Дисертації з теми "Continental magmatism"
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Klöcking, Marthe. "Continental magmatism and dynamic topography." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/271750.
Повний текст джерелаBrodie, James A. "Early tertiary magmatism in the North Atlantic." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360036.
Повний текст джерелаPedrazzi, Dario. "Hydrmagmatic monogenetic volcanism in continental and oceanic island enronments." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/229382.
Повний текст джерелаEl vulcanismo monogenético se caracteriza por una gran diversidad de estilos eruptivos, morfologías y depósitos. Los tipos de edificios que se forman son el resultado de una compleja combinación de parámetros que rigen la física de la erupción. La atención de este trabajo se centra en la relación entre los edificios volcánicos monogenéticos y las variables externas que influyen en la dinámica de las erupciones (es decir, magmatismo vs freatomagmatismo) a través de un punto de vista multidisciplinar, en ambientes continentales y marinos en los que el vulcanismo puede desarrollar. Diferentes estudios, representativos de este tipo de actividad en diferentes entornos geográficos y geológicos, se han llevado a cabo. El primer ejemplo corresponde al volcán de La Crosa de Sant Dalmai (Campo Volcánico de La Garrotxa) donde se han reconstruido las condiciones hidrogeológicas del sustrato y la implicación para la dinámica eruptiva. Como segundo caso de estudio, se ha realizado una estratigrafía de detalle del cono de toba de El Golfo (Lanzarote, Islas Canarias), donde se han estudiado los mecanismos de emplazamiento de los depósitos para inferir cambios en la interacción magma/agua. Otro tipo de erupción se ha investigado en el mismo archipiélago, en la Isla de El Hierro, determinando las características físicas de un episodio félsico de origen hidrovolcánico ocurrido en una isla que se caracteriza esencialmente por el vulcanismo basáltico tanto Estromboliano como Hawaiiano. Por último, este mismo tipo de metodología se ha aplicado a la Isla Decepción (archipiélago de las Shetland del Sur, Antártida), estableciendo los parámetros físicos de la erupción del 1970 con el fin de comparar este episodio con el evento anterior del 1967, y deducir sus consecuencias para llevar a cabo la evaluación de peligrosidad en la isla. Los resultados obtenidos pueden ser aplicados a campos volcánicos monogenéticos en todo el mundo y, por tanto, son útiles para reconstruir la evolución de ciertos campos volcánicos, a través del estudio de volcanes monogenéticos individuales, para evaluar los posibles riesgos volcánicos, teniendo en cuenta como erupciones similares representan una grave amenaza, que es a menudo subestimada.
Hendrie, Derek Bruce. "Numerical modelling of extension and magmatism in continental rift basins." Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240846.
Повний текст джерелаAlbaric, Julie. "Relations entre déformation active, rhéologie et magmatisme dans un rift continental : étude sismologique de la divergence nord-tanzanienne, rift est-africain." Brest, 2009. https://tel.archives-ouvertes.fr/tel-00495984v2.
Повний текст джерелаThe objective of this study is to better understand the role and the interaction between the different mechanisms that control rift initiation and development (magmatism, fauting, lithospheric fabric, rheology). To this end, a local seismic network has been deployed for the first time in the youngest part of the East African Rift, the North Tanzanian Divergence, for six months. Seismic signal was analyzed to characterize earthquake triggering mechanisms, crustal strength, strain and stress field, and seismic anisotropy. A seismic crisis occurred in North Tanzania (Gelai) involving dyking, seismic and aseismic slip. The Gelai crisis highlights the potential major role of aseismic processes in strain accommodation. Deep crustal earthquakes were recorded in the Lake Manyara region, Manyara seismicity is associated with strike-slip and normal faulting most Iikely triggered by fluids at depth. The influence of structural inheritance on rifting is indicated at lithospheric scale by seismicity and seismic anisotropy
Peace, Alexander Lewis. "Structural inheritance and magmatism during continental breakup in West Greenland and Eastern Canada." Thesis, Durham University, 2016. http://etheses.dur.ac.uk/11877/.
Повний текст джерелаKorenaga, Jun 1970. "Magmatism and dynamics of continental breakup in the presence of a mantle plume." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/55334.
Повний текст джерелаIncludes bibliographical references (p. 255-270).
This thesis studies the dynamics of mantle melting during continental breakups by geophysical, geochemical, and numerical analyses. The first part focuses on the mantle melting and crustal accretion processes during the formation of the Southeast Greenland margin, on the basis of deep-crustal seismic data. A new seismic tomographic method is developed to jointly invert refraction and reflection travel times for a compressional velocity structure, and a long-wavelength structure with strong lateral heterogeneity is successfully recovered, including 30- to 15-km-thick igneous crust within a 150-km-wide continent-ocean transition zone. A nonlinear Monte Carlo analysis is also conducted to establish the absolute uncertainty of model parameters. The derived crustal structure is first used to resolve the origin of a margin gravity high, with new inversion schemes using both seismic and gravity constraints. Density anomalies producing the gravity high seem to be confined within the upper crust, not in the lower crust as suggested for other volcanic margins. A new robust framework is then developed for the petrological interpretation of the velocity structure of igneous crust, and the thick igneous crust formed at the continentocean transition zone is suggested to have resulted from vigorous active upwelling of mantle with only somewhat elevated potential temperature. In the second part, the nature of mantle melting during the formation of the North Atlantic igneous province is studied on the basis of the major element chemistry of erupted lavas. A new fractionation correction scheme based on the Ni concentrations of mantle olivine is used to estimate primary melt compositions, which suggest that this province is characterized by a large degree of major element source heterogeneity. In the third part, the nature of preexisting sublithospheric convection is investigated by a series of finite element analyses, because the strength of such convection is important to define the "normal" state of mantle, the understanding of which is essential to identify any anomalous behavior of mantle such as a mantle plume. The results suggest that small-scale convection is likely in normal asthenosphere, and that the upwelling velocity in such convection is on the order of 1- 10 cm/yr.
by Jun Korenaga.
Ph.D.
Brunner, Anna Elizabeth. "Decarbonization related to continental arc magmatism as a possible mechanism for Cretaceous warming." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/114357.
Повний текст джерелаCataloged from PDF version of thesis.
Includes bibliographical references (pages 53-56).
Elevated concentrations of CO₂ have been proposed as the reason that the Cretaceous climate was 6-14°C warmer than the present, however the source of Cretaceous CO₂ is unknown [Barron, 1983]. This study examines the possibility of continental arc magmatism as a mechanism for CO2 release, specifically as a volatile produced during crustal assimilation and contact metamorphism of carbonates around plutons. Bedrock maps of the North American Cordillera (a region of active continental arc magmatism during the Cretaceous), the relative locations of the carbonates, the Cretaceous plutons, and the calculated "decarbonation zones"around the plutons. These measurements were then input in a thermal and petrologoical model in order to estimate the quantity of CO₂ released by continental arc magmatism. Testing a number of cases with varying parameters, the model found the arc-magmatism-induced temperature difference between the present and Cretaceous global climates to have a lower limit of [Delta]T < 1°C and an upper limit of 5.1 < [Delta]T < 12.3°C. Decarbonation from continental arc magmatism is shown to be a possible mechanism of paleoclimatic warming, and more work is required to either confirm or refute the hypothesis.
by Anna Elizabeth Brunner.
S.B.
Orme, Helen M. "Silicic magmatism and continental break-up : the Frontal Cordillera Composite Batholith, Mendoza, Argentina." Thesis, Kingston University, 1999. http://eprints.kingston.ac.uk/20359/.
Повний текст джерелаJohnson, Nicholas Edward. "Magnetotelluric studies of the crust and upper mantle in a zone of active continental breakup, Afar, Ethiopia." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7739.
Повний текст джерелаDevès, Maud. "Continental magmatism by shear heating in "Process Zones" : at geometric complexities on fault systems." Paris, Institut de physique du globe, 2010. http://www.theses.fr/2010GLOB0004.
Повний текст джерелаMercer, Celestine Nicole. "Mineralogical indicators of magmatic and hydrothermal processes in continental arc crust /." Connect to title online (Scholars' Bank) Connect to title online (ProQuest), 2009. http://hdl.handle.net/1794/10250.
Повний текст джерелаWorthington, James, and James Worthington. "Paleozoic–Cenozoic Tectonics of Central Asia." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625855.
Повний текст джерелаJones, Rosemary Ellen. "Subduction zone processes and continental crust formation in the southern Central Andes : insights from geochemistry and geochronology." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/9672.
Повний текст джерелаSerrano, Lina. "Jurassic magmatism in Patagonia, Mauritania and Mali: Examples of silicic and basaltic Large Igneous Provinces." Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3423851.
