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Magmatism and extension rates at rifted margins

Erik R. Lundin, Anthony G. Dore and Thomas F. Redfield
Magmatism and extension rates at rifted margins
Petroleum Geoscience (May 2018) 24 (4): 379-392

Abstract

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.


ISSN: 1354-0793
Serial Title: Petroleum Geoscience
Serial Volume: 24
Serial Issue: 4
Title: Magmatism and extension rates at rifted margins
Affiliation: Statoil, Research Centre, Trondheim, Norway
Pages: 379-392
Published: 20180515
Text Language: English
Publisher: Geological Society Publishing House for EAGE (European Association of Geoscientists & Engineers), London, United Kingdom
References: 106
Accession Number: 2018-062645
Categories: Solid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sect., sketch maps
N70°00'00" - N72°00'00", W09°00'00" - W07°30'00"
N66°15'00" - N71°45'00", W19°00'00" - W13°00'00"
Secondary Affiliation: Norwegian Geological Survey, NOR, Norway
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201834
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