Field evidence for the lateral emplacement of igneous dykes: Implications for 3D mechanical models and the plumbing beneath fissure eruptions.

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Authors

David Healy, Roberto Emanuele Rizzo , Marcus Duffy, Natalie Farrell, Malcolm Hole, David Muirhead

Abstract

Seismological and geodetic data from modern volcanic systems strongly suggest that magma is transported significant distance (tens of kilometres) in the subsurface away from central volcanic vents. Geological evidence for lateral emplacement preserved within exposed dykes includes aligned fabrics of vesicles and phenocrysts, striations on wall rocks and the anisotropy of magnetic susceptibility. In this paper, we present geometrical evidence for the lateral emplacement of segmented dykes restricted to a narrow depth range in the crust. Near-total exposure of three dykes on wave cut platforms around Birsay (Orkney, UK) are used to map out floor and roof contacts of neighbouring dyke segments in relay zones. The field evidence suggests emplacement from the WSW towards the ENE. Geometrical evidence for the lateral emplacement of segmented dykes is likely more robust than inferences drawn from flow-related fabrics, due to the prevalence of ubiquitous ‘drainback’ events (i.e. magmatic flow reversals) observed in modern systems.

DOI

https://doi.org/10.31223/osf.io/gwhfn

Subjects

Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure, Volcanology

Keywords

volcanic, Igneous, Magma, bridge, relay, segment

Dates

Published: 2018-06-06 10:28

Last Updated: 2018-06-08 08:01

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License

CC BY Attribution 4.0 International

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