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NEAR-CONTINENT INTRAPLATE VOLCANISM IN THE ATLANTIC: IMPLICATIONS FOR MANTLE DYNAMICS, COMPOSITION AND MELTING

English title NEAR-CONTINENT INTRAPLATE VOLCANISM IN THE ATLANTIC: IMPLICATIONS FOR MANTLE DYNAMICS, COMPOSITION AND MELTING
Applicant Ballmer Maxim Dionys
Number 165682
Funding scheme Project funding
Research institution Institut für Geophysik ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geophysics
Start/End 01.10.2016 - 30.09.2020
Approved amount 243'054.00
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All Disciplines (2)

Discipline
Geophysics
Geochemistry

Keywords (4)

mantle melting; mantle plumes; edge-driven convection; intraplate volcanism

Lay Summary (German)

Lead
Da Tiefbohrungen bisher lediglich in eine Tiefe von etwa 10 km vorgedrungen sind, sind wir zur Erforschung des Erdmantels auf indirekte Methoden angewiesen. Eine solche Methode beinhaltet die Untersuchung von Intraplattenvulkanismus. Vulkane, die weit entfernt von Plattengrenzen aktiv sind, speien basaltische Laven (“ocean island basalt”, OIB) mit einem Ursprung im Erdmantel. Dabei ist im je nach Vulkan unklar, ob das Ursprungsmaterial aus dem oberen Mantel kommt und durch kleinskalige Konvektion “aufgewirbelt” wurde, oder entlang eines Mantelaufstroms (oder “Mantelplumes”) von der Kern-Mantel-Grenze in 2900 km Tiefe aufgestiegen ist. Während Vulkanismus entlang von Plattengrenzen vor allem über plattentektonische Prozesse Aufschluss gibt, können Analysen von OIBs über die Zusammensetzung und Dynamik des Erdmantels Zeugnis ablegen.
Lay summary

Durch die Modellierung (d.h. Computersimulation) der Dynamik von Mantelplumes und kleinskaliger Konvektion auf der einen Seite, und des Aufschmelzens von Mantelgesteinen auf der anderen Seite, werden wir die Prozesse, die zur Entstehung von Intraplattenvulkanismus führen, besser verstehen. Ein tieferes Verständnis dieser Prozesse ist die Grundvorrausetzung dafür, dass von tatsächlichen Beobachtungen (Chemie der Lavagesteine, Geophysikalische Messungen) auf die unerreichbare Welt unter unseren Füssen (Zusammensetzung und Dynamik des Erdmantels) geschlossen werden kann. Insbesondere sind wir daran interessiert, welchen Anteil kleinskalige Konvektion und Mantelplumes an der Bildung von Schmelzen im Erdmantel, zum Beispiel under den Kanaren und Kapverden, haben. Dieses Projekt wird unser Veständnis sowohl des Aufbaus des Erdmantels, als auch vulkanischer Prozesse vertiefen. Dieser Erkenntnisgewinn kann u.a. zur Vorbeugung von Naturkatastrophen in vulkanischen Gebieten eigesetzt werden.

Direct link to Lay Summary Last update: 31.03.2016

Responsible applicant and co-applicants

Employees

Collaboration

Group / person Country
Types of collaboration
Prof. Gazel (Virginia Tech) United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Prof. Schmerr (Univ. Maryland United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication

Abstract

The study of volcanism far away from plate boundaries can inform about mantle chemistry and dynamics. For example, intraplate lavas have been used as probes for mantle isotopic composition, and hence as a record for mantle evolution. Plume theory, in which a hot columnar upwellings rise through the whole mantle to sustain “hotspot” melting, has successfully explained intraplate volcanic activity. However, not all locations that are considered hotspots have the seismic and geochemical signatures to back up a deep-rooted source. For example, small-scale convection triggered by the presence of variations in lithospheric thickness, or “edge-driven” convection (EDC), has been proposed as an alternative mechanism for intraplate volcanism near continental margins. Here, we propose to test mantle plume vs. EDC as mechanisms for mantle melting and intraplate volcanism using Cape Verde and the Canaries as natural laboratories. These locations were selected due to their location close to a continental margin but away from plate boundaries, making them ideal to test our working hypotheses. Also, Cape Verde and the Canaries are the only two oceanic settings where carbonatites have been found, suggesting the importance of mantle outgassing at intraplate volcanoes, a missing link in the deep global water and carbon cycles. We will apply integrated petrologic-geodynamical modeling to study the origin of intraplate volcanism. Convection code CITCOM will be used to model mantle flow and melting of a source that consists of a fine-scale mixture of various rock types. Model predictions will be directly compared to seismic observations and seafloor topography. In order to allow direct comparison with geochemical data, petrologic modeling software MELTS will be used to calculate mineral-melt equilibria during partial melting and fractional crystallization. Such an integrated approach is key to exploit the complementary nature of geochemical and geophysical datasets, and to resolve the feedback mechanisms between source composition, mantle upwelling and magmatism. Accordingly, the proposed effort will be able to distinguish between geodynamic mechanisms (plume vs. non-plume) as well as to constrain mantle composition. Defining the diagnostic criteria to distinguish between geodynamic mechanisms will not only help to understand intraplate volcanism in the Atlantic, but can be also applied to other hotspots worldwide. Deciphering the message carried by intraplate magmas will indeed expand our understanding of heat and material fluxes through the mantle.We request funding for one PhD student and the involved research costs. The proposed project will support the education of the PhD student, and the early-career development of the Applicant, who will be involved in the supervision of the student. In addition to advancing our understanding of our host planet Earth, results from this project will be used for public-education purposes (museum exhibits, planetarium show).
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