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Al-Kindi, Mohammed. « Structural evolution and fracture pattern of Salakh Arch ». Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434242.
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Williams, Devin N. « The Association of Size Variation in the Dental Arch to Third Molar Agenesis for a Modern Population ». Scholar Commons, 2018. http://scholarcommons.usf.edu/etd/7247.
Texte intégralRésumé :
The frequency with which individuals do not develop their third molars, or wisdom teeth, is increasing worldwide. This current topic of human evolution is relevant to the research of anthropologists, geneticists, dentists, and other researchers involved in the study of human dentition. Many explanations have been offered to account for the prevalence of molar agenesis including, evolutionary, environmental, and genetic theories. The purpose of this research project is to determine the frequency of third molar agenesis and investigate the relationship between third molar agenesis and maxillomandibular jaw dimensions in a sample of orthodontic patients. This research tests the hypotheses that: H1: Individuals with agenesis of third molars will be significantly different in maxillomandibular dimensions than individuals without agenesis, H2: The agenesis of maxillary third molars is associated with the anteroposterior dimensions of the maxilla, and H3: The agenesis of mandibular third molars is not associated with the anteroposterior dimensions of the mandible. Therefore, the null hypothesis for this research is H0: An individual’s sex and the presence/absence of the third molar are independent. The sample for this research project includes 543 individuals from the University of New Mexico’s Maxwell Museum of Anthropology Orthodontics Case File System. This study examines panoramic radiographs of the dentition for each individual to ascertain whether any of the third molars was congenitally absent, and records the cephalometric measurements for each case for statistical analysis. This study uses descriptive statistics, crosstabulation analysis, chi-square tests, non-parametric Kruskal-Wallis tests, and logistic regression analysis to investigate any associations between third molar agenesis and maxillomandibular jaw dimensions.
The results show that Native Americans (9.2%), Hispanics (8.46%), and European Americans (8.37%) have a higher frequency of third molar agenesis than African Americans (0.17%) and Asians (0.17%). This finding is consistent with the published body of work on third molar agenesis, in spite of the small sample sizes for diverse populations. There is a significant difference in the number of molars missing among groups. For the present study, based on crosstabulation analysis, most individuals are missing two molars (34.9%), followed by one absent (31.7%), a lack of four molars (25.3%), and finally a lack of 3 molars (7.9%). Individuals with third molar agenesis are nearly twice as likely to be missing a molar from the mandible (62.8%) than the maxilla (36.9%).
This study uses crosstabulation analysis, chi-square analysis, non-parametric Kruskal-Wallis tests, and logistic regression analysis to assess the association between third molar agenesis and measurements of the dental arcade. This study did not find an association between an individual’s maxillomandibular dimensions and third molar agenesis. Therefore, this study did not find support for the hypothesis that individuals with third molar agenesis would have smaller maxillomandibular dimensions than individuals without agenesis. Based on the findings of this study, an association between the size of an individual’s mouth and third molar agenesis does not exist in the sample analyzed. Third molar agenesis is not occurring due to a lack of room in the mouth, but possibly results from heredity. Therefore, it may be more likely that genetic variation influences third molar agenesis, rather than an evolutionary change in diet.
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PIGAZZINI, ILARIA. « Evaluating and Detecting Architecture Erosion ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/365009.
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Un'architettura software è erosa (o degradata) se mostra una progressiva perdita di integrità strutturale a causa di violazioni dei principi di progettazione. I sistemi erosi soffrono di Architectural Technical Debt (ATD), lo sforzo aggiuntivo richiesto agli sviluppatori per gestire i difetti causati dall'erosione. Un sintomo dell'accumulo di ATD è la presenza di Architectural Smells (AS), decisioni di software design che hanno un impatto negativo sulla qualità interna del sistema software. I sistemi affetti da AS soffrono di maggiori costi di manutenzione e sono più difficili da evolvere. Questa tesi indaga sei diversi tipi di AS che violano diversi principi di design in progetti Java monolitici Open-Source e industriali. Identifichiamo gli AS con il nostro strumento, Arcan, e introduciamo la sua nuova estensione per la rappresentazione dei software concerns. Discutiamo poi gli AS dal punto di vista dei professionisti, cercando di riassumere come gli AS sono percepiti e validando i risultati di Arcan. Riportiamo anche i risultati dei nostri studi empirici riguardanti l'evoluzione e la correlazione di AS e ATD. Infine, presentiamo i nostri primi risultati riguardanti la migrazione e la manutenzione di architetture a microservizi, con particolare attenzione al rilevamento degli odori dei microservizi.A software architecture is eroded (or degraded) if it shows a progressive loss of structural integrity due to design principle violations which leads to the deviation of the implemented architecture from the intended architecture. Eroded systems suffer from Architectural Technical Debt (ATD), the additional effort required by developers to manage the shortcomings caused by the erosion. A symptom of the accumulation of ATD is the presence of Architectural Smells (AS), design decisions that impact negatively on the internal system quality. Systems affected by AS suffer from higher maintenance costs and are harder to evolve. This thesis investigates six different types of AS violating different design principles in Open-Source and industrial monolithic Java projects. We identify AS with our tool, Arcan, and introduce its new extension for the representation of software concerns. We then discuss AS from the point of view of practitioners, trying to summarise how AS are perceived and validating Arcan results. We also report the results of our empirical studies concerning AS and ATD evolution and correlation. Finally, we present our first results concerning the migration and maintenance of microservices architectures, with a focus on the detection of microservices smells.
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Talbot, Jared Coffin 1982. « Patterning and Stabilizing the Zebrafish Pharyngeal Arch Intermediate Domain ». Thesis, University of Oregon, 2011. http://hdl.handle.net/1794/11982.
Texte intégralRésumé :
xv, 76 p. : ill. (some col.) Includes 4 video files.Improved understanding of pharyngeal arch (PA) patterning and morphogenesis can reveal critical insights into the origins of craniofacial diseases, such as Fraser syndrome. PAs contain mesenchymal condensations, which give rise to most of the facial skeleton in vertebrates. Studies of Endothelin1 signaling reveal that the skeleton derived from the first two PAs are patterned into dorsal, intermediate, and ventral domains. Previous work has indicated that endothelin targets, including the Dlx genes, homeotically pattern dorsal versus ventral PA identity. I show that the Dlx gene family plays a vital role in PA intermediate-domain identity establishment. In WT fish, the PA intermediate domain is delineated by combined expression of all Dlx genes. Reduction of Dlx gene function results in loss of intermediate-domain identity. Conversely, ventral expansion of Dlx expression, seen in hand2 mutants, results in ventral expansion of intermediate-domain identity. Hence, PA intermediate-domain identity is defined by co-expression of Dlx genes. Epithelial-mesenchymal interactions play an important part in PA intermediate-domain morphogenesis. Zebrafish fras1 (epithelially expressed) and itga8 (mesenchymally expressed) mutants also show specific defects within intermediate-domain skeleton and epithelia. Facial phenotypes in fras1;itga8 double mutants look extremely similar to either single mutant, suggesting that fras1 and itga8 might participate in the same epithelial-mesenchymal interaction during PA intermediate-domain formation. Our developmental studies reveal that fras1 - and itga8 -dependent epithelial segmentation of the PA intermediate domain stabilizes developing skeletal elements. Lesions in human FRAS1 underlie many cases of Fraser syndrome, and this work provides an excellent developmental model for the craniofacial defects found in Fraser syndrome. Loss of either Dlx or fras1 function produces defects in the PA intermediate domain, yet seemingly during different developmental periods. Nonetheless, combined reduction of both Dlx and fras1 function synergistically increases skeletal defects, implying a molecular connection between early (Dlx -mediated) pattern formation and later (fras1 -mediated) pattern stabilization. Elucidation of the Dlx-fras1 interaction is an interesting topic which may unveil new molecules pertinent to Fraser syndrome. Supplemental movies highlighting skeletal and epithelial morphogenesis accompany this dissertation.
Committee in charge: Judith S. Eisen, Chairperson; Charles B. Kimmel, Advisor; John H. Postlethwait, Member; Chris Q. Doe, Member; Kennith E. Prehoda, Outside Member
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Morris, Aisha R. « Emplacement of deep submarine lava flows on the North Hawaiian Arch : a study of thermal and rheological evolution using a numerical model ». Thesis, University of Hawaii at Manoa, 2003. http://hdl.handle.net/10125/6982.
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Edwards, Caroline Marion Hawkey. « A comparison of arc evolution on continental and oceanic crust, Sunda Arc, Indonesia ». Thesis, Royal Holloway, University of London, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361452.
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Kadarusman. « Rainbowfishes from west Papua (Melanotaeniidae) : evolution and systematics ». Toulouse 3, 2012. http://www.theses.fr/2012TOU30079.
Texte intégralRésumé :
Située au Nord de l'Australie, la Nouvelle Guinée se caractérise par des reliefs montagneux très développés et demeure l'une des dernières régions inexplorées de la planète. Des processus complexes de géodynamique couplés a son isolement géographique ont contribué à la mise en place d'un panel complexe d'écosystèmes et à l'évolution d'une biodiversité exceptionnelle. Cette particularité vaut également pour la diversité de sa faune ichtyologique. Les poissons arc-en-ciel (Melanotaeniidae) constituent avec les Eleotridae et les Gobiidae, les 3 familles de poissons les plus diversifiées des eaux douces de Nouvelle Guinée et même d'Australie. La taxonomie des poissons arc-en-ciel est ancienne et a connu un regain d'intérêt durant ces dernières décennies avec la description d'une cinquantaine d'espèces nouvelles. Malgré un nombre important d'espèces décrites, la taxonomie des Melanotaeniidae demeure encore confuse avec des diagnoses incomplètes basées sur des comptages ou des caractères morphologiques. Les rares données moléculaires et phylogénétiques disponibles pour quelques espèces de Melanotaeniidae sont également incomplètes et ne permettent pas de valider les hypothèses taxonomique ou évolutive proposées par plusieurs auteurs. Les résultats présentés dans cette thèse apportent une contribution significative dans la compréhension des processus de diversification des poissons arc-en-ciel de Papouasie Occidentale et plus largement des régions adjacentes comprenant le reste de la Nouvelle Guinée et le nord de l'Australie. Ils proposent également une révision taxonomique complète des espèces peuplant la Papouasie Occidentale avec 28 espèces valides et incluant 15 espèces nouvellesNew Guinea Island is an immense, rugged landscape and remains one of the last unexplored places. This is particularly true for its ichthyological fauna. With freshwater Gudgeon and Gobiids, the Austro-New Guinean rainbowfishes are the most diverse groups with important endemism. Rainbowfish taxonomy is ancient and recently attracted much attention for various domains interest. Despite a large number of species already described, their taxonomy remains incomplete and somewhat confused. Data on their phylogenetic relatedness or biogeographical history are scarce. The results presented here give a contribution to diversification processes of Rainbowfishes from West Papua and adjacent biogeographic region and provide a complete taxonomic revision of the Western New Guinean species. A total of 716 specimens belonging to 3 genera have been studied in morphology and molecular relatedness. Molecular phylogenies were inferred from 3 mitochondrial regions (Cox-1, Cyt-b, D-loop) and 1 nuclear intron (S7). The dataset includes more than 5,000 base pairs with a portion of DNA Barcodes. The choice of both mitochondrial and nuclear molecular markers was driven by the multiple objectives to resolve deeper and shallow radiations and to evidence possible hybridization events. The phylogenies revealed an unexpected cryptic diversity within the genus Melanotaenia and strongly supported the polyphyly of the genera Glossolepis and Chilatherina. The results also revealed a strong congruence between phylogenetic relatedness, clade composition and geography and confirmed that the center of origin of Melanotaenia sensu lato was dated to the Mid-Miocene in the Bird's Head Peninsula. The eological context of the area revealed that the formation of the Lengguru fold-and-thrust Belt together with the ridge of the Central Dividing Range were the main events responsible of the basal diversification processes within this group of obligate freshwater fishes
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Bignold, Stella Mary. « The initiation and magmatic evolution of a juvenile island arc : the Kohistan arc, Pakistan Himalaya ». Thesis, Kingston University, 2001. http://eprints.kingston.ac.uk/20671/.
