Potassium-argon ages and strontium isotope ratio measurements from volcanic rocks in northeastern Nigeria

Grant, Norman K.; Rex, D. C.; Freeth, S. J.

doi:10.1007/bf00371310

Cited by 77 publications

(37 citation statements)

References 21 publications

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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%

“…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: 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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“…rhyolites) have demonstrated the diversity of their source regions (mantle, continental and/or oceanic crust). So, on the one hand, rhyolites are believed to be derived by fractional crystallization from basaltic liquids generated by partial melting of the upper mantle, either in oceanic domains (Iceland: Furman et al, 1992: Galapagos: Geist et al, 1995 or in continental ones (Upper Benue: Grant et al, 1972;Adamawa: Nono et al, 1994). On the other hand, rhyolites are believed to be derived from the anatexis either of oceanic crust (Iceland: Oskarsson et al, 1982;Galapagos: McBirney, 1993) or of continental crust (Deccan Trap: Lightfoot et al, 1987;Basin and Range Province: Draper, 1991).…”

Section: Introductionmentioning

confidence: 99%

Petrology of the bimodal Cenozoic volcanism of the Kapsiki plateau (northernmost Cameroon, Central Africa)

Ngounouno

Dennielou

Demaiffe

2000

Journal of Volcanology and Geothermal Research

101

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“…This Yshaped system ( Figure 1) has a long history of magmatic activity, both plutonic and volcanic, spanning over ~70 Ma and basaltic flows that mark the onset of volcanism along the line are recognisable in the Adamawa Plateau (Déruelle et al, 2007) even though activity at this end remained high until ~5 Ma (Grant et al, 1972). Volcanic rocks of the CVL range in age from ~32 Ma to Recent considering that Mt Cameroon at the southern end of the line is still active.…”

Section: Geological Settingmentioning

confidence: 99%

Polymagmatic processes at monogenetic volcanoes: insights from Baossi monogenetic lava flows, Adamawa Plateau, Cameroon Volcanic Line

Tiabou¹,

Temdjim²,

Ngwa³

et al. 2015

JGG

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This paper presents principally the textural and geothermometric evidence of polymagmatic activity at a monogenetic volcano along the Cameroon Volcanic Line (CVL) in a bid to contribute to the global understanding of how such volume-limited basaltic magmatic systems operate. Preliminary geochemical data presented show that the lavas are alkali basalt and basanite (SiO 2 : 40.42 -47.59 wt%, MgO: 7.61 -9.13 wt%) and are petrographically indistinguishable. They outcrop as low mounds of columnar basalts associated with sparse pyroclastic materials. The lavas are fine, porphyritic with phenocrysts of olivine and clinopyroxene set in a plagioclase microlite-dominated hypocrystalline groundmass. Olivine has two distinct populations: grains that are anhedral to glomerocrystic with spinel and plagioclase inclusions and usually have resorbed margins (olivine 1); and grains that are euhedral, sometimes skeletal, with a thin and well preserved rim (olivine 2). Similarly two clinopyroxene crystal populations are recognizable: clinopyroxene grains that are resorbed, dismembered, with sieve-textured cores and irregular core-rim margins (clinopyroxene 1); and euhedral clinopyroxene grains partially enclosing olivine phenocrysts with sector and hour glass shape zoning (clinopyroxene 2). These textural features suggest that the eruption was caused by an influx of a fresh batch of magma (that crystallized olivine 2 and clinopyroxene 2) into a fractionated crystal mush (olivine 1 and clinopyroxene 1) in the chamber. The crystal mush was re-heated by the intruding basaltic magma resulting in a broad pre-eruption liquidus temperature of 1040 -1156 o C calculated using mineral chemistry of equilibrium olivine-clinopyroxene pairs.

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Potassium-argon ages and strontium isotope ratio measurements from volcanic rocks in northeastern Nigeria

Cited by 77 publications

References 21 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

Petrology of the bimodal Cenozoic volcanism of the Kapsiki plateau (northernmost Cameroon, Central Africa)

Polymagmatic processes at monogenetic volcanoes: insights from Baossi monogenetic lava flows, Adamawa Plateau, Cameroon Volcanic Line

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