Дисертації з теми "Mantel plumes"
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Treml, Markus. "The Seismic Signature of Mantle Plumes." Diss., lmu, 2006. http://nbn-resolving.de/urn:nbn:de:bvb:19-62692.
Повний текст джерелаStyles, Elinor Elizabeth. "Seismic expressions of thermochemical mantle plumes." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/9002.
Повний текст джерелаMailer, Tina. "Neon, Helium and Argon isotope systematics of the Hawaiian hotspot." Phd thesis, Universität Potsdam, 2009. http://opus.kobv.de/ubp/volltexte/2009/3963/.
Повний текст джерелаOzeaninselbasalte (OIBs), die durch Intraplatten-Vulkane gebildet werden wie z.B. Hawaii, sind geochemisch oft durch variable Isotopensignaturen charakterisiert, die verschiedene Mantelquellen widerspiegeln. Diese Variationen können über kurze Distanzen auf lokalem Maßstab auftreten. Im Rahmen dieser Arbeit wurden Edelgasisotopenzusammensetzungen (He, Ne, Ar, Kr, Xe) verschiedener hawaiianischer Vulkane ermittelt. Bohrkernproben vom Hawaii Scientific Drilling Project (HSDP), Oberflächenproben von den Vulkanen Mauna Kea, Mauna Loa, Kilauea, Hualalai, Kohala und Haleakala, sowie Proben aus einer Bohrung am Gipfel des Kilauea wurden untersucht. Edelgase, insbesondere Helium, dienen als geochemische Tracer. Dies ist auf der Annahme begründet, dass hohe 3He/4He Verhältnisse (> 8 RA) (RA ist das atmosphärische 3He/4He Verhältnis) Material aus dem tiefen Erdmantel repräsentieren, während niedrigere 3He/4He Verhältnisse (~ 8 RA) dem oberen Erdmantel entsprechen. Mauna Kea, Kohala und Kilauea Laven erreichten 3He/4He Verhältnisse zwischen 8 und 18 RA, während Haleakala Laven 3He/4He Verhältnisse von ~ 8 RA nicht überschreiten. Nur wenige Proben zeigten 20Ne/22Ne und 21Ne/22Ne Verhältnisse unterschiedlich vom Luftwert, was auf eine Herkunft aus dem tiefen Erdmantel schließen lässt. Edelgasisotopenwerte weisen auf eine Fraktionierung von He und Ar hin, mit einem Defizit an He. Berechnete 4He/40Ar*, 3He/22Nes (22NeS ist solares Ne) and 4He/21Ne Verhältnisse für die Proben sind niedriger als die entsprechenden Produktions- und primordialen Verhältnisse. Dies unterstützt die Beobachtung einer Fraktionierung von He gegenüber den schwereren Edelgasen, mit einer Verarmung von He gegenüber Ne und Ar. Ein beitragender Faktor bei der He Verarmung ist der löslichkeitskontrollierte Gasverlust während des Magmenaufstiegs. Der bevorzugte Verlust von He lässt jedoch auch darauf schließen, dass He sich bei magmatischen Prozessen inkompatibler verhält als Ne und Ar. Inwiefern die hohen 3He/4He Verhältnisse in hawaiianischen Laven ihren Ursprung in primitiven Komponenten innerhalb des hawaiianischen Plumes haben oder vielmehr in dem Verteilungsverhalten zwischen Mineralphase und Schmelze begründet sind, bleibt zu klären.
Xue, Jing. "Wavefront Healing and Tomographic Resolution of Mantle Plumes." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/50423.
Повний текст джерелаMaster of Science
Bredow, Eva [Verfasser], and Bernhard [Akademischer Betreuer] Steinberger. "Geodynamic models of plume-ridge interaction : case studies of the Réunion, Iceland and Kerguelen mantle plumes / Eva Bredow ; Betreuer: Bernhard Steinberger." Potsdam : Universität Potsdam, 2017. http://d-nb.info/1219514403/34.
Повний текст джерелаHalkett, Angus Rex William. "Mantle plumes and the sedimentary record : onshore-offshore India." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268908.
Повний текст джерелаHassan, Raquibul. "Dynamics of Mantle Plumes and Their Influence on Paleotopography." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/15171.
