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Imaging lithospheric discontinuities beneath the northern East African Rift using S‐to‐P receiver functions

Imaging lithospheric discontinuities beneath the northern East African Rift using S‐to‐P receiver functions
Imaging lithospheric discontinuities beneath the northern East African Rift using S‐to‐P receiver functions
Imaging the lithosphere is key to understand mechanisms of extension as rifting progresses. Continental rifting results in a combination of mechanical stretching and thinning of the lithosphere, decompression upwelling, heating, sometimes partial melting of the asthenosphere and potentially partial melting of the mantle lithosphere. The northern East African Rift System is an ideal locale to study these processes as it exposes the transition from tectonically active continental rifting to incipient seafloor spreading. Here we use S‐to‐P receiver functions to image the lithospheric structure beneath the northernmost East African Rift System where it forms a triple junction between the Main Ethiopian rift, the Red Sea rift and the Gulf of Aden rift. We image the Moho at 31±6 km beneath the Ethiopian plateau. The crust is 28±3 km thick beneath the Main Ethiopian rift and thins to 23±2 km in northern Afar. We identify a negative phase, a velocity decrease with depth, at 67±3 km depth beneath the Ethiopian plateau, likely associated with the lithosphere‐asthenosphere boundary (LAB), and a lack of a LAB phase beneath the rift. Using observations and waveform modelling, we show that the LAB phase beneath the plateau is likely defined by a small amount of partial melt. The lack of a LAB phase beneath the rift suggests melt percolation through the base of the lithosphere beneath the northernmost EARS.
1525-2027
4048-4062
Lavayssiere, Aude
4754825b-d4c7-45ec-b715-b46a7c92f042
Rychert, Catherine
70cf1e3a-58ea-455a-918a-1d570c5e53c5
Harmon, Nicholas
10d11a16-b8b0-4132-9354-652e72d8e830
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Hammond, James O. S.
d5d7a0da-98a7-4c45-8eed-3155120b450f
Kendall, J-Michael
0a1d10dd-0a0a-4b02-aefd-cde8741307ce
Doubre, Cecile
9f348925-f5b6-445c-8663-7f58f58b97f3
Leroy, Sylvie
627c503b-1036-41fc-a24c-3d09954fab0a
Lavayssiere, Aude
4754825b-d4c7-45ec-b715-b46a7c92f042
Rychert, Catherine
70cf1e3a-58ea-455a-918a-1d570c5e53c5
Harmon, Nicholas
10d11a16-b8b0-4132-9354-652e72d8e830
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Hammond, James O. S.
d5d7a0da-98a7-4c45-8eed-3155120b450f
Kendall, J-Michael
0a1d10dd-0a0a-4b02-aefd-cde8741307ce
Doubre, Cecile
9f348925-f5b6-445c-8663-7f58f58b97f3
Leroy, Sylvie
627c503b-1036-41fc-a24c-3d09954fab0a

Lavayssiere, Aude, Rychert, Catherine, Harmon, Nicholas, Keir, Derek, Hammond, James O. S., Kendall, J-Michael, Doubre, Cecile and Leroy, Sylvie (2018) Imaging lithospheric discontinuities beneath the northern East African Rift using S‐to‐P receiver functions. Geochemistry, Geophysics, Geosystems, 19 (10), 4048-4062. (doi:10.1029/2018GC007463).

Record type: Article

Abstract

Imaging the lithosphere is key to understand mechanisms of extension as rifting progresses. Continental rifting results in a combination of mechanical stretching and thinning of the lithosphere, decompression upwelling, heating, sometimes partial melting of the asthenosphere and potentially partial melting of the mantle lithosphere. The northern East African Rift System is an ideal locale to study these processes as it exposes the transition from tectonically active continental rifting to incipient seafloor spreading. Here we use S‐to‐P receiver functions to image the lithospheric structure beneath the northernmost East African Rift System where it forms a triple junction between the Main Ethiopian rift, the Red Sea rift and the Gulf of Aden rift. We image the Moho at 31±6 km beneath the Ethiopian plateau. The crust is 28±3 km thick beneath the Main Ethiopian rift and thins to 23±2 km in northern Afar. We identify a negative phase, a velocity decrease with depth, at 67±3 km depth beneath the Ethiopian plateau, likely associated with the lithosphere‐asthenosphere boundary (LAB), and a lack of a LAB phase beneath the rift. Using observations and waveform modelling, we show that the LAB phase beneath the plateau is likely defined by a small amount of partial melt. The lack of a LAB phase beneath the rift suggests melt percolation through the base of the lithosphere beneath the northernmost EARS.

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Lavayssi-re_et_al-2018-Geochemistry%2C_Geophysics%2C_Geosystems - Accepted Manuscript
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Accepted/In Press date: 26 August 2018
e-pub ahead of print date: 3 September 2018
Published date: October 2018

Identifiers

Local EPrints ID: 424361
URI: http://eprints.soton.ac.uk/id/eprint/424361
ISSN: 1525-2027
PURE UUID: 3cb9786f-a233-4785-9aa6-807efda104ba
ORCID for Nicholas Harmon: ORCID iD orcid.org/0000-0002-0731-768X
ORCID for Derek Keir: ORCID iD orcid.org/0000-0001-8787-8446

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Date deposited: 05 Oct 2018 11:36
Last modified: 28 Apr 2022 04:46

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Contributors

Author: Aude Lavayssiere
Author: Nicholas Harmon ORCID iD
Author: Derek Keir ORCID iD
Author: James O. S. Hammond
Author: J-Michael Kendall
Author: Cecile Doubre
Author: Sylvie Leroy

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