Segmented lateral dyke growth in a rifting event at Bárðarbunga volcanic system, Iceland

Sigmundsson, Freysteinn and Hooper, Andrew and Hreinsdóttir, Sigrún and Vogfjörd, Kristín S. and Ófeigsson, Benedikt G. and Heimisson, Elías Rafn and Dumont, Stéphanie and Parks, Michelle and Spaans, Karsten and Gudmundsson, Gunnar B. and Drouin, Vincent and Árnadóttir, Thóra and Jónsdóttir, Kristín and Gudmundsson, Magnús T. and Högnadóttir, Thórdís and Fridriksdóttir, Hildur María and Hensch, Martin and Einarsson, Páll and Magnússon, Eyjólfur and Samsonov, Sergey and Brandsdóttir, Bryndís and White, Robert S. and Ágústsdóttir, Thorbjörg and Greenfield, Tim and Green, Robert G. and Hjartardóttir, Ásta Rut and Pedersen, Rikke and Bennett, Richard A. and Geirsson, Halldór and La Femina, Peter C. and Björnsson, Helgi and Pálsson, Finnur and Sturkell, Erik and Bean, Christopher J. and Möllhoff, Martin and Braiden, Aoife K. and Eibl, Eva P. S. (2014) Segmented lateral dyke growth in a rifting event at Bárðarbunga volcanic system, Iceland. Nature. ISSN 0028-0836 DOI 10.1038/nature14111

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Abstract

Crust at many divergent plate boundaries forms primarily by the injection of vertical sheet-like dykes, some tens of kilometres long1. Previous models of rifting events indicate either lateral dyke growth away from a feeding source, with propagation rates decreasing as the dyke lengthens or magma flowing vertically into dykes from an underlying source with the role of topography on the evolution of lateral dykes not clear. Here we show how a recent segmented dyke intrusion in the Bárðarbunga volcanic system grew laterally for more than 45 kilometres at a variable rate, with topography influencing the direction of propagation. Barriers at the ends of each segment were overcome by the build-up of pressure in the dyke end; then a new segment formed and dyke lengthening temporarily peaked. The dyke evolution, which occurred primarily over 14 days, was revealed by propagating seismicity, ground deformation mapped by Global Positioning System (GPS), interferometric analysis of satellite radar images (InSAR), and graben formation. The strike of the dyke segments varies from an initially radial direction away from the Bárðarbunga caldera, towards alignment with that expected from regional stress at the distal end. A model minimizing the combined strain and gravitational potential energy explains the propagation path. Dyke opening and seismicity focused at the most distal segment at any given time, and were simultaneous with magma source deflation and slow collapse at the Bárðarbunga caldera, accompanied by a series of magnitude M > 5 earthquakes. Dyke growth was slowed down by an effusive fissure eruption near the end of the dyke. Lateral dyke growth with segment barrier breaking by pressure build-up in the dyke distal end explains how focused upwelling of magma under central volcanoes is effectively redistributed over long distances to create new upper crust at divergent plate boundaries.

Item Type: Article
Uncontrolled Keywords: 2014AREP; IA68;
Subjects: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Divisions: 02 - Geodynamics, Geophysics and Tectonics
05 - Petrology - Igneous, Metamorphic and Volcanic Studies
10 - Explosive Earth
Journal or Publication Title: Nature
Identification Number: 10.1038/nature14111
Depositing User: Sarah Humbert
Date Deposited: 23 Dec 2014 13:56
Last Modified: 22 Jun 2016 16:51
URI: http://eprints.esc.cam.ac.uk/id/eprint/3189

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