Risk Link to the Volcanic Activity of the Mt. Cameroon in Cameroon

The Mt. Cameroon is a large volcanic horst belonging to the majure tectonic line (Cameroon volcanic line). The geographical morphology of the mountain is controlled by regional tectonics. The Mt. Cameroon is consisted of precambrian metamorphic basement covered with Cretaceous to recent sediments distributed mainly in the Douala and Riodel Rey basin. The oldest lava could be of upper Miocene age. The Mt. Cameroon has erupted six times in the 20th century. The 1982 eruption took place inside the crater of an ancient cone. The lavas are picrites (with forsteritic olivine phenocrysts), alkali basalts (with salitic augite phenocrysts), hawaiites (with labrador-bytownite plagioclase phenocrysts) and mugearites (with scarce kaersutite phenocrysts and microlitic phlogopite or nosean). According to Deruelle et al.(1987), the Mt. Cameroon lava series is typically alkaline with no tholeiitic or transitional trend. Risk related to volcanism is actual for the human constructions especially along the axis of the horst. The severe volcanic risk has been limited to explosion, lava flows and lahar. It is possibility that explosion, laver flow and earthquarke take place anywhere on the volcanic mountain. Nevertheless, these explosions are most likely to occur in the delimited sector which is shown in a map presented in this paper. Even if we could divert the course of the lava flows to certain safer direction, flows caused by sudden earthquarke and explosion may cause serious damages

Preliminary geological study and physicochemical characteristics of talc of Boumnyebel (Centre-Cameroon)

Two talc schist occurrences were discovered in the Boumnyebel area, embedded in the Pan-African mica schist, at the junction between Archean, Eburnean and Neoproterozoic formations in Cameroon. They have been analysed by different techniques such as chemical analyses, XRD, DRIFTS, DTA and TG. The talc schist of the northern deposit contains talc (up to 95 wt %) with chlorite, goethite and lepidocrocite as minor minerals. The talc schist of the southern deposit has up to 88 % of talc and is speckled with dark green phenoblasts of amphiboles (coexisting prismatic tremolite and magnesio-riebeckite). Due to its high talc content, the amphibole-free talc schist is economically attractive. Chemical analyses show that most of the rocks consist of SiO2, MgO and Fe2O3, except the sample from the southern deposit that displays some amounts of Al2O3 and CaO. Among trace elements, Ni, Co and Cr are as high as in serpentinized peridotites, and suggest a protolith of ultrabasic nature. Chromium concentration in tremolite reaches 6178 ppm; most of the trace elements (Cd, Cr, Dy, Er, Eu, Ga, Gd, Ho, Lu, Nd, Pr, Sm, Sn, Sr, Tb, Tm, Y, Yb, Zr) are compatible with a tremolite lattice. The regional metamorphism yielded garnet micaschist nappes and thus belongs to the upper greenschist facies. Based on the high talc contents of the rocks and occasional coexisting tremolite an