Повний текст джерелаAlla fine del Triassico e durante il Giurassico si sono formate le grandi province magmatiche (LIP) della Central Atlantic Magmatic Province (CAMP) e della Patagonia (PA) contemporanee con la rottura della Pangea. Dichi e sills di composizione basaltica e basaltica-andesitica d’età e composizione affine alla CAMP, sono stati riportati nelle regioni di Hank e Hodh, in Mauritania, e di Kaarta in Mali, che sono oggetto della prima parte di questa tesi. I dati geochimici indicano che i campioni sono caratterizzati da variabili contenuti di TiO2 (0.39 - 2.29 wt.%) e da anomalie negative di Nb-Ta e anomalie positive di Pb, accompagnati da una firma arricchita negli isotopi di Nd-Sr-Pb (143Nd/144Nd201Ma: 0.51224 - 0.51241, 87Sr/86Sr201Ma: 0.70572 - 0.70795, 207Pb/204Pb201Ma: 15.61 – 15.68 208Pb/204Pb201Ma: 38.44 – 38.07 e 206Pb/204Pb201Ma: 18.11 – 18.48). I bassi rapporti di Nb/U (= 12 – 15) sono indicatori dell’apporto di materiale crostale, possibilmente riciclato. Questi valori di Nb/U suggeriscono, insieme alle composizioni isotopiche arricchite, un contributo della crosta continentale nella origine dei magmi CAMP in Mauritania e Mali. Variazioni nei rapporti di La/Yb mostrano l’esistenza di un gruppo arricchito tra le rocce di Kaarta (La/YbN> 4.3). Questa osservazione è anche supportata dalle correlazione positive con Nb/Zr e Th/Y e probabilmente riflette minori gradi di fusione parziale del mantello. Le composizione geochimiche osservate in Hank, Hodh e Kaarta, mostrano una forte affinità con le rocce intrusive del bacino di Taoudenni e le colate CAMP del Marocco. La correlazione fra queste regioni, fa pensare a una possibile distribuzione geografica oppure alla presenza di domini geochimici all’interno della CAMP. Comunque, quest’osservazione è basata su una stima qualitativa e per verificarla son necessari ulteriori studi. Il vulcanismo della Provincia è rappresentato da un’importante sequenza di età Giurassica ed è a composizione bimodale. Comprende infatti lave e ignimbriti riolitiche denominate come Formazione Marifil (ca. 189-177 Ma) e Chon Aike (ca. 170 – 153 Ma). Altre formazioni meno voluminose ma non meno importanti sono rappresentate dall’andesite della Formazione Bajo Pobre (BP) (ca. 166 – 154 Ma), e dai i basalti di Cañadón Asfalto (ca. 179 – 176 Ma) e Lonco Trapial. L’attività magmatica registrata per questa Provincia dura al meno per 38 Ma. Nuove datazioni U-Pb ottenute in questo progetto, confermano l’età delle rioliti di Marifil, che rappresentano quindi l’attività più antica della Provincia, comparabile solo parzialmente con le età conosciute per la LIP del Karoo (ca. 184 – 174 Ma). Le differenze geochimiche e di durata fra queste due LIP (Karoo: ca. 10 Ma e un magmatismo mafico, PA: 38 Ma e un magmatismo dominante acido) non appoggiano l’ipotesi d’un origine comune eventualmente da un mantle-plume unico. Lo studio del vulcanismo mafico – intermedio, rappresentato dalle Formazione Cañadon Asfalto (CA) e Bajo Pobre (BP), è stato sviluppato in questa tesi con l’obiettivo di conoscere le caratteristiche dei magmi meno evoluti che potrebbero portare informazioni sull’ambiente tettonico in cui si è formata la provincia. Con questo fine sono stati realizzati analisi di cromiti incluse in cristali di ortopirosseno e olivina. Le composizioni trovate nei cristali più primitivi (Mg# 62 – 36 e Cr# 46 – 32) di queste formazioni sono quasi identiche anche se sono geograficamente distanti. Il loro contenuto di Al2O3 (22 – 31 wt.%) e TiO2 (1.3 – 1.3 wt.%) è simile alla composizione di Cr-spinelli nei MORB. I dati geochimici in queste rocce, evidenziano una firma d’arco magmatico caratterizzata da una composizione calco-alcalina, anomalie negative di Nb-Ta, arricchimento di LILE e un’affinità peraluminosa. In particolare, alcune rocce mafiche mostrano alti valori di Al2O3 (>16 wt.%) e di Sr (>400ppm), assenza dell’anomalia di Eu e alti rapporti di Sr/Y (86-30) e Gd/Yb (3 - 1.8) comparabili alle composizione di magmi adakitici. La continua attività magmatica registrata dalla PA suggerisce che l’origine di queste rocce sia stato relazionata a processi costanti per almeno 38 Ma, più che ad eventi sporadici e di corta durata. Le evidenze geochimiche qui sposte suggeriscono il contributo di crosta oceanica e materiale continentale nell’origine di questa LIP. Perciò si propone un modello alternativo per l’origine della PA chesarebbe il risultato di un ambiente tettonico ibrido tra la subduzione di una placca giovane e calda che fonde (la placca Pheonix) e un regime distensivo relazionato alla disgregazione della Gondwana.
Martil, Mariana Maturano Dias. "O magmatismo de Arco Continental Pré-Colisional (790 Ma) e a reconstituição espaço-temporal do regime transpressivo (650 Ma) no Complexo Várzea do Capivarita, Sul da Província Mantiqueira." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/149194.
Повний текст джерелаThis study focuses in the Várzea do Capivarita Complex (VCC), exposed in the southern part of the Neoproterozoic Mantiqueira Province (PM), Brazil. To investigate the evolutionary processes that lead the VCC construction, a multidisciplinary approach is taken, which includes field and structural geology, petrography, major and trace-element geochemistry, Sr-Nd isotope and U-Pb zircon geochronology by LA-MC-ICP-MS and SHRIMP. The complex comprises a compositional and age variety of ortho- and paragneisses tectonically interleaved during a high grade event. Subordinate volumes of syntectonic syenites are also part of CVC. The VCC deformation is partitioned into thrusting (D1) and transcurrent (D2) shear zones, suggestive of transpressive tectonics. This structural framework is possibly related to an oblique collision event. Petrological and goechronological studies emphasize the VCC orthogneisses in order to evaluate magmatic sources and related paleo-environments. Igneous crystallization ages obtained in the typical magmatic domains presenting oscillatory zoning in zircons vary between 780 and 790 Ma. Zircon overgrowths have ages mostly in the 650 – 640 Ma range and are interpreted to record the timing of high-grade metamorphism and associated partial melting. Geochronological data presented also indicates that boths kinematic regimes are contemporaneous, offering, therefore, further evidence for the oblique collisional event hypothesis. The VCC ortogneisses comprise tonalitic to granitic compositions and are metaluminous to peraluminous, calc-alkaline rocks, with high 87Sr/86Sr (i) ratios from 0.71628 to 0.72509 and εNd (790) values from -7.19 to -10.06. Their geochemical composition and trace-element patterns are compatible with a continental mature arc. VCC magmatism is correlated with other ca. 800 Ma arc sequences from southern PM, including part of the Porongos Metamorphic Complex (PMC) metavolcanic rocks and the orthogneisses from Cerro Bori, Uruguay. All these associations show signatures typical of accretionary orogens, TDM and Meso to Paleoproteroic inheritance ages, and present strong evidences of crustal assimilation/contamination. Thus, these sequences may be interpreted as part of the same magmatism, or at least as fragments of similar magmatic arcs. Geochemical and Sr-Nd signatures suggest that at least part of the PMC metavolcanic rocks may represent the protoliths of the VCC high grade orthogneisses. This, together with the isotope evidence of similarity between the sedimentary fractions of both unities, suggest that the VCC and PMC are, at least in part, expressions of the same context, wherein the magmatic and sedimentary activity occurred in a single continental arc environment. The corroboration of this premise is the main goal of provenience studies in prep, which previous results points to the volcano-sedimentary character of part of the VCC metapelites and its co-genetic relation with the VCC orthogneisses. Sr-Nd isotope data suggest that the orthogneiss protoliths were generated by crustal assimilation processes associated with fractional crystallization. Binary mixing models indicate that the VCC magmatism originates from evolved EM II mantle sources. A Paleoproterozoic TTG association (ca. 2.0 Ga) from the Arroio dos Ratos Complex (ARC) seems to be the main crustal contaminant assimilated. Together with the small inheritance contribution at ca. 2.0, this suggests that the melted crust at ca. 790-800 Ma was predominantly like ARC.
Medynski, Sarah. "Interactions entre phénomènes tectoniques et magmatiques en contexte d'extension : l'exemple du segment de rift de Dabbahu." Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0121/document.
