / xvii, 259 p. ill. (some col.)
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Evolution volcano-tectonique du nord de la plaque arabique (la syrie) : cadre géodynamique, chronologie K-Ar, caractères géochimiques et éléments de cartographie (SIG et télédétection) / The volcano-tectonic evolution of the northern part of the arabian plate (syria) : geodynamic framework, chronology K-Ar, geochemical characters, mapping (remote sensing and GIS)Al Kwatli, Mohamad Amer 20 June 2011 (has links)
L'activité volcanique Cénozoïque de la plaque arabique offre l’exemple d’un volcanisme intra-plaque développé dans un contexte géodynamique complexe. Après la construction des trapps basaltiques du plateau yémeno-ethiopien, vers 31 Ma, à partir de l’Oligocène terminal, une importante activité volcanique se développe, liée à la déchirure du bouclier arabo-nubien (l’ouverture de la Mer Rouge) et la convergence des plaques Arabique et Eurasienne (zone de suture du Bitlis-Zagros). Au nord de la plate-forme arabique, le volcanisme syrien s’implante dans un contexte général de compression, autour de la ceinture de plissement des Palmyrides et des zones de déformation adjacentes (graben de l'Euphrate et système de faille de la Mer Morte). Cette thèse porte sur l'évolution volcano-tectonique de la partie nord de la plaque Arabique, en particulier celle de la Syrie, combinant des études géochronologiques, géochimiques et morpho-structurales et modélisation géophysique. Notre analyse morpho-structurale de la province volcaniques de Harrat Ash Shaam (HASV), au sud des Palmyrides, a permis de caractériser numériquement plus de 800 cônes volcaniques monogéniques répartis entre le Sud Syrien, la Jordanie et le Nord de l’Arabie Saoudite. Cette étude de la distribution des cônes volcaniques, jointe aux données existantes sur l’épaisseur de la couverture sédimentaire traversée démontre que la corrélation négative constante entre l’intensité des éruptions volcaniques et la profondeur au socle est, de fait, influencée par le contexte tectonique. L’analyse normative de la distribution des cônes volcaniques, comparée à l'épaisseur des sédiments, est essentielle pour caractériser la tectonique d'extension dans des différentes zones. La télédétection, les observations sur le terrain, et notre base de données de plus de 40 nouvelles datations potassium-argon, entre 50 ka et 18 Ma, nous permettent de préciser l’évolution volcano-tectonique de la Syrie. Cette approche pluri-disciplinaire, appliquée au plateau du Al-Lajat, le champ volcanique le plus récent de HASV, nous a permis, d’abord, de proposer un modèle chronologique pour le processus d'altération en relation aux changements paléoclimatiques du Quaternaire. Elle a surtout permis de reconstituer l'évolution volcano-tectoniques du Nord de la plaque arabique, au cours du Cénozoïque et de situer différents styles d’extension responsables de l’activité volcanique. Le volcanisme commence à la fin de l’Oligocène et au Miocène inférieur, entre ~ 26 Ma et ~ 16 Ma, au sud des Palmyrides, dans la province de HASV, dans un contexte tectonique extensif. Du Miocène au Quaternaire, entre ~ 19 Ma et ~ 0,08 Ma, des champs volcaniques se développe au nord des Palmyrides, conséquence d’extensions tectoniques de second ordre. A partir du milieu du Miocène, la compression augmente et le développement magmatique se poursuit potentiellement dans une ambiance tectonique de rotation antihoraire. Au sud des Palmyrides cela correspond à l’activité volcanique constante au cours des 13 derniers millions d’années. Au nord, cette phase d’activité liée à la tectonique de rotation est concentrée dans l’espace et le temps ; elle correspond au Plateau d’Homs, dans le NW Palmyre, entre 6,3 et 4,3 Ma.Nous proposons un nouveau modèle d'évolution volcano-tectoniques pour la province volcanique de HASV. Il souligne le rôle essentiel joué par l'hétérogénéité de la lithosphère (sous les chaînes du Liban – anti-Liban et la zone de plissement des Palmyrides) dans la formation du volcanisme à partir du milieu du Miocène. Nos modèles géophysiques permettent d’estimer à ~150 km la profondeur moyenne de la limite lithosphère-asthénosphère. A l’analyse des données géochimiques des laves, la zone à l’ouest de HASV où cette limite apparaît moins profonde, à ~ 110 km, s’expliquerait par une anomalie thermique plutôt que par une remontée asthénosphérique. Géochimiquement, les laves Cénozoïques syriennes sont alcalines et sub-alcalines et présentent les caractères de magma émis dans un contexte continental intra-plaque. Ce sont des basanites et des téphrites, des basaltes, des andésites et des trachy-andésites basaltiques et des trachybasaltes. 