Isotopic variations with distance and time in the volcanic islands of the Cameroon line: evidence for a mantle plume origin

Lee, Der-Chuen; Halliday, Alex N.; Fitton, J. Godfrey; Poli, Giampero

doi:10.1016/0012-821x(94)90262-3

Cited by 228 publications

(212 citation statements)

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“…Volcanism continues to the present at both onshore and offshore volcanic centers. Although there is no evidence for age progression of volcanics along the onshore portion of the CVL [e.g., Hedberg, 1969;Grant et al, 1972;Grunau et al, 1975;Dunlop and Fitton, 1979;Cornen and Maury, 1980;Dunlop, 1983;Fitton and Dunlop, 1985;Lee et al, 1994;Ngounouno et al, 1997;Marzoli et al, 1999Marzoli et al, , 2000Ngounouno et al, 2001Ngounouno et al, , 2003Njilah et al, 2004;Ngounouno et al, 2005Ngounouno et al, , 2006Aka et al, 2009;Dongmo et al, 2010;Kamgang et al, 2010], some studies have suggested a possible seaward progression for the oceanic sector; however, this possibility remains unclear due to small numbers of samples [Grunau et al, 1975;Meyers and Rosendahl, 1991;Meyers et al, 1998]. Volcanics throughout the CVL consist primarily of alkaline basalts [Hedberg, 1969].…”

Section: The Cameroon Volcanic Linementioning

confidence: 99%

“…Although some studies have suggested this as a possible source for the CVL (Figure 13a) [e.g., Morgan, 1983;Van Houten, 1983;Lee et al, 1994;Burke, 2001], geochemical studies indicate a lack of age progression along the line, making this simple hot spot model an unlikely source for the CVL [e.g., Hedberg, 1969;Grant et al, 1972; …”

Section: Models For the Formation Of The Cameroon Volcanic Linementioning

confidence: 99%

“…10.1002/2014JB011580 Grunau et al, 1975;Dunlop and Fitton, 1979;Cornen and Maury, 1980;Dunlop, 1983;Fitton and Dunlop, 1985;Lee et al, 1994;Ngounouno et al, 1997;Marzoli et al, 1999Marzoli et al, , 2000Ngounouno et al, 2001Ngounouno et al, , 2003Njilah et al, 2004;Ngounouno et al, 2005Ngounouno et al, , 2006Aka et al, 2009;Dongmo et al, 2010;Kamgang et al, 2010]. Other plume-based models have been proposed, however, including multiple plumes impinging on the lithosphere, with volcanics from one hot spot track overprinting the linear age progression created by another [Ngako et al, 2006].…”

Section: Journal Of Geophysical Research: Solid Earthmentioning

confidence: 99%

“…Numerous studies have noted that the CVL does not display a clear age progression along the line as is exhibited by "typical" hot spot chains [e.g., Hedberg, 1969;Grant et al, 1972;Grunau et al, 1975;Dunlop and Fitton, 1979;Cornen and Maury, 1980;Dunlop, 1983;Fitton and Dunlop, 1985;Lee et al, 1994;Ngounouno et al, 1997;Marzoli et al, 1999Marzoli et al, , 2000Ngounouno et al, 2001Ngounouno et al, , 2003Njilah et al, 2004;Ngounouno et al, 2005Ngounouno et al, , 2006Aka et al, 2009;Dongmo et al, 2010;Kamgang et al, 2010;see Njome and de Wit, 2014, Figure 2]. The absence of age progression along the line has led to much debate over the geodynamic origin of this feature, with suggested formation mechanisms ranging from multiple mantle plumes [Ngako et al, 2006], to reactivation of previously existing shear zones [Ebinger and Sleep, 1998], to mantle upwellings driven by convection currents of various sources Anderson, 1995, 1998;Meyers et al, 1998;King and Ritsema, 2000].…”

Section: Introductionmentioning

confidence: 99%

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Lithospheric instability and the source of the Cameroon Volcanic Line: Evidence from Rayleigh wave phase velocity tomography

et al. 2015

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The Cameroon Volcanic Line (CVL) is a 1800 km long volcanic chain, extending SW-NE from the Gulf of Guinea into Central Africa, that lacks the typical age progression exhibited by hot spot-related volcanic tracks. This study investigates the upper mantle seismic structure beneath the CVL and surrounding regions to constrain the origin of volcanic lines that are poorly described by the classic plume model. Rayleigh wave phase velocities are measured at periods from 20 to 182 s following the two-plane wave methodology, using data from the Cameroon Seismic Experiment, which consists of 32 broadband stations deployed between 2005 and 2007. These phase velocities are then inverted to build a model of shear wave velocity structure in the upper mantle beneath the CVL. Results show that phase velocities beneath the CVL are reduced at all periods, with average velocities beneath the CVL deviating more than -2% from the regional average and +4% beneath the Congo Craton. This distinction is observed for all periods but is less pronounced for the longest periods measured. Inversion for shear wave velocity structure indicates a tabular low velocity anomaly directly beneath the CVL at depths of 50 to at least 200 km and a sharp vertical boundary with faster velocities beneath the Congo Craton. These observations demonstrate widespread infiltration or erosion of the continental lithosphere beneath the CVL, most likely caused by mantle upwelling associated with edge-flow convection driven by the Congo Craton or by lithospheric instabilities that develop due to the nearby edge of the African continent.