Повний текст джерелаIn this thesis we quantify the interactions between tectonic and magmatic processes in the active Dabbahu rift segment, which experienced in 2005 a major rifting event. Here, we provide accurate constraints at this time scale by producing cosmogenic exposure ages of lavas surfaces and faults scarps, in order to decipher the morphological evolution of a rift depression, and to identify the processes that are responsible for the topography acquisition. The study is based on samples taken on two separate areas of the rift. The field areas were systematically mapped, and all lavas were chemically analysed in major and trace elements. The first studied focused the northern portion of the rift segment, where the lavas of the segment terminating volcano meets the neo-volcanic zone. This area allowed the influence of the presence of such volcanic edifice to be assessed. The second studied area is located at the middle of the segment, and covers the rift western margin up to the rift axis. The topography in this area is sensitive to the evolution in space and time of the location of the different axial magma reservoirs. Our results show that along the rift segment, topography develops during phases of low magmatic activity, and is inhibited during phases of lower magmatic activity. The 2005 appears to be an unusual event that represents about a tenth of the total intrusions necessary to build the depression. The maintaining of magmatic accretion at the axis seems to be the result of a relay between different magma reservoirs. The position of these reservoirs can vary between 0 and 15 km from both sides of the rift axis
Oliveira, Roberto Gusm?o de. "Arcabou?o geof?sico, isostasia e causas do magmatismo cenoz?ico da prov?ncia Borborema e de sua margem continental (Nordeste do Brasil)." Universidade Federal do Rio Grande do Norte, 2008. http://repositorio.ufrn.br:8080/jspui/handle/123456789/18344.
Повний текст джерелаConselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
The Borborema Province (BP) is a geologic domain located in Northeastern Brazil. The BP is limited at the south by the S?o Francisco craton, at the west by the Parna?ba basin, and both at the north and east by coastal sedimentary basins. Nonetheless the BP surface geology is well known, several key aspects of its evolution are still open, notably: i)its tectonic compartmentalization established after the Brasiliano orogenesis, ii) the architecture of its cretaceous continental margin, iii) the elastic properties of its lithosphere, and iv) the causes of magmatism and uplifting which occurred in the Cenozoic. In this thesis, a regional coverage of geophysical data (elevation, gravity, magnetic, geoid height, and surface wave global tomography) were integrated with surface geologic information aiming to attain a better understanding of the above questions. In the Riacho do Pontal belt and in the western sector of the Sergipano belt, the neoproterozoic suture of the collision of the Sul domain of the BP with the Sanfranciscana plate (SFP) is correlated with an expressive dipolar gravity anomaly. The positive lobule of this anomaly is due to the BP lower continental crust uplifting whilst the negative lobule is due to the supracrustal nappes overthrusting the SFP. In the eastern sector of the Sergipano belt, this dipolar gravity anomaly does not exist. However the suture still can be identified at the southern sector of the Maranc? complex arc, alongside of the Porto da Folha shear zone, where the SFP N-S geophysical alignments are truncated. The boundary associated to the collision of the Cear? domain of the BP with the West African craton is also correlated with a dipolar gravity anomaly. The positive lobule of this anomaly coincides with the Sobral-Pedro II shear zone whilst the negative lobule is associated with the Santa Quit?ria magmatic arc. Judging by their geophysical signatures, the major BP internal boundaries are: i)the western sector of the Pernambuco shear zone and the eastern continuation of this shear zone as the Congo shear zone, ii) the Patos shear zone, and iii) the Jaguaribe shear zone and its southwestern continuation as the Tatajuba shear zone. These boundaries divide the BP in five tectonic domains in the geophysical criteria: Sul, Transversal, Rio Grande do Norte, Cear?, and M?dio Corea?. The Sul domain is characterized by geophysical signatures associated with the BP and SFP collision. The fact that Congo shear zone is now proposed as part of the Transversal domain boundary implies an important change in the original definition of this domain. The Rio Grande do Norte domain presents a highly magnetized crust resulted from the superposition of precambrian and phanerozoic events. The Cear? domain is divided by the Senador Pompeu shear zone in two subdomains: the eastern one corresponds to the Or?s-Jaguaribe belt and the western one to the Cear?-Central subdomain. The latter subdomain exhibits a positive ENE-W SW gravity anomaly which was associated to a crustal discontinuity. This discontinuity would have acted as a rampart against to the N-S Brasiliano orogenic nappes. The M?dio Corea? domain also presents a dipolar gravity anomaly. Its positive lobule is due to granulitic rocks whereas the negative one is caused by supracrustal rocks. The boundary between M?dio Corea? and Cear? domains can be traced below the Parna?ba basin sediments by its geophysical signature. The joint analysis of free air anomalies, free air admittances, and effective elastic thickness estimates (Te) revealed that the Brazilian East and Equatorial continental margins have quite different elastic properties. In the first one 10 km < Te < 20 km whereas in the second one Te ? 10 km. The weakness of the Equatorial margin lithosphere was caused by the cenozoic magmatism. The BP continental margin presents segmentations; some of them have inheritance from precambrian structures and domains. The segmentations conform markedly with some sedimentary basin features which are below described from south to north. The limit between Sergipe and Alagoas subbasins coincides with the suture between BP and SFP. Te estimates indicates concordantly that in Sergipe subbasin Te is around 20 km while Alagoas subbasin has Te around 10 km, thus revealing that the lithosphere in the Sergipe subbasin has a greater rigidity than the lithosphere in the Alagoas subbasin. Additionally inside the crust beneath Sergipe subbasin occurs a very dense body (underplating or crustal heritage?) which is not present in the crust beneath Alagoas subbasin. The continental margin of the Pernambuco basin (15 < Te < 25 km) presents a very distinct free air edge effect displaying two anomalies. This fact indicates the existence in the Pernambuco plateau of a relatively thick crust. In the Para?ba basin the free air edge effect is quite uniform, Te ? 15 km, and the lower crust is abnormally dense probably due to its alteration by a magmatic underplating in the Cenozoic. The Potiguar basin segmentation in three parts was corroborated by the Te estimates: in the Potiguar rift Te ? 5 km, in the Aracati platform Te ? 25 km, and in the Touros platform Te ? 10 km. The observed weakness of the lithosphere in the Potiguar rift segment is due to the high heat flux while the relatively high strength of the lithosphere in the Touros platform may be due to the existence of an archaean crust. The Cear? basin, in the region of Munda? and Icara? subbasins, presents a quite uniform free air edge effect and Te ranges from 10 to 15 km. The analysis of the Bouguer admittance revealed that isostasy in BP can be explained with an isostatic model where combined surface and buried loadings are present. The estimated ratio of the buried loading relative to the surface loading is equal to 15. In addition, the lower crust in BP is abnormally dense. These affirmations are particularly adequate to the northern portion of BP where adherence of the observed data to the isostatic model is quite good. Using the same above described isostatic model to calculate the coherence function, it was obtained that a single Te estimate for the entire BP must be lower than 60 km; in addition, the BP north portion has Te around 20 km. Using the conventional elastic flexural model to isostasy, an inversion of crust thickness was performed. It was identified two regions in BP where the crust is thickened: one below the Borborema plateau (associated to an uplifting in the Cenozoic) and the other one in the Cear? domain beneath the Santa Quit?ria magmatic arc (a residue associated to the Brasiliano orogenesis). On the other hand, along the Cariri-Potiguar trend, the crust is thinned due to an aborted rifting in the Cretaceous. Based on the interpretation of free air anomalies, it was inferred the existence of a large magmatism in the oceanic crust surrounding the BP, in contrast with the incipient magmatism in the continent as shown by surface geology. In BP a quite important positive geoid anomaly exists. This anomaly is spatially correlated with the Borborema plateau and the Maca?-Queimadas volcanic lineament. The integrated interpretation of geoid height anomaly data, global shear velocity model, and geologic data allow to propose that and Edge Driven Convection (EDC) may have caused the Cenozoic magmatism. The EDC is an instability that presumably occurs at the boundary between thick stable lithosphere and oceanic thin lithosphere. In the BP lithosphere, the EDC mechanism would have dragged the cold lithospheric mantle into the hot asthenospheric mantle thus causing a positive density contrast that would have generated the main component of the geoid height anomaly. In addition, the compatibility of the gravity data with the isostatic model, where combined surface and buried loadings are present, together with the temporal correlation between the Cenozoic magmatism and the Borborema plateau uplifting allow to propose that this uplifting would have been caused by the buoyancy effect of a crustal root generated by a magmatic underplating in the Cenozoic