Повний текст джерелаAdena, Katherine Jane Daly. "Geochemical probing of mantle plume dynamics." Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.707705.
Повний текст джерелаIto, Garrett Tetsuo. "Mantle plume-midocean ridge interaction : geophysical observations and mantle dynamics." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/59638.
Повний текст джерелаMota, Carlos Eduardo Miranda. "Petrogênese e geocronologia das intrusões alcalinas de Morro Redondo, Mendanha e Morro de São João: caracterização do magmatismo alcalino no Estado do Rio de Janeiro e implicações geodinâmicas." Universidade do Estado do Rio de Janeiro, 2012. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=5883.
Повний текст джерелаThe models for formation of alkaline plutons of the Southeastern Brazil Alkaline Province or Poços de Caldas-Cabo Frio Magmatic Lineament, which genetic modeling associates crust reactivations or mantle plumes, with definition of a hot spot track. The objective of this work is to report new data and interpretations to contribute to a better understanding and discussion about the model of alkaline rock generation. The studies involved geological mapping, petrography, litogeochemistry, Sr-Nd-Pb isotopes and 40Ar/39Ar geochronology. The selected alkaline complexes are the Morro Redondo, Mendanha and Morro de São João, located at Rio de Janeiro State. These intrusions are well-distributed along the Poços de Caldas-Cabo Frio Magmatic Lineament. The Morro Redondo alkaline intrusion is composed mainly by nepheline syenites and nepheline-bearing syenites and mafic rocks are rare. It was defined as a sodic silica-undersaturated alkaline suite, with metaluminous to peralkaline characteristics. The intrusion was dated at 74 Ma (40Ar/39Ar plateau age). The Mendanha alkaline intrusion is compose by various types of syenitic rocks, breccias and subvulcanic structures, as pyroclastic rocks and dikes. It was defined by a sodic silica-saturated alkaline suite with metaluminous characterisics. The intrusion presented two distinct 40Ar/39Ar ages for the magmatism: 64 Ma for Mendanha rocks and 54 Ma to lamprophyre dike, which illustrates a polycyclic magmatism. The Morro do Marapicu 40Ar/39Ar age yielded 80 Ma. The Morro de São João alkaline intrusion has a large variety of silica-undersaturated to silica-saturated rocks, as syenites, alkali-syenites and monzosyenites (some pseudoleucite-bearing), with melanocratic varieties, as malignites and ferguites. These rocks defined distinct alkaline silica-undersaturated suggenting sodic and potassic types. There was found an alkaline silica-saturated suite, defined by alkaline gabbros and shonkinites. The petrogenesis of these intrusions corresponds to the fractional crystallization, with assimilation of host rocks, and the crustal contamination is indicated by high variability of Sr isotope ratios. For Morro de São João origin is suggested a K-Na bimodal magma. These intrusions were generated from enriched mantle-derived magmas, possible associated to ancient subduction zone of Ribeira orogen. In terms of the new 40Ar/39Ar data, the hot spot model is not plausible, because the Morro do Marapicu is older than the other studied intrusions. Some models projected mantle plumes with 1000 Km size, what may explain the reason for Mendanha and Morro de São João have the nearly the same age. The obtained isotopic signatures for these intrusions were not associated to Trindade signature and, if the mantle plumes model is correct, the plume that has the most similar signature is Tristão da Cunha.
Staples, Robert Kay. "Crustal structure above the Iceland mantle plume." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627379.
Повний текст джерелаWatson, Sarah Penelope. "Hotspots and volcanism." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386840.
Повний текст джерелаLiu, Mian. "Evolution of mid-plate hotspot swells, mantle plumes, and Hawaiian basalts." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184924.
Повний текст джерелаSmallwood, John Richard. "Oceanic crust formed near the Iceland mantle plume." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627183.
Повний текст джерелаFranken, Thijs. "Analysing partial melting in the Réunion mantle plume." Thesis, Université de Paris (2019-....), 2019. http://www.theses.fr/2019UNIP7129.