30 échantillons des différentes provinces volcaniques syriennes montrent une variation significative des signatures des éléments traces incompatibles. Le processus de genèse de ces magmas montre une influence négligeable de la contamination crustale, et un effet de la cristallisation fractionnée limité à l'olivine et au clinopyroxène. Nos résultats montrent que les laves syriennes ont été produites par des taux variables de fusion partielle à partir de niveaux différents dans le manteau lithosphériques présentant localement des hétérogénéités. Le rapport LREE / MREE nous permet de montrer non seulement comment le degré de fusion partielle varie spatialement et temporellement au cours des derniers 18 Ma, mais encore d’illustrer comment varie le degré et le style de la tectonique au cours de cette période. L’une des conséquences de ce contexte tectonique pourrait être la migration d’hydrocarbures vers l’ouest du fait de l’extension crustale au Plio-Quaternaire dans la zone du graben de l’Euphrate à l’Est ; cette migration pourrait être guidée vers une zone de la croûte préalablement fracturée située au NW de la Syrie.En conclusion, le volcanisme cénozoïque de la Syrie résulte d’une tectonique extensive, influencée périodiquement par la convergence arabo-eurasienne, au nord et à l’est, convergence qui provoque des styles tectoniques de rotation ; cette tectonique contrôle la fusion partielle à différents niveaux dans le manteau. Le volcanisme du Nord de la plaque arabique se développe dans le cadre de l’ouverture de la Mer Rouge et débute en même temps que l’activité au sud de la mer Rouge. Il se poursuit jusqu’à la période historique, progressivement amorti vers le nord, l’extension étant contrariée par le cadre compressif à la marge Arabie-Eurasie. / The Cainozoic volcanic activity in the Arabian plate offers an excellent opportunity to study the intra-plate volcanism related to a complex tectonic setting. After the emplacement of the Yemeni-Ethiopian continental flood basalt plateau, ~ 31 Ma, since the Late Oligocene, widespread volcanic activity has erupted, accompanying the separation of the Arabian-Nubian Shield (development of Red Sea rifting) and the convergence between the Arabian and Eurasian plates (building of the Bitlis-Zagros thrust belts). In the northern part of the Arabian platform, the Syrian volcanism has taken place in a general compressional context, surrounding the Palmyride fold belt and adjacent to other deformation zones (e.g. the Euphrates graben and Dead Sea fault system). This thesis focuses on the volcano-tectonic evolution of the northern part of the Arabia plate, particularly in Syria, and essentially combines geochronological, geochemical, and morpho-structural studies, in addition to supplementary geophysical models. Our morpho-structural analyses of the Harrat Ash Shaam volcanic province (HASV) to the south of Palmyride, digitally characterise more than 800 monogenic volcanic cones placed in Syria, Jordan, and Saudi Arabia. These new data, together with the availability of sediment thickness data, give rise to a new volcano-tectonic approach. This study shows that the consistent negative correlation between the intensity of volcanism and basement depth is influenced by the tectonic setting. The normative analysis of the distribution of volcanic cones in relation to sediment thicknesses is critical when comparing the extension of tectonics in different zones. Remote sensing imagery, field work and our > 40 new K-Ar ages dataset ranging from ~0.05 million years (Ma) to ~18 Ma allow us to precise the Syria volcano-tectonic evolution through time. Regarding the youngest lava flows of HASV, the integration of the results makes it possible to suggest a chronological model for the alteration processes in relation to Quaternary palaeoclimatic changes. We reconstruct the volcano-tectonic evolution in Syria during the Cainozoic, and suggest different extension styles to explain the volcanism. It started during the Late Oligocene and the Early Miocene, between ~26 Ma and ~16 Ma to the South of Palmyride at HASV in an extensional tectonic context. From the Miocene to the Quaternary, between ~19 Ma and ~0.08 Ma, the volcanism developed to the North under second order extension tectonic conditions. Since the Mid-Miocene, the compression has increased and the magma erupted in relation with a possible counter-clockwise rotation tectonic relative motion. South of Palmyride it corresponds to the widespread eruptive phase during the last 13 Ma. To the North, this phase, linked to rotational tectonics appears concentrated in superficies and time; it corresponds to the Homs plateau, NW Palmyride, between 6.3 and 4.3 Ma. We suggest a new volcano-tectonic evolution model for the HASV. It highlights the essential role of lithosphere heterogeneity beneath Lebanon, in particular the anti Lebanon Mountains and Palmyride thrust belts, in triggering the Mid-Miocene volcanism. Our geophysical models estimate mean lithosphere – asthenosphere boundaries at about 150 km depth. According to geochemical data, the zone of shallowest depth ~110 km, W of HASV, could be the result of a thermal anomaly, instead of an asthenospheric upwelling. Geochemically, the Cainozoic Syrian lavas are alkaline and subalkaline rocks, typical of magma emitted in continental intraplate contexts. They are basanites and tephrites, basalts, basaltic andesites, basaltic trachyandesites, and trachybasalts. Thirty samples from different Syrian volcanic provinces show significant variation in terms of incompatible trace element signatures. Crustal contamination plays a negligible role in the process of magma genesis, as does crystal fractionation, essentially restricted to olivine and clinopyroxene. Our results show that the Syrian lava has been generated by variable rates of partial melting from different levels of a locally heterogeneous lithospheric mantle. The LREE/MREE ratio not only illustrates how the degree of partial melting was changed spatially and temporally during the last ~18 Ma, but it also illustrates how the degree and style of extension tectonics changed through time.