Texte intégralRésumé :
The Kohistan arc, situated in the northwestern Himalaya of North Pakistan, is a Cretaceous intra-oceanic island arc which was erected during subduction of the Tethys Ocean consequent on the northward flight of India. Following accretion to the Asian margin, the arc behaved as an Andean-type continental arc prior to the collision of India with the Asian continent, which uplifted the arc and tilted it, thus providing a unique opportunity to study a complete succession of rocks from the very earliest stages of arc evolution. A combination of fieldwork, geochemical and radiogenic isotope analysis, and rare earth element modelling are used to determine the main magma sources in the mantle beneath the arc. The Kamila Amphibolites fall into two successions. The 'E-type' rocks have a MORB-type signature and were formed from 6% partial melting of a primitive, garnet¬bearing, mantle source. The 'D-type' Kamila Amphibolites have an arc signature and represent the earliest arc volcanic rocks. They originated from 15.5% partial melting of a primitive spinel-bearing, mantle source. The Jaglot Group (Gashu Confluence Volcanics and Peshmal Volcanics) and Western Volcanics of the Chalt Volcanic Group were generated by 7.5%, 13% and 2.5% partial melting, respectively, of a primitive, garnet¬bearing, mantle source. The Hunza Valley Volcanics of the ChaIt Volcanic Group, which contain boninites, have MORB-type chemistries and an arc signature. These rocks were generated from 15% melting of a depleted, spinel-bearing mantle source which may be the residuum from partial melting which produced the 'E-type' Kamila Amphibolites. That the Hunza Valley Volcanics were generated from this source is consistent with the 'E-type' Kamila Amphibolites fonning the basement and the Hunza Valley Volcanics occurring in the back-arc. Radiogenic Nd, Sr and Pb isotope analyses address an hypothesis that the magmas were generated from 'Dupal' -type mantle. The results indicate that this is not the case, but show that the isotopic chemistry of the rocks is the result of fluids from dehydration and melting of sediments carried on the downgoing ocean crust into the subduction zone affecting magma chemistry. A recent controversy concerns the polarity of subduction beneath the arc. This is partly' based on the presence of boninites, and the prevalent understanding that this rock-type occurs solely in the fore-arc. Evidence from this thesis suggests that the boninites of the Hunza Valley Volcanics were erupted into a back-arc setting, and arguments are made that boninites may also be erupted into the back-arc, and that the polarity of subduction was to the north. A model is presented for the erection of the Kohistan arc in which subduction was initiated by gravitational instability at an oceanic transform fault which connected two mid-ocean spreading ridge segments. The first arc magmas were generated by decompression melting beneath extending lithosphere during initial subsidence, and as this turned into subduction, magmas were generated at progressively greater depths in the spinel and garnet lherzolite facies, respectively. Lithospheric extension and rifting behind the volcanic front provided the setting for deompression melting to produce the back-arc Hunza Valley Volcanics, including high-Mg basalts and andesites. The arc signature in these rocks became reduced as the spreading centre developed and became progressively removed from the vicinity of the subduction zone.
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Noury, Mélanie. « Evolution géologique de l'avant-arc sud péruvien : apports des données géo-thermochronologiques ». Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENU058/document.
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La marge sud péruvienne est située au niveau d’une zone majeure de subduction océan continent depuis au moins le Paleozoique inférieur. C’est dans ce cadre que s’est formé l’un des plus importants orogènes du monde : les Andes Centrales. En effet, l’épaisseur crustale y est >60 km et ce sur une importante surface. Cependant, on considère actuellement que ce surrépaississement a été acquis incrémentalement seulement depuis ~30 Ma. Dans le but de comprendre comment et quand ce surrépaississement est apparu, la majeure partie des études précédentes s’est focalisée sur l’évolution de l’arc magmatique et sur l’histoire de la déformation, du soulèvement et de l’érosion de la zone d’arrière arc. Cependant, l’évolution tectonique et thermique de l’avant arc reste mal connue bien que cette zone soit susceptible de bien enregistrer les changements liés à la dynamique de subduction.Cette thèse à pour objectif de mieux contraindre l’évolution thermique et les couplages entre les processus magmatiques, tectoniques et sédimentaires depuis 200 Ma dans l’avant-arcactuel du sud du Pérou. De nouvelles données géo-thermochronologiques couplées à une nouvelle carte tecto-stratigraphique éclaircissent l’évolution de la marge péruvienne depuis le Jurassique. Trois périodes clefs sont analysées dans ce mémoire : le début de l’épaississement crustal, les déformations de l’avant-arc associées à la formation de l’Orocline bolivien et l’épaississement crustal de l’orogène des Andes Centrales pendant le Néogène.Nous montrons que l’épaississement crustal a probablement commencé entre 90 et 50Ma après plus de 200 Ma d’amincissement, et ce a la faveur d’une évolution en trois étapes :croissance initiale (90-74 Ma), « flare-up » (74-62 Ma) et effondrement extensionnel (62-50Ma). L’extension a ensuite prédominé dans l’avant-arc tout en diminuant progressivement jusqu’à ~30 Ma. Par ailleurs, nous mettons en évidence d’importantes zones de faillesnormales orientées perpendiculairement à la marge sud-péruvienne et qui délimitent de grands blocs basculés vers le nord-ouest. Ces déformations révèlent une extension parallèle à l’orogène dans l’avant arc pendant le Paléogène, probablement due à la formation de l’Orocline bolivien par rotation antihoraire de blocs rigides. Enfin, les traits géomorphiques visibles dans la zone cotiere du sud du Pérou permettent de définir deux périodes de soulèvement de la surface (entre 23 et 10 Ma et depuis ~4.5 Ma), séparées par une période de subsidence (entre ~10 et ~4.5 Ma). La même chronologie ayant été décrite sur le versant Amazonien de l’orogène, nous proposons que cette évolution soit due à des variations à grande échelle de l’épaisseur crustale ; le soulèvement de la surface étant provoqué par addition à la croûte de magma d’origine mantellique et la subsidence par un flux de matériel crustal ductile depuis les zones précédemment sur-épaissiesThe southern Peruvian margin has been located above a major ocean-continentsubduction zone since at least the Early Paleozoic, resulting in the formation of one of thelargest orogens in the world: the Central Andes, where crustal thickness is >60 km over a largearea. This overthickening is currently thought to have occurred incrementally only during thelast 30 Ma. To understand how and when crustal overthickening was acquired, most of theprevious studies have focused on the magmatic arc evolution and on deformation, uplift anderosion history of the backarc. The tectono-thermal Cenozoic evolution of the forearc remainspoorly known, whereas it is a zone prone to recording changes in subduction dynamics.The objective of this dissertation is to address the thermal evolution and the couplingbetween magmatic, tectonic and sedimentary processes over the past 200 Ma in the presentdayforearc of southern Peru where the crust thickens from ~30 km along the coastline tomore than 60 km under the present-day volcanic arc. New geo- and thermochronological datacoupled to a novel geological map illuminate the evolution of the south Peruvian margin sincethe Jurassic. Three key periods of the margin evolution are addressed in this dissertation: theonset of crustal thickening, the deformations associated in the forearc with the formation ofthe Bolivian Orocline and the Neogene crustal thickening of the Central Andean orogen.We show that crustal thickening likely began between 90 and ~50 Ma after more than200 My of lithospheric thinning during a three step evolution of the magmatic arc as follows:growth (90-74 Ma), flare-up (74-62 Ma), extensional collapse (62-50 Ma). Extension prevailedin the forearc since then and waned until ~30 Ma. In addition, we evidence important normalfault zones striking perpendicular to the southern Peruvian margin that delineate largenorthwestward tilted blocks. This deformation reveals orogen parallel extension in the forearcduring the Paleogene likely due to the formation of the Bolivian Orocline by counterclockwiserotation of rigid blocks. Finally, geomorphic features in the coastal area of southern Perureveal two periods of surface uplift (~23 to 10 Ma and since ~4.5 Ma), separated by a period ofsurface subsidence (from ~10 to ~4.5 Ma). The same chronology has been described on theAmazonian side of the Central Andean orogen. We thus propose that this evolution is due tolarge-scale crustal thickness variations; surface uplift being triggered by addition of mantlederivedmagmas to the crust and subsidence by ductile flow away from the previouslyoverthickened crust
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Hollis, Steven Philip. « Evolution and mineralization of volcanic arc sequences : Tyrone Igneous Complex, Northern Ireland ». Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/359062/.
Texte intégralRésumé :
The Tyrone Igneous Complex of Northern Ireland forms an integral part of the Grampian-Taconic orogen, linking the well documented sectors of Scotland, western Ireland and Newfoundland. The orogen records the accretion of a series of peri-Laurentian affinity arcs, ophiolites and microcontinental blocks to the Laurentian margin between the Late Cambrian and Middle Ordovician. The Tyrone Igneous Complex is broadly divisible into two distinct units: the c. 484-480 Ma ophiolitic Tyrone Plutonic Group and the structurally overlying c. 475-469 Ma arc-related Tyrone Volcanic Group. Both were intruded by a synvolcanogenic and syncollisional, to postcollisional high-level ensialic intrusive suite between c. 470 and 464 Ma associated with their coeval obduction to an outboard peri-Laurentian microcontinental block, the Tyrone Central Inlier, at c. 470 Ma. The Tyrone Plutonic Group is principally composed of amphibolite-facies layered and isotropic gabbros, sheeted dolerite dykes and rare pillow lavas. Tholeiitic suprasubduction affinity geochemical characteristics, Nd- isotope constraints, zircon inheritance, and the presence of late Fe-Ti enriched post-obduction dykes suggest the Tyrone Plutonic Group formed above a N-dipping subduction zone by the propagation of a spreading centre into a microcontinental block. The Tyrone Volcanic Group is characterized by mafic to intermediate lavas, tuffs, rhyolite, banded chert, ironstone and argillaceous sedimentary rocks cut by numerous high-level synvolcanogenic intrusive rocks. Geochemical signatures are consistent with formation in an evolving peri-Laurentian island-arc which underwent several episodes of rifting. High LILE and LREE enrichment, calc- alkaline geochemical signatures and strongly negative εNd t values suggest the Tyrone arc was at least partially founded on a fragment of microcontinental crust, which may have rifted off the Tyrone Central Inlier during the formation of the Tyrone Plutonic Group. Stong temporal, stratigraphic, and geochemical correlations with elements within the Annieopsquotch Accretionary Tract of Newfoundland suggest the Tyrone Igneous Complex represents a third phase of arc-ophiolite obuction in the Irish Caledonides during the Grampian-Taconic orogeny and may potentially host significant VMS mineralization. Through a combination of field mapping and petrochemistry several stratigraphic horizons have been identified in the Tyrone Igneous Complex, favourable for the formation and preservation of VMS deposits. Each is closely associated with hydrothermal alteration, synvolcanogenic faults and high-level synvolcanogenic intrusions of dolerite, gabbro, diorite and tonalite. Episodic rifting is recorded by the eruption of: abundant non-arc type Fe-Ti enriched eMORB (‘icelandite’), island-arc tholeiite, OIB-like alkali basalt, high-temperature tholeiitic rhyolites with flat to U-shaped REE profiles, and high-Zr rhyolites, within the calc-alkaline dominated sequence. Rift related mafic lavas occur in the hangingwall to VMS-style mineralization and are closely associated with ironstones (often Au-bearing) and/or argillaceous sedimentary rocks representing volcanic quiescence. Extensive hydrothermal alteration, characterized by Na-depletion, high Ba/Sr, Bi, Sb, Ni, CCPI, AI and variable MgO and CaO, allows specific target areas to be identified. In the lower bimodal-mafic Tyrone arc and backarc, hydrothermal alteration is associated with Zn-Cu mineralized float. Pb-Zn-Cu-Au mineralization occurs in silicified auriferous rhyolite domes/flows and/or volcaniclastic rocks of the syncollisional bimodal-felsic upper Tyrone arc. Ophiolite hosted Cu mineralization is characterized by chalcopyrite stringers hosted in sheeted dyke sequences.
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Mukti, Muhammad Ma'ruf. « Tectonic Evolution of the South Sumatra-Java Forearc System from Deep Seismic Reflection Data ». Paris, Institut de physique du globe, 2013. http://www.theses.fr/2013GLOB1101.