Повний текст джерелаPartial melting in the upper mantle is prevalent in areas of mantle upwelling such as rifts, mid-ocean ridges and hotspots. The presence of low shear-wave velocity zones in the shallow mantle (∼ 80km) are often associated with these locations, revealing velocity anomalies of −4 to −5% which are generally attributed to the presence of melt. However, studies on the quantity of melt responsible for the velocity reduction are divided, where experimental results from petrology, geochemical observations and geodynamical models suggest melt retention of < 1%, whereas seismic interpretations call for 1 > %. In this thesis I attempt to resolve the disagreement on melt retention in the asthenosphere by combining forward modelling of melt production and seismic wave propagation to relate geodynamic condition of partial melting directly to seismic observations of the Réunion mantle plume. I developed a 1D model of melt production that approximates melt retention for a range of permeability coefficients, initial mantle temperatures and upwelling velocities through a set of modified Stokes equations assuming porous flow. 210 melting model scenarios are converted to anharmonic seismic P- and S-wave velocities using a mineral parameter database, which are embedded into the ak135 earth reference model to generate synthetic seismograms of the melting scenarios for 21 source events using the Direct Solution Method for a laterally homogeneous and spherically symmetrical Earth. I explore the effect of melt presence on the radial, transverse and vertical wave component for the P, S, Pdiff and SKS phase arrivals, band-pass filtered to upper corner frequencies of 0.05, 0.1, 0.15 and 0.2 Hz. Through an automated cross-correlation procedure I compute relative traveltime differences between the observed seismograms and the 210 synthetic model traces for each iteration of the 21 source events, 4 phase arrivals, 3 wave components, and 4 band-pass filter frequencies. I analyse 70,896 relative traveltime datapoints to reach a solution for the minimised relative traveltimes between the model traces and the seismic observations, in order to discover which melting model scenario describes the upper mantle beneath Réunion. The solution to the best-fit model scenario is non-unique, since several combinations of the permeability coefficient, temperature and upwelling velocity give the same solution. By seperately analysing the parameter distribution of the free model parameters over the minimised relative traveltime solution of the 70,896 datapoints for the different phase arrivals and wave components, two likely regimes of upper mantle conditions can be constrained that can resolve the seismic observations. These regimes indicate that mantle conditions beneath Réunion are either in the 1300−1350 °C temperature range with melt fractions of ∼ 1%, or in the 1400−1450 °C temperature range with melt fractions of < 0.3%. Constraints from studies on upper mantle temperature, permeability and melt transportation velocities correspond to the latter case, showing that low retention of melt in the shallow mantle beneath Réunion simultaneously satisfy seismic observations and the expected geodynamic conditions
Xu, Guangping. "Origin of geochemical heterogeneity in the mantle : constraints from volcanism associated with Hawaiian and Kerguelen mantle plumes." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42275.
Повний текст джерелаIncludes bibliographical references.
Lavas derived from long-lived mantle plumes provide important information of mantle compositions and the processes that created the geochemical heterogeneity within the mantle. Kerguelen and Hawaii are two long-lived mantle plumes and lavas associated with them have very different geochemical characteristics. In this thesis I studied the geochemical compositions of the lavas associated with Kerguelen plume (Mt. Capitole in Kerguelen Archipelago) and Hawaiian plume (Mauna Kea, East Molokai and West Molokai volcanoes) to understand what processes contributed to the geochemical variations observed in Kerguelen and Hawaiian lavas and the geochemical structure of the mantle beneath them. Mt. Capitole is in the central part of the Kerguelen Archipelago and is attributed to Cenozoic volcanism arising from the Kerguelen hotspot. Based on the study of Mt. Capitole and previous isotopic data for the Kerguelen Plateau, Kerguelen Archipelago and Heard Island, I propose that two stages of mixing can explain the significant Sr, Nd, Hf and Pb isotopic heterogeneity. The first mixing process, best shown by the submarine lavas from Northern Kerguelen Plateau, is between a depleted component (i.e., relatively low 87Sr/86Sr with high 143Nd/144Nd and 176Hf/177Hf), probably related to Southeast Indian Ocean mid-ocean ridge basalt, but possibly intrinsic to the Kerguelen plume, and an enriched Kerguelen plume component. From -34 Ma to <1 Ma, on average the proportion of the depleted component decreased. Subsequently, a second mixing process involved addition of a component with relatively high 87Sr/86Sr (>0.7060) and low 143Nd/144Nd (<0.5125) and 176Hf/177Hf (<0.2827) and non-radiogenic Pb isotope ratios (<17.9 for 206Pb/204Pb).
