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Use of a high-precision gravity survey to understand the formation of oceanic crust and the role of melt at the southern Red Sea rift in Afar, Ethiopia

By
E. Lewi
E. Lewi
1
Institute of Geophysics, Space Science and Astronomy, Addis Ababa University, King George VI Street, PO Box 1176, Addis Ababa, Ethiopia
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D. Keir
D. Keir
2
National Oceanography Centre Southampton, University of Southampton, European Way, Southampton SO14 3ZH, UK
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Y. Birhanu
Y. Birhanu
3
Department of Geosciences, University of Montana, 32 Campus Drive #1296, Missoula, MT 59812-1296, USA
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J. Blundy
J. Blundy
4
School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK
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G. Stuart
G. Stuart
5
School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
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T. Wright
T. Wright
5
School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
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E. Calais
E. Calais
6
Department of Geosciences, Ecole Normale Supérieure, UMR CNRS 8538, 24 rue Lhomond, 75231 Paris cedex 05, France
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Published:
January 01, 2016

Abstract

The Red Sea arm of the triple junction in northeastern Ethiopia provides an opportunity to investigate rift-forming processes at divergent boundaries. In an attempt to study the subsurface, especially the distribution and role of melt in the rifting process, we carried out a high-precision gravity survey with a mean-square error of 0.011 mgal, assisted by differential global positioning system measurements. The profile is 162 km long and strikes ENE–WSW across the southern part of the Red Sea rift at a latitude of approximately 11.75° N. Modelling of the Bouguer anomaly, constrained by a priori information, showed detailed in-rift variations in the crustal structure and the distribution of melt beneath the rift axis. Our interpretation suggested that the process of continental break-up is governed by crustal stretching and rifting accompanied by the emplacement of melt into the lower crust above a lower density upper mantle. In addition, we interpreted the thickness of the crust beneath this part of the rift axis to be 25 km. The subsurface distribution of density beneath the profile shows that the south-central part of the Red Sea rift has modified thinned crust, intruded by high-density material, which resembles the crust formed during seafloor spreading.

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Contents

Geological Society, London, Special Publications

Magmatic Rifting and Active Volcanism

T. J. Wright
T. J. Wright
University of Leeds, UK
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A. Ayele
A. Ayele
Addis Ababa University, Ethiopia
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D. J. Ferguson
D. J. Ferguson
University of Leeds, UK
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T. Kidane
T. Kidane
Addis Ababa University, Ethiopia
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C. Vye-Brown
C. Vye-Brown
British Geological Survey, UK
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Geological Society of London
Volume
420
ISBN electronic:
9781862391345
Publication date:
January 01, 2016

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