Évolution volcanologique du mont Manengouba (Ligne du Cameroun) ; nouvelles données pétrographiques, géochimiques et géochronologiques<br /> Volcanological evolution of the mount Manengouba (Cameroon line), new petrographical, geochemical, and geochronological data

Le mont Manengouba est un complexe volcanique polygénique de la Ligne du Cameroun édifié au Quaternaire, entre 1,55 et 0 Ma, en trois phases principales. La première phase, de 1,55 à 0,7 Ma, correspond à la construction du volcan Elengoum. La deuxième, entre 0,7 et 0,56 Ma, est marquée par l'effondrement de la partie sommitale de l'Elengoum. La troisième, de 0,56 à 0 Ma, voit l'édification du volcan Eboga, puis la formation de la caldeira, et comporte une activité fissurale adventive à partir de 0,48 Ma. Les produits émis définissent une série alcaline sodique, allant des basaltes à néphéline à des trachytes. Toutes ces laves ont évolué par cristallisation fractionnée dans une chambre magmatique périodiquement réalimentée. The mount Manengouba is a polygenic volcanic complex of the Cameroon line, which was built in the Quaternary, between 1.55 and 0 Ma, during three stages. The first stage, from 1.55 to 0.7 Ma, corresponds to the building of the Elengoum volcano. The second, between 0.7 and 0.56 Ma, points to the collapse of the Elengoum summit. The third, from 0.56 to 0 Ma, fits with the erection of the Eboga volcano and its caldera sinking, and, from 0.48 Ma, with the adventive fissural activity. The products define an alkaline sodic series, from nepheline-bearing basalts to trachytes. All the lavas evolved by fractional crystallization in a periodically replenished magmatic chamber

First delivery of a COVID-19 positive patient in Cameroon

Since its appearance in China in December 2019, COVID-19 which is caused by the SARS-CoV-2 virus has become a real global health problem. Pregnant women are not immune to this novel infection, which makes it difficult for proper management of pregnancy and childbirth. Authors present here the first case of childbirth in Cameroon of a 19-year-old adolescent tested positive for COVID-19

MODES DE FINANCEMENT ET INNOVATION TECHNOLOGIQUE DANS LES ENTREPRISES FAMILIALES AU CAMEROUN

L’object de cette étude est d’analyser l’effet des modes de financement sur l’innovation technologique dans les entreprises familiales au Cameroun. De ce fait, nous avons eu recours à une démarche hypothético-déductive et une approche quantitative. Après une justification éclairée par les principales théories, la recherche met en relief une étude empirique qui permet d’explorer l’effet qu’a les modes de financement sur les innovations dans les entreprises familiales. Les données sont collectées auprès de 100 entreprises familiales au Cameroun. Ces données recueillies sont soumis grâce au logiciel Stata 17 à différents tests statistiques. Par le biais de la régression logistique, nos résultats indiquent que les facteurs financement par dette, financement par action, financement interne et financement public ont une influence significative sur l’innovation technologique dans les entreprises familiales au Cameroun. Nos résultats indiquent également qu’une grande majorité des entreprises sondées (60%) ont des projets technologiquement innovants retardés, abandonnés ou non démarrés du fait de l’absence ou mauvaise connaissance des circuits de financements de l'innovation, du coût de l'innovation trop élevé, de la lenteur de la mise en place des financements, de la complexité de montage des dossiers ou de la politique délibérée de l'entreprise et du manque de personnel qualifié

Adhésion des entreprises familiales du Cameroun aux nouveaux modes de paiement

L’Object de cette étude est de comprendre et d’expliquer le niveau de résistance des entreprises familiales aux nouveaux modes de paiement. Après une justification éclairée par les principales théories, la recherche met en relief une étude empirique qui permet d’explorer le niveau d’adhésion des entreprises familiales aux nouveaux modes de paiement et de dégager les facteurs pouvant influencer ce niveau d’acceptation. Les données sont collectées auprès de 52 entreprises familiales au Cameroun. Par le biais de la régression logistique ordinale nos résultats indiquent que les facteurs coûts d’utilisation, niveau de sécurité et taille de l’entreprise ont une influence significative sur le niveau d’acceptation des nouveaux modes de paiement dans les entreprises familiales

Tchabal Gangdaba Massif in the Cameroon volcanic line : a bimodal association

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Petrology of high-pressure granulite facies metapelites and metabasites from Tcholliré and Banyo regions: Geodynamic implication for the Central African Fold Belt (CAFB) of north-central Cameroon

