The University of Southampton
University of Southampton Institutional Repository

Formation and stability of magmatic segments in the Main Ethiopian and Afar rifts

Formation and stability of magmatic segments in the Main Ethiopian and Afar rifts
Formation and stability of magmatic segments in the Main Ethiopian and Afar rifts
As rifting progresses to seafloor spreading, extension within the continental crust commonly is accommodated by a combination of fault slip and dike intrusion. Consistent patterns in the spatial arrangement of long-lived magma intrusion zones in the Ethiopian and Afar rift sectors, East Africa, suggest that the magma intrusions help to localize strain during repeated rifting episodes. Within the broad Main Ethiopian Rift, extensional deformation has localized since 3 m.y. in narrow magmatic segments, that are oriented oblique to the orientation of the Miocene border faults, but (sub-) orthogonal to the extension direction. Numerical models combined with geophysical and geological observations from East Africa are used to examine the viability of self-sustaining magmatic segmentation. Initiation of the magmatic segments is shown to result from magma injections, which focus strain in narrow elongated zones. During magmatic phases of segment evolution the segments are weak, and extensional stresses localize at the rift tips, promoting along-axis lengthening. During amagmatic phases of extension, the numerical models predict strain localization within the magmatic segments and, to a lesser extent, broadly distributed extension within the rift zone. This promotes segment stability; the segments remain the preferred location for magma intrusion during new magmatic phases. These results are applied to the formation and maintenance of MER segmentation. The Fentale–Dofen segment is currently in a non-magmatic phase of extension; the Dabbahu segment in the Red Sea Rift is currently experiencing a rifting episode and therefore is in a transient magmatic cycle. The observed patterns of instantaneous localized deformation, seismicity, and dike intrusions sometimes propagating beyond the tip of the magmatic segments occur as predicted by the models.
east african rift, continental rifting, magmatic intrusion, stress, lithospheric extension, rupturing continental lithosphere
0012-821X
225-235
Beutel, Erin
b92255df-2af9-439d-aa8b-a16e06e25400
van Wijk, Jolante
d1fe713a-8a06-4742-9df1-8ba3900f0013
Ebinger, Cindy
cf261414-c6ef-41b1-90f0-ac7371d44e72
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Agostini, Andrea
de724094-9546-4ed5-84b3-60c46f514d0e
Beutel, Erin
b92255df-2af9-439d-aa8b-a16e06e25400
van Wijk, Jolante
d1fe713a-8a06-4742-9df1-8ba3900f0013
Ebinger, Cindy
cf261414-c6ef-41b1-90f0-ac7371d44e72
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Agostini, Andrea
de724094-9546-4ed5-84b3-60c46f514d0e

Beutel, Erin, van Wijk, Jolante, Ebinger, Cindy, Keir, Derek and Agostini, Andrea (2010) Formation and stability of magmatic segments in the Main Ethiopian and Afar rifts. Earth and Planetary Science Letters, 293 (3-4), 225-235. (doi:10.1016/j.epsl.2010.02.006).

Record type: Article

Abstract

As rifting progresses to seafloor spreading, extension within the continental crust commonly is accommodated by a combination of fault slip and dike intrusion. Consistent patterns in the spatial arrangement of long-lived magma intrusion zones in the Ethiopian and Afar rift sectors, East Africa, suggest that the magma intrusions help to localize strain during repeated rifting episodes. Within the broad Main Ethiopian Rift, extensional deformation has localized since 3 m.y. in narrow magmatic segments, that are oriented oblique to the orientation of the Miocene border faults, but (sub-) orthogonal to the extension direction. Numerical models combined with geophysical and geological observations from East Africa are used to examine the viability of self-sustaining magmatic segmentation. Initiation of the magmatic segments is shown to result from magma injections, which focus strain in narrow elongated zones. During magmatic phases of segment evolution the segments are weak, and extensional stresses localize at the rift tips, promoting along-axis lengthening. During amagmatic phases of extension, the numerical models predict strain localization within the magmatic segments and, to a lesser extent, broadly distributed extension within the rift zone. This promotes segment stability; the segments remain the preferred location for magma intrusion during new magmatic phases. These results are applied to the formation and maintenance of MER segmentation. The Fentale–Dofen segment is currently in a non-magmatic phase of extension; the Dabbahu segment in the Red Sea Rift is currently experiencing a rifting episode and therefore is in a transient magmatic cycle. The observed patterns of instantaneous localized deformation, seismicity, and dike intrusions sometimes propagating beyond the tip of the magmatic segments occur as predicted by the models.

Full text not available from this repository.

More information

Published date: 2010
Keywords: east african rift, continental rifting, magmatic intrusion, stress, lithospheric extension, rupturing continental lithosphere

Identifiers

Local EPrints ID: 175163
URI: https://eprints.soton.ac.uk/id/eprint/175163
ISSN: 0012-821X
PURE UUID: 8d028be4-f6f1-4a1a-90fa-82d1ee18209f
ORCID for Derek Keir: ORCID iD orcid.org/0000-0001-8787-8446

Catalogue record

Date deposited: 22 Feb 2011 16:25
Last modified: 06 Jun 2018 12:31

Export record

Altmetrics

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×