A Prov?ncia Borborema (PB) ? um dom?nio geol?gico-estrutural localizado no Nordeste do Brasil, limitado a sul pelo Cr?ton do S?o Francisco, a oeste pela Bacia do Parna?ba e a norte e leste pelas bacias costeiras. Embora bastante estudada por geologia de superf?cie, na PB ainda est?o em aberto aspectos importantes de sua evolu??o, notadamente: i) a sua compartimentagem tect?nica ap?s a Orog?nese Brasiliana, ii) a arquitetura da margem continental implantada no Cret?ceo, iii) as propriedades el?sticas de sua litosfera, e iv) as causas do magmatismo e do soerguimento no Cenoz?ico. Esta Tese empregou dados geof?sicos de cobertura regional (eleva??o, gravimetria, magnetometria, altura geoidal e tomografia), para aportar informa??es de geologia profunda aos problemas acima colocados. A sutura gerada pela colis?o neoproteroz?ica entre o Dom?nio Sul da PB e a Placa Sanfranciscana (PSF) ? marcada, na Faixa Riacho do Pontal e no oeste da Faixa Sergipana, por uma forte anomalia gravim?trica dipolar, cujo pico positivo corresponde ao al?amento da crosta inferior da PB e o negativo corresponde ?s nappes de supracrustais empurradas sobre a PSF. Na regi?o leste da Faixa Sergipana n?o h? assinaturas gravim?tricas que indiquem cavalgamento e flexura de placas, mas a interpreta??o de truncamentos de assinaturas geof?sicas de dire??o N-S da PSF permite localizar a sutura na margem sul do complexo de arco Maranc?, ao longo da Z. C. Porto da Folha. Por sua vez, o limite colisional do Dom?nio Cear? da PB com o Cr?ton Oeste-Africano, ao longo da Z. C. Sobral-Pedro II, ? tamb?m marcado por uma anomalia gravim?trica dipolar, cujo pico positivo coincide com a Z. C. Sobral-Pedro II, e o negativo coincide com o arco magm?tico de Santa Quit?ria. A julgar pela express?o geof?sica, os limites internos mais importantes da PB s?o: i) a Z. C. Pernambuco Oeste e sua continua??o na Z. C. Congo, ii) a Z. C. Patos e iii) a Z. C. Jaguaribe e sua continua??o na Z. C. Tatajuba. Estes limites dividem a PB em cinco grandes dom?nios geof?sicos-tect?nicos: Sul (ou Externo), Transversal, Rio Grande do Norte, Cear? e M?dio Corea?. O Dom?nio Sul ? marcado por assinaturas geof?sicas associadas ? colis?o da PB com a PSF. O Dom?nio Transversal teve a sua concep??o original de limites modificada porque a parte leste do seu limite sul foi associada com a Z. C. Congo. O Dom?nio Rio Grande do Norte apresenta a crosta mais magn?tica da PB, com superposi??o de fontes pr?-cambrianas e faneroz?icas. No Dom?nio Cear?, a Z. C. Senador Pompeu ? o divisor de dois subdom?nios: o leste corresponde ? Faixa Or?s-Jaguaribe e o oeste corresponde ao Cear?-Central, onde ocorre uma assinatura gravim?trica interpretada como uma descontinuidade crustal de dire??o ENE-WSW, que funcionou como um anteparo para as nappes brasilanas, com sentido de deslocamento para sul. O Dom?nio M?dio Corea? apresenta uma anomalia gravim?trica dipolar, cujo pico positivo est? associado com rochas granul?ticas, e o negativo com rochas supracrustais. A assinatura geof?sica do seu limite com o Dom?nio Cear? ? evidente, apesar dos sedimentos da Bacia do Parna?ba. A an?lise conjunta da anomalia ar-livre, admit?ncia ar-livre e estimativas da espessura el?stica efetiva (Te) evidenciou que as margens Leste e Equatorial possuem propriedades el?sticas bastante diferentes: enquanto a primeira tem Te entre 10 e 20 km, a segunda tem Te em torno ou inferior a 10 km. Essa diferen?a ? devida ao enfraquecimento da litosfera da Margem Equatorial produzida pelo magmatismo cenoz?ico. A margem continental da PB apresenta segmenta??es que incorporaram heran?as das estruturas e dos dom?nios pr?-cambrianos, que se correlacionam com os limites conhecidos das bacias. Descrevendo de sul para norte, o limite da separa??o da Bacia Sergipe - Alagoas em duas sub-bacias coincide com a sutura entre o Dom?nio Sul da PB e a PSF; as estimativas de Te indicam, concordantemente, que a Sub-bacia Sergipe (Te ? 20 km) se instalou em uma litosfera mais resistente do que a da Sub-bacia Alagoas (Te ? 10 km). Adicionalmente, no interior da crosta da Sub-bacia Sergipe ocorre um grande corpo denso (underplating ou heran?a crustal?) que n?o continua na Sub-bacia Alagoas. A margem da Bacia de Pernambuco (15 < Te < 25 km) apresenta caracter?sticas diferentes das outras bacias costeiras, porque no Plat? de Pernambuco h? duas anomalias do efeito de borda , o que indica a exist?ncia no plat? de uma crosta continental afinada, contudo ainda relativamente espessa. A Bacia da Para?ba se apresenta bastante uniforme, com Te em torno de 15 km, e possui uma crosta inferior relativamente densa, que foi interpretada como uma modifica??o por underplating magm?tico relacionado com o magmatismo cenoz?ico. A segmenta??o da Bacia Potiguar em tr?s partes ? corroborada pelas estimativas de Te: Rifte Potiguar (Te ? 5 km), Plataforma de Aracati (Te ? 25 km) e Plataforma de Touros (Te ? 10 km). A fragilidade da litosfera na regi?o do Rifte Potiguar est? associada com fluxo t?rmico atual alto, e a resist?ncia relativamente maior da Plataforma de Touros pode ser devida a uma crosta arqueana. A margem da Bacia do Cear?, no trecho das sub-bacias Munda? e Icara?, possui anomalia ar-livre uniforme, com Te entre 10 e 15 km. A an?lise da admit?ncia Bouguer revelou que a condi??o isost?tica da PB ? compat?vel com um modelo em que ocorrem carregamentos combinados na superf?cie e na base da crosta, com a carga da base 15 vezes maior que a do topo. Em adi??o, a PB possui uma crosta inferior anormalmente densa. Estas afirma??es s?o especialmente adequadas para a parte norte da PB porque a? a ader?ncia dos dados observados ao modelo ? maior. Para o mesmo modelo isost?tico e usando a fun??o coer?ncia, estimou-se que a Te da PB deve ser inferior a 60 km, embora sua por??o norte tenha Te de apenas 20 km. A invers?o de espessura de crosta, usando o modelo isost?tico com carga apenas na superf?cie, indicou que existem na PB duas regi?es de espessamento: uma abaixo do Planalto da Borborema (de origem cenoz?ica) e a outra no Dom?nio Cear?, sob o arco magm?tico de Santa Quit?ria (vestigial do Pr?-cambriano). Por outro lado, ocorre um afinamento ao longo do Trend Cariri-Potiguar, que representa o registro no interior do continente de um rifteamento cret?ceo abortado. A interpreta??o das anomalias ar-livre de fontes oce?nicas levou ? proposi??o de que ocorreu um volumoso magmatismo na ?rea oce?nica adjacente ? PB, ao contr?rio da ?rea continental, como indicam as informa??es de geologia de superf?cie. A PB apresenta uma expressiva anomalia positiva de ge?ide, com correla??o espacial com o Planalto da Borborema e o Alinhamento Macau-Queimadas. A integra??o de dados de tomografia de ondas superficiais e de anomalias residuais de ge?ide permitiu interpretar que uma convec??o em pequena escala (Edge Driven Convection-EDC), gerada na interface entre a raiz da litosfera continental fria e o manto quente da ?rea oce?nica, pode ter sido a causa do magmatismo cenoz?ico. O mecanismo de EDC teria causado o arrasto do manto litosf?rico continental frio para dentro do manto astenosf?rico quente, ocasionando assim contraste positivo de densidade, que seria uma componente importante da origem da anomalia de ge?ide. A compatibilidade dos dados gravim?tricos da PB com o modelo isost?tico que combina carregamentos no topo e na base da crosta, e a correla??o temporal entre o magmatismo cenoz?ico e o soerguimento do planalto, permite propor que o soerguimento deste ocorreu por causa do empuxo provocado pela raiz da crosta, produzida por um underplating magm?tico no Cenoz?ico
Couzinié, Simon. "Evolution of the continental crust and significance of the zircon record, a case study from the French Massif Central." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSES035.