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Dissler, Eric. « Evolution geodynamique cadomienne du nord-cotentin (massif armoricain) ». Caen, 1987. http://www.theses.fr/1987CAEN2048.
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La structuration actuelle des terrains brioveriens resulte en grande partie de l'evolution tectono-metamorphique varisque. La chaine cadomienne accuse une vergence nord-ouest. L'identification geochimique des series volcaniques brioveriennes revele une affinite tholeitique generalisee. Une tendance calcoalcaline s'exprime en revanche au sein du batholite de la hague. L'enchainement des premieres etapes de l'evolution geodynamique cadomienne est ainsi etablie, le magmatisme du brioverien inferieur traduisant le fonctionnement d'un dispositif arcs insulaires-bassins marginaux de type marge ouest du pacifique, installe sur des lambeaux de croute pentevrienne
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Zagorevski, Alexandre. « Tectono-magmatic evolution of peri-Laurentian and peri-Gondwanan arc-back arc complexes along the Red Indian Line, central Newfoundland Appalachians ». Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/29325.
Texte intégralRésumé :
The Appalachian-Caledonian Orogen is a classic example of a Paleozoic accretionary orogen which turned into a collisional orogen. The Newfoundland Appalachians represent a critical element of the Appalachian-Caledonian Orogen to evaluate terrane linkages and tectonic models between the North American and European segments, especially those formed during the closure of lapetus. This thesis presents new geochemical, geochronological, Sm/Nd isotope, structural and P/T data and proposes informal tectonostratigraphic framework for the central Newfoundland Appalachians. The data presented in this thesis are used to test tectonic models for closure of the lapetus and thus have important implications for the interpretation of tectonic relationships in other parts of the northern Appalachians (e.g. New England) and the British Caledonides.
Central Newfoundland is underlain by the peri-Laurentian Annieopsquotch Accretionary Tract and peri-Gondwanan Victoria Lake Supergroup, separated by the Red Indian Line, the main lapetan suture zone. Subduction in the Annieopsquotch Accretionary Tract initiated at c. 480 Ma. Subsequently two distinct continental arc-backarc terranes (c. 473 Ma Buchans and 465-460 Ma Red Indian Lake arcs) were formed over an approximately 15 Ma period. A refined tectonic model is proposed for the Annieopsquotch Accretionary Tract involving both thrust and strike-slip displacements. The data require rapid accretion of arc-backarc complexes to the Laurentian margin less than 10 Ma after their formation. This accretion forms part of the Taconic Orogeny and is associated with development of D1 shear zones as early as c. 470 Ma.
The subduction in the Victoria Lake Supergroup initiated prior to 513 Ma. Subsequently two distinct arc complexes were formed (513-485 Ma Penobscot arc and 473-453 Victoria arc). The Penobscot arc has been previously interpreted as an intraoceanic arc, however Sm/Nd isotopes, zircon inheritance data and stratigraphic relationships indicate formation of the Penobscot arc on continental crust. This crust is similar to Ganderia, which is a postulated peri-Gondwanan microcontinent. The gap in arc magmatism between the Penobscot and Victoria arcs coincides with the obduction of ophiolites onto Ganderia (Penobscot Orogeny). The data presented herein support a new model for the tectonic evolution of the Penobscot arc above an east dipping subduction zone. In this model the Penobscot ophiolites are obducted as a result of backarc basin inversion, possibly due to accretion of a seamount (Summerford Group) or ridge subduction. Following the Penobscot Orogeny, arc volcanism recommenced as the Victoria arc which rifted from the Ganderia margin opening a wide Exploits-Tetagouche backarc in its wake. (Abstract shortened by UMI.)
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Sumption, Alan. « The evolution of break arc erosion from arc initiation to extinction on silver alloy electrical contacts in low voltage DC switches ». Thesis, University of Southampton, 2005. https://eprints.soton.ac.uk/47499/.
Texte intégralRésumé :
This study concerns the evolution of electrical contact erosion in low voltage 42V DC (24A) applications. The aim is to describe the erosion mechanisms of a single arc discharge at both contact surfaces during operation. To this end the experiments conducted are designed to produce results that enable close examination of the surface profile changes, volumetric contact material movements, and relative quantities of metallic and gaseous species in the arc discharge. The experimental procedure is arranged so that the contacts undergo a low number of operation cycles in order to limit the cumulative effects of arc erosion. To obtain results portraying the evolution of arc erosion in a 42V system the apparatus allows for interruption of the arc at any desired voltage level. A series of tests are conducted at specified voltage steps from arc initiation to extinction. The samples collected are analysed using a non-contact laser profile apparatus giving 2D and 3D surface scans. During each arc discharge a record of spectral emissions is collected by a spectrometer and later analysed to show the constituents of the arc. The data is represented with reference to voltage level and shows how the erosion evolution from a low number of operation cycles is related to arc phenomena. In addition the voltage profiles of the arc are recorded and represented by amplitude modulation. It has been found that the erosion site dimensions are related to the arc voltage fluctuations. In these tests a marked change of voltage slope is seen but is not found to be related to the metallic to gaseous phase transition as often thought. It is determined that the anodic to cathodic arc transition is not due to a metallic to gaseous phase transition. Changes in surface profile at the cathode occurring during the cathodic arc phase, and before gaseous phase initiation, are affected by density per unit area of ions impacting the surface. The vaporization of the cathode requires a critical ion density. This determines the anodic to cathodic transition point. Conversely the anode is thought to endure intense electron sputtering throughout the arc lifetime and its volumetric loss is greater than that of the cathode.
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Wang, Baiqiu, et 王伯秋. « Magmatic and sedimentary constraints on the evolution of the triassic Yidun Arc, eastern Tibet ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B50605719.
Texte intégralRésumé :
The Yidun Terrane in the eastern Tibetan plateau is separated from the Songpan-Ganzi Terrane by the Ganzi-Litang suture zone to the east and Qiangtang Block by the Jinsha suture zone to the west. Both suture zones are marked by eastern Paleo-Tethyan ophiolites. The western part of the Yidun Terrane, the Zhongza Massif, is dominated by Paleozoic sedimentary sequences. In the eastern part, Triassic subduction-related plutonic rocks and volcanic-flysch successions of the Yidun Group are important elements for understanding the evolution of eastern Paleo-Tethys and amalgamation of East Asia.
The Yidun Group includes the Lieyi, Qugasi, Tumugou and Lanashan Formations from base upwards. Two major depocenters for the Yidun Group can be recognized. Sedimentary detritus supplying for the northern depocenter were dominantly sourced from the Zhongza Massif and received recycling components in a passive margin setting. In the southern depocenter, the Qugasi Formation accumulated materials from the Zhongza Massif, whereas the Tumugou Formation received additional materials from locally distributed Triassic arc rocks and crystalline basement rocks, which indicates transition from a passive margin to a magmatic arc setting.
In the southern Yidun Terrane, (quartz-) dioritic hypabyssal intrusions are spatially associated with andesites and dacites and have zircon U-Pb ages from ~230 to 215 Ma. They have adakitic geochemical features and are divided into the ~230-215 Ma high silica (HSA) and ~215 Ma low silica (LSA) adakitic rocks. The HSA formed from subducted slab melts with limited interaction with the overlying mantle wedge, whereas the LSA were generated from slab melts with more extensive interaction with mantle due to slab break-off at ~215 Ma.
In the northern Yidun Terrane, granitic plutons and volcanic rocks occur in two parallel N-S belts. The ~228 Ma volcanic rocks in the Xiangcheng region are adakites generated from slab melts, whereas the ~231-230 Ma volcanic rocks in the Changtai region, including basalts, andesites, dacites and rhyolites, formed in a back-arc setting. The Changtai basalts were produced by low degrees of partial melting of an OIB-like mantle source with minor involvement of subducted slab components. The Changtai andesites/dacites represent evolved members from the basaltic magmas through an AFC process, whereas the rhyolites formed from anatexis of a garnet-bearing crustal source. These volcanic rocks are 4-6 mys older than arc granitic rocks in the northern Yidun Terrane.
The spatio-temporal framework of all the subdution-related igneous rocks suggests initiation of subduction of the Ganzi-Litang oceanic lithophere under the southern Yidun Terrane at ~230 Ma, resulting in the adakitic magmatism in the Shangri-La and Xiangcheng regions and the back-arc magmatism in the Changtai region. Subsequently at ~224 Ma, the subduction extended to the northern Yidun Terrane, leading to the formation of the arc granitic plutons. From south to north, the Yidun Terrane was sequentially amalgamated with the Songpan-Ganzi Terrane during the Late Triassic.published_or_final_version
Earth Sciences
Doctoral
Doctor of Philosophy
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Wainwright, Alan John. « Volcanostratigraphic framework and magmatic evolution of the Oyu Tolgoi porphyry Cu-Au district, South Mongolia ». Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2760.
Texte intégralRésumé :
The super-giant Oyu Tolgoi porphyry copper-gold deposits in the South Gobi
desert, Mongolia, consist of multiple discrete porphyry centers aligned within a north-northeast trending, >6.5 km long, arc-transverse mineralized corridor. The porphyries are linked to a tectono-magmatic event at ~372 Ma within a Devonian to Carboniferous volcanic arc, and U-Pb (zircon) geochronology records magmatic activity from ~390 Ma to ~320 Ma. The Oyu Tolgoi district underwent at least three discrete periods of syn- to post-mineral shortening and there is evidence for at least three unconformities within the Paleozoic sequence. Although the deposits were formed in an active orogenic
environment characterized by rapid uplift, their preservation is a reflection of climactic effects as well insulation from erosion by rapid burial under mass-wasted and pyroclastic material in the volcaniclastic apron of late-mineral dacitic volcanoes.
The porphyry copper-gold deposits are spatially and temporally related to
medium- to high-K calc-alkaline quartz monzodiorite (~372 Ma) and granodiorite (~366
Ma) intrusive phases that comprise the Late Devonian Oyu Tolgoi Igneous Complex
(OTIC). Adakite-like wholerock compositions as well as zircon grains with high
CeN/CeN*, EuN/EuN* and Yb/Gd in the sample populations from syn- and late-mineral
porphyry intrusions are different from younger intrusions that are not related to porphyry Cu-Au deposit formation. Moreover, mixed zircon populations within OTIC intrusions indicate that efficient assimilation of material from different host rocks by a convecting magma chamber occurred.
Mafic to intermediate volcanic units evolved from tholeiitic to calc-alkaline compositions, which is interpreted to be a reflection of marine arc maturation and
thickening. Felsic rock suites are dominantly high-K calc-alkaline, regardless of age.
Nd-isotopic geochemistry from all suites is consistent with magma derivation from
depleted mantle in an intra-oceanic volcanic arc and lead isotopic compositions indicate
that the sulfides in the porphyry Cu-Au deposits are genetically linked to the Late
Devonian magmas.
Magma mixing, adakite-like magmatism and rapid uplift and erosion in a juvenile
marine arc setting differentiate the ore-stage geologic environment at Oyu Tolgoi from other settings in active and fossil volcanic arcs.
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Calkins, Josh A. « An Investigation of Lithospheric Structure and Evolution in Convergent Orogenic Systems using Seismic Receiver Functions and Surface Wave Analysis ». Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/195366.
Texte intégralRésumé :
Whether by accretion, magmatic addition, or refinement of more mafic lithologies, continental arcs are likely zones for the creation of "average" continental crust with intermediate silica content. This dissertation contains the results of broadband seismic studies carried out in two field areas, an active subduction zone and the remnants of an extinct arc, with the aim of understanding lithospheric evolution at convergent margins. The analytical techniques of receiver function calculation and surface wave tomography are applied to data sets collected above the Andean subduction zone in Chile and western Argentina and in the Coast Mountains Batholith of central British Columbia. We present the first in-depth comparison of receiver functions calculated using the high frequencies available in records of intermediate-depth local earthquakes with those calculated from the lower frequency data in records of larger teleseismic events. The comparison reveals that the lower crust beneath the Western Sierras Pampeanas contains a gradational velocity increase over ~20km above a small velocity step at the Moho. Surface wave tomography confirms the existence of an unusually high velocity anomaly in the mantle above the slab and yields estimates of slab thickness on the order of 50 km. To the south of the flat slab region, we see evidence of active mantle wedge convection above the steep slab, but no evidence of the lithosphere-asthenosphere boundary beneath the subducting Nazca plate. In the Coast Mountains Batholith (CMB), receiver functions image a bright, continuous Moho throughout the study region. Combined with petrologic modeling, the receiver function data point toward convective removal of any ultramafic root that formed beneath the CMB. Low absolute shear wave velocities in the upper mantle resolved via surface wave analysis strengthen the case for root removal beneath the eastern section of the CMB. On the far western edge of the CMB, we find evidence of a partially reformed lithosphere outboard of a major tectonic boundary. These observations shed light on the distillation of felsic to intermediate continental crust from more mafic primary magmas in active subduction zones and the eventual return of the complementary ultramafic residuals to the convecting mantle.
