The Cameroon Line (CL) appears as a SW-NE straight line characterized by an intense volcanic activity of basaltic composition with alkaline plutonic complexes, including the Nlonako ring complex (NRC) emplaced in the southern part of the CL. Many hypotheses have been proposed to explain the origin and petrogenetic evolution of these complexes but very few of these works focus or attempt to propose their structural emplacement model, though structural data recorded by them can permit such studies. Using petrographic, structural data and space images, we propose an emplacement model of the NRC and other ring complexes along the CL. The NRC is a ring complex of 10 km diameter slightly elongated in the NNE-SSW direction mainly composed of plutonites among which syenites, gabbros, diorites and biotite-amphibole granites, and a few volcanites made up of rhyolites and basalts occurring as veins or boulders in syenites. This complex was emplaced as sill intrusive body within Pan-African k-feldspars megacrysts granites and gneiss host rocks under fractures control. These fractures developed as result of stress release consecutive to the readjustment of the crust during and after the late Cretaceous general extension, therefore facilitating the upwelling of the mantle plume and the generation of magma that vertically uplift. The progressive magmatic pressure decreases after the NRC emplacement in addition to conjugated fractures networks developed at superficial crust level finally lead to the cauldron subsidence of the NRC summit. This subsidence was facilitated by the downward sliding of rocks along the WNW-ESE fault, finally leading to the formation of a caldera at the summit of the NRC. The NRC and other anorogenic complexes aligned along the CL are located in a tension gash form by the Cretaceous sinistral activation of the N70E Adamawa fault. This left lateral wrench movements developed a tension gash, overprinted on pre-existing transcurrent mega-faults with as result, the development of "en-echelon" fractures. Stress release during the late Cretaceous general extensional phase probably accelerated the uplift of magmas and emplacement of ring complexes along the "en-echelon" regional fractures in an extensional setting during the Tertiary (60 - 30 Ma). This therefore explained the alignment of anorogenic complexes along the N30E CL corridor that are highly correlated to lineament networks and Pan-African megafaults

The Mount Cameroon region is investigated using 2-D spectral analysis of the gravity data, in order to determine the depth of subsurface interfaces beneath the region. New gravity data are combined to existing ones to determine the depth of the major subsurface discontinuities throughout the region. Depths are established from the slope of the log-power radial spectrum et the lower end of the wave number band. Three major subsurface density discontinuities are determined beneath the Mount Cameroon: (1) 0.41 ± 0.02 km, (2) 1.26 ± 0.06 km, (3) 4.73 ± 0.24 km. This result has the best precision comparing with the those from the former Bouguer anomaly where the major subsurface discontinuities obtained are: (1) 0.48 ± 0.02 km for the first layer, 1.81 ± 0.09 km for the second and 6.87 ± 0.34 km for the third. This difference is probabely due to the densification of gravity data. The knowledge on the depth of different interfaces in the crust is very important in the reconstitution of the earth history. These results will the support of prospective investigations throughout this region.

The Bamenda Volcano (BV) (2621 m) is a stratovolcano situated in the Cameroon Line (CL). BV includes Mount Lefo (2534 m) which is situated on its southern slopes and contains one elliptical caldera (3 × 4 km). This caldera is propitious to farming and breeding activity. Despite these profitable assets, Lefo caldera (LC) is an amphitheater of the occurrence of multi-origin hazards that have direct or indirect impacts on the biodiversity and human patrimony. The most present hazards are those of meteorological origin. Numerous combined factors (steepest slopes, heavy rainfalls, weathered state of volcanic products…) rule these hazards. These factors gave rise to the occurrence of landslides, gullies erosion and rock falls which occur precisely on caldera northern and eastern rims. Hazards of anthropogenic origin are based on the destruction of the vegetation cover by the population for dealing, firewood and building issues. Moreover, during the breeding activity, the cattle covers the caldera throughout the day; this unevens the topography and destroys the meadow. Hazards of volcanological origin are not yet occurring in LC; but the recent Lake Monoun (1984) and Nyos (1986) CO2 eruptions, mount Cameroon eruptions (1999 and 2000) and mount Oku Lake event (2011) which are close to the BV and, the age of 0 Myr of basalt, constitutes a subject of controversy toward the reactivation of the Cameroonian hotspot faults. The assessment of risks in LC was based on the average income of breeding activity and house investment. The economy of LC is valued at about US$527472.527. The level of such risk will be important in case of loss of human beings and the destruction of geomorphosites' values. In order to reduce the level of looses in this zone, hazard and risks maps are provided in this paper as well as some recommendations. Z. T. Ghislain et al.

Distillation sous pression réduite L'huile de vidange obtenue après traitement aux sels fondus est ensuite soumise à une distillation sous pression réduite dans un distillateur muni d'une pompe à vide et équipé pour le suivi de la pression et de la température à l'intérieur du réacteur. La pression mesurée à l'intérieur du distillateur est de 0,303.10 5 Pa. La température a été fixée à 210 o C. De la pierre ponce a été utilisée pour réguler l'ébullition de l'huile. Le traitement permet en 2 heures de récupérer 6,65 L d'huile distillée à partir d'un volume initial de 6,8 L.

The granitoids of Guéra Massif are composed of biotite-granite, amphibole-biotite granite and gabbro-diorite and commonly contain micro granular mafic enclaves which vary from monzogabbro to syenite composition. They are metaluminous, high-K calc-alkaline to shoshonitic series. Gabbro-diorite rocks are magnesian while amphibole-biotite granites are magnesian to ferroan, and biotite granites are ferroan. They are enriched in LREEs relative to HREE and display negative anomalies in Nb, Ta and Ti. Fields relationships, petrology and geochemistry indicate that mixing and mingling processes could be more relevant for the genesis of granitoids associated to fractional crystallization. Thus, the presence of mafic enclaves of gabbro-diorite composition in the granites, the resumption of alkaline feldspar xenocrystals in the gabbro-diorites, as well as the linear correlation between the granites and the gabbro-diorites and the intermediate position of the mafic enclaves between the two formations, enable us to propose magmatic mixing as the major process that presided over the evolution of the Guéra granitoids. The delamination of the continental lithosphere during the post-collisional phase of the Pan-African orogeny would have caused the partial melting of the subduction-modofied mantle and lower continental crust and thus produced the magmas of the Guéra granitoids.