Повний текст джерелаThe formation of the continental crust is a major consequence of Earth differentiation. Understanding how the crust formed and evolved through time is paramount to locate the vast mineral deposits hosted therein and address its influence on the global climate, ultimately affecting the development of terrestrial life. Recent advances on the topic of continental crust evolution benefited from improvements of analytical techniques enabling in situ measurements of U-Pb- Hf-O isotope compositions in zircon, a widespread accessory mineral of continental igneous rocks. The time constrains derived from the U-Pb chronometer coupled with the petrogenetic information retrieved from Hf-O isotope signatures are currently used to unravel the diversity and succession of magmatic events affecting the continental crust at the regional and global scales. This study reconstructs the evolutionary path followed by the crust segment today exposed in the eastern part of the French Massif Central (FMC), a portion of the Variscan belt of Western Europe, with the aim to investigate the potential flaws of the zircon record of crust evolution. In this scope, the origin and geodynamic significance of the constituent FMC lithological units are tackled by combining conventional petrological observations with zircon U-Pb-Hf-O isotope data. The results obtained following this integrated approach are then confronted to the conclusions that would have been drawn solely from zircon isotopic signatures, taken out of their petrological context, as is commonly performed in studies investigating crust evolution. The oldest rocks of the FMC correspond to Ediacaran (590_550 Ma) meta-sediments deposited in back-arc basins along the northern Gondwana margin. Such basins were fed by a mixed detritus originating from the adjacent Cadomian magmatic arc and a distal Gondwana source, presumably the Sahara Metacraton. Partial melting of these meta-sediments at the Ediacaran/Cambrian boundary led to voluminous S-type granitic magmatism, pinpointing a first major crust reworking event in the FMC. The origin of anatexis likely stems from the transient thickening of the hot, back-arc crust caused by the flattening of the Cadomian subduction. Subordinate melting of the depleted backarc mantle at that time is also documented. During the Lower Paleozoic, rifting of the northern Gondwana provoked coeval crust and (limited) mantle melting. Mantle-derived igneous rocks show markedly diverse trace element and isotopic signatures, consistent with a very heterogeneous mantle source pervasively modi_ed by the Cadomian subduction. Finally, the Variscan collision resulted in crustal melting as evidenced by the emplacement of S-type granites and the formation of migmatite domes, the spatial distribution of which being partly controlled by the crustal architecture inherited from pre-orogenic events. Synchronous intrusion of mafic mantle-derived magmas and their differentiates testify for Variscan post-collisional new continental crust production in the FMC. Two major inconsistencies exist between these results and the zircon record. First, zircon Hf model ages would point to substantial Mesoproterozoic crust formation in the FMC whereas more than 60% of the crust is actually Neoproterozoic in age. Second, new additions to the continental crust volume during the Variscan orogeny are not recorded even though 5 to 10% of the exposed crust formed at that time. The origin of both discrepancies inherently lies in the mixed isotopic signature carried by many zircon grains. Such equivocal information can only be detected when additional petrological constrains on the zircon host rocks are available and provide guidance in interpreting the zircon record of crust evolution
Sbisa', Andrea. "Structure and eruptive history of the Sesia caldera, North West Italy." Doctoral thesis, Università degli studi di Trieste, 2011. http://hdl.handle.net/10077/4560.
Повний текст джерелаQuesta tesi di dottorato è focalizzata sui meccanismi dei sistemi magmatici che possono causare super-eruzioni, e ha come oggetto una sezione fossile che comprende le zone Ivrea-Verbano e la zona Serie dei Laghi (Italia, Nord-Ovest). Questa ricerca presenta evidenze di una caldera di età Permiana che espone il sistema magmatico fino alla profondità di 25 km. La correlazione delle età delle rocce vulcaniche e plutoniche della crosta media ed inferiore, mette in luce come queste costituiscano l’esposizione di un sistema magmatico che ha alimentato una caldera, e evidenzia la relazione cause-effetto tra l’intrusione di fusi basaltici derivanti dal mantello e il vulcanesimo acido. L’eruzione associata al collasso della caldera è stata di VEI > a 8 (Newhall and Self, 1982) e caratterizzata da una unica unità eruttiva a composizione riolitica. Il collasso della caldera è avvenuto in un campo vulcanico maturo, probabilmente tagliando il bordo di una caldera precedente. Il maggior volume di lave eruttate è composto da dacite alte in silice, i termini meno evoluti sono andesi-basalti. Le caratteristiche della caldera e del campo vulcanico sono simili a caldere formatesi durante la transizione da un regime tettonico compressionale ad uno estensionale-transpressivo. Il lavoro documenta una struttura interna della caldera simile a quella descritta per la caldera Grizzly Peak Colorado, USA (Fridrich et al., 1991) dove le frane escono come cunei dal “caldera wall” con una geometria simile ad un “albero di natale rovesciato” insieme ad una zonazione tra zone ricche di litici a zone di ignimbrite con pochi litici. Dopo il collasso, il riempimento della caldera è stato intruso direttamente da granito senza alcune evidenze di “caldera floor”. La composizione delle rocce della caldera del Sesia è compatibile con una ibridazione tra fusi basaltici derivanti dal mantello e una o più componenti anatettiche. La comparazione dell’eruzione che ha causato il collasso della caldera con le rocce del plutone sottostante non mette in luce una parentela con la zona superiore (Upper Valle Mosso); si aprono quindi nuove problematiche che richiedono ulteriori studi isotopici. Abbiamo documentato due stadi di alterazione idrotermale nel riempimento della caldera del Sesia, uno a più alta temperatura ed uno seguente a più bassa temperatura. Si può osservare che la circolazione idrotermale ha causato impoverimento di silice e un inizio di metasomatismo della roccia. La disposizione areale delle vene di quarzo e delle zone di silicificazione indicano che la deposizione ha interessato i confini tra materiali a differente porosità, in particolare tra la porosa ignimbrite intracaldera e materiali meno porosi come le rocce del “caldera wall” (grandi frane intracaldera ed il granito che ha intruso la caldera). Non abbiamo osservato alcuni dei fenomeni associati alla circolazione idrotermale nel granito che intrude il riempimento della caldera, perciò riteniamo che il contatto sia stato un importante confine alla circolazione dei fluidi idrotermali che circolavano principalmente nel riempimento della caldera.
XXIII Ciclo
1976
Cowie, Leanne. "Determination of ocean continent transition structure, continent ocean boundary location and magmatic type at rifted continental margins." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/2008044/.
Повний текст джерелаKorostelev, Felicie. "La lithosphère du point triple Aden - Afar - sud mer Rouge et du golfe d'Aden : magmatisme et rupture continentale." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066341/document.
Повний текст джерелаThe Afar triple junction is a unique region that links the Red Sea, the Gulf of Aden and the Ethiopian rift, and where it is possible to study the different stages of continental breakup, from early rifting to seafloor spreading and development of continental passive margins. Extension and magmatic activity are generally thought to be restricted to the active volcanic segments of the rift or to oceanic ridges. However, magmatic activity is also present on the continental margins flanks of the Afar rift, southern Red Sea and Gulf of Aden. The ambient noise tomography and teleseismic body-wave tomography are complementary methods that allow imaging the crust and upper mantle, and help to reveal magmatic systems. Our tomographic studies of the Afar region provide evidence for the presence of complex magmatic systems under the Afar rift flanks, currently modifying the crust and linked with hydrothermal systems near the surface. The emplacement of intruded or under-plated dense magmatic material in the Afar lower crust accommodates the extension outside of the active magmatic segments. In addition, the Red Sea margin flanks in Yemen are affected by magmatism caused by localized small-scale upwellings of mantle material, from a broad abnormally hot mantle zone located beneath Afar and southwestern Yemen. We also suggest the presence of magmatic systems with or without a volcanic expression at the surface, beneath the passive margins shoulders of the eastern Gulf of Aden. We propose that these systems could be fed by small-scale convection caused by lithosphere thickness variations at the edge of the Arabian plate and near the Gulf of Aden main fracture zones
Holbik, Sven P. "Arc Crust-Magma Interaction in the Andean Southern Volcanic Zone from Thermobarometry, Mineral Composition, Radiogenic Isotope and Rare Earth Element Systematics of the Azufre-Planchon-Peteroa Volcanic Complex, Chile." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1524.
Повний текст джерелаMatzel, Jennifer E. Piontek 1973. "Rates of tectonic and magmatic processes in the North Cascades continental magmatic arc." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/30292.
Повний текст джерелаIncludes bibliographical references.
Continental magmatic arcs are among the most dynamic. geologic systems, and documentation of the magmatic, thermal, and tectonic evolution of arcs is essential for understanding the processes of magma generation, ascent and crustal growth. The primary goal of this research is to determine rates of tectonic and magmatic processes in the mid to deep crustal levels of the crystalline core of the Cretaceous North Cascades arc. This region was selected for study because it preserves a -10-40 km depth-section through the arc, which allows an assessment of magmatic and structural processes over a range of crustal levels. The relatively young age of the arc (ca. 100-45 Ma) and the inherent high-precision of U-Pb zircon dates permit absolute uncertainties of <100 ky. Meta-supracrustal rocks of the Cascades core record some of the highest pressures obtained in the North American Cordillera. The timing of deposition and metamorphism of the 9-12 kbar Swakane Gneiss constrain tectonic burial models and the timescales of large crustal displacements within an arc setting. These models involve rapid burial (-7 mm/yr) of a fore- or back-arc basin from ca. 73-68 Ma. Nd isotopic signatures of all meta-clastic terranes of the Cascades core reflect mixing of arc- and craton-derived sediment, and the Swakane Gneiss has the most isotopically-evolved signature of these terranes. Nd isotopic signatures of plutons that intrude the core lack evidence of melting of this isotopically-evolved unit. 40Ar/39Ar and U-Pb thermochronologic data define regional cooling patterns that suggest mid- to Late Cretaceous exhumation coincident with contraction and crustal thickening at the deepest levels of the core, followed by Early Tertiary extension.