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Haugen, Emily A. « Magmatic Evolution of Early Subduction Zones : Geochemical Modeling and Chemical Stratigraphy of Boninite and Fore Arc Basalt from the Bonin Fore Arc ». DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/5934.
Texte intégralRésumé :
The Izu-Bonin-Mariana arc stretches south from Japan to Guam in the Western Pacific. International Ocean Discovery Project Expedition 352 drilled four core in the fore arc of the Izu-Bonin arc east of the Bonin Islands: U1439C, U1440B, U1441A, and U1442A. From the four core, 124 samples were retrieved and analyzed for major and trace elements. Two main rock types were identified: FAB and boninite. FAB is a Mid-Ocean Ridge Basalt (MORB)-like tholeiite with variable fluid mobile element enrichment such as Rb, Ba, and Sr, and low Ti/V ratios more similar to an island arc volcanic than a mid-ocean ridge volcanic. Boninite is a hydrous high-Mg andesite with low TiO2 and distinctive subduction zone characteristics in the form of elevated fluid mobile elements and melt mobile elements. FAB was assumed to be formed from a Depleted MORB-Mantle (DMM) source and the boninite was formed from a depleted mantle source, presumably the mantle after FAB melt was extracted. Here, we used the Rare Earth Elements (REE) of the samples to model melt scenarios for the FAB and boninite in order to better understand the initial volcanic product of subduction zones.
This research was funded by in joint by the National Science Foundation, Consortium for Ocean Leadership, and International Ocean Discovery Program. 124 samples were analyzed using an X-Ray Fluorescence (XRF) and Inductively Coupled Plasma - Mass Spectrometer (ICP-MS) to determine the major and trace elements. These analyses were then used to recreate the chemostratigraphy defined by the shipboard crew and determine variations within the core. We found that there was variability as the magma evolved over time and mixed with other melts, seen in magma mixing horizons. Boninite samples were separated based on their SiO2 and MgO concentrations into Basaltic Boninite (BB), Low-Silica Boninite (LSB), and High-Silica Boninite (HSB) with BB being more primitive and HSB being more evolved.
These volcanics are the first known products of the subduction zone and were used to model the early evolution of the subduction zone. FAB was the first product due to its proximity to the trench and greater age than the boninite. Assumed to be generated from DMM, FAB was modeled with a total melt extraction of ~20% spinel lherzolite and 1% garnet lherzolite. Boninite was assumed to be generated from the FAB residue because it requires a depleted source and because the FAB residue was within the hydrous flux melt zone of the subduction factory. Boninite was modeled at high degree of melt from the FAB residue, however an additional melt must be added to the model to match the observed samples. We proposed a small fraction of FAB melt mixed with the models because it is still present in the subduction factory, observed in core U1439C with a FAB sample in the HSB regime.
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Sutanto. « Evolution temporelle du magmatisme d'arc insulaire : géochronologie, pétrologie et géochimie des magmatismes mésozoiques et cenozoiques de Sumatra (Indonésie) ». Brest, 1997. http://www.theses.fr/1997BRES2047.
Texte intégralRésumé :
L'île de Sumatra est le site de la subduction de l'ocean indien sous la bordure du bloc continental eurasiatique. Les massifs plutoniques et volcaniques meso et cenozoiques, qui affleurent notamment dans la partie ouest de l'ile selon une bande nnw-sse longue de 1650 km, ont ete echantillonnes systematiquement. 175 datations #4#0k-#4#0ar sur roches totales pour le volcanisme et/ou sur mineraux separes (biotites, amphiboles et feldspaths) pour le plutonisme et des analyses geochimiques par icp-aes permettent de preciser la distribution spatio-temporelle des episodes magmatiques, d'en discuter le contexte geodynamique et d'evaluer les modifications subies par le manteau de l'arc de la sonde au cours d'une subduction prolongee. Au cours de la longue histoire magmatique de sumatra, huit episodes associant etroitement volcanisme et plutonisme sont identifies : trias superieur a lias ; bathonien a callovien ; valanginien a aptien ; albien a campanien ; paleocene a eocene inferieur ; eocene moyen et superieur ; oligocene a miocene superieur ; miocene terminal a actuel. Les plutons dates de 215 a 180 ma et 165 a 150 ma se situent au coeur du substratum permo-carbonifere du centre de l'ile et les plus recents se disposent selon des segments etroits, paralleles a la bande volcanique cotiere. Un grand arc volcano-plutonique est identifie des le cretace inferieur. La position et la geometrie de l'ensemble n'ont pratiquement pas varie depuis. Les echantillons analyses presentent les signatures geochimiques de magmas d'arc, depuis des series calco-alcalines faiblement potassiques jusqu'a des series shoshonitiques. Globalement, l'augmentation au cours du temps des teneurs en elements incompatibles (notamment a grand rayon ionique) est compatible avec l'enrichissement progressif de la source mantellique des magmas par des fluides hydrates vehiculant les elements extraits principalement des sediments subductes.
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McCarron, Joseph John. « Evolution and tectonic implications of late Cretaceous - early Tertiary fore-arc magmatism : Alexander Island, Antarctica ». Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389878.
Texte intégral
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Heath, Emily. « Genesis and evolution of calc-alkaline magmas at Soufriere volcano, St Vincent, Lesser Antilles arc ». Thesis, Lancaster University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360643.
Texte intégralRésumé :
Soufriere of St. Vincent is the most active subaerial volcano in the Lesser Antilles arc, and is composed of basalts and basaltic andesites. Eruptive style has tended to alternate between predominantly effusive and explosive, although magma compositions show no systematic variations with time. New Ar-Ar and 14C dates help to constrain the geological evolution of the (- 0.6 Ma) volcano. Parental, possibly primary, magmas at Soufriere had MgO contents exceeding 12 wt.% (mg# 75) and were probably nepheline-normative. They may be representative of the parental magmas of the calc-alkaline suites of the Lesser Antilles arc. The source mantle probably resembled that of N-MORB, prior to metasomatic enrichment by hydrous slab-derived fluids, containing contributions from subducted sediments and oceanic crust. Parental magmas last equilibrated with the mantle at - 17 kbar pressure, with temperatures greater than 1130·C and f02 exceeding FMQ +1. Near-primary basaltic lavas were only erupted during the earliest (Pre-Somma) phase of volcanism. Basaltic andesites (and occasional andesites) were produced by fractionation of 01 + spinel + cpx + plag ± opx over a range of crustal pressures (5-10kbar), at temperatures mainly in the range 1000 - 1l00·C. The total amount of crystallization was some 76 wt. %, and amphibole was apparently not a fractionating phase. There is conflicting evidence as to the pre-eruptive water contents of Soufriere magmas; phenocryst compositions suggest H20 > 3 wt. %, whereas various projections into phase diagrams are more consistent with relatively anhydrous magmas. Magma mixing did not apparently play a significant role in the evolution of most Soufriere magmas, and fractional crystallization was not accompanied by crustal assimilation, judging from trace element and Sr-Nd isotope systematics. New U-Th mineral isochrons suggest that magmas resided for tens of thousands of years within the crust, which requires rather stable thermodynamic conditions in the magma chamber(s) beneath Soufriere.
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Hebert, Ronan. « Evolution tectonometamorphique d'un arc insulaire au proterozoique superieur : le domaine de saint-brieuc (massif armoricain) ». Rennes 1, 1993. http://www.theses.fr/1993REN10084.
Texte intégralRésumé :
L'orogene cadomien est une chaine d'age proterozoique superieur qui affleure au sein de le croute continentale ouest-europeenne. Le nord du massif armoricain represente le plus large temoin de cette chaine precambrienne dont l'evolution geodynamique, malgre de nombreuses contraintes geophysiques, structurales, sedimentologiques et magmatiques, reste controversee. Le but de ce travail est d'apporter de nouvelles contraintes a l'evolution geodynamique cadomienne par l'etude du metamorphisme. Cette etude est consacree au domaine de saint-brieuc: 1) l'evenement tectonique majeur prend place entre 590 et 570 ma. La deformation et le metamorphisme presentent un gradient croissant vers le sud. Au nord, la formation de lanvollon est essentiellement constituee de metabasaltes et de metasediments interstratifies. Les conditions p-t sont estimees a 3-5 kbar et 55050c. Au sud, la formation d'yffiniac presente une sequelle cumulative de roches basiques a ultrabasiques. Les estimations p-t sont de 8 2kbar et 70050c; 2) des intrusions granitiques et dioritiques se mettent en place vers 540 ma. Elles ne sont pas deformees et developpent des aureoles de metamorphisme de contact dans les roches encaissantes. Le domaine de la baie de saint-brieuc est donc affecte par un metamorphisme ht-bp. Ceci suggere que l'orogene cadomien ne s'inscrit pas dans un modele de collision continentale. Un modele impliquant une collision entre un arc insulaire et une marge continentale est envisageable
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Hebert, Ronan. « Evolution tectonométamorphique d'un arc insulaire au Protérozoïque supérieur : le domaine de Saint-Brieuc, Massif armoricain / ». Orléans : Ed. BRGM, 1994. http://catalogue.bnf.fr/ark:/12148/cb357075261.
Texte intégral
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Narayanan, Badri Kannan. « Effect of Alloying on Microstructure and Precipitate Evolution in Ferritic Weld Metal ». The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243965903.
Texte intégral
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Lafoy, Yves. « Evolution géodynamique des bassins marginaux Nord-Fidjien et de Lau (Sud-Ouest Pacifique) ». Brest, 1989. http://www.theses.fr/1989BRES2024.
Texte intégralRésumé :
Le bassin nord fidjien est un bassin marginal cree entre les plaques pacifique et indo-australienne, par accretion en arriere de l'arc neo hebridais. Le bassin de lau, situe a l'est du bassin nord fidjien, est un bassin marginal plus recent, cree par accretion oceanique en arriere de l'arc des tonga-kermadec. Un nouveau modele d'evolution de la region inter-arc est propose pour les 10 derniers millions d'annees. Il y a moins d'1 ma, la seconde reorientation qui affecte la region inter-arc, se traduit, dans le bassin nord fidjien, par le debut de fonctionnement de la jonction triple, et dans le bassin de lau, par la mise en place du systeme d'accretion de valu fa. Ces differentes reorientations revelent l'extreme instabilite de la region inter-arc, affectee par des contraintes extensives de second ordre qui accentuent probablement l'affaiblissement et la deformation des lithospheres oceaniques des bassins nord fidjien et de lau
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El, Bakili Asmae. « Evolution tectono-metamorphique et chronologique des unités métamorphiques du Rif interne (Beni Bousera, Nord du Maroc) ». Thesis, Université Côte d'Azur, 2021. http://www.theses.fr/2021COAZ4034.