(cont.) I infer that this component was lower continental crust. At Hawaii there are systematic geochemical differences between the < 3 My Hawaiian shields forming the subparallel spatial trends, known as Loa and Kea. East Molokai (> 1.5 Ma), the oldest volcano on the Kea-trend, maintains the Kea-like geochemical characteristics. As East Molokai and other Kea-trend volcanoes (Mauna Kea, Kohala, Haleakala and West Maui) migrate away from the hotspot and evolve from the shield to postshield stage, isotopic ratios of 87Sr/86Sr decrease and 143Nd/144Nd and 176Hf/177Hf increase in postshield lavas; however, all Kea postshield lavas have similar ratios of Sr, Nd, Hf and Pb showing that the periphery of the hotspot sampled by Kea-trend postshield lavas had long-term geochemical homogeneity (>1.5 My). The temporal changes in Sr, Nd and Hf isotope ratios are attributed to incorporation of a depleted component that dominantly sampled by rejuvenated stage lavas. This depleted component has Kea-trend Pb isotopic characteristics, relatively low 208Pb/204pb at a given 206Pb/204Pb, and it is probably not related to oceanic lithosphere or the source of mid-ocean ridge basalt. The Loa-Kea spatial geochemical differences end at West Molokai shield (- 1.9 Ma) which is the oldest Loa-trend volcano on the double parallel chains. West Molokai shield includes lavas with Loa- and Kea-like geochemical characteristics; a mixed Loa- Kea source is required. In contrast, West Molokai postshield lavas are exclusively Kea-like. This change in source geochemistry can be explained by the observed change in strike of the Pacific plate near Molokai Island so that as West Molokai volcano moved away from a mixed Loa-Kea source it sampled only the Kea side of a bilaterally zoned plume (Abouchami et al., Nature, v434, 2005).
by Guangping Xu.
Ph.D.
Hards, Victoria L. "The evolution of the Snaefell Volcanic Centre, eastern Iceland." Thesis, Durham University, 1995. http://etheses.dur.ac.uk/1452/.
Повний текст джерелаAgrusta, Roberto. "How do mantle plumes help to thin and break up the lithosphere?" Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20135/document.
Повний текст джерелаMantle plumes are traditionally proposed to play an important role in thinning the lithosphere. Seismic images beneath Hawaii and Cape Verde, for instance, show a lithosphere-asthenosphere boundary (LAB) up to 50 km shallower than the surroundings. However, previous numerical modeling of plume-lithosphere interaction implies that unless the plate is stationary the thermo-mechanical erosion of the lithosphere does not exceed 30 km. We used 2D petrological-thermo-mechanical numerical models based on a finite-difference method on a staggered grid and marker in cell method to further study the plume-lithosphere interaction. We focused on: (1) analyzing the dynamics of the small-scale convection (SSC) in the plume wake as a function of the plume vigor and plate velocity and (2) quantifying the effect of partial melting on this SSC. A homogeneous peridotite composition with a Newtonian temperature- and pressure-dependent viscosity is used to simulate both the plate and the convective mantle. A constant velocity, ranging from 5 to 12.5 cm/yr, is imposed at the top of the plate. Plumes are created by imposing a thermal anomaly of 150 to 350 K on a 50 km wide domain at the base of the model (700 km depth); the plate right above the thermal anomaly is 40 Myr old. Partial melting is modeled using the batch-melting solidus and liquidus in anhydrous conditions. We model the progressive depletion of peridotite and its effect on partial melting by assuming that the melting degree only strictly increases through time. Melt is accumulated until a porosity threshold is reached and the excess melt is instantaneously extracted. The rheology of the partially molten peridotite is determined using a viscous constitutive relationship based on a contiguity model, which enables to take into account the effects of grain-scale melt distribution. The density varies as a function of the melt fraction and of the depletion of the residue. We analyze the kinematics of the plume as it impacts a moving plate, the dynamics of time-dependent small-scale convection (SSC) instabilities developing in the low-viscosity layer formed by spreading of hot plume material at the lithosphere base, and the resulting thermal rejuvenation of the lithosphere. The onset time and the vigor of SSC and, hence, the new equilibrium thermal state of the lithosphere atop the plume wake depends on the Rayleigh number (Ra) in the unstable layer at the base of the lithosphere, which is controlled by the temperature anomaly and rheology in the plume-fed layer. For vigorous, hot plumes, SSC onset times do not depend on plate velocity. For more sluggish plumes, SSC onset times decrease with increasing plate velocity. This behavior is explained by differences in the thermal structure of the lithosphere, due to variations in the spreading behavior of the plume material at the lithosphere base. Reduction of the viscosity in partial molten domains and decrease in density of the depleted residuum accelerate and enhance the vigor of small-scale convection in the plume-fed low-viscosity layer at the lithosphere base. It also reduces SSC onset times, leading to more effective erosion closer to the plume-lithosphere impact
Kahn, Aaron M. "Geophysical attributes of earth's hotspots and their potential associations with mantle plumes /." Columbus, Ohio : Ohio State University, 2004. http://hdl.handle.net/1811/6087.
