Banding in the Margins of Basaltic Dykes Indicates Pulsatory Propagation During Emplacement

Allgood, C.; Llewellin, E. W.; Humphreys, M. C. S.; Mathias, S. A.; Brown, R. J.; Vye‐Brown, C.

Abstract

Basaltic fissure eruptions, which are the most common type of eruption on Earth, are fed by dykes which mediate magma transport through the crust. Dyke propagation processes are important because they determine the geometry of the transport pathway and the nature of any geophysical signals associated with magma ascent. Here, we investigate small‐scale (mm–cm wide) banding features at the margins of dykes in the Teno Massif (Tenerife, Spain) and the Columbia River Basalt Province (CRBP) (USA). Similar marginal bands have been reported for dykes in numerous localities around the world. Dyke margins record valuable information about propagation because they are the first material to solidify against the host rock at the propagating dyke tip. We find that the marginal bands are defined by cyclic variations in phenocryst concentration and vesicularity, and we infer that these cyclic variations in texture are a product of cyclic variations in magma flow rates and pressures within the dyke tip. This indicates that dyke emplacement occurs in pulses, with propagation repeatedly hindered by the rapid cooling and solidification of magma in the narrow dyke tip. Using a 1D conduction model, we estimate the time taken for each band to cool and solidify, which provides a timescale of several minutes to tens of minutes for the pulses. The occurrence of similar bands in various volcanic settings suggests that pulsatory propagation is a common, if not ubiquitous, process associated with dyke emplacement.

Citation

Allgood, C., Llewellin, E. W., Humphreys, M. C. S., Mathias, S. A., Brown, R. J., & Vye‐Brown, C. (2024). Banding in the Margins of Basaltic Dykes Indicates Pulsatory Propagation During Emplacement. Journal of Geophysical Research: Solid Earth, 129(4), Article e2023JB028007. https://doi.org/10.1029/2023jb028007

• Journal Article Type: Article
• Acceptance Date: Mar 23, 2024
• Online Publication Date: Apr 4, 2024
• Publication Date: Apr 1, 2024
• Deposit Date: May 13, 2024
• Publicly Available Date: May 13, 2024
• Journal: Journal of Geophysical Research: Solid Earth
• Print ISSN: 2169-9313
• Electronic ISSN: 2169-9356
• Publisher: American Geophysical Union
• Peer Reviewed: Peer Reviewed
• Volume: 129
• Issue: 4
• Article Number: e2023JB028007
• DOI: https://doi.org/10.1029/2023jb028007
• Keywords: dyke textures, dyke cooling model, dyke margins, dyke propagation, dyke emplacement
• Public URL: https://durham-repository.worktribe.com/output/2378634