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Der Thüringer Wald im Zeitraum der Stefan-Unterperm-Entwicklung - ein Abschnitt der Zentraleuropäischen N-S-Riftzone innerhalb des Mitteleuropäischen GroßschollenscharniersAndreas, Dieter 11 December 2013 (has links) (PDF)
Die einer unterschiedlichen Genese zuordenbaren tektonischen Strukturen, welche sich im Raum des Thüringer Waldes bündeln, formten in einem gerichteten Entwicklungsablauf das komplizierteste und vielseitigste hochoberkarbonisch-unterpermische Strukturgebäude Mitteleuropas. In dieser Arbeit wird der Versuch einer Synthese der strukturellen und der daran geknüpften vulkanogen-sedimentären Entwicklung innerhalb der permokarbonischen Thüringer Wald-Senke und ihres unmittelbaren mitteleuropäischen Umfeldes unternommen. Sie stützt sich dabei maßgeblich auf die Ergebnisse langfristig durchgeführter Kartierungsarbeiten, die in diskontinuierlichen Bearbeitungsphasen seit 1957 bis in die 90er Jahre des vergangenen Jahrhunderts erfolgten. Einbezogen werden die Ergebnisse von insgesamt 54 Forschungs- und Erkundungsbohrungen, die zu einem Großteil im Kontext dieser Arbeiten geteuft worden sind. 36 Bohrprofile werden hier erstmals vollständig beschrieben und publiziert. Neben einer nochmaligen Überprüfung der gesamten lithostratigraphischen Abfolge in der permokarbonischen Thüringer Wald-Senke besteht die Zielstellung der Arbeit in deren Einbindung in die regionale mitteleuropäische strukturelle Entwicklung während dieser Zeitspanne, beginnend bei den potenziellen variszisch-kollisional angelegten Wurzeln der permokarbonischen Strukturen, über ihre weitere tektono-magmatische Ausgestaltung bis hin zur Ausprägung der postvariszischen Großschollenfelderung Mitteleuropas am Ende des Permokarbons.
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Der Thüringer Wald im Zeitraum der Stefan-Unterperm-Entwicklung - ein Abschnitt der Zentraleuropäischen N-S-Riftzone innerhalb des Mitteleuropäischen GroßschollenscharniersAndreas, Dieter 26 July 2013 (has links)
Die einer unterschiedlichen Genese zuordenbaren tektonischen Strukturen, welche sich im Raum des Thüringer Waldes bündeln, formten in einem gerichteten Entwicklungsablauf das komplizierteste und vielseitigste hochoberkarbonisch-unterpermische Strukturgebäude Mitteleuropas. In dieser Arbeit wird der Versuch einer Synthese der strukturellen und der daran geknüpften vulkanogen-sedimentären Entwicklung innerhalb der permokarbonischen Thüringer Wald-Senke und ihres unmittelbaren mitteleuropäischen Umfeldes unternommen. Sie stützt sich dabei maßgeblich auf die Ergebnisse langfristig durchgeführter Kartierungsarbeiten, die in diskontinuierlichen Bearbeitungsphasen seit 1957 bis in die 90er Jahre des vergangenen Jahrhunderts erfolgten. Einbezogen werden die Ergebnisse von insgesamt 54 Forschungs- und Erkundungsbohrungen, die zu einem Großteil im Kontext dieser Arbeiten geteuft worden sind. 36 Bohrprofile werden hier erstmals vollständig beschrieben und publiziert. Neben einer nochmaligen Überprüfung der gesamten lithostratigraphischen Abfolge in der permokarbonischen Thüringer Wald-Senke besteht die Zielstellung der Arbeit in deren Einbindung in die regionale mitteleuropäische strukturelle Entwicklung während dieser Zeitspanne, beginnend bei den potenziellen variszisch-kollisional angelegten Wurzeln der permokarbonischen Strukturen, über ihre weitere tektono-magmatische Ausgestaltung bis hin zur Ausprägung der postvariszischen Großschollenfelderung Mitteleuropas am Ende des Permokarbons.
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