International audienceThe Tcholliré and Banyo high-pressure granulites occur mainly as highly strained small lenses, bands or elongated bodies interbedded with gneisses and migmatites in the Central African Fold Belt (CAFB) in north-central Cameroon. They were previously attributed to Palaeoproterozoic but are now shown to be Pan-African. These granulites are made up of two occurrences of metapelites with garnet-kyanite-sillimanite-cordierite-biotite-quartz-plagioclase and metabasites containing garnet-clinopyroxene-orthopyroxene-hornblende-quartz-plagioclase.Eight samples were analysed in detail by electron microprobe for mineral chemistry.Parageneses in both metapelites and metabasites highlight three main stages witnessed by prograde, peak and retrograde mineral assemblages. The prograde stage is preserved as well-defined inclusion trails of kyanite, biotite, plagioclase, quartz, and rutile within porphyroblasts of garnet in metapelites; or with more or less clinopyroxene, hornblende, plagioclase, quartz, ilmenite, rutile and apatite, within porphyroblasts of garnet in metabasites. The peak stage, displaying heterogranular granoblastic texture is characterised by porphyroblastic garnet-kyanite-K-feldspar-biotite in metapelites and garnet-clinopyroxene-plagioclase-quartz in metabasites. This was followed by decompression and cooling during the retrograde stage marked by aggregate of sillimanite prisms presumably after kyanite and cordierite corona around garnet in metapelites and by symplectites or vermicular structures of orthopyroxene-plagioclase and orthopyroxene corona around garnet in metabasites. Geothermobarometric study shows that granulite facies metapelites and metabasites from both Tcholliré and Banyo regions recrystallised under peak pressure-temperature conditions of 13–14 kbar and 800–900 °C. They experienced similar clockwise P-T path with nearly isothermal decompression.Our results provide evidence for a substantial crustal thickening during the Pan-African continent–continent collision but show that there is no significant isothermal decompression as commonly observed in recent collisional orogens. The reconstructed P-T paths are in some ways reminiscent of the ones reported in Precambrian “mixed-hot orogens”

Rhyolites of the Mbépit Massif in the Cameroon Volcanic Line: an early extrusive volcanic episode of Eocene age

International audienceThe Mbépit Massif, one of the oldest volcanoes of the Cameroon Volcanic Line, was built up during the Eocene (40K/40Ar ages of 45.5 and 44.0 Ma). Located in the Eastern part of the Noun Plain, North-East of Foumbot, this massif is made up mainly of rhyolitic domes and thick, viscous lava flows. Such felsic lavas are rather rare in the Cameroon Volcanic Line. Most rhyolites are porphyritic and contain phenocrysts of K-feldspars (Or97–89), Na-feldspars (Ab99–88) and quartz. Scarce Fe–Ti oxides comprise titanohaematite and hemo-ilmenite. Owing to their low CaO contents, rhyolite compositions range from metaluminous to peraluminous (with normative corundum) and less commonly, peralkaline (normative aegirine). Chondrite-normalised REE patterns show LREE enrichment; and LaN/YbN ratios between 12.2 and 17.2, with prominent negative Eu anomalies (0.16 < Eu/Eu* < 0.62). The Th/Ta ratios range between 2.6 and 3. Initial 87Sr/86Sr ratios (0.7047 and 0.7050) and 143Nd/144Nd ratios (0.5125 and 0.5126, εNd of −1.04 to +1.22) suggest mantle sources (HIMU (high µ with μ = 238U/204Pb), EM (Enriched Mantle), FOZO (FOcal ZOne) components) of the rhyolites accompanied by little or no crustal contamination

The Mount Cameroon stratovolcano (Cameroon Volcanic Line, Central Africa): Petrology, geochemistry, isotope and age data

International audienceMount Cameroon, a Plio-Quaternary stratovolcano, is the most important volcano along the Cameroon Volcanic Line, located at the boundary between the continental and oceanic lithosphere. Effusive, explosive and hydromagmatic eruptions were the three main types of volcanic activity. Mount Cameroon has a weakly differentiated alkaline series: mainly basanites, alkaline basalts, hawaiites, and mugearites. Mount Cameroon lavas are a typical alkaline series, characteristic of the interior of plates: high TiO$_2$ contents (2.4-3.7 wt.%), Na$_2$O between 2.9 and 5.2 wt.%, K$_2$O between 1.1 and 3.0 wt.%. Trace element patterns confirm the general evolution by fractional crystallization from a source in a mantle plume. Magmas beneath Mount Cameroon were generated at great depths from a garnet-lherzolite mantle, with an additional contribution from spinel-lherzolite, with small amounts (0.2-2 %) of melting. $^{40}$ K-$^{40}$Ar analyses have yielded ages of 2.83 to 0 Ma. The $^{87}$Sr/$^{86}$Sr ratios of mafic lavas are low (0.703198-0.703344), and $^{143}$Nd/ $^{144}$Nd ratios are intermediate (0.512851-0.512773), as typical of a mantle origin with a HIMU component. $^{206}$Pb/$^{204}$Pb, $^{207}$Pb/$^{204}$Pb and $^{208}$Pb/$^{204}$Pb ratios are respectively 18.8270-20.3911, 15.5999-15.6793 and 40.2093-38.6517