(cont.) High-precision U-Pb geochronology reveals internal complexities inherent in the construction of an intrusive magmatic system. The Mount Stuart batholith was constructed over a ca. 5.6 Myr time period with four punctuated intervals of magma emplacement, whereas the Tenpeak intrusion was emplaced in a more continuous process over ca. 2.7 Myr time period. U-Pb zircon dates from two elongate intrusions, the Seven- Fingered Jack and Entiat suites, suggest that they were constructed from multiple magmatic sheets that were partially homogenized at the level of emplacement.
by Jennifer E. Piontek Matzel.
Ph.D.
Beslier, Marie-Odile. "Formation des marges passives et remontée du manteau : modélisation expérimentale et exemple de la marge de la Galice /." Rennes : Centre armoricain d'étude structurale des socles, 1991. http://catalogue.bnf.fr/ark:/12148/cb354853593.
Повний текст джерелаSoltanmohammadi, Azam. "Sources du magmatisme alcaline dans le plateau turco-iranien : un lien avec la dynamique des lithosphères stagnantes dans la zone de transition du manteau." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30070/document.
Повний текст джерелаContinental alkaline lavas are volatile-rich mantle derived magmas erupted either in orogenic setting, close to subduction zones, or in intracontinental setting far away from any active subduction zone. Their genesis involves partial melting of mantle sources either at shallow depths (< 150 km) or either at greater depths (> 150 km) down to the top of the Mantle Transition Zone. In the Turkish-Iranian Plateau, alkaline lavas younger than 80 Ma have geochemical signatures pointing to both types, i.e. subduction-influenced and intraplate (Oceanic Island Basalt-like). Based on SiO2 content and alkalinity index, the lavas can be grouped into three main types, group I, II and II. Groups I and II are ultrapotassic-potassic and sodic alkaline lavas with subduction-influenced and Oceanic Island Basalt-like chemical patterns, respectively whereas group III lavas have a transient composition between high-K calc-alkaline to calc-alkaline series with subduction-influenced chemical patterns. Particularly the Salavat Range, located in NW Iran, is characterised by lavas (flow, pillow structures dykes) displaying an abundant population of zoned clinopyroxene macrocrysts. A combination of mineral chemistry of the zoning patterns with the bulk rock major and trace element features evidence that the different populations of zoned clinopyroxene are representative of melts of group I and/or II. Our synthesis of the most recent available seismic tomography images show the presence of a large set of elliptic, ~100 km size, low velocities bodies, we named "Compaction pockets", scattered from ~400 km up to ~ 100 km depth. A model is developed showing that the low velocity of the compaction pockets result from the percolation and concentration into large pockets of volatile-rich melt liberated at ~ 410 km depth in the "Big Mantle Wedge". It is shown to result from interaction of volatile-rich melts with the surrounding mantle at a temperature ~100-200 °C lower than the usual sub-continental mantle adiabat, which eventually results in the precipitation of hydrated and carbonated mineral phases at ~8-6.5 GPa, partial melting of metasomatized mantle at 6.5 down to 4 GPa and finally in the precipitation of hydrated/carbonated phases below 4 GPa. Melt extraction occurs via swarm of dykes triggered when the top of the compaction pocket successively crosses these critical depths: ~240 km (8GPa), ~165 km (5.5 GPa) and ~135 km (4.5 GPa). It is shown that the three groups of lavas (group I, II and III) may be linked to these three successive melt extraction events. Strikingly, the clinopyroxene zonings recorded in the Salavat Range lavas may be representative of group I melt transported by a dyke generated at 240 km depth which pond close to the spinel-garnet mantle transition and eventually partially crystalized there. About 0.3 Ma later, when a 135 km deep dyke transporting a group II melt crosses that last interface, it traps partially crystalized assemblage of group I melt. Thereafter, the couple of mantle-derived melts may pound in a cold horizon where they simultaneously solidify and can explain the formation of clinopyroxene zonings in equilibrium with different alkaline melts
Abbassene, Fatiha. "Contraintes chronologiques et pétro-géochimiques du magmatisme sur l'évolution pré-et post-collisionnelle de la marge algérienne : secteur de la Petite Kabylie." Thesis, Brest, 2016. http://www.theses.fr/2016BRES0028/document.
Повний текст джерелаThe Miocene igneous activity in Lesser Kabylia includes a ~130 km-long EW-trending lineament that extends along the eastern Algerian margin from Kabylie de Collo to Ouest-Edough-Cap de Fer area. It includes mostly medium-K to High-K calc-alkaline plutonic and volcanic rocks. In the studied area, these magmatic rocks crosscut and/or overlie the inner zones of the Maghrebides represented by basement and Kabylian cretaceous and Numidian flyschs nappes. New U-Pb dating on zircons and K-Ar ages on whole rocks and separated minerals document a 17 Ma onset for the post-collisional K-rich calc-alkaline magmatism. These Upper Burdigalian ages obtained on the Bougaroun pluton are the oldest presently identified for Krich calc-alkaline rocks in the whole 1200 km-long EW trending magmatic belt located along the Mediterranean coast of Maghreb. However, according to new K-Ar ages, magmatic activity started in Ouest Edough zone at ~16 then persisted intermittently in the two studied areas at ~15.5 Ma, 14-13 Ma and stopped at ~11 Ma, with the emplacement of mafic and felsic dykes in Kabylie de Collo. In addition, we measured older (Upper Oligocene) Ar-Ar hornblende ages of 27.0 ± 3.0 Ma and 23.3 ± 3.2 Ma on LREE-depleted gabbros outcropping at Cap Bougaroun sensu stricto. According to our new geochemical and isotopic data, we distinguish two sources for magmatic rocks in the studied area: a depleted mantle source which could represent the ambient asthenosphere still not modified by the subduction processes at the time of emplacement of the Upper Oligocene LREE-depleted gabbros. The latter could be related to the Upper-Oligocene rifting before the back-arc crust formation in Algerian basin or to dyke systems or gabbroic intrusions crosscutting the stretched Kabylian continental crust. An enriched mantle source modified by a subduction component (melt or fluid) escaping from a northward-dipping subducted Tethyan oceanic lithosphere. The enriched mafic magmas are believed to come from this metasomatized mantle and are genetically related to the differentiated rocks through crystal fractionation and assimilation of large amounts of crustal lithologies, during their ascent through the African continental crust. We propose a tectono-magmatic model involving an Early Miocene Tethyan slab breakoff combined with delamination of the edges of the African and Kabylian continental lithospheres. At 17 Ma, the asthenospheric thermal flux upwelling through the slab tear induced the thermal erosion of the Kabylian lithospheric mantle metasomatized during the previous subduction event and triggered its partial melting. We attribute the strong trace element and isotopic crustal signature of Bougaroun felsic rocks to extensive interactions between ascending mafic melts and the African crust underthrust beneath the Kabylie de Collo basement
Ducea, Mihai N., George W. Bergantz, James L. Crowley, and Juan Otamendi. "Ultrafast magmatic buildup and diversification to produce continental crust during subduction." GEOLOGICAL SOC AMER, INC, 2017. http://hdl.handle.net/10150/623057.
Повний текст джерелаMercer, Celestine Nicole 1979. "Mineralogical indicators of magmatic and hydrothermal processes in continental arc crust." Thesis, University of Oregon, 2009. http://hdl.handle.net/1794/10250.
Повний текст джерелаThis dissertation explores several important consequences of H 2 O-rich fluids in magmatic and ore-forming systems within continental arc crust. North Sister, a stratovolcano in the Oregon High Cascades, provides a window into magma generation processes in the deep crust. Eruption of a remarkably limited basaltic andesite composition over the lifespan of this volcano may reflect last equilibration of mantle derived magma within a deep crustal hot zone. High pressure, water-undersaturated phase equilibrium experiments show that an anhydrous, augite-rich gabbro at ∼12 kbar (40 km depth) and ∼ 1175°C is the most probable lithology with which North Sister basaltic andesite with ∼3.5 wt% H 2 O last equilibrated within the deep crust before erupting. While magma often erupts at the planets surface as at North Sister, a greater volume never reaches the surface and solidifies within the upper crust. Exsolution of magmatic fluids is an inevitable consequence of crystallization of hydrous crustal magmas. The fate of these fluids is the focus of the remainder of this dissertation. Modeling of CO 2 and H 2 O variations during crystallization of granitic magma reveals that exsolution of a large mass of fluid occurs only after CO 2 is largely degassed, creating ideal conditions for hydrofracturing and formation of porphyry copper deposits. CO 2 and H 2 O solubility relations suggest that H 2 O-rich magma was required to produce the porphyry-Cu-Mo deposit at Butte, Montana, which may explain its distinctively deep generation. Electron microprobe analyses of Ti in quartz and Zr in rutile in samples from Butte yield porphyry magma temperatures (630-770°C) that overlap substantially with hydrothermal vein temperatures (<430-750°C). Veins display large temperature ranges (50-250°C) that signify variable degrees of cooling of hot magmatic fluids upon contact with cooler wall rock during vein growth. Modeling of Ti diffusion in quartz suggests that individual dikes and veins likely cooled over short timescales (10s-1000s years), indicating that porphyry systems may evolve by episodic magmatic fluid injections with discrete thermal spikes. Modeling of Ti diffusion in quartz combined with electron backscatter diffraction maps show that small hydrothermal quartz veins likely formed by epitaxial growth. This dissertation includes co-authored material both previously published and in preparation for submission.