Повний текст джерелаPoore, Heather Rachel. "Neogene epeirogeny and the Iceland Plume." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612116.
Повний текст джерелаPears, M. I. B. "Stall and collapse in mantle plumes : an experimental and numerical fluid dynamics perspective." Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1465981/.
Повний текст джерелаTan, Eh Ahrens T. J. "I. Multi-scale dynamics of mantle plumes : and II. Compressible thermo-chemical convection and the stability of mantle superplumes /." Diss., Pasadena, Calif. : Caltech, 2006. http://resolver.caltech.edu/CaltechETD:etd-05142006-210236.
Повний текст джерелаSmit, Yvonne. "The Snaefellsnes transect : a geochemical cross-section through the Iceland Plume." Thesis, Open University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247048.
Повний текст джерелаMazza, Sarah Elizabeth. "Understanding Non-Plume Related Intraplate Volcanism." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/83554.
Повний текст джерелаPh. D.
Wölbern, Ingo. "Spuren des Plumes und Strukturen des oberen Mantels unter Hawaii abgeleitet aus konvertierten Wellen /." [S.l.] : [s.n.], 2003. http://www.gfz-potsdam.de/bib/pub/str0405/0405.htm.
Повний текст джерелаWölbern, Ingo. "Spuren des Plumes und Strukturen des oberen Mantels unter Hawaii abgeleitet aus konvertierten Wellen." [S.l. : s.n.], 2004. http://www.diss.fu-berlin.de/2004/172/index.html.
Повний текст джерелаGee, Margaret Anne Mary. "Volcanology and geochemistry of Reykjanes Peninsula : plume-mid-ocean ridge interaction." Thesis, Royal Holloway, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313752.
Повний текст джерелаGeorgen, Jennifer E. "Interactions between mantle plumes and mid-ocean ridges : constraints from geophysics, geochemistry, and geodynamical modeling." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/29052.
Повний текст джерела"September 2001." Vita. Page 223 blank.
Includes bibliographical references.
This thesis studies interactions between mid-ocean ridges and mantle plumes using geophysics, geochemistry, and geodynamical modeling. Chapter 1 investigates the effects of the Marion and Bouvet hotspots on the ultra-slow spreading, highly-segmented Southwest Indian Ridge (SWIR). Gravity data indicate that both Marion and Bouvet impart high-amplitude mantle Bouguer anomaly lows to the ridge axis, and suggest that long-offset transforms may diminish along-axis plume flow. Building upon this observation, Chapter 2 presents a series of 3D numerical models designed to quantify the sensitivity of along-axis plume-driven mantle flow to transform offset length, spreading rate, and mantle viscosity structure. The calculations illustrate that long-offset transforms in ultra-slow spreading environments may significantly curtail plume dispersion. Chapter 3 investigates helium isotope systematics along the western SWIR as well as near a global array of hotspots. The first part of this study reports uniformly low 3He/4He ratios of 6.3-7.3 R/Ra along the SWIR from 9⁰-24⁰E, compared to values of 8 +/- 1 Ra for normal mid-ocean ridge basalt. The favored explanation for these low values is addition of (U+Th) into the mantle source by crustal and/or lithospheric recycling. Although high He/4He values have been observed along the SWIR near Bouvet Island to the west, there is no evidence for elevated 3He/4He ratios along this section of the SWIR. The second part of Chapter 3 investigates the relationship between 3He/4He ratios and geophysical indicators of plume robustness for nine hotspots.
