Volcanism and Evolution of the African Lithosphere
Cameroon Line alkaline magmatism (central Africa): A reappraisal
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Published:June 01, 2011
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Emmanuel Njonfang, Alexandre Nono, Pierre Kamgang, Vincent Ngako, Félix M. Tchoua, 2011. "Cameroon Line alkaline magmatism (central Africa): A reappraisal", Volcanism and Evolution of the African Lithosphere, Luigi Beccaluva, Gianluca Bianchini, Marjorie Wilson
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Alkaline magmatism along the Cameroon Line has been active for at least 67 m.y. and is currently defined by an almost SW-NE geological lineament (mean value: N30°E). Available petrological, geochemical, and structural data obtained over the last 20 yr lead us to reappraise its mechanism of emplacement. Known as the second most important geological curiosity in Africa, after the East African Rift system, it displays a continental part and an oceanic part, a unique feature in Africa and even in the world. The continental part contains both plutonic and volcanic massifs, and the oceanic part consists only of volcanic massifs. Plutonic rocks as a whole define a complete series of gabbro-diorite-monzonite-syenite-granite type, whereas volcanic rocks display abundant basic (basalt-hawaiite) and felsic (trachyte-phonolite-rhyolite) lavas with very few intermediate ones (mugearite-benmoreite). The formerly entire alkaline nature of these rocks is here ruled out by the discovery of volcanoes with geochemically transitional affinities in some areas of the continental sector. On the other hand, new K-Ar and 40Ar/39Ar dates confirm the absence of any age migration associated with the SW-NE linear trend. This lack of steady time-space migration and the SW-NE trend have also been observed in the magmatic provinces of Nigeria and Benue Trough, which share similar geochemical features with the Cameroon Line, and along the NE-SW major igneous lineaments in South Africa. The mechanism of such episodic emplacement of alkaline magmatism can be better explained in terms of complex interactions between hotspots and lithospheric fractures during African plate motion.
- Africa
- African Plate
- alkali basalts
- alkalic composition
- basalts
- benmoreite
- Benue Valley
- Cameroon Line
- Central Africa
- chemical composition
- diorites
- East African Rift
- emplacement
- faults
- felsic composition
- fractures
- gabbros
- granites
- hawaiite
- hot spots
- igneous rocks
- ignimbrite
- Jos Plateau
- lineaments
- lithosphere
- mafic composition
- magmatism
- monzonites
- mugearite
- Nigeria
- orientation
- peridotites
- plate tectonics
- plutonic rocks
- pyroclastics
- pyroxenite
- scoria
- shear zones
- syenites
- tectonics
- ultramafics
- volcanic rocks
- West Africa
- Tikar Plain
- Bamenda Mountains
- Mount Bambouto