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Article Dans Une Revue Open Journal of Geology Année : 2022

Xenoliths Evidence of Alkaline Magmatic Infiltrations Beneath Lake Nyos (Cameroon Volcanic Line, West Africa)

Les xénolithes comme preuve de l'infiltrations magmatiques alcalines sous le lac Nyos (ligne volcanique du Cameroun, Afrique de l'Ouest)

Résumé

Xenoliths enclosed in Lavas of the Nyos volcano (Cameroon Volcanic Line, continental sector) range from fertile lherzolites to harzburgites. One spi- nel-free wehrlite has been also sampled. The occurrence of phlogopites and pargasites in some harzburgites together with specific textural rock-type (lher- zolites transitional porphyroclastic to equigranular), including major and trace element compositions both in peridotites bulk rocks and minerals point out interactions between the mantle and basaltic magmas responsible for the for- mation of wehrlites beneath the Nyos volcano. Hydrous minerals (phlogo- pites and pargasites) and metasomatic events are their main petrogeochemi- cal signatures different from group 1 samples which are characterized by spoon-shaped REE patterns. Later on, hydrous phases, Ti-rich Cpx, CaO rich Ol, Ti, and V rich Ol wehrlite precipitated from melt enrichments due to the percolation of the mantle by basaltic magmas of alkaline affinity. The meta- somatic liquid which percolates the Nyos mantle column was a dense alkaline silicate rich in volatile, displaying low HFSE abundances in the metasomatic hydrous melts compared to the LILE. It is suggested that Nyos mantle perido- tites have experienced: 1) variable metasomatic events related to the perco- lating of the depleted mantle by a alkaline silicate liquid, 2) the spinel-free wehrlite is a group 2 sample corresponding to a cumulate of a similar melt, 3) amphibole may be a potassium-bearing mineral instead of or in addition to phlogopite at shallower levels of Nyos upper mantle and 4) transitional tex- tural rock facies express also the fingerprint of rising mantle plume which were percolated by alkaline magma during their transit to the surface.
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Dates et versions

hal-03826707 , version 1 (24-10-2022)

Identifiants

Citer

Merlin Isidore Teitchou, Joseph Legrand Tchop, Michel Grégoire, Pauline Wokwenmendam Nguet, Eddy Ferdinand Mbossi, et al.. Xenoliths Evidence of Alkaline Magmatic Infiltrations Beneath Lake Nyos (Cameroon Volcanic Line, West Africa). Open Journal of Geology, 2022, 12, pp.433 - 469. ⟨10.4236/ojg.2022.126021⟩. ⟨hal-03826707⟩
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