Texte intégralRésumé :
Située à l'extrême-ouest de la Méditerranée occidentale, la chaîne bético-rifaine s’est formée au travers d’une histoire orogénique alpine complexe, impliquant des processus de subduction liés à la convergence entre l’Afrique et l’Eurasie depuis le Crétacé. Une découverte importante de ces quatre dernières décennies d'investigations géologiques, a été la mise en évidence des vestiges d’un événement varisque dans les zones internes de la chaîne. Ces résultats soulignent bien la présence de deux systèmes orogéniques superposés, les zones internes de la chaîne bético-rifaine demeurent donc des zones privilégiées pour étudier l’importance de l’héritage structural et métamorphique dans les réactivations partielles ou totale par les évènements les plus récents. Ce travail est localisé dans le secteur de Beni Bousera, ou affleurent les roches crustales et mantéliques qui forment les unités les plus internes de la chaîne. Il s’appuie sur une étude menée à partir des analyses structurales et pétrologiques, des datations U-Th-Pb sur monazite et 40Ar-39Ar sur des micas et des amphiboles. Il nous permet de résumer l’histoire de la chaîne bético-rifaine de la manière suivante : 1) un événement de HP-HT affecte la base du domaine interne à ca 281 ± 3 Ma. Ces nouvelles données pétrologiques et géochronologiques obtenues dans le Rif interne sont corrélées avec les Bétiques, les Kabylies et le massif de l'Edough en Algérie, la ceinture mauritanienne et les Appalaches. Elles attestent d'un domaine convergent au cours du Carbonifère supérieur- Permien inférieur. Tous ces segments orogéniques font partie des Variscides nord-africains construits à la marge nord-ouest du Gondwana en réponse à une convergence entre cette dernière et la Laurentia. 2) autour de 29-26 Ma, un événement métamorphique avec un gradient de type Barrovien à Abukuma affecte les Sebtides (les unités les plus internes de la chaîne), et il est interprété comme résultant de l'évolution de la plaque supérieure d'une zone de subduction. Cet évènement alpin est caractérisé par un chemin prograde marqué par un réchauffement à la base des Sebtides entre 26 et 22 Ma. De telles conditions reflètent un amincissement et un réchauffement de la croûte liée à la remontée asthénosphérique due au retrait de la plaque plongeante ; cet événement marque le début d’un évènement extensif majeur. 3) Au Miocène inférieur à 22-20 Ma, les zones internes (ou domaine d’Alboran) sont affectées par une extension E-W contemporaine de l’ouverture du bassin d'Alboran dans un contexte arrière-arc, et par l’intrusion de filons granitiques dans les péridotites et les unités métamorphiques crustales du domaine interne. Cet évènement a permis l’exhumation finale des Sebtides. 4) Du Miocène inférieur au Miocène moyen, la chaîne bético-rifaine a acquis sa géométrie arquée (l’arc de Gibraltar) suite à la collision entre les zones internes et les zones externes, attestée par une phase de raccourcissement majeur de direction NE-SW à E-W, et 5) l’arc de Gibraltar est affecté par une phase de raccourcissement N-S ante-Pliocène de direction N-S, qui a modifié considérablement sa géométrieLocated at the extreme tip of the western Mediterranean, the Betic-Rif orogenic system is built through a complex alpine orogenic history involving processes of subduction related to convergence between Africa and Eurasia since the Cretaceous. A remarkable discovery during the last four decades of geological investigations, has been the remains of a variscan event in the internal zones of the belt. These results underline the presence of two superimposed orogenic systems, the internal zones of the belt thus remain a privileged area to study the importance of the structural and the metamorphic heritage in the partial or total reactivation by the most recent events. This work is located in the Beni Bousera sector, where crustal and mantle rocks that form the innermost units of the chain are exposed. Based on structural and petrological analyses, U-Th-Pb dating on monazite and 40Ar-39Ar dating on micas and amphiboles. The history of the Betic-Rif belt can be summarized as it follows: 1) a HP-HT event affects the base of the internal domain at around 281 ± 3 Ma. These new petrological and geochronological data obtained in the internal Rif, are correlated with the Betics, the Kabyle, the Edough massif of Algeria, the Mauritanian, and the Appalachian belts, attesting a convergent domain during the late Carboniferous – early Permian. All of these orogenic segments are part of the North African Variscides built at the north-western margin of Gondwana in response to convergence between the later and Laurentia. 2) at around 29-26 Ma, a Barrovian to Abukuma metamorphic event affects the Sebtides (the innermost units of the chain) and interpreted as the evolution of the upper plate of a subduction zone. This alpine event is typically characterized by a prograde metamorphic path marked by heating affecting the base of the Sebtides between 26 to 22 Ma, such conditions reflect thinning and heating of the crust related to the asthenosphere upwelling due to slab roll-back. This event marks the beginning of a major extensive event. 3) In the Miocene around 22-20 Ma, the internal zones are affected by an E-W extension contemporary to the opening of the Alboran Basin in a back-arc context, and the intrusion of granitic dykes into the peridotites and crustal metamorphic units, the exhumation of the Sebtides was complete at this time. 4) From early to middle Miocène, the Betic-Rif belt acquired its arcuate geometry (the Gibraltar Arc) during the collision between the Internal and the external zones, attested by de NE-SW to E-W shortening phases across the arc. 5) more lately prior to Pliocene, the Gibraltar arc was subjected to contractional possess related to a N-S shortening phase, which drastically altered its geometry
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Major, Jonathan R. « Evolution and Emergence of the Hinterland in the Active Banda Arc-Continent Collision : Insights From the Metamorphic Rocks and Coral Terraces of Kisar, Indonesia ». BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2946.
Texte intégralRésumé :
Coral terrace surveys and U-series ages of coral and mollusk shells yield a surface uplift rate of ~0.6 m/ka for Kisar Island. The small island is located NE of Timor in the active Banda Arc of Indonesia. Based on this rate, Kisar first emerged from the ocean as recently as ~450 ka. Terrace surveys show warping that follows a pattern of east-west striking folds, which are along strike of thrust-related folds of similar wavelength imaged by a seismic reflection profile just offshore. This deformation shows that the emergence of Kisar can be attributed to forearc closure along the south-dipping Kisar Thrust. Terrace morphology and coral ages are best explained by recognizing major terraces as mostly growth terraces and minor terraces as mostly erosional into older growth terraces. All reliable and referable coral U-series ages are marine isotope stage (MIS) 5e (118-128 ka), which encrusted the coast up to 60 m elevation. All coral samples are found below 6 m elevation, but a tridacna (giant clam) shell in growth position at 95 m elevation yields an age of 195 +/- 31 ka, which corresponds to MIS Stage 7. Loose deposits of coral fragments found on top of low terraces between 8 and 20 m elevation yield ages of < 100 years and may represent paleotsunami deposits from previously undocumented seismic activity in the region. The metamorphic rocks of Kisar, Indonesia, which correlate with the Aileu Metamorphic Complex of East Timor, record the breakup of a supercontinent with associated rifting, metamorphism from arc-continent collision, and the growth and exhumation of a new orogenic belt. The protoliths of these rocks are mostly psammitic with minor basaltic and felsic igneous rocks. Geochemical analyses of mafic meta-igneous rocks show rift affinities that are likely related to rifting of Gondwana and later breakup in the Jurassic Period. The Aileu Complex is overlain by younger sedimentary rocks deposited on the northern passive margin of Australia, which collided with the Banda Arc in latest Miocene time. This collision caused metamorphism of the distal edge of the continental margin rocks at conditions of 600-700°C at 6-8 kbar and up to 700-850°C at 8-9 kbar locally, corresponding to depths from 25 to 30 km. These rocks were then rapidly uplifted and exhumed. U-Pb analysis of detrital zircons indicates a Permian to Late Jurassic age of the sedimentary sources and confirm an Australian provenance. The timing of metamorphism of the Aileu Complex is poorly constrained by previous studies, of which only a white mica cooling age of 5.36 +/- 0.05 Ma proved reliable. Prior apatite fission track studies show that all tracks are partially to completely annealed suggesting recent rapid cooling. A domal geometry of the island above the sea floor is expressed in the pinnacle shape. Foliations on Kisar Island generally strike parallel to the coastline, which is may be suggestive of doming. The Kisar Thrust, which is imaged in offshore seismic reflection data, may indicate that the doming corresponds to diapirism into the hinge of an active thrust-related anticline or diapirism of buoyant continental material along the thrust itself.
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Coussens, Maya. « The 1 MA evolution of constructive and destructive processes at the island arc volcano of Montserrat ». Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/397318/.
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Montserrat is a small island arc volcano in the Caribbean island arc. The island comprises three main volcanic centres: Silver Hills, active between 2.5-1 Ma; Centre Hills, active between ~1 to 0.5 Ma; and the Soufrière Hills-South Soufrière Hills volcanic complex, active from ~0.3 Ma. Here an extensive (> 1 Ma) and detailed stratigraphic record is compiled for Montserrat using both the subaerial and submarine (in the form of three International Ocean Drilling Program cores) records. This combined record gives valuable insight into the evolution of volcanic and mass-wasting processes at Montserrat, and may be useful for future hazard mitigation. The stratigraphic record shows that eruptive styles, volcanic intensity and mass-wasting processes have varied through time. Dome-style eruptions have dominated the past 1 Ma of volcanic activity at Montserrat. At the older edifice of Centre Hills, regular large-magnitude explosive eruptions (represented by >1m thick pumiceous sequences onshore) also occurred, but such explosive eruptions are rare at the younger Soufrière Hills-South Soufrière Hills volcanic complex. Periods of heightened volcanic activity occurred between 1.1-0.9 Ma, 0.3 Ma, and 0.2-0.1 Ma. Another period of increased volcanism may have also occurred at ~0.5±0.2 Ma. These coincide with periods of increased, mass-wasting, identified at 1.1-0.9 Ma, 0.6-0.5 Ma, 0.3 Ma, and 0.2-0.1 Ma and suggest that increased volcanic activity may facilitate mass-wasting processes. This may be due to increased deposition of material on the island flanks, or increased seismic activity that can trigger collapses. The ages of the largest landslide deposits (volumes >0.3 km3) observed offshore of Montserrat also coincide with periods of faster sea-level rises. Analysing the global database, large landslides coincide with rapid sea-level rise at other island arc volcanoes, but not at ocean islands. The reason for this difference in behavior is unclear, but maybe associated with differences in island composition and size, or tectonic regimes.
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Saylor, Joel Edward. « The Late Miocene through Modern Evolution of the Zhada Basin, South-Western Tibet ». Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/194652.
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The uplift history of the Tibetan Plateau is poorly constrained in part due to its complex and extended tectonic history. This study uses basin analysis, stable isotope analysis, magnetostratigraphy, detrital zircon U-Pb dating, and paleoaltimetry, and frequency analysis to reconstruct the tectonic, spatial, and environmental evolution of the Zhada basin in southwestern Tibet since the late Miocene. The Zhada Formation, which occupies the Zhada basin and consists of ~ 850 m of fluvial, alluvial fan, eolian, and lacustrine sediments, is undeformed and lies in angular unconformity above Tethyan sedimentary sequence strata. The most negative Miocene δ¹⁸Opsw (paleo-surface water) values reconstructed from aquatic gastropods are significantly more negative than the most negative modern δ¹⁸O(sw) (surface water) values. In the absence of any known climate change which would have produced this difference, we interpret it as indicating a decrease in elevation in the catchment between the late Miocene and the present. Basin analysis indicates that the decrease in elevation was accomplished by two low-angle detachment faults which root beneath the Zhada basin and exhume mid-crustal rocks. This exhumation results from ongoing arc-parallel extension and provides accommodation for Zhada basin fill. Sequence stratigraphy shows that the basin evolved from an overfilled to an underfilled basin but that further evolution was truncated by an abrupt return to overfilled, incising conditions. This evolution is linked to progressive damming of the paleo-Sutlej River. During the underfilled portion of basin evolution, depositional environments were strongly influenced by Milancovitch cyclicity: particularly at the precession and eccentricity frequencies.
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Mohan, Soumya. « Understanding Low temperature Impact Toughness of 2.25Cr-1Mo steel Submerged Arc Welds ». The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429879752.
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Tribe, Ian Roger. « Deformation of granitoid rocks, Channel Islands, UK : Implications for the structural evolution of a late Precambrian arc ». Thesis, Oxford Brookes University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262069.
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Zhu, Jianqiang. « Microstructure evolution of Ti-based and Cr cathodes during arc discharging and its impact on coating growth ». Doctoral thesis, Linköpings universitet, Nanostrukturerade material, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-96790.