Committee in charge: A. Dana Johnston, Chairperson, Geological Sciences; Mark Reed, Member, Geological Sciences; Paul Wallace, Member, Geological Sciences; Richard P. Taylor, Outside Member, Physics
Pearson, David M., Douglas R. MacLeod, Mihai N. Ducea, George E. Gehrels, and Patchett P. Jonathan. "Sediment underthrusting within a continental magmatic arc: Coast Mountains batholith, British Columbia." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/626287.
Повний текст джерелаSoler, Pierre. "Contribution à l'étude du magmatisme associé aux marges actives : pétrographie, géochimie et géochimie isotopique du magmatisme crétacé à pliocène le long d'une transversale des Andes du Pérou central : implications géodynamiques." Paris 6, 1991. http://www.theses.fr/1991PA066637.
Повний текст джерелаOhnenstetter, Daniel. "Minéralisations associées aux complexes mafiques-ultramafiques en domaine océanique et continental." Nancy 1, 1990. http://docnum.univ-lorraine.fr/public/SCD_T_1990_0539_OHNENSTETTER.pdf.
Повний текст джерелаRoman, Alberto M. "Emplacement and Post-Emplacement Dynamics of Magma Reservoirs." Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCC179.
Повний текст джерелаThe evolved bulk composition of the continental crust suggests that a large mafic portion has been lost during the geological time. However, mafic and ultramafic bodies, such as the Bushveld complex, South Africa, and the Great Dyke Zimbabwe, have been preserved in the crust for billions of years. The implied question, then, is how mafic cumulates are lost and, more specifically, what is the long-term evolution of a magma reservoir, possibly including post-emplacement and post-crystallization processes. This work aims at this question with the following approach. First , we perform laboratory experiments with viscous fluids to investigate the instability associated to a buoyancy reversai and derive simple scaling laws governing the different dynamical regimes. Many mafic intrusions preserve flow structures, proving that they were affected by gravitational instabilities consistent with the regimes observed in the laboratory. In a second part, we investigate the physical conditions under which mafic intrusions become unstable using extensive numerical simulations which reproduce crustal flows. The mort important finding is that the main control on the instability is the emplacement depth. The results of this work thus suggests that many of the mafic intrusions we obsei:ve4today at the outcrop are the vestiges of much larger systems that became unstable. Consequently foundering and sinking of mafic cumulates through the crust may be a very common process in volcanic regions. This mechanism should shed light on the processes governing the formation and differentiation of the Barth crust
Dosseto, Anthony. "Etude du magmatisme aux zones de subduction et de l'érosion continentale, par les séries de l'Uranium : contraintes sur les processus et leur temps caractéristique." Paris 7, 2003. http://www.theses.fr/2003PA077038.
Повний текст джерелаDautria, Jean-Marie. "Relations entre les hétérogénéités du manteau supérieur et le magmatisme en domaine continental distensif : exemple des basaltes alcalins du Hoggar, Sahara central, Algérie et de leurs enclaves /." Montpellier : Centre géologique et géophysique de l'Université des sciences et techniques du Languedoc, 1988. http://catalogue.bnf.fr/ark:/12148/cb36148832z.
Повний текст джерелаWhalen, Lisa Marie. "Supercontinental Inheritance and its Influence on Supercontinental Breakup: The Central Atlantic Magmatic Province and the Breakup of Pangea." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/71423.
Повний текст джерелаMaster of Science
Garrison, Jennifer Marie. "Magmatic processes at Cotopaxi Volcano, Ecuador geochemical and petrological constraints and interferences for continental arc volcanoes /." Diss., Restricted to subscribing institutions, 2004. http://proquest.umi.com/pqdweb?did=795958281&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
Повний текст джерелаAhmed, Abdulhakim. "Structure lithosphérique des marges continentales du Yémen et sismicité récente : implications géodynamiques." Paris 6, 2013. http://www.theses.fr/2013PA066046.
Повний текст джерелаIn the framework of YOCMAL ANR project, we map crustal thickness, structure and bulk seismic velocity variations across the western Gulf of Aden, southern Red Sea and Socotra (southeastern margin of the Gulf of Aden). We analyse P-wave receiver functions in order to address the role of magmatism, faulting and crustal thinning in both volcanic and nonvolcanic margins setting. We analyse teleseismic data from 46 stations of the temporary networks with permanent (GFZ-Yemen) in Yemen mainland and Socotra Island. We show that: (1) for western Yemen the thickness of unextended crust on the Yemen plateau is ~35 km and thins to ~22 km in coastal areas reaching less than 14 km on the Red Sea coast, with the evidence of the presence of a high velocity lower crust (HVLC). The average Vp/Vs ratio for the western Yemen Plateau is 1. 79, increasing to ~1. 92 near the Red Sea coast and decreasing to 1. 68 for stations located on or near the granitic rocks; and (2) for Socotra Island the thickness of unextended crust for the central Socotra is ~28 km thins to ~21 km to the west with a trend of crustal thinning to ~16 km on the west-northernmost coast of the Island. Low Vp/Vs ratio of 1. 65-1. 71 is observed for the stations located on or near granitic bodies, intermediate values of 1. 75-1. 84 are observed for the sedimentary basins and higher value more than 1. 89 is observed below the northern coast. In the spreading axis of the western Gulf of Aden, a significant seismo-volcanic event occurred. We used regional seismic networks in Djibouti and Yemen to locate 1134 moderate size earthquakes occurred from Nov. 2010 to Mar. 2011, along N115°E segment of the axial valley centered at 44. 024°E and 12. 021°N. The cumulative seismic moment associated with this sequence 6. 8x1017N. M, and taking into account a very low seismic versus geodetic moment, we estimate anhorizontal opening of ~0. 4 to 2. 2m. We interpreted this event to be mainly caused by magmatic activity focused along a single spreading segment of the Aden ridge, followed by strike-slip focal mechanisms at the locus of the change of trend and limit of the oceanic lithosphere
Santos, Emerson Barreto dos. "Magmatismo Alcalino-Potássico Paleoproterozóico no Sudoeste da Bahia e Nordeste de Minas Gerais: Evidência de Plutonismo Orogênico Associado a Arco Continental." Instituto de Geociências, 2005. http://repositorio.ufba.br/ri/handle/ri/23050.
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Os maciços do Estreito (MES), Canabrava (MCB) e Mato Verde (MMV) localizam-se no extremo sudoeste do Estado da Bahia e nordeste do Estado de Minas Gerais. Estes maciços possuem forma alongada, controlada por sistemas de falhas regionais, estão intrudidos nas rochas arqueanas do Complexo Santa Izabel (CSI), e são constituídos essencialmente por rochas monzoníticas, sieníticas e graníticas, com grandes cristais de feldspato alcalino, tendo a biotita como mineral máfico principal. Os dados geocronológicos (U-Pb e 207Pb/206Pb) existentes para o Maciço do Estreito possibilitam estabelecer que 2,05 Ga, representa sua idade de colocação e cristalização. As similaridades entre os maciços estudados permitem sugerir que foi nesta época que se colocaram os corpos Canabrava e Mato Verde. Esta idade confirma que este magmatismo faz parte não só do Batólito Guanambi, mas, também, do magmatismo alcalino-potássico Transamazônico no Estado da Bahia. Os maciços em estudo são compostos predominantemente por rochas hololeucocráticas a leucocráticas, levemente anisotrópicas. A mineralogia e história de cristalização destas rochas são muito semelhantes, e apontam para condições de evolução e de cristalização similares. Os dados químicos mostram que as rochas do MES, MCB e MMV são: saturadas a super-saturadas em sílica; alcalinas, com alcalinidade média; potássicas a fortemente potássicas; metaluminosas a peraluminosas; enriquecidas em Ba, Sr, K, P2O5, ETR e empobrecidas em Y, Nb e Ti. Os padrões dos ETR mostram um forte enriquecimento dos ETRL em relação aos ETRP. Os espectros obtidos nos diagramas multielementares são caracterizados por: acentuados vales em Nb, P e Ti; vales ocasionais em Ba e Sr; picos em Rb; e anomalias positivas e negativas de Th. As relações entre os elementos maiores, elementos incompatíveis e compatíveis, bem como o modelamento petrogenético, indicam que a cristalização fracionada foi o principal processo atuante na evolução das rochas destas intrusões. Os diversos dados químicos e petrográficos evidenciam uma afinidade shoshonítica para as rochas dos maciços em estudo. As assinaturas geoquímicas identificadas são compatíveis com a de magmas associados a ambiente orogênico do tipo arco continental.
