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  • 1
    Call number: M 20.93496
    Description / Table of Contents: According to the classical plume hypothesis, mantle plumes are localized upwellings of hot, buoyant material in the Earth’s mantle. They have a typical mushroom shape, consisting of a large plume head, which is associated with the formation of voluminous flood basalts (a Large Igneous Province) and a narrow plume tail, which generates a linear, age-progressive chain of volcanic edifices (a hotspot track) as the tectonic plate migrates over the relatively stationary plume. Both plume heads and tails reshape large areas of the Earth’s surface over many tens of millions of years. However, not every plume has left an exemplary record that supports the classical hypothesis. The main objective of this thesis is therefore to study how specific hotspots have created the crustal thickness pattern attributed to their volcanic activities. Using regional geodynamic models, the main chapters of this thesis address the challenge of deciphering the three individual (and increasingly complex) Réunion, Iceland, and Kerguelen hotspot histories,…
    Type of Medium: Dissertations
    Pages: 104 Seiten , Illustrationen, Diagramme, Karten
    Language: English
    Location: Upper compact magazine
    Branch Library: GFZ Library
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  • 2
    Publication Date: 2018-01-08
    Description: For at least 120 Myr, the Kerguelen plume has distributed enormous amounts of magmatic rocks over various igneous provinces between India, Australia, and Antarctica. Previous attempts to reconstruct the complex history of this plume have revealed several characteristics that are inconsistent with properties typically associated with plumes. To explore the geodynamic behavior of the Kerguelen hotspot, and in particular address these inconsistencies, we set up a regional viscous flow model with the mantle convection code ASPECT. Our model features complex time-dependent boundary conditions in order to explicitly simulate the surrounding conditions of the Kerguelen plume. We show that a constant plume influx can result in a variable magma production rate if the plume interacts with nearby spreading ridges and that a dismembered plume, multiple plumes, or solitary waves in the plume conduit are not required to explain the fluctuating magma output and other unusual characteristics attributed to the Kerguelen hotspot. ©2017. American Geophysical Union. All Rights Reserved.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
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  • 3
    Publication Date: 2018-11-12
    Description: In the classical concept, a hotspot track is a line of volcanics formed as a plate moves over a stationary mantle plume. Defying this concept, intraplate volcanism in Greenland and the North Atlantic region occurred simultaneously over a wide area, particularly around 60 million years ago, showing no resemblance to a hotspot track. Here, we show that most of this volcanism can nonetheless be explained solely by the Iceland plume interacting with seafloor spreading ridges, global mantle flow and a lithosphere (the outermost rigid layer of the Earth) with strongly variable thickness. An east–west corridor of thinned lithosphere across central Greenland, as inferred from new, highly resolved tomographic images, could have formed as Greenland moved westward over the Iceland plume between 90 and 60 million years ago. Our numerical geodynamic model demonstrates how plume material may have accumulated in this corridor and in areas east and west of Greenland. Simultaneous plume-related volcanic activities starting about 62 million years ago on either side of Greenland could occur where and when the lithosphere was thin enough due to continental rifting and seafloor spreading, possibly long after the plume reached the base of the lithosphere. © 2018, The Author(s), under exclusive licence to Springer Nature Limited.
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 4
    Publication Date: 2016-04-01
    Description: Hotspot tracks are thought to originate when mantle plumes impinge moving plates. However, many observed cases close to mid-ocean ridges do not form a single age-progressive line, but vary in width, are separated into several volcanic chains, or are distributed over different plates. Here we study plume-ridge interaction at the example of the Tristan plume, which features all of these complexities. Additionally, the South Atlantic formed close to where plume volcanism began, opening from the south and progressing northward with a notable decrease in magmatism across the Florianopolis Fracture Zone. We study the full evolution of the Tristan plume in a series of three-dimensional regional models created with the convection code ASPECT. We then compute crustal thickness maps and compare them to seismic profiles and the topography of the South Atlantic. We find that the separation of volcanism into the Tristan and Gough chain can be explained by the position of the plume relative to the ridge and the influence of the global flow field. Plume material below the off-ridge track can flow toward the ridge and regions of thinner lithosphere, where decompression melting leads to the development of a second volcanic chain resembling the Tristan and Gough hotspot tracks. Agreement with the observations is best for a small plume buoyancy flux of 500 kg/s or a low excess temperature of 150 K. The model explains the distribution of syn-rift magmatism by hot plume material that flows into the rift and increases melt generation. © 2016. American Geophysical Union. All Rights Reserved.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
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  • 5
    Publication Date: 2017-08-01
    Description: The Réunion mantle plume has shaped a large area of the Earth's surface over the past 65 million years: from the Deccan Traps in India along the hotspot track comprising the island chains of the Laccadives, Maldives, and Chagos Bank on the Indian plate and the Mascarene Plateau on the African plate up to the currently active volcanism at La Réunion Island. This study addresses the question how the Réunion plume, especially in interaction with the Central Indian Ridge, created the complex crustal thickness pattern of the hotspot track. For this purpose, the mantle convection code ASPECT was used to design three-dimensional numerical models, which consider the specific location of the plume underneath moving plates and surrounded by large-scale mantle flow. The results show the crustal thickness pattern produced by the plume, which altogether agrees well with topographic maps. Especially two features are consistently reproduced by the models: the distinctive gap in the hotspot track between the Maldives and Chagos is created by the combination of the ridge geometry and plume-ridge interaction; and the Rodrigues Ridge, a narrow crustal structure which connects the hotspot track and the Central Indian Ridge, appears as the surface expression of a long-distance sublithospheric flow channel. This study therefore provides further insight how small-scale surface features are generated by the complex interplay between mantle and lithospheric processes. © 2017. American Geophysical Union. All Rights Reserved.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
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