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This thesis explores the microstructure evolution of cathodes with various material compositions and grain sizes during cathodic arc evaporation processes as well as the impact on the arc movement, and the microstructure and properties of the deposited nitride coatings. The studied cathode material systems include conventionally metal forged Ti and Ti -Si cathodes, novel Ti3SiC2 MAX-phase cathodes, and dedicatedly designed powder-metallurgical Ti-Si and Cr cathodes with different grain size. The microstructure and chemical composition of the virgin and arced cathodes together with the microstructure and mechanical properties of the deposited coatings were analyzed with various characterization techniques, including x-ray diffractometry, x-ray photoelectron spectroscopy, elastic recoil detection analysis, scanning electron microscopy, focused ion beam sample preparation technique, transmission electron microscopy, energy dispersive x-ray, electron energy loss spectroscopy, and nanoindentation. In general, a converted layer forms on the cathode surfaces during cathodic arc evaporation. The thickness, the microstructure and the chemical composition of such layer are dependent on the composition and the grain size of the virgin cathodes, the nitrogen pressure, and the cathode fabrication methods. For Ti based materials, the converted layer is 5-12 μm thick and consists of nanosized nitrided grains caused by the high reactivity of Ti to the ambient nitrogen gas. In comparison, the Cr cathode is covered with a 10-15 μm converted layer with micrometer/sub-micrometer sized grains. Only very limited amounts of nitrogen are detected within the layer due to the low reactivity of Cr to nitrogen. For Ti-Si cathodes, the existence of multiple phases of Ti and Ti5Si3 with different work function renders preferential arc erosion on the Ti5Si3 phase during discharging. The preferential erosion generates higher roughness of the Ti-Si cathode surface compared with Ti. By increasing the grain size of the virgin Ti-Si cathodes from ~8 μm to ~620 μm, the average roughness increases from 1.94±0.13 μm to 91±14 μm due to the amplified impact of preferential erosion of the enlarged Ti5Si3 grains. The variation of the preferential erosion affects the arc movement, the deposition rate, and the macroparticle distribution of the deposited Ti-Si-N coatings. A novel Ti3SiC2 MAX phase is used as cathode material for the growth of Ti-Si-C-N coating. During arcing, the cathode surface forms a converted layer with two sublayers, consisting of a several-micrometer region with a molten and resolidified microstructure followed by a region with a decomposed microstructure. The microstructure and hardness of the deposited Ti -Si-C-N coatings is highly dependent on the wide range of coating compositions attained. In the coatings with abundance of N, the combined presence of Si and C strongly disturbs cubic phase growth and compromises their mechanical strength. At a nitrogen pressure of 0.25-0.5 Pa, 45-50 GPa superhard (Ti,Si)(C,N) coatings with a nanocrystalline feathered structure were obtained. By increasing the grain size of the elemental Cr cathodes from ~10 μm and ~300 μm, the grain structure of the converted layer on the cathode surface varies from equiaxed grains to laminated grains after evaporating in a nitrogen atmosphere. When evaporated with a stationary fixture, the worn Cr cathode surface contains an organized pattern of deep ditches in the surface. The formation of such patterns is enhanced by increasing the cathode grain size. The fixture movement, which is either stationary or single rotating, affects the phase composition, the droplet density and the microstructure of the deposited Cr-N coatings, which consequently determines the mechanical properties of the coatings.
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Chapman, Timothy. « Deciphering Igneous and Metamorphic Histories from Exposed Deep Arc Crust, Fiordland, New Zealand : Crustal Differentiation and Evolution ». Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/16751.
Texte intégralRésumé :
Fiordland, New Zealand, preserves extensive arc plutons, that formed as part of a Cretaceous flare-up event in a long-lived subduction zone forming the proto-Pacific Gondwanan margin. Plutonic rocks of the c. 126–105 Ma Western Fiordland Orthogneiss (WFO) and related Separation Point Suite (SPS), were emplaced syn-tectonically throughout a thickened (>65 km) continental arc. Unique exposures of mid and lower crustal components of the arc provide insights into processes forming Cordilleran margins, which can be used to evaluate and validate inferred deep arc processes. A major difficulty in interpreting such rocks is presented by the extensive overlap of mineral assemblages forming plutonic protoliths and their metamorphic equivalents. However, there is an imperative to correctly distinguish igneous from metamorphic parageneses to interpret plutonic and metamorphic events and establish robustly their roles in forming Cordilleran arcs. This thesis develops a method to distinguish igneous and metamorphic histories utilising mineral trace element chemistries and microstructural relations from exposed lower crustal arc rocks. In deciphering protolith and metamorphic histories constraints on the dynamics of crustal differentiation and evolution are explored using the example from Fiordland.
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Hannon, Jeffrey S. « Reconstructing the Generation, Evolution, and Migration of Arc Magmatism using the Whole-rock Geochemistry of Bentonites : A Case Study from the Cretaceous Idaho-Farallon Arc System ». University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613745220524224.
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Schmidt, Angelika. « Temporal and spatial evolution of the Izu Island Arc, Japan in terms of Sr-Nd-Pb isotope geochemistry ». [S.l. : s.n.], 2001. http://e-diss.uni-kiel.de/diss/d465.pdf.
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Germa, Aurélie. « Evolution volcano-tectonique de l'île de la Martinique (arc insulaire des Petites Antilles) : nouvelles contraintes géochronologiques et géomorphologiques ». Phd thesis, Université Paris Sud - Paris XI, 2008. http://tel.archives-ouvertes.fr/tel-00447342.
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Nous présentons ici un travail qui combine des études de géochronologie, géochimie et géomorphologie sur l'île de la Martinique afin de contraindre l'évolution de l'activité volcanique de l'île. L'arc insulaire des Petites Antilles, double dans sa moitié nord, résulte de la subduction vers l'ouest de la plaque Atlantique sous la plaque Caraïbe à 2 cm/an. Grâce à sa position centrale où les deux branches nord se rejoignent, la Martinique est la seule île des Petites Antilles où l'histoire la plus complète de l'arc affleure. Nos âges K-Ar montrent que l'Arc Ancien a été actif de 25 à 21 Ma. L'Arc Intermédiaire s'est ensuite mis en place en milieu sous-marin puis subaérien entre 16 et 7 Ma. Au cours du Miocène, l'activité volcanique s'est déplacée vers l'ouest avec la mise en place de petits volcans monogéniques, alignés le long de failles, entre 3 Ma et 340 ka. Au même moment, le compartiment septentrional s'est édifié au niveau du volcan bouclier du Morne Jacob (5.5 – 1.5 Ma), du Complexe du Carbet (1 Ma – 322 ka), du Mont Conil (550 – 190 ka) et enfin de la Montagne Pelée. Nous avons mis en évidence l'étroite relation de l'évolution chimique des laves et des taux d'éruption avec les modifications de surface, ainsi que l'influence de la subduction de rides asismiques sur la migration et la répartition de l'activité volcanique à travers et le long de l'arc. En conclusion, notre compilation de 56 nouveaux âges K-Ar entre 26 Ma et 190 ka, nous permet de mieux contraindre les différentes phases volcaniques de l'île de la Martinique, et d'identifier des épisodes de forte production magmatique liés aux changements géodynamiques régionaux et/ou les événements d'effondrement de flanc.
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Scott, Craig Russell. « Physical volcanology, stratigraphy, and lithogeochemistry of an archean volcanic arc : evolution from plume-related volcanism to arc rifting within the SE Abitibi Greenstone Belt, Val d'Or, Quebec, Canada ». Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2005. http://theses.uqac.ca.
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Sarkar, Tapabrato [Verfasser]. « Formation and evolution of a Proterozoic magmatic arc – the Ongole domain of the Eastern Ghats Belt, India / Tapabrato Sarkar ». Kiel : Universitätsbibliothek Kiel, 2014. http://d-nb.info/1052529240/34.
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Paquet, Fabien. « Evolution morphostructurale des bassins de marge active en subduction : L'exemple du bassin avant-arc de Hawke Bay en nouvelle Zélande ». Phd thesis, Université Rennes 1, 2007. http://tel.archives-ouvertes.fr/tel-00342682.
Texte intégralRésumé :
La croissance des reliefs et les flux sédimentaires associés à la dynamique des marges actives en subduction sont des processus encore mal connus. Les archives géologiques sont souvent difficiles d'accès ou bien simplement mal préservées à cause de déformations importantes. Le bassin avant arc d'Hawke Bay de la marge Hikurangi en Nouvelle-Zélande constitue un objet d'étude privilégié. En effet, il est peu déformé, partiellement émergé et actif pendant le Pléistocène, période au cours de laquelle l'âge des séries sédimentaires et certains facteurs comme le climat et l'eustatisme sont bien contraints. Une étude pluridisciplinaire, intégrant l'interprétation de données sismiques marines et terrestres, l'analyse de puits, de carottes et de coupes de terrain et l'observation des bassins versants a permis d'établir l'architecture stratigraphique à très haute résolution sur le dernier 1.1 Ma de ce domaine avant arc. Cette stratigraphie montre une organisation en un empilement complexe de 11 séquences de dépôt d'origine climato-eustatique (20, 40 et 100 ka) préservées dans des sous bassins contrôlés par les structures chevauchantes actives. Ces séquences sont caractérisées par des changements paléogéographiques profonds qui évoluent entre deux états extrêmes à chaque maximum glaciaire et optimum interglaciaire. Ainsi, le domaine avant arc d'Hawke Bay montre une segmentation en sous bassins isolés par des rides tectoniques émergeantes pendant les bas niveaux marins et submergées lors des hauts niveaux marins. Aux échelles de temps supérieures à 100 ka, ces structures actives sont à l'origine, dans chacun des bassins, d'une migration progressive vers l'arc des dépocentres des séquences sous l'influence combinée de la tectonique et la charge sédimentaire. Le calcul des volumes de sédiments préservés dans chacune des séquences de dépôt, depuis les sources les plus en amont jusqu'au pied des systèmes sédimentaires les plus profonds à l'aval, permet d'estimer des flux sédimentaires qui ont transité à travers le domaine avant arc au cours de Pléistocène supérieur. Ces flux varient de ~3 à ~6 Mt.a-1. Les variations de flux à long terme (100 ka à 1 Ma) correspondent à des changements de configuration tectonique (distribution de la déformation sur les structures) du domaine avant arc et traduisent la capacité des bassins à stocker des sédiments. Les variations enregistrées à plus court terme (<100 ka) sont corrélées aux importants changements climatiques Pléistocènes, qui modifient les taux d'érosion dans le bassin versant et par conséquent, le flux sédimentaire. Cette observation montre la forte sensibilité et réactivité du domaine amont aux variations environnementales, également illustrée par le doublement des valeurs de flux sédimentaires depuis l'arrivée des européens sur le territoire néo-zélandais au 18ème siècle et le déboisement intensif qui lui a succédé.
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Zobell, Elizabeth A. « Origin and tectonic evolution of Gondwana Sequence units accreted to the Banda Arc : a structural transect through Central East Timor / ». Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1837.pdf.
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Zobell, Elizabeth Anick. « Origin and Tectonic Evolution of Gondwana Sequence Units Accreted to the Banda Arc : A Structural Transect through Central East Timor ». BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/898.
Texte intégralRésumé :
Petrographic and age analysis of sandstones, detailed structural analysis and gravity modeling were conducted to investigate the origin of the Gondwana Sequence in the Timor Region, and to better constrain the tectonic evolution of the active Banda Arc. Our field studies and U/Pb zircon age analysis helped assign most units to either Asian or Australian affinity. Detrital zircon from uplifted Banda forearc units (Asian affinity) have U/Pb ages as young as 80 Ma (Standley and Harris, in press). In contrast, analysis of detrital zircon from Gondwana Sequence sandstones accreted to the Banda Arc from Savu to East Timor are no younger than 234.6 ± 4.0 Ma, and have peak ages at 301 Ma and 1873 Ma with some Archean ages. These age constraints provide a reliable new application for distinguishing rocks units as Asian or Australian affinity. Petrographic and provenance analysis of Triassic Australian affinity greywacke units yield QFL abundances consistent with a proximal, syn-rift, intracratonic or recycled orogen source, from the northeast. The Mount Isa region to the east has the most similar peak U/Pb zircon ages to the Gondwana Sequence. However an extension of this terrane to the west, which would have rifted away during Jurassic breakup, is required to account for the immaturity of the sandstones. Structural measurements of Gondwana Sequence units accreted to the Banda Arc show a northwest - southeast paleo and current maximum stress direction, and vergence mostly to the southeast. Individual thrust sheets are 3 km thick and account for 50% total shortening. The deformational grain of Timor is a hybrid of the east-west strike of Banda Arc and northeast-southwest strike of incoming Australian continental margin structures. The Banda forearc, which is 200 km wide north of Savu, progressively narrows towards East Timor. In order to constrain the location of the forearc, three area-balanced structural models were tested against the gravity field of the Banda Arc. The best fit model requires internal shortening and under-stacking of the forearc beneath the arc, which may account for the cessation of volcanism and uplifted coral terraces north of East Timor.