(cont.) A close correlation between a plume's flux and maximum 3He/4He ratio suggests a link between plume upwelling strength and origination in the deep, relatively undegassed mantle. Chapter 4 studies 3D mantle flow and temperature patterns beneath oceanic ridge-ridge-ridge triple junctions (TJs). In non-hotspot-affected TJs with geometry similar to the Rodrigues TJ, temperature and upwelling velocity along the slowest-spreading of the three ridges are predicted to increase within a few hundred kilometers of the TJ, to approach those of the fastest-spreading ridge. Along the slowest-spreading branch in hotspot-affected TJs such as the Azores, a strong component of along-axis flow directed away from the TJ is predicted to advect a hotspot thermal anomaly away from its deep-seated source.
by Jennifer E. Georgen.
Ph.D.
Pritchard, Matthew James. "A seismological study of the mantle beneath Iceland." Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4609/.
Повний текст джерелаMacLeod, Sarah J. "Characteristics of extinct spreading centers and the relationship between spreading ridges, hotspots and deep mantle structure." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17988.
Повний текст джерелаDelavault, Helene. "L'alignement volcanique de Pitcairn-Gambier : étude pétrologique et géochimique de la partie sud-est du panache polynésien." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENU020/document.
Повний текст джерелаPlume volcanism is one of the most puzzling features of present-day activities of the Earth. The origin of this type of volcanism remains a matter of debate, but it is generally agreed that its source is hot material containing some potentially recycled material. Most studies have focused on ‘strong' plumes with high magmatic production, e.g. Hawaii or Réunion, but weaker plumes such as Polynesia (South Pacific) may provide useful complementary information.This work presents a petrological and geochemical study of the Pitcairn-Gambier chain, situated at the South East of the Polynesian plume. I report major and trace element concentrations and Pb, Sr, Nd and Hf isotopic measurements of ~100 samples as well as probe analyses on olivine and sulphides in a few selected samples.Both isotopes and trace elements show a strong correlation with the age of the volcanoes (from the oldest island of Mururoa to the younger Pitcairn Seamounts), from « Young HIMU » isotopic compositions associated with high positive Nb anomalies (1.8), to typical EMI compositions with a slight negative anomaly (0.8). Geochemical modeling enables to constrain the age, the nature and the proportion of the recycled components in the source. Mururoa, Fangataufa and Gambier show in their source, the presence of 1.5 Gy recycled oceanic crust, along with 1-1.5 Gy sediments (<0.36%). The source of Gambier Island basalts is ‘cold' (~1450°C) compared to that of other plumes like Hawaii (1550°C). In contrast, the Pitcairn Island and Seamounts source is different as it contains 1.5 Gy recycled basaltic oceanic crust, as well as up to ~18% Archean (~2.5 Ga) cherts. The unexpected discovery of Archean cherts in the source of Pitcairn islands (which have the most extreme EMI compositions) is at odd with previous models on the origin of the EMI component.Positive Nb anomalies indicate the presence of recycled oceanic crust in the source, and this anomaly decreases with time along the chain. This feature can be explained by the increasing contribution of the sediment input in the source of the plume, since sediments display a negative Nb anomaly.The isotopic heterogeneities evidenced in this study are best explained by melting, beneath the islands, of different materials with various ages and compositions. The general structure of the Polynesian plume can be explained by the presence of small plumes generated from a superplume. These small plumes create small alignments, and they randomly sample various materials present in the plume. Overall the data and models in this study give new insights into the geochemical variations observed across the Polynesian plume, and at a larger scale they provide new perspectives to better understand crustal recycling processes and the evolution of the mantle through time
Williams, Alice Josiane. "The nature of the chemically enriched components of the Iceland mantle plume." Thesis, University of Edinburgh, 2005. http://hdl.handle.net/1842/14667.
Повний текст джерелаHarrison, Lauren Nicole. "Isotopic and chemical heterogeneity of the Hawaiian mantle plume : evaluating mantle geodynamics and characterization of the Loa geochemical trend." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/63408.
Повний текст джерелаScience, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
Starkey, Natalie. "Evolution of the Earth's mantle-crust-atmosphere system from the trace element and isotope geochemistry of the plume-mantle reservoir." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/5934.
