The Cameroon Hot Line (CHL): A unique example of active alkaline intraplate structure in both oceanic and continental lithospheres

The Cameroon Hot Line (CHL) is an active N30°E tectono-magmatic alignment, extending from Pagalu Island to Lake Chad. Its oceanic sector is comprised of six major volcanoes, and the continental sector of seven major volcanoes, numerous monogenic cones and more than sixty plutonic anorogenic ring complexes. The lavas and plutonic rocks have the typical mineralogy of the alkaline series. Nephelinites and alkaline lamprophyres are also present. The basalts from the oceanic and continental sectors have similar trace elements and Sr and Nd isotope compositions, attesting that the source is sublithospheric and that the continental crust plays no significant role in the magma genesis. Uncommon intermediate lavas originate through mixing between basaltic and felsic magmas. The evolution from basaltic to phonolitic magmas is explained through crystal fractionation. Compositions of most continental trachytes and of rhyolites require a crustal component. Metasomatism of carbonatitic affinity affected the lithospheric mantle during the magma ascent. DM and FOZO mantle components were involved in the genesis of the CHL parental magmas. © 2007 Académie des sciences.SCOPUS: sh.jinfo:eu-repo/semantics/publishe

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

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Genesis of adakite-like lavas of Licancabur volcano (Chile-Bolivia, Central Andes)

The Licancabur volcano is located on the Bolivia-Chile Altiplano (Central Andes). The lavas are andesites and dacites. Numerous mineralogic features attest that magma mixing occurred. Andesites have concave (spoon-shaped) REE patterns whereas dacites have steep slopes. A spectacular crossover of patterns occurs with increasing SiO2. Most geochemical discrimination criteria of adakites are satisfied by Licancabur dacites, except their high Sr-isotope compositions (> 0.7075). For the genesis of the Licancabur adakite-like lavas, a four-step model is proposed: (1) partial melting (5 to 10 wt %) of a subducted altered oceanic crust; (2) hybridation (< 10 wt %) of the magmas with melts derived from the overlying lithospheric mantle; (3) contamination (≈ 1 wt %) of these hybrid magmas by TTG-type granodiorites of the Archean lower continental crust (with present-day Sr-isotope ratios ≈ 0.820); (4) evolution and differentiation by crystal fractionation (< 6 wt %) and magma mixing at upper crustal levels. © 2008 Académie des sciences.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

The camptonites from Mount Cameroon, Cameroon, Africa

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Tchabal Nganha volcano in Adamawa (Cameroon): petrology of a continental alkaline lava series

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Petrology and geochemistry of monchiquites from Tchircotché (Garoua rift, north Cameroon, Central Africa)

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Les camptonites du mont Cameroun, Cameroun, Afrique

Camptonites have been discovered at Mount Cameroon. They contain phenocrysts of olivine + clinopyroxene + plagioclase ± kaersutite ± bi and ocelli of nepheline or analcite and carbonates. 87Sr/86Sri values are similar to those of the basalts of Mount Cameroon (≈ 0.7033). The camptonites are interpreted as resulting from fractional crystallization of a basaltic magma generated by a low degree of melting of an infra-lithospheric metasomatized mantle tapped by huge lithospheric cracks. To cite this article: I. Ngounouno et al. C. R. Geoscience 338 (2006). © 2006 Académie des sciences.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Données nouvelles sur le volcanisme cénozoïque du fossé de Garoua (Nord du Cameroun)

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Les monchiquites de Tchircotché, vallée de la haute Bénoué (Nord du Cameroun)

Dykes of monchiquites of Cainozoic age (37.5 ± 2.3 Ma) are intrusive in Cretaceous sandstones in the Tchircotché area, Upper Benue valley (northern Cameroon). The differentiation of the monchiquites is explained by crystal fractionation ofolivine, clinopyroxene, magnetite, ilmenite and apatite. A studied rock has low Sr-isotope ratio (0.703 69 ± 10), which issimilar to those of the alkali basalts of the Cameroon Line. Therefore the continental crust appears to have no significant role inthe genesis of the monchiquites. 2003 Académie des sciences. Publié par Éditions scientifiques et médicales Elsevier SAS. Tous droits réservés.SCOPUS: ar.jinfo:eu-repo/semantics/publishe