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Carneiro, Márcia Caroline Rodrigues. « O Arco Magmático Cauaburi : Revisão litoestratigráfica e sua contribuição na evolução do Domínio Imeri, Província Rio Negro, Cráton Amazônico ». Universidade Federal do Amazonas, 2016. http://tede.ufam.edu.br/handle/tede/5525.
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Studies in Complex Cauaburi are products of regional geological surveys. Given the scarcity of structural, geochemical and metamorphic dates of Cauaburi Complex this work aimed the study of these rocks, a profile held in Rio Negro, between the cities of São Gabriel da Cachoeira and Santa Izabel do Rio Negro (AM), eastern portion Imeri Domain, in order to set parameters for distinguishing the lithofacies the Cauaburi Complex and contribute to the understanding of the evolution of Imeri Domain and Rio Negro Province. The gneiss were grouped into three lithofacies: Santa Izabel do Rio Negro, Cumati and São Jorge. Gneisses of Santa Izabel do Rio Negro and Cumati Lithofacies are metaluminous and have a calc-alkaline affinity, and the rocks of São Jorge Lithofacies are peraluminous and have an alkaline affinity. Compositionally they vary between (amphibole) -biotite granodiorite / monzogranite (lithofacies Cumati and Santa Izabel do Rio Negro) and biotite mozogranits with espessartite (São Jorge lithofacies). The geochemical signature of Cauaburi Complex is compatible with granites generated in collisional environment (magmatic arc?) and its evolution is related to 3 tectonic metamorphic distinct events: D1 responsible for generating S1 foliation during Complex Cauaburi (Cauaburi Orogeny) syntectonics emplacement; D2 responsible for S2foliation and M2metamorphism in high amphibolite facies reaching isograd of anatexis (717,9°C and 5,84 kbars) and generation and emplacement of I-type Uaupés Suite and S Içana Suite granites (Içana Orogeny) and D3 lower temperature responsible for generating the S3foliation and reworking by transcurrent shear zone in greenschist facies associated with the K'Mudku shear belt Event.
Os estudos realizados no Complexo Cauaburi são produtos de levantamentos geológicos regionais. Diante da escassez de dados estruturais, geoquímicos e metamórficos do Complexo Cauaburi este trabalho teve como objetivo o estudo destas rochas, num perfil realizado no Rio Negro, entre as cidades de São Gabriel da Cachoeira e Santa Izabel do Rio Negro (AM), porção leste do Domínio Imeri, com o intuito de definir parâmetros que permitam diferenciar as litofácies que compõem o Complexo Cauaburi e contribuir para o entendimento da evolução do Domínio Imeri e da Província Rio Negro. Os gnaisses aflorantes no perfil estudado foram grupados em três litofácies distintas: Litofácies Santa Izabel do Rio Negro, Litofácies Cumati e Litofácies São Jorge. Os gnaisses da Litofácies Santa Izabel do Rio Negro e Cumati são metaluminosos e de afinidade cálcio-alcalina, e as rochas da Litofácies São Jorge são peraluminosa e de afinidade alcalina. Composicionalmente variam de (anfibólio)-biotita granodioritos/monzogranitos (litofácies Cumati e Santa Izabel do Rio Negro) e biotita monzogranitos com espessartita (litofácies São Jorge). A assinatura geoquímica do Complexo Cauaburi é compatível com a de granitos gerados em ambiente colisional (arco magmático?) e sua evolução está relacionada a 3 eventos tectonometamórficos distintos: D1 responsável pela geração da foliação S1 durante a colocação sintectônica do Complexo Cauaburi (Orogenia Cauaburi); D2 responsável pela foliação S2 e metamorfismo M2 em fácies anfibolito alto chegando a isógrada da anatexia (717,9°C e 5,84 kbars) e geração e alojamento dos granitos Tipo I da Suíte Uaupés e S da Suíte Içana (Orogenia Içana) e D3 de mais baixa temperatura responsável pela geração da foliação S3 e retrabalhamento por zonas de cisalhamentos transcorrentes em fácies xisto verde associado ao Evento denominado cinturão de cisalhamento K´Mudku.
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Beucher, Romain. « Evolution Néogène de l'arc~alpin~sud-occidental : Approches sismotectonique et thermochronologique ». Phd thesis, Université Joseph Fourier (Grenoble), 2009. http://tel.archives-ouvertes.fr/tel-00444816.
Texte intégralRésumé :
Cette thèse cible l'évolution Néogène de la branche sud de l'arc alpin occidental. Une approche multi-méthodes associant études de terrain, sismotectonique et thermochronologie basse température y met en évidence un régime tectonique complexe ainsi qu'une évolution morphologique et structurale originale au sein de l'arc. La fracturation s'organise autour d'un faisceau d'accidents NW-SE, à jeu principalement dextre, accompagnant la courbure de l'arc et commandant structure et morphologie. Par ailleurs, à l'échelle des massifs, une structuration en failles normales conjuguées NE-SW traduit une extension parallèle à la chaîne. D'autres failles normales traduisent une extension perpendiculaire à la chaîne. L'inversion des données microtectoniques a permis de caractériser des régimes de paléocontraintes décrochant et extensif. L'absence d'une chronologie cohérente à l'échelle régionale suggère que ces régimes ont coexisté. Je propose que ces régimes constituent deux extrêmes d'un régime de contrainte unique variable, résultant de l'interférence entre un champ de contraintes extensif, à tendance multidirectionnelle et propre à la partie interne, surépaissie de la chaîne, et un champ de contraintes décrochant à transpressif commandé aux limites de la chaîne. L'analyse sismologique montre que l'arc interne subit actuellement un régime transtensif en zone Briançonnaise et un régime purement extensif en Zone Piémontaise, plus interne. La direction d'extension reste proche d'E-W, comme plus au nord à la latitude du Pelvoux, et indépendante de la courbure de l'arc. La caractérisation du régime extensif actuel en termes de directions tangentes ou radiales à l'arc est donc ici inadaptée. La Zone Externe présente un régime globalement transpressif à nuancer puisqu'elle est également affectée par de l'extension dans sa partie la plus interne. Je propose une corrélation entre la zone subissant l'extension et la zone d'épaisseur crustale maximum. Ce modèle s'inspire et étend celui proposé par [Delacou et al., 2004]. Il favorise un processus d'extension lié à un effondrement gravitaire de la chaîne. La structure arquée concerne surtout la croûte supérieure, les structures plus profondes étant plus linéaires. Ce découplage vertical des structures est probablement hérité du poinçonnement syncollision oligocène, responsable de la formation de l'arc interne. Il peut expliquer qu'au Néogène le découplage tectonique entre arc interne en extension et zone externe en transpression ne réactive pas, près de la surface, l'ancien front chevauchant de l'arc interne, comme c'est le cas plus au nord au sein de l'arc. Quelques nouvelles données thermochronologiques (traces de fission dans l'apatite), replacées dans une synthèse des données existantes, confirment que les Alpes sud-occidentales ont connu une évolution structurale et morphologique originale au Néogène. Les zones internes présentent un refroidissement final homogène et rapide dès la fin de l'Oligocène. Le saut d'âge entre zone externe et zones internes, récemment mis en évidence à la latitude du Pelvoux, est confirmé dans l'ensemble de la branche sud de l'arc. Il témoigne de l'inversion du front chevauchant des zones internes peu de temps après le paroxysme de la collision. Je relie l'exhumation rapide des zones internes de la branche sud à la forte érosion d'une cordillère alpine axée sur les zones internes au front du poinçon apulien. La quantification de l'évolution du relief à partir du système traces de fission sur Apatite a été testée sur la base de deux transects échantillonnés dans les massifs du Pelvoux et Dora-Maira. Les relations âges-altitudes à différentes longueurs d'onde permettent d'estimer un taux d'exhumation moyen de 0.4km/Ma pour le Pelvoux au cours des 7 derniers Ma, et de 0.1Km/Ma pour Dora-Maira au cours des 20 derniers Ma. Pour ces deux massifs, aucune évolution probante du relief n'est mise en évidence. On souligne dès lors le manque de résolution du système apatite pour quantifier l'évolution du relief. Une synthèse des résultats permet de proposer que la déformation soit le résultat d'un équilibre instable entre l'étalement de la chaîne sous l'effet des forces de volume et la cinématique complexe de l'Apulie qui intègre à la fois une composante en translation et une composante rotationnelle.
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Mason, Andrew James. « Palaeoproterozoic evolution of the Lewisian complex of the Outer Hebrides, Northwest Scotland : the South Harris complex, a possible accreted island arc ? » Thesis, University of Leicester, 2003. http://hdl.handle.net/2381/30453.
Texte intégralRésumé :
The Palaeoproterozoic evolution of the central Outer Hebrides can be explained by modern plate-tectonic processes and is consistent with the products of a Wilson cycle. Local continental crust comprising c. 2.8 Ga tonalitic orthogneiss underwent extension and rifting leading to the deposition of clastic sediments derived from a late Archaean source, and was followed by the emplacement of c. 2 Ga mafic dykes. The latter are probably not directly equivalent to the Scourie dykes of the Scottish mainland. Rupturing and the formation of an ocean basin followed, and this was subsequently subducted around 1.9 Ga leading to the development of a volcanic arc, which now forms much, but not all of the South Harris Complex. This arc was founded on continental crust formed in part by the c. 2.5 Ga South Harris anorthosite. During subsequent collision events the late Archaean tonalitic gneisses and enclosed dykes were sutured back together trapping arc and probable ophiolitic material in the process. The latter is concentrated in a major imbricate zone lying immediately NE of the arc rocks, and formed by the Langavat Belt. In addition to probable ophiolitic material, this zone includes Archaean-derived metasediments, and slivers of Archaean basement gneiss. This represents the most probable location of the major suture zone associated with the reassembly of the Archaean gneisses. Suturing was followed by the initiation of kilometre-scale post-collisional shear zones. One of these, the Langavat Shear Zone was initiated prior to -1740 Ma, and exploits the Langavat Belt imbricate zone. The evolution of the Lewisian Complex of the Outer Hebrides is closely comparable to the Nagssugtoqidian orogen of southern Greenland, with which it is correlated. In fact, the geology of the Outer Hebrides bears a closer affinity with the Nagssugtoqidian belt than it does to the Lewisian rocks of the Scottish mainland.
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Buick, Glen. « Structural analysis and regional interpretation of the Sprigg Inlet Shear Zone, with implications for the tectonic evolution of the Fleurieu Arc / ». Title page, abstract and contents only, 2000. http://web4.library.adelaide.edu.au/theses/09SB/09sbb9321.pdf.
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Bouilhol, Pierre. « Structural, petrological and geochemical constraints on transfer and evolution of arc magmas in the mafic-ultramafic Sapat Complex (Kohistan ; Northern Pakistan) / ». Zürich : Eidgenössische Technische Hochschule, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=18081.
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Omrani, Jafar. « The geodynamic evolution of Zagros : tectonic and petrological constraints from the internal zones ». Paris 6, 2008. http://www.theses.fr/2008PA066207.
