Magmatism and extension rates at rifted margins

TitleMagmatism and extension rates at rifted margins
Publication TypeJournal Article
Year of Publication2017
AuthorsLundin, ER, Doré, AG, Redfield, TF
JournalPetroleum Geoscience
Date Publishedsep

Rifted margins are commonly classified as either magma-rich or magma-poor. Magma-poor margins are often implicitly related to ultraslow–slow extension. Conversely, therefore, magma-rich margins should represent more rapid extension. Although supported by numerical modelling, these relationships are based on limited data and depend on a perhaps spurious comparison between continental margins and spreading ridges. Three case studies from the Atlantic margins are therefore presented here as a local, by no means complete, examination of this concept.Extension rates for magma-poor margins are mainly derived from offshore Iberia, while the best documented rates on magma-rich margins are probably those in the NE Atlantic. Particularly for the NE Atlantic, there is a dependence on the initial oceanic spreading rate as pre-break-up rates are very difficult to quantify. Our two southerly examples, the Central Atlantic and southern South Atlantic, are both magma-rich in parts and have been described as opening during ultraslow–slow plate separation. Both would therefore seem to contradict the positive ‘rate-magmatism’ correlation. However, on closer examination, a wide range of initial extension rates are actually possible. This is largely due to poor constraints on break-up ages. The assumption that break-up is synchronous with flood basalt extrusion is flawed, and may have caused initial extension rates to have been significantly underestimated. Additionally, averaging between widely spaced oceanic magnetic anomalies allows for a wide range of extension rates. New, well-constrained ages and event chronologies from critical areas of conjugate margins are needed to determine whether this relationship has global validity.


Scholarly Lite is a free theme, contributed to the Drupal Community by More than Themes.