The Estreito, Canabrava and Mato Verde massifs are located in the southwester of Bahia State and northeast of Minas Gerais State. Theses massifs have elongated shape, are controlled by faults regional systems and intrude Archean rocks from Santa Izabel Complex. They are composed by monzonitic, syenitic and granitic rocks with porphires of alkali feldspar and biotite as the main mafic mineral. The geochronological data (U-Pb and 207Pb/206Pb) for the Estreito Massif demonstrate that it was emplaced 2.05 Ga ago, and the similarity with the others studied massifs suggest that they were emplaced at the same time. This age also allow us to relate this magmatism with the Guanambi Batholith and the Transamazonic alkaline-potassic magmatism in the Bahia State. These massifs are composed by hololeucocratic to leucocratic and anisotropic rocks. The mineralogy and crystallization history are very similar and point out to the same conditions of crystallization and evolution. Geochemical data show that all the rocks of these massifs are Si-satured to – oversatured; alkaline, with medium alcalinity; potassic; metaluminous to peraluminous; Ba, Sr, K, P2O2 and REE enriched; low Ti, Nb and Y content. Chondrite-normalized REE patterns show strongly fractionated LREE. The multielementar diagrams are characterized by Nb, P and Ti depletions, occasionally with Ba and Sr; peak in Rb; and negative and positive anomalies in Th. The relationship between major, incompatible and compatible elements, together with the petrogenetic modeling show that fractionated crystallization was the main controlled process during the massifs rocks evolution. Chemical and petrographic data reveal a shoshonitic affinity for these massifs. The geochemical signature point to a magma associated with orogenic environment as continental arc.
Albaric, Julie. "Relations entre déformation active, rhéologie et magmatisme dans un rift continental : Etude sismologique de la Divergence Nord-Tanzanienne, Rift Est-Africain." Phd thesis, Université de Bretagne occidentale - Brest, 2009. http://tel.archives-ouvertes.fr/tel-00495984.
Повний текст джерелаAhmed, Daoud Mohamed. "Dynamique du rifting continental de 30 MA à l'actuel dans la partie Sud Est du Triangle Afar : tectonique et magmatisme du rift de Tadjoura et des domaines Danakil et d'Ali Sabieh, République de Djibouti." Brest, 2008. https://tel.archives-ouvertes.fr/tel-00312800.
Повний текст джерелаThe results of our study supply new constraints about the recent kinematical history of the Tadjoura Gulf and the Ali Sabieh range in the eastern part of the Afar Triangle. The Tadjoura rift is interpreted as a typical half-graben, accommodating 25-30% of bulk extension, and showing a progressive focussing of strain along its axial part with times. The geometrical and statistical analysis of fault networks indicates a gradient of extensional strain that we ascribe to the lateral locking of faut tip propagation against the Arta submeridian inherited faut zone. That mechanical disturbance is assumed to have caused the transfer of extension from the Tadjoura rift into the Ghoubbet-Asal trough, via a rift jump process. From structural and geochemical-radiometrical studies of older (Miocene) synrift volcanics in the Ali Sabieh range, their regional-scale antiformal structure is assigned to the emplacement of a shallow-level mafic intrusion (laccolith-type) during Miocene times. By contrast, the edification of the Danakil range is related to more recent Tadjoura/Asal rift tectonics. From our results, new asumptions are teatatively proposed to a number of key-issues dealing with the overall kinematic development of the Afar rift system, such as : the sens of active rift axes propagation, the spatial distribution of initial trap volcanism (30 Ma), the evolution of the Danakil microblock, as well as the nature of the eastern margin with the Red Sea fault-basinal domain to the E
Bonson, Christopher G. "Fracturing, fluid processes and mineralisation in the Cretaceous continental magmatic arc of Northern Chile (25°15'-27°15'S)." Thesis, Kingston University, 1998. http://eprints.kingston.ac.uk/20612/.
Повний текст джерелаPoitrasson, Franck. "Apports du système radiométrique Samarium-Néodyme à la connaissance du magnétisme anorogénique intracontinental. Exemple du sud-est de la France (Corse et Estérel)." Clermont-Ferrand 2, 1994. http://www.theses.fr/1994CLF21601.
Повний текст джерелаSuarez, Tatiana Arenas. "Resfriamento de corpos intrusivos no interior da crosta continental: o efeito da liberação do calor latente." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/14/14132/tde-02072018-164306/.
Повний текст джерелаThe purpose of this work is to study the thermal evolution of intrusive bodies formed by successive sills injection in different levels of the crust, taking into account the phase change and latent heat release in a finite temperatures interval. Our numerical models involve heat transfer only by conduction. Thermal evolution of the system is found with the energy balance equation of enthalpy that includes phase and composition change of magmas. The thermal evolution of the basaltic igneus body intruded into the lower crust is evaluated using finite difference scheme. At this level of the crust we develop two different ways of igneus body construction: over- accretion and under-accretion. Over-accretion is the more efficient way for keeping high temperatures in the time. In the upper crust, the thermal evolution of a tonalite igneus body formed by successive sils injection is computed with finite elements method in a geometry with rotational symmetry about z axis. Thermal and geological development of this igneus bodys strongly depends on magma emplacement rate and magma and crust thermal proprerties. These features defines if the igneus body develops in a magmatic chamber, a melt reservior or a high crystalline body. In the second part of this work we examine heat transfere from magamatic chambers of different geometries into the country rock, solving the entalphy equation with latent heat release effects with finite element method. The magmatic chambers geometries constructed are oblate spheroid, prolate spheroid and spherical. The viscosity of the rock is also obteined from temperature field.
Popoff, Michel. "Déformation intracontinentale Gondwanienne : rifting mézoique en Afrique : évolution meso-cénozoique du fossé de la Bénoué, Nigéria : relations avec l'ouverture de l'Océan Atlantique Sud." Aix-Marseille 3, 1990. http://www.theses.fr/1990AIX3A002.
Повний текст джерелаLane, Christine Irene. "Rifted margin formation in the Northwest Indian ocean : the ectensional and magmatic history of the Laxmi Ridge continential margin." Thesis, University of Southampton, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500747.
Повний текст джерелаBrueseke, Matthew Edward. "Mid-Miocene Magmatic System Development in the Northwestern United States." Miami University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=miami1144773179.
Повний текст джерелаMelleton, Jérémie. "Modalités du recyclage de la croûte continentale dans l'orogène varisque par traçage in situ des zircons hérités (mesures U -Pb/LA-MC-ICPMS)." Phd thesis, Université d'Orléans, 2008. http://tel.archives-ouvertes.fr/tel-00388706.
Повний текст джерелаMorand, Alexandra. "Formation et instabilité de réservoirs de magma silicique dans la croûte continentale." Thesis, Université de Paris (2019-....), 2019. https://theses.md.univ-paris-diderot.fr/MORAND_Alexandra_va2.pdf.
Повний текст джерелаHuge silicic magmatic systems can produce devastating eruptions with emitted volumes above 100 km³. The shape and the organisation of magmatic storage are still debated, despite their crucial influence on the results of theoretical predictions. We choose to look at the problem in a new light, by thinking about the physical reasons that explain the formation of a storage zone. This is in order to better understand stresses produced by the magma chamber in the host rocks. Our hypothesis is that silicic magma, due to its positive buoyancy, rises through the ductile continental crust as a diapir, and is then stopped by the brittle-ductile transition. This PhD follows three axes. The first presents the adaptation of a published theoretical plate-model which enables us to describe the stresses and displacements due to the storage of a buoyant liquid under an elastic plate. The second axis is an experimental one. An apparatus was built to reproduce experimentally the storage configuration assumed. Our results, allow us to test our model. Thirdly, in order to validate our starting hypothesis, numerical results are compared with data from natural systems. We show that our model can reproduce the large observed deformation at Uturuncu volcano in Bolivia. Then, more broadly, we show that stresses produced in the plate by the magma chamber can produce circular faults above the storage zone. This result has direct implications for the understanding of caldera formation during large silicic eruptions
Boumehdi, Moulay Ahmed. "Les clinopyroxènes dans les basaltes alcalins continentaux (Massif central, France) : implications pétrogénétiques, barométriques et caractérisation de la profondeur des réservoirs magmatiques." Clermont-Ferrand 2, 1988. http://www.theses.fr/1988CLF21123.
Повний текст джерела