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Multiple mantle upwellings in the transition zone beneath the northern East-African Rift system from relative P-wave travel-time tomography

Multiple mantle upwellings in the transition zone beneath the northern East-African Rift system from relative P-wave travel-time tomography
Multiple mantle upwellings in the transition zone beneath the northern East-African Rift system from relative P-wave travel-time tomography



Mantle plumes and consequent plate extension have been invoked as the likely cause of East African Rift volcanism. However, the nature of mantle upwelling is debated, with proposed configurations ranging from a single broad plume connected to the large low-shear-velocity province beneath Southern Africa, the so-called African Superplume, to multiple lower-mantle sources along the rift. We present a new P-wave travel-time tomography model below the northern East-African, Red Sea, and Gulf of Aden rifts and surrounding areas. Data are from stations that span an area from Madagascar to Saudi Arabia. The aperture of the integrated data set allows us to image structures of ?100 km length-scale down to depths of 700–800 km beneath the study region. Our images provide evidence of two clusters of low-velocity structures consisting of features with diameter of 100–200 km that extend through the transition zone, the first beneath Afar and a second just west of the Main Ethiopian Rift, a region with off-rift volcanism. Considering seismic sensitivity to temperature, we interpret these features as upwellings with excess temperatures of 100?±?50 K. The scale of the upwellings is smaller than expected for lower mantle plume sources. This, together with the change in pattern of the low-velocity anomalies across the base of the transition zone, suggests that ponding or flow of deep-plume material below the transition zone may be spawning these upper mantle upwellings.
tomography, East-Africa, mantle plumes, transition zone, mantle temperature
1525-2027
2949-2968
Civiero, C.
a3b2cccd-ea46-4a3b-a2fb-02eb3758c38a
Hammond, J.O.S.
df081c77-2e69-4753-8846-549826d905bb
Goes, S.
7a2932d0-4492-47b2-9cbb-9d4a8b377360
Fishwick, S.
c57bdb9c-1f33-4484-96dc-fca044dcca86
Ahmed, A.
29a81242-835e-4661-bffd-3831f02ee2b6
Ayele, A.
2a0d90e9-a4be-4484-9301-5c4df46f9407
Doubre, C.
88889cf7-e5ad-4a6c-8361-6934b8c83a18
Goitom, B.
e136980f-049f-47f8-9526-59cc785127db
Keir, D.
5616f81f-bf1b-4678-a167-3160b5647c65
Michael, J.
687981f9-0531-4ed0-970e-7ed80a68526b
Leroy, S.
627c503b-1036-41fc-a24c-3d09954fab0a
Ogubazghi, G.
468612ef-14a9-4332-a841-5733d556340c
Rumpker, G.
77828472-e418-4597-892f-b58bf2a66b13
Stuart, G.W.
42655128-f55d-42a7-afd8-7a2fca1c01a3
Civiero, C.
a3b2cccd-ea46-4a3b-a2fb-02eb3758c38a
Hammond, J.O.S.
df081c77-2e69-4753-8846-549826d905bb
Goes, S.
7a2932d0-4492-47b2-9cbb-9d4a8b377360
Fishwick, S.
c57bdb9c-1f33-4484-96dc-fca044dcca86
Ahmed, A.
29a81242-835e-4661-bffd-3831f02ee2b6
Ayele, A.
2a0d90e9-a4be-4484-9301-5c4df46f9407
Doubre, C.
88889cf7-e5ad-4a6c-8361-6934b8c83a18
Goitom, B.
e136980f-049f-47f8-9526-59cc785127db
Keir, D.
5616f81f-bf1b-4678-a167-3160b5647c65
Michael, J.
687981f9-0531-4ed0-970e-7ed80a68526b
Leroy, S.
627c503b-1036-41fc-a24c-3d09954fab0a
Ogubazghi, G.
468612ef-14a9-4332-a841-5733d556340c
Rumpker, G.
77828472-e418-4597-892f-b58bf2a66b13
Stuart, G.W.
42655128-f55d-42a7-afd8-7a2fca1c01a3

Civiero, C., Hammond, J.O.S., Goes, S., Fishwick, S., Ahmed, A., Ayele, A., Doubre, C., Goitom, B., Keir, D., Michael, J., Leroy, S., Ogubazghi, G., Rumpker, G. and Stuart, G.W. (2015) Multiple mantle upwellings in the transition zone beneath the northern East-African Rift system from relative P-wave travel-time tomography. Geochemistry, Geophysics, Geosystems, 16 (9), 2949-2968. (doi:10.1002/2015GC005948).

Record type: Article

Abstract




Mantle plumes and consequent plate extension have been invoked as the likely cause of East African Rift volcanism. However, the nature of mantle upwelling is debated, with proposed configurations ranging from a single broad plume connected to the large low-shear-velocity province beneath Southern Africa, the so-called African Superplume, to multiple lower-mantle sources along the rift. We present a new P-wave travel-time tomography model below the northern East-African, Red Sea, and Gulf of Aden rifts and surrounding areas. Data are from stations that span an area from Madagascar to Saudi Arabia. The aperture of the integrated data set allows us to image structures of ?100 km length-scale down to depths of 700–800 km beneath the study region. Our images provide evidence of two clusters of low-velocity structures consisting of features with diameter of 100–200 km that extend through the transition zone, the first beneath Afar and a second just west of the Main Ethiopian Rift, a region with off-rift volcanism. Considering seismic sensitivity to temperature, we interpret these features as upwellings with excess temperatures of 100?±?50 K. The scale of the upwellings is smaller than expected for lower mantle plume sources. This, together with the change in pattern of the low-velocity anomalies across the base of the transition zone, suggests that ponding or flow of deep-plume material below the transition zone may be spawning these upper mantle upwellings.

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More information

e-pub ahead of print date: 10 September 2015
Published date: September 2015
Keywords: tomography, East-Africa, mantle plumes, transition zone, mantle temperature
Organisations: Geology & Geophysics

Identifiers

Local EPrints ID: 381529
URI: http://eprints.soton.ac.uk/id/eprint/381529
ISSN: 1525-2027
PURE UUID: e44fef9f-841a-433f-a6eb-9b63f6986f2d
ORCID for D. Keir: ORCID iD orcid.org/0000-0001-8787-8446

Catalogue record

Date deposited: 15 Sep 2015 08:27
Last modified: 15 Mar 2024 03:38

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Contributors

Author: C. Civiero
Author: J.O.S. Hammond
Author: S. Goes
Author: S. Fishwick
Author: A. Ahmed
Author: A. Ayele
Author: C. Doubre
Author: B. Goitom
Author: D. Keir ORCID iD
Author: J. Michael
Author: S. Leroy
Author: G. Ogubazghi
Author: G. Rumpker
Author: G.W. Stuart

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