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Section: The Cameroon Volcanic Linementioning

confidence: 99%

Section: Models For the Formation Of The Cameroon Volcanic Linementioning

confidence: 99%

Section: Journal Of Geophysical Research: Solid Earthmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Lithospheric instability and the source of the Cameroon Volcanic Line: Evidence from Rayleigh wave phase velocity tomography

et al. 2015

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“…Instead, volcanic centers along the entire length of the chain have recently been active [Fitton and Dunlop, 1985]. However, initiation of volcanism in the ocean islands shows a pattern of outward progression, where basaltic rocks in the basal portions of each subaerial stratigraphic sequence become younger with distance from the COB, e.g., Prfncipe, 31 Ma; S•o Tom& 13 Ma; and Annobon, 4.8 Ma [Lee et al, 1994]. Lee et al [1994] interpret this feature as the outward propagation and lengthening of a sublithospheric "hot zone.…”

Section: Introductionmentioning

confidence: 99%

Noble gases in the Cameroon line and the He, Ne, and Ar isotopic compositions of high μ (HIMU) mantle

Barfod¹,

Ballentine²,

Halliday³

et al. 1999

J. Geophys. Res.

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reproduce the data with minimum He/ Ne fractionation at reasonable U/3He ratios.However, diffusive exchange of He and to a lesser extent Ne between aged MORB source and aged plume veins could explain the occurrence of low 3He/4He compositions in all HIMU centers and the apparent low time-integrated 3He/22Ne of the Cameroon line. IntroductionThe majority of terrestrial volcanism is the direct result of plate tectonic processes, with the notable exception of intraplate volcanism. Isotopic heterogeneity among ocean island basalts (OIB) results from the isolation of source reservoirs having distinct time-integrated chemical compositions. These requirements have led to the development of several models for generating these reservoirs including delamination of continental lithosphere, metasomatism of the upper mantle, and melting of a primitive mantle or "predominant" mantle. The most widely accepted model is recycling and storage of oceanic Treatment of noble gas systematics is conspicuously absent from recycling models, despite a considerable database for oceanic islands and MORB. As the oceanic crust is strongly degassed of primitive volatiles upon formation, by hydrothermal alteration near the surface, and by dehydration during subduction, it should possess a highly fractionated set of parent/daughter ratios (U + Th/He, U + Th/Ne, K/Ar). In a simple closed system, recycled oceanic crust should therefore rapidly acquire noble gas isotopic compositions that are highly radiogenic rather than retain primitive (MORB-like, R a = 8 _+ 1) compositions [Hart, 1984a;Farley, 1995]. In no case has any mantle sample produced isotopic compositions equivalent to the estimated mantle production ratios of He (R/R a • 0.01-0.02) and Ne (2•Ne/22Ne -0.4 to 32, see below). , 1995]. In this respect, it is essential to also identify the role of the lithosphere in controlling the observed noble gas isotopic compositions. Straddling both oceanic and continental lithosphere, the volcanic province of the Cameroon line is the ideal setting to evaluate the effects of migration through the lithosphere on the noble gas composition of HIMU magmas. We present results of the first combined HeNe-Ar isotopic study of a HIMU system using the Cameroon line as a study area. Geologic Setting and Sample SelectionThe Cameroon line is an intraplate, alkaline volcanic province extending 1600 km from the African continental interior into the Gulf of Guinea to the island of Annobon Analytical ProceduresBoth xenolith and lava samples were coarsely crushed and sieved to 300 to 850 /•m and then passed through a FrantzIsodynamic magnetic separator. The minerals were ultrasonically cleaned for 30 min in 3.0 N HC1 followed by 30 min in deionized H20 to remove basalt adhering to crystal surfaces. Finally, samples were hand picked in ethanol under a binocular microscope using oblique illumination. In the early stages of this study, noble gases were extracted from mineral phases using an off-line crushing device. The device utilized two 1-cm stainless steel ball be...

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The development of magmatism along the Cameroon Volcanic Line: Evidence from seismicity and seismic anisotropy

et al. 2014

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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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Isotopic variations with distance and time in the volcanic islands of the Cameroon line: evidence for a mantle plume origin

Cited by 228 publications

References 48 publications

Lithospheric instability and the source of the Cameroon Volcanic Line: Evidence from Rayleigh wave phase velocity tomography

Lithospheric instability and the source of the Cameroon Volcanic Line: Evidence from Rayleigh wave phase velocity tomography

Noble gases in the Cameroon line and the He, Ne, and Ar isotopic compositions of high μ (HIMU) mantle

The development of magmatism along the Cameroon Volcanic Line: Evidence from seismicity and seismic anisotropy

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