Texte intégralRésumé :
L’orogène de collision du Zagros appartient aux chaînes Alpines et résulte de la convergence entre l’Arabie et l’Eurasie et de la disparition de la Neotéthys. Cette longue histoire de convergence s’est traduite notamment par la subduction océanique, depuis la fin du Trias – début du Jurassique, l’obduction d’une lithosphère océanique au Crétacé supérieur, puis la collision, au Tertiaire, et le raccourcissement qui se poursuit aujourd’hui. Afin de mieux contraindre l’évolution géodynamique du Zagros, cette étude s’est focalisée sur son enregistrement par les unités de la plaque supérieure, dites “internes” et relativement peu étudiées, que sont les zones de Sanandaj-Sirjan et d’Urumieh-Dokhtar (SSZ and UDMA, respectivement). Cette étude apporte ainsi des données nouvelles sur l’évolution tectonométamorphique de la SSZ et de la zone broyée (“ou “Crush zone”) et sur l’évolution pétrologique et géochimique des roches magmatiques de l’ensemble des zones internes, SSZ et UDMA. En premier lieu, les caractéristiques structurales et pétrologiques de la SSZ et de la Crush zone confirment la localisation de la zone de suture le long de l’accident chevauchant principal du Zagros, ou Main Zagros Thrust. La déformation indique que ce contact s’enracine très en profondeur, probablement jusqu’au Moho. Les relations structurales dans ces zones permettent également de préciser l’âge du début de la collision, qui doit être antérieur à 25-23 Ma, dans le nord du Zagros du moins. Les roches magmatiques des zones internes fournissent un enregistrement assez continu de la convergence. Le magmatisme de la SSZ dure jusqu’à la fin du Mésozoïque puis migre vers l’Iran Central, dans l’UDMA, à partir de l’Eocène inférieur à moyen. Ces deux ceintures magmatiques, parallèles, montrent des caractéristiques géochimiques typiques d’un magmatisme d’arc impliquant la fusion du coin de manteau asthénosphérique sous-continental (mantle wedge). Par contraste, le magmatisme de la Crush zone, rencontré dans le secteur de Kermanshah, et qui couvre grosso modo la période comprise entre l’activité de la SSZ et celle de l’UDMA (c. 65-45 Ma), montre une signature géochimique hybride entre celle d’un arc et d’un arrière-arc et se développe sur un substratum harzburgitique au pied de la marge Eurasiatique. Incidemment, nous montrons que plus rien ne subsiste, semble-t-il, de l’ophiolite prétendument obductée de Kermanshah. Nous proposons que la période de convergence lente du Paléocène, qui succéda à une période d’accélération marquée à la fin du Crétacé (soulignée par une obduction et une exhumation de schistes bleus d’ampleur régionale, sur plus de 3000km), s’accompagna d’un retrait du panneau plongeant (ou “slab”) et de la migration de l’activité magmatique vers le bord de la marge Eurasiatique. Les structures extensives contemporaines, ductiles, rencontrées autour de larges batholithes comme celui de l’Alvand, suggèrent également l’existence de mouvements extensifs et partiellement décrochants à cette époque. Une diminution du pendage du slab Neotéthysien, induite par un probable détachement de celui-ci, aurait entraîné la migration de l’activité magmatique vers l’UDMA. L’imposante activité magmatique Eocène de l’UDMA cessa presque totalement jusqu’au Miocène supérieur – Plio-Quaternaire, avant de redémarrer mais avec de grandes disparités au long de l’arc UDMA. Nous avons en effet découvert des adakites dans la région centrale de l’UDMA (dans une région comprise entre le sud de Qom et le nord de Baft), qui attestent de l’existence d’une rupture localisée du slab (ou “slab break-off “) à partir de 10-5 Ma. L’existence de ce slab break-off récent est étayée par les images tomographiques ; il est par ailleurs contemporain de la propagation de la déformation dans le bassin d’avant-pays du Zagros, la “Zagros Fold and Thrust Belt”. Nous proposons enfin deux séries de coupes synthétiques d’échelle lithosphérique, centrées sur le nord et le centre du Zagros, fournissant des reconstructions géodynamiques depuis 90 Ma jusqu’à l’actuel.
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Worthington, James R., Paul Kapp, Vladislav Minaev, James B. Chapman, Frank K. Mazdab, Mihai N. Ducea, Ilhomjon Oimahmadov et Mustafo Gadoev. « Birth, life, and demise of the Andean-syn-collisional Gissar arc : Late Paleozoic tectono-magmatic-metamorphic evolution of the southwestern Tian Shan, Tajikistan ». AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/626289.
Texte intégralRésumé :
The amalgamation of the Central Asian Orogenic Belt in the southwestern Tian Shan in Tajikistan is represented by tectono-magmatic-metamorphic processes that accompanied late Paleozoic ocean closure and collision between the Karakum-Tarim and Kazakh-Kyrgyz terranes. Integrated U-Pb geochronology, thermobarometry, pseudosection modeling, and Hf geochemistry constrain the timing and petro-tectonic nature of these processes. The Gissar batholith and the Garm massif represent an eastward, along-strike increase in paleodepth from upper-batholith (similar to 21-7km) to arc-root (similar to 36-19km) levels of the Andean-syn-collisional Gissar arc, which developed from similar to 323-288Ma in two stages: (i) Andean, I-type granitoid magmatism from similar to 323-306Ma due to northward subduction of the Gissar back-arc ocean basin under the Gissar microcontinent, which was immediately followed by (ii) syn-collisional, I-S-type granitoid magmatism in the Gissar batholith and the Garm massif from similar to 304-288Ma due to northward subduction/underthrusting of Karakum marginal-continental crust under the Gissar microcontinent. A rapid isotopic pull-up from similar to 288-286Ma signals the onset of juvenile, alkaline-syenitic, post-collisional magmatism by similar to 280Ma, which was driven by delamination of the Gissar arclogite root and consequent convective asthenospheric upwelling. Whereas M-HT/LP prograde metamorphism in the Garm massif (650-750 degrees C/6-7kbar) from similar to 310-288Ma was associated with subduction-magma inundation and crustal thickening, HT/LP heating and decompression to peak-metamorphic temperatures (similar to 800-820 degrees C/6-4kbar) at similar to 2886Ma was driven by the transmission of a post-collisional, mantle-derived heat wave through the Garm-massif crust.
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Diener, Fernando Santos. « Geologia das suítes Travessia, Bonfim e Novo Planalto : granitoides de três estágios evolutivos do Arco Magmático de Mara Rosa ». reponame:Repositório Institucional da UnB, 2015. http://dx.doi.org/10.26512/2015.03.D.18425.
Texte intégralRésumé :
Dissertação (mestrado)—Universidade de Brasília, Instituto de Geociências, Programa de Pós-Graduação, 2015.Submitted by Andrielle Gomes (andriellemacedo@bce.unb.br) on 2015-07-02T17:20:23Z No. of bitstreams: 1 2015_FernandoSantosDiener.pdf: 36493566 bytes, checksum: bb3df19ab303c7d8696a9f5bff25029a (MD5)
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No Neoproterozoico, após a fragmentação do Supercontinente Rodínia, uma série de esforços predominantemente compressivos culminou com a formação do Gondwana no início do Cambriano. O Arco Magmático de Mara Rosa, localizado na porção noroeste do Estado de Goiás e sul de Tocantins, é um exemplo de crosta juvenil relacionada a formação do Gondwana Ocidental na Plataforma Sul Americana. Na porção noroeste do Estado de Goiás, foram estudas 3 suítes graníticas que representam o magmatismo de três estágios distintos da evolução deste arco. A Suíte Travessia é representada por uma extensa faixa de direção NE-SW composta por tonalitos e granodioritos com assinatura cálcio-alcalina de baixo à médio potássio de arco de ilhas intraoceânico. Foi possível distinguir duas fácies desta suíte, uma mais primitiva mesocrática e outra mais evoluída leucocrática e altamente peraluminosa com a presença de biotita rica em alumínio e muscovita rica em ferro e titânio, provavelmente de origem magmática. Amostra do granodiorito leucocrático indicou idade de 860 ±13Ma interpretada como idade de cristalização. Análise isotópica de Sm- Nd em gnaisse tonalítico resultou em idade modelo TDM de 852 Ma e _Nd(840)de +5,9 indicando a natureza juvenil desta rocha. As rochas da Suíte Travessia podem ser correlacionadas ao arco de ilhas intraoceânico que foi acrescido à margem do Maciço de Goiás por volta de 800 Ma. A Suíte Bonfim é caracterizada por 3 corpos graníticos intrusivos nas rochas de arco de ilhas intracoceânico. Esta suíte apresenta composição variando entre quartzo monzonítica à monzogranítica, geralmente peraluminosa. Esta suíte apresenta assinaturas de granitos tardi colisionais, do tipo I, e cálcio-alcalina de alto potássio. A biotita desta suíte é reequilibrada, mas ainda apresenta assinatura de suítes cálcio-alcalinas orogênicas. Datação U-Pb em zircão de amostra do Corpo Esmeril obteve idade de cristalização de 605 ±6Ma, além de zircões herdados de idade mesoproterozóica, indicando contaminação de crosta antiga na gênese destas rochas. As rochas da Suíte Bonfim podem ser associadas a magmatismo de colisão continental da Orogenia Brasiliana, relacionado a amalgamação do Gondwana Ocidental que ocorreu por volta de 600 Ma. A Suíte Novo Planalto é constituída por uma série de corpos monzograníticos indeformados, de composição química álcali-cálcica de natureza meta a peraluminosa. Apresenta assinatura de granitos do tipo I de estágio tardi à pós tectônico. A biotita desta suíte é magmática, rica em TiO2 , tem composição da siderofilita e caráter peraluminoso. Datação U-Pb em zircão em amostra do Granito Infusão obteve idade de cristalização de 511 ±3Ma. Zircão herdado com idade de 583 ±31 Ma e idade modelo TDM de 1446 e _Nd(t)= -7,1 indicam interação de diferentes fontes na geração deste magma. Estes dados mostram que o magmatismo da Suíte Novo Planalto pode ser correlacionados ao estágio tardi a pós tectônico da Orogenia Brasiliana.
In Neoproterozoic, after Rodinia fragmentation, a series of mainly compressive stresses resulted in the formation of Gondwana in the early Cambrian. An important example of juvenile crust related to formation of West Gondwana is Mara Rosa Magmatic Arc, which lies on the northern portion of Goiás Magmatic Arc in the South American Platform. Three granitic suites occurring in northwestern Goiás were studied. They represent clear-cut three different evolution stages of this arc. The Travessia Suite is composed of low to medium potassium calc-alkaline tonalite and granodiorite with intraoceanic island arc signature. It occurs in an extensive direction ranging from SW to NE. Two facies of this suite were separated: a more primitive mesocratic one; and other highly peraluminous leucocratic containing Al rich biotite and Ti- and Fe-bearing muscovite, probably of magmatic origin. The U-Pb zircon age determination obtained for a leucocratic granodiorite indicated age of 860 ± 13Ma (crystallization age). Isotopic analysis for a mesocratic tonalite gneiss yielded Sm-Nd TDM model age of 852 Ma and _Nd(840) of +5.9. These data point to the juvenile nature of Travessia Suite and allow a correlation between it and the intraoceanic island arc that was accreted to Goiás Massif margin 800 Ma ago. The Bonfim Suite is characterized by three granitic bodies intrusive in the intraoceanic island arc rocks. The composition of this suite ranges from quartz monzonite to monzogranite. It is usually peraluminous and presents signature of I-type granites, tardi-collisional and high potassium calcalkaline series. The biotite of this suite is rebalanced featuring orogenic calc-alkaline signature. This unit has been dated, through U-Pb in zircon of a monzogranite, at crystallization of 605 ±6Ma. Besides, Mesoproterozoic inherited zircons were found, indicating contamination of old crust in the genesis of Bonfim Suite. This magmatism may be associated with the collision event in the Brasilian Orogeny during the amalgamation of the West Gondwana wich occurred around 600 Ma. The Novo Planalto Suite consists of a series of alkali-calcic monzogranitic undeformed bodies featuring meta- to peraluminous nature. It displays late to post tectonic I-type granite signature. The Ti-bearing biotite of this suite has siderophyllite composition and peraluminous character. Dating U-Pb in zircon of monzogranite sample yielded crystallization age of 511 ±3 Ma. Zircon inherited age of 583 ±31 Ma,TDM model age of 1,446 Ma, and _Nd(t) = -7.1 indicate interaction of different sources in the generation of this magma. These data show that the magmatism of Novo Planalto Suite can be correlated to the tardi to post tectonic stage of Brasiliano Orogeny.
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DIENER, Fernando Santos. « Geologia das suítes Travessia, Bonfim e Novo Planalto : granitoides de três estágios evolutivos do arco magmático de Mara Rosa ». reponame:Repositório Institucional da CPRM, 2015. http://rigeo.cprm.gov.br/xmlui/handle/doc/14785.
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