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The present work focuses on the volcanic basement rock geochemistry of Mount Makabaï (Maroua-Cameroon city) in relation to groundwater geochemistry. Investigations were centered on an approach involving an association of several methods such as geological cartography, hydrogeology, and geochemistry. Three rock samples, four disturbed soil samples, three undisturbed soil samples, and 20 samples of groundwater in 10 wells were collected during fieldwork and prepared for laboratory analyses. Bedrocks exhibit porphyritic, aphyric, and sub-aphiric textures. The phenocryst phases are mainly olivine, clinopyroxene, and plagioclase. Based on whole rock major element chemical compositions, the Makabaï samples, plotted on Na2O + K2O versus SiO2 diagram, are mugearite, hawaiite, and basalt. The ratio of (MgO + CaO)/(Na2O + K2O) exceeds unity and shows dominance of alkaline Earth metals (MgO: 2.99–4.48 %; CaO: 6.19–9.80 %) relatively to alkali metals (Na2O: 2.27–4.46 %; K2O: 2.09–2.51 %). Exchangeable base contents are high, mostly represented by Ca and Mg, whose contents vary from 14.6 to 35.28 cmol(+) kg−1 and from 3.28 to 9.48 cmol(+) kg−1 respectively. The CECclay is likewise high, fluctuating between 116.80 and 181.38 cmol(+) kg−1, values in line with the presence of 2:1 clay minerals represented in the study area by montmorillonite. In the water samples, the Ca2+ and Na+ contents are generally higher than K+ and Mg2+, reflecting the relative abundance of Na2O and CaO oxides to K2O and MgO oxides in rocks where different waters were sampled. The waters of Makabaï are acidic to neutral (6.3 ≤ pH ≤ 7.4) and weakly to highly mineralized (110.0 ≤ EC ≤ 1190.0 µS/cm). Hydro-geochemical classification by using the Piper diagram revealed two water types: (1) CaMg–HCO3 (40%) and (2) CaMg–Cl or CaMg–SO4 (60%). The average content of ions in all the analyzed samples was HCO3− ≫ NO3− > SO42− > Cl− for anions and Ca2+ ≫ Mg2+ > Na+ > K+ for cations. Major mechanisms governing ionic constituents of groundwater in the study area are water–rock interactions, silicate weathering, and ion exchange. [ABSTRACT FROM AUTHOR]

This study presents major and trace elements, and Sr-Nd-Pb isotope data of the Mokolo-Kosséhone volcanic rock (basanite, trachybasalt, trachyte, and rhyolite) from the northernmost segment of the Cameroon Volcanic Line (CVL). The basanite sample exhibits primitive character (MgO: 12–14 wt%; Mg#: 69–72; Ni: 327–427 ppm; Cr: 524–599 ppm; Co: 57–60 ppm). Trace element and isotopic signatures of the mafic lavas are similar to those of OIB. The trends observed in the major oxides and compatible trace elements against SiO2 from basanite to rhyolite are attributed to the fractionation of different mineral phases such as Fe-Ti oxides, olivine, clinopyroxene, feldspar, and quartz. The enrichment in LREEs and depletion in HREEs associated with (La/Yb)N > 5 (12.39–32.65), (Tb/Yb)N > 1.7 (1.71–2.89), and Dy/Yb > 2 (2.16–3.63), suggest the presence of a garnet phase in a mantle source. The lavas were produced at varying depths by low degrees of partial melting (< 4%) of a source containing less than 5% of garnet peridotite. The 206Pb/204Pb values of basanite (19.69630–19.79122) are similar to those of FOZO (206Pb/204Pb > 19.5). The trachybasalt samples with 206Pb/204Pb values of 19.25 and 19.37 suggest the probable enrichment of magma with a high-μ (HIMU) signature (206Pb/204Pb < 19.5) by a crustal component. Trace elements and isotopic compositions (87Sr/86Sr: 0.70308–0.70378, 143Nd/144Nd: 0.51287–0.51296, 206Pb/204Pb: 19.24652–19.79122) of the Mokolo-Kosséhone lavas are consistent with a mixture of different source material from the sub-continental lithospheric mantle (SCLM) and the asthenosphere with minor crustal contamination. The composition of the source is analogous to those described in the northern portion of the CVL and other volcanic massifs along the CVL. [ABSTRACT FROM AUTHOR]

The locality of Lara (Far-North Region, Cameroon) is made up of a pediplain strewn with coalescent plutons. The interaction of internal and external geological processes has contributed to transform the latter into inselbergs, whose geotouristic values are yet to be studied. Field and laboratory work enabled us to select the geomorphosites through their aesthetic value (particular size and shape) and, geomorphological and geological features. Moreover, it permitted to study and map the geomorphosites using Optic Microscope, Google Earth, GIS software and many other interfaces. Hence, four inselbergs have been selected and studied in the locality of Lara. The petrographic study of these inselbergs shows that granites are the main components of inselbergs and they present a fine to coarse-grained texture, materialized by quartz, micas, plagioclases and alkali feldspars (white and pink in colour). Inselbergs exhibit vertical and parallel networks of diaclases giving them a stratified appearance in some flanks. In addition, on some inselberg limbs and piedmonts, are built tors which contribute to their beauty. The tops of inselbergs, are embellished by several alluring pedestal rocks. On their flanks, shelters of various shapes and sizes (about 12 m length) have developed through the heaps of blocks field. Among the ten shelters selected, some have a fairly high cultural value as they are sacred places for the local population. Moreover, Lara's granitic inselbergs include enclaves (cognate enclaves and xenocrysts) that also significantly improve their geoheritage value. Inselbergs are landforms with high education and aesthetic value that attracted a larger local and foreign population of about 863 visitors between 2017–2019. They constitute an exceptional geoheritage that could attract more tourists in the locality of Lara; but the promotion of geotourism is needed through interpretative panels, marketing of geomorphosites through leaflets, web, media, and geotours, to mention a few. [ABSTRACT FROM AUTHOR]

