Petrology and geochemical framework of dolerites dykes of Temté, North Cameroon

International audienceThe Temté basement in North Cameroon is crosscut by dyke swarms with N 20°–40° trending, including dykes 15–30 m wide, up to 3 km-long. Representative rocks exhibit intersertal to sub-ophitic textures. Electron microprobe analyses identified diopside, augite, pargasite, biotite, Ti-magnetite, plagioclase, and sanidine. Whole-rock ICP-MS and ICP-AES chemical analyses showed compositions of basaltic andesite, basaltic trachyandesite and trachyandesite in composition. Igneous differentiation was likely governed by fractional crystallization associated with limited fluid metasomatism. Some lavas could have been moderately contaminated by crustal materials during feeding of local cracks through turbulent magma flows. Discrimination geochemical diagrams and immobile trace and REE element ratios show that the mantle source of Temté dolerites was a deep phlogopite-bearing EMII mantle component and has undergone moderate to high partial melting rate. Correlations of fieldwork and analytical data with previous results evidence the Temté dolerite dyke swarms as fingerprints of crustal extension accompanying regional uplift in an active continental margin when early rifting led to the formation of the Poli marginal basin

Segregation Of Olivine Grains In Volcanic Sands In Iceland - Implications For Mars

Poster n° 200

New K-Ar ages of Tchabal Mbabo alkaline volcano massif, Cameroon Volcanic Line and Adamawa plateau (Central Africa)

International audienceTchabal Mbabo in Central Africa is a voluminous volcano massif composed of alkali lava series. K-Ar geochronology data obtained from three samples of basanite - trachyandesite composition defined at least two volcanic activities. The first at end Eocene (38.22 ± 0.80 Ma) and the second during Oligocene (28.88 ± 0.61 and 28.60 ± 0.60Ma). The distribution of different ages along the Cameroon Volcanic Line is difficult to council with any migration of magmatic activity, as previously suggested. The most realistic scenario for the formation of Cameroon Line is that the ascent of lavas has been favored by the crustal discontinuities inherited from the Pan-African orogeny and reactivated during Mesozoic and Cenozoic. ICP MS and ICP AES analyses show that basanite lavas are the result of 2 % melting of sub-lithospheric mantle source containing garnet and phlogopite phases; the trachyandesites are formed by fractional crystallization of K-feldspar, amphibole, clinopyroxene and Fe-Ti oxides

Quantitative compositional analysis of martian mafic regions using MEx/OMEGA reflectance data 1. Methodology, uncertainties and examples of application

International audienc

Geohazards (floods and landslides) in the Ndop Plain, Cameroon Volcanic Line

International audienceThe Ndop Plain, located along the Cameroon Volcanic Line (CVL), is a volcano-tectonic plain, formed by a series of tectonic movements, volcanic eruptions and sedimentation phases. Floods (annually) and landslides (occasionally) occur with devastating environmental effects. However, this plain attracts a lot of inhabitants owing to its fertile alluvial soils. With demographic explosion in the plain, the inhabitants (143,000 people) tend to farm and inhabit new zones which are prone to these geohazards. In this paper, we use field observations, laboratory analyses, satellite imagery and complementary methods using appropriate software to establish hazard (flood and landslide) maps of the Ndop Plain. Natural factors as well as anthropogenic factors are considered. The hazard maps revealed that 25% of the area is exposed to flood hazard (13% exposed to high flood hazard, 12% to moderate) and 5% of the area is exposed to landslide hazard (2% exposed to high landslide hazard, 3% to moderate). Some mitigation measures for floods (building of artificial levees, raising foundations of buildings and the meticulous regulation of the flood guards at Bamendjing Dam) and landslides (slope terracing, planting of trees, and building retaining walls) are proposed

Quaternary geology and the environment

International audienc

Le Quaternaire. Géologie et milieux naturels

International audienc