Повний текст джерелаTrela, Jarek. "The Evolution of the Galapagos Mantle Plume: From Large Igneous Province to Ocean Island Basalt." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/77438.
Повний текст джерелаPh. D.
Robinson, Danielle D. Sandvol Eric Alan. "Seismic anisotropy beneath the southern Puna Plateau." Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/5362.
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.
Pilidou, Sylvana Demetriou. "Upper mantle shear-wave velocity and anisotropy structure beneath the North-Atlantic : a seismic image of the Iceland mantle plume." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615904.
Повний текст джерелаKundargi, Rohan. "Melting and dehydration within mantle plumes and the formation of sub-parallel volcanic trends at intra-plate hotspots." Thesis, Boston University, 2013. https://hdl.handle.net/2144/12802.
Повний текст джерелаOne of the defining characteristics of plume-fed hotspots is the formation of a linear chain of age-progressive volcanoes [Wilson, 1963; Morgan, 1972; Courtillot et al, 2003]. The most prominent example of this is the Hawaii-Emperor Seamount Chain, a 6000-km long age-progressive chain of volcanoes that stretch from the present-day island of Hawaii to the Aleutian Trench [van Ark and Lin, 2004; Sharp and Clague, 2006] However, recent volcanism at Hawaii does not form a simple linear trend, but rather is organized into two physically distinct sub-parallel chains, known as the Loa and Kea trends [Jackson, 1972]. Furthermore, recent studies have revealed that volcanism at several other hotspots, including the Samoa [Workman et al., 2004], Marquesas [Chauvel et al., 2009; Huang et al., 2011], and Society [Payne et al., submitted] hotspots are similarly organized into sub-parallel trends. Hieronymus and Bercovici [1999] developed a model in which lithospheric flexure in response to loading and combined with a change in plate motion, could generate sub-parallel trends of discrete volcanoes at plume-fed hotspots. Here, we develop an alternative mechanism for the formation of dual-chain volcanism at hotspots in which melting and dehydration of upwelling material within the plume conduit creates a buoyant, highly viscous plug of residuum that extends downwards from the base of the lithosphere above the plume conduit, causing the flow to bifurcate [Hall and Kincaid, 2003]. We report on a series of 3-D numerical experiments using CitcomCU in which an upwelling plume impinges on the base of an overriding oceanic plate. These experiments employ a diffusion creep rheology that includes the effect of water content on viscosity. Melting and dehydration are modeled using a Lagrangian particle method. This study analyzes the effect of dehydration on a plume-lithosphere setting, displaying results for both end members. Our results demonstrate the formation of the proposed viscous plug is plausible within a range of parameter space relevant to the Earth. The presence of this plug inhibits upwelling directly above the plume conduit, diverting plume flow to the edges of the plug and effectively bifurcating magma production in the mantle in the process.
Peto, Maria Kocsisne. "Application of noble gas isotopic systems to identify mantle heterogeneities." Thesis, Harvard University, 2014. http://nrs.harvard.edu/urn-3:HUL.InstRepos:13070050.
Повний текст джерелаEarth and Planetary Sciences
Arnould, Maëlis. "Some surface expressions of mantle convective instabilities." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/19901.
Повний текст джерелаSpice, Holly Elizabeth. "Viscosity of fayalite melt at high pressure and the evolution of the Iceland mantle plume." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/20971.
Повний текст джерелаGenske, Felix [Verfasser], and Karsten [Akademischer Betreuer] Haase. "Assessing the heterogeneous source of the Azores mantle plume / Felix Genske. Betreuer: Karsten Haase." Erlangen : Universitätsbibliothek der Universität Erlangen-Nürnberg, 2013. http://d-nb.info/1033029955/34.
Повний текст джерелаSchoonman, Charlotte Maria. "Vertical motions at the fringes of the Icelandic plume." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/267950.
Повний текст джерелаParnell-Turner, Ross Ernest. "Observations of transient mantle convection in the North Atlantic Ocean." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648620.
Повний текст джерелаSaal, Alberto Edgardo. "Evaluating mantle and crustal processes using isotope geochemistry." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/69186.
Повний текст джерела"September 1999."
Includes bibliographical references.