The Baïbokoum syenitic pluton (BSP), located in southern Chad, to the NE of the Adamawa-Yadé domain, is one of the few strongly potassic magmatic bodies in the southern part of the Central African Fold Belt (CAFB) in Chad. It has been previously studied petrologically, but its petrogenesis has remained poorly known. Petrographic and whole-rock geochemical data presented in this article highlight their magma genesis and geodynamic evolution. The BSP consists of medium- to coarse-grained syenites associated with minor microdiorites, which occur as syn-plutonic dikes and mafic microgranular enclaves (MME) coarse- and medium-grained syenites outcrop respectively to the core and the border of the BSP. The syenite displays high-K and alkaline to trans-alkaline affinity. Petrographic and geochemical data suggest that medium- to coarse-grained syenites are from single magma source that evolved and differentiated by fractional crystallization in a magma reservoir. REE profiles show enriched LREEs (LaN/YbN = 6.19–45.55) while HREEs show an almost flat profile (DyN/YbN = 1.0–2.23), and the La/Sm and Sm/Yb ratios have led to propose that the aforementioned rocks derived from the partial melting of a garnet-spinel-lherzolite mantle source. Negative Nb and Ta anomalies indicate that this mantle source was modified by the addition of subduction-related material. Th/Yb ratios associated with high Ba/La ratios indicate that enrichment of the source could be related to slab-derived fluids. The parental magma of the BSP was generated by partial melting of the metasomatized lithospheric mantle that was modified into arc-magmatism material in a subduction setting. Its emplacement took place in two successive stages: a static stage of fractional crystallization and crystal settling in a deep magma source and a dynamic stage in a shear deformation setting during which stratified magma rises towards the upper crust, with evolved syenite magma being emplaced first and diorite later. The emplacement of the BSP was probably controlled by the evolution of the Tcholliré-Banyo Fault and M'Béré Shear Zone during the Pan-African orogeny. [ABSTRACT FROM AUTHOR]

This study presents mineralogical, major, and trace element data for ten samples of ignimbrite matrix, one of fiamme and fourteen samples of rock enclave from Bamenda volcano ignimbritic formations situated in the Western Cameroon Highland (central part of Cameroon Volcanic Line). The mineralogy of the deposits comprises alkali feldspars, plagioclase, quartz, clinopyroxene, amphibole, biotite, and oxides (titanohematite, titanite, goethite, pseudorutile, ilmenorutile, and ilmenite). Subangular fragments of trachytes, rhyolites, ignimbrites, and fiammes and debris of glass are found in these deposits. The representative matrix samples and enclaves are rhyolitic in composition and both peralkaline (PI > 1) and alkaline (PI ≤ 1). Like other felsic and mafic lavas of the Bamenda volcano, the studied ignimbrites and their enclaves show an evolution dominated by fractional crystallization (FC). The later petrogenetic process is highlighted by the minor variation in Ce/Zr, Th/Nb, and La/Yb ratios for the Bamenda volcano ignimbrites (0.12–0.81, 0.08–0.33, 12.60–45.40, respectively) and the Western Cameroon Highlands (WCH) lavas (0.05–1.11, 0.04–0.2, 16.1–37.91, respectively). The low La/Nb (0.5–3.45) and Th/La (0.04–0.25) values in the ignimbrites, positive to negative Zr–Hf (0.25–1.73) and Nb–Ta (0.3–1.14) anomalies, negative Eu spikes, and low Th/Ce ratios (0.02–0.12) underline an intervention of crustal contamination in the petrogenetic processes, though their high Rb/Sr ratios (0.30–182.88) and weak ratios of LILE/HFSE compared to the very high value of the same ratios in the Pan-African country rocks preclude their melting from this Pan-African basement. [ABSTRACT FROM AUTHOR]

Mount Manengouba is a volcanic complex, age between 1.5 and 0 Myr, situated in the Cameroon Line in Cameroon, approximately 120 km NE of Mount Cameroon. It comprises some important geomorphological features, of geoheritage significance, i.e., geomorphosites, namely, two nested sub-circular calderas, broken cones, crater lakes (Female Lake, Male Lake, and Beme Lake), domes and basins. The scientific values, aesthetic appeal, and the uniqueness of Mt Manengouba geomorphosites are suitable for geotourism. However, there are conflicting land-use values as its fertile soils favor farming in the downslope areas of the volcano, and the pyroclastic cones are quarried for pozzolana. While there are field excursions and research programs undertaken by Universities to educate the public about its geoheritage values, currently, tourism at Mt Manengouba is not well developed. It is proposed to promote better local environmental management of the area, improve roads to facilitate the accessibility to these geomorphosites, and produce interpretative panels, guide books and postcards to educate tourists on the geological setting and geoheritage values of the Mt Manengouba area. [ABSTRACT FROM AUTHOR]