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Age, geochemical characteristics and petrogenesis of Cenozoic intraplate alkaline volcanic rocks in the Bafang region, West Cameroon ArchiMer
Ngongang, Nicaise Blaise Tchuimegnie; Kamgang, Pierre; Chazot, Gilles; Agranier, Arnaud; Bellon, Herve; Nonnotte, Philippe.
The origin of the volcanism in the Cameroon Volcanic Line and the nature of its mantle sources are still highly controversial. We present major and trace element compositions as well as Sr-Nd-Pb-Hf isotopic results on mafic and intermediate lavas from the Bafang area in the central part of the Cameroon Volcanic Line. The lavas range from basanites and basalts to hawaiites and mugearites with an alkaline affinity and were emplaced between 10 and 6 Ma ago. The evolution from basalts and basanites to more differentiated rocks involved fractionation of olivine, clinopyroxene and Fe-Ti oxides, but the isotopic compositions show that crustal contamination processes affected some magmas during their ascent in the crust. Basalts and basanites originated from a...
Tipo: Text Palavras-chave: Cameroon Volcanic Line; Geochemistry; Magmatism; Mantle source.
Ano: 2015 URL: https://archimer.ifremer.fr/doc/00221/33255/32158.pdf
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Miocene detachment faulting predating EPR propagation: Southern Baja California ArchiMer
Bot, Anna; Geoffroy, Laurent; Authemayou, Christine; Bellon, Herve; Graindorge, David; Pik, Raphael.
At the southern tip of the Baja California peninsula, we characterize the onshore structures and kinematics associated with crustal necking leading up to the Pliocene breakup and early East Pacific Rise seafloor spreading. From a combination of tectonic field investigations, K-Ar and cosmogenic isotope dating and geomorphology, we propose that the Los Cabos block represents the exhumed footwall of a major detachment fault. This north trending detachment fault is marked by a conspicuous low-dipping brittle-ductile shear zone showing a finite displacement with top to the SE ending to the ESE. This major feature is associated with fluid circulations which led to rejuvenation of the deformed Cretaceous magmatic rocks at a maximum of 17.5Ma. The detachment...
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Ano: 2016 URL: https://archimer.ifremer.fr/doc/00639/75085/75553.pdf
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