Geochemical studies are fundamental for understanding how the dynamic Earth works and evolves. These studies place constraints on the composition, formation, age, distribution, evolution and scales of geochemically distinct reservoirs such as the Earth's crust, mantle and core. In this dissertation the strategy has been to work on a broad range of topics to evaluate crustal and mantle processes. This study presents Re-Os systematics to constrain the composition, formation and age of the lower continental crust and the mantle lithosphere, examines melt inclusion from oceanic island basalts to evaluate the scale of the mantle heterogeneities, and uses U-series isotope to constrain geodynamic parameters, such as the upwelling velocities and porosities of mantle plumes. The lower continental crust plays a pivotal role in understanding the composition and evolution of the continental crust and the petrogenesis of continental basalts.
by Alberto Edgardo Saal.
Ph.D.
Villagomez, Diaz Darwin R. 1973. "Crustal and upper mantle structure beneath the Galapagos arechipelago from seismic tomography." Thesis, University of Oregon, 2010. http://hdl.handle.net/1794/11071.
Повний текст джерелаTo explain the origin of several distinct aspects of the Galápagos volcanic hotspot, such as the broad geographical extent of recent volcanism and the unusual pattern of geochemical anomalies, we conducted seismic tomography studies of the upper mantle and crust beneath the Galápagos Archipelago. The studies combine measurements of group and phase velocities of surface waves and delay times of body waves. We find that upper mantle seismic velocities are lower than those beneath other regions of comparable age in the Pacific and consistent with an excess temperature of 30 to 150°C and ∼0.5% melt. We attribute the excess temperature and presence of melt to an upwelling thermal mantle plume. Crustal seismic velocity is up to 25% lower than that of very young crust at the East Pacific Rise (EPR) and is comparable to that of Hawaii, which we attribute to heating by increased intrusive activity above the Galápagos plume and the construction of a highly porous volcanic platform. In addition, we find that the Galápagos hotspot is underlain by a high-velocity region whose thickness varies from 40 to 100 km. The tomographic images reveal that the upwelling mantle plume tilts northward (towards the nearby Galápagos Spreading Center) as it rises and then spreads laterally when it reaches the bottom the lid. The lid, which we attribute to residuum from melting, is thickest where it is farthest from the spreading center, suggesting that ridge processes may affect the generation and amount of thinning of the residuum layer. In addition, the thickness of the lid correlates well with the geographical pattern of geochemical anomalies of erupted lavas, suggesting that the lid may control the final depth of decompression melting. We conclude that many of the distinct characteristics of the Galápagos can be attributed to the interaction of the upwelling plume with the lid and the nearby ridge. We further suggest that the ridge affects the geometry of plume upwelling in the upper mantle and also the pattern of lateral spreading of the plume due to its effect on the thickness of the residuum layer. This dissertation includes previously published co-authored material.
Committee in charge: Dr. Douglas R. Toomey, Chairperson; Dr. Eugene Humphreys, Member; Dr. Emilie Hooft Toomey, Member; Dr. Paul Wallace, Member; Dr. John Conery, Outside Member
Wölbern, Ingo [Verfasser]. "Spuren des Plumes und Strukturen des oberen Mantels unter Hawaii abgeleitet aus konvertierten Wellen / Geoforschungszentrum Potsdam. Von Ingo Wölbern." Potsdam : Geoforschungszentrum, 2004. http://d-nb.info/97182438X/34.
Повний текст джерелаDannberg, Juliane [Verfasser], Stephan Vladimir Akademischer Betreuer] Sobolev, Michael [Akademischer Betreuer] [Weber, and Volker [Akademischer Betreuer] John. "Dynamics of mantle plumes : linking scales and coupling physics / Juliane Dannberg ; Stephan Vladimir Sobolev, Michael H. Weber, Volker John." Potsdam : Universität Potsdam, 2016. http://d-nb.info/1218400463/34.
Повний текст джерелаDannberg, Juliane [Verfasser], Stephan Vladimir [Akademischer Betreuer] Sobolev, Michael H. [Akademischer Betreuer] Weber, and Volker [Akademischer Betreuer] John. "Dynamics of mantle plumes : linking scales and coupling physics / Juliane Dannberg ; Stephan Vladimir Sobolev, Michael H. Weber, Volker John." Potsdam : Universität Potsdam, 2016. http://d-nb.info/1218400463/34.
Повний текст джерела