The development of magmatism along the Cameroon Volcanic
Line: evidence from seismicity and seismic anisotropy
The development of magmatism along the Cameroon Volcanic
Line: evidence from seismicity and seismic anisotropy
The Cameroon Volcanic Line (CVL) straddles the continent-ocean boundary in West Africa but exhibits no clear age progression. This renders it difficult to explain by traditional plume/plate motion hypotheses; thus, there remains no consensus on the processes responsible for its development. To understand better the nature of asthenospheric flow beneath the CVL, and the effects of hotspot tectonism on the overlying lithosphere, we analyze mantle seismic anisotropy and seismicity. Cameroon is relatively aseismic compared to hotspots elsewhere, with little evidence for magmatism-related crustal deformation away from Mount Cameroon, which last erupted in 2000. Low crustal Vp/Vs ratios (?1.74) and a lack of evidence for seismically anisotropic aligned melt within the lithosphere both point toward a poorly developed magmatic plumbing system beneath the CVL. Null SKS splitting observations dominate the western continental portion of the CVL; elsewhere, anisotropic fast polarization directions parallel the strike of the Precambrian Central African Shear Zone (CASZ). The nulls may imply that the convecting upper mantle beneath the CVL is isotropic, or characterized by a vertically oriented olivine lattice preferred orientation fabric, perhaps due to a mantle plume or the upward limb of a small-scale convection cell. Precambrian CASZ fossil lithospheric fabrics along the CVL may have been thermomechanically eroded during Gondwana breakup ?130?Ma, with an isotropic lower lithosphere subsequently reforming due to cooling of the slow-moving African plate. Small-scale lithospheric delamination during the 30?Ma recent development of the line may also have contributed to the erosion of the CASZ lithospheric fossil anisotropy, at the same time as generating the low-volume alkaline basaltic volcanism along the CVL
cameroon volcanic line, seismic anisotropy, seismicity, mount cameroon, delamination, hotspot tectonism
4233-4252
De Plaen, R.S.M.
116ea81e-db1c-42e1-a0c4-589949f359cd
Bastow, I.D.
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Chambers, E.L.
a986e780-2bae-4256-b5dd-242f73c6747d
Keir, D.
5616f81f-bf1b-4678-a167-3160b5647c65
Gallacher, R.J.
689f755f-b4a0-4a3b-9959-93c2fae0ac2c
Keane, J.
cefa5c3e-79d1-4109-bc37-d05dad5107ea
May 2014
De Plaen, R.S.M.
116ea81e-db1c-42e1-a0c4-589949f359cd
Bastow, I.D.
fa3f4d3f-8ec5-4dee-8de5-57d987d8d7ed
Chambers, E.L.
a986e780-2bae-4256-b5dd-242f73c6747d
Keir, D.
5616f81f-bf1b-4678-a167-3160b5647c65
Gallacher, R.J.
689f755f-b4a0-4a3b-9959-93c2fae0ac2c
Keane, J.
cefa5c3e-79d1-4109-bc37-d05dad5107ea
De Plaen, R.S.M., Bastow, I.D., Chambers, E.L., Keir, D., Gallacher, R.J. and Keane, J.
(2014)
The development of magmatism along the Cameroon Volcanic
Line: evidence from seismicity and seismic anisotropy.
Journal of Geophysical Research, 119 (5), .
(doi:10.1002/2013JB010583).
Abstract
The Cameroon Volcanic Line (CVL) straddles the continent-ocean boundary in West Africa but exhibits no clear age progression. This renders it difficult to explain by traditional plume/plate motion hypotheses; thus, there remains no consensus on the processes responsible for its development. To understand better the nature of asthenospheric flow beneath the CVL, and the effects of hotspot tectonism on the overlying lithosphere, we analyze mantle seismic anisotropy and seismicity. Cameroon is relatively aseismic compared to hotspots elsewhere, with little evidence for magmatism-related crustal deformation away from Mount Cameroon, which last erupted in 2000. Low crustal Vp/Vs ratios (?1.74) and a lack of evidence for seismically anisotropic aligned melt within the lithosphere both point toward a poorly developed magmatic plumbing system beneath the CVL. Null SKS splitting observations dominate the western continental portion of the CVL; elsewhere, anisotropic fast polarization directions parallel the strike of the Precambrian Central African Shear Zone (CASZ). The nulls may imply that the convecting upper mantle beneath the CVL is isotropic, or characterized by a vertically oriented olivine lattice preferred orientation fabric, perhaps due to a mantle plume or the upward limb of a small-scale convection cell. Precambrian CASZ fossil lithospheric fabrics along the CVL may have been thermomechanically eroded during Gondwana breakup ?130?Ma, with an isotropic lower lithosphere subsequently reforming due to cooling of the slow-moving African plate. Small-scale lithospheric delamination during the 30?Ma recent development of the line may also have contributed to the erosion of the CASZ lithospheric fossil anisotropy, at the same time as generating the low-volume alkaline basaltic volcanism along the CVL
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Published date: May 2014
Keywords:
cameroon volcanic line, seismic anisotropy, seismicity, mount cameroon, delamination, hotspot tectonism
Organisations:
Geology & Geophysics
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Local EPrints ID: 366818
URI: http://eprints.soton.ac.uk/id/eprint/366818
ISSN: 0148-0227
PURE UUID: 7452a5f7-abb1-42a7-80c2-1e41c18f484b
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Date deposited: 14 Jul 2014 09:26
Last modified: 15 Mar 2024 03:38
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Author:
R.S.M. De Plaen
Author:
I.D. Bastow
Author:
E.L. Chambers
Author:
R.J. Gallacher
Author:
J. Keane
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