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In this study, field descriptions of the dolerite dykes cross‐cutting the Pan‐African basement (DPB) and the dolerite and gabbroic dykes cross‐cutting the Cretaceous sedimentary basin (DGCSB) are used together with petrographic, bulk‐rock geochemistry, as well as Sr–Nd–Pb isotopic data to constrain the geodynamic setting and origin of these mafic (basanite, basalt and basaltic andesite in composition) rocks that outcrop in the Figuil–Léré area. The DPB dykes are alkaline with SiO2 of 46.63–49.03 wt% and MgO of 3.93–7.11 wt%. In contrast, the DGCSB dykes are subalkaline with SiO2 ranging between 50.24 and 53.16 wt% and MgO fluctuating between 5.22 and 7.90 wt%, comparable to dykes described in other regions of the Cameroon Line (CL). The rocks studied belong to the tholeiitic series and were emplaced in within‐plate basalts (WPB) and mid‐ocean ridge basalts (MORBs) setting. The variations in major and trace elements from the basanite to basaltic andesite compositions are dependable with fractional crystallization (FC) of different mineral phases such as opaque minerals, olivine, clinopyroxene, amphibole and alkali feldspar. Most samples exhibit negative Nb–Ta and positive Sr anomalies, which together with the negative correlation between MgO and 87Sr/86Sr, and isotopic ratio of 206Pb/204Pb <19.5 (18.27–19.49) suggests interactions of crustal components. Nevertheless, this contamination seems limited because there is a positive correlation between SiO2 and 143Nd/144Nd plot and low Ba contents (72–210 ppm) of the samples compared to the mid‐continental crust (259–628 ppm). Trace element modelling proposes a derivation of the Figuil–Léré dykes from parental melts generated by 4%–15% partial melting of a source containing garnet peridotite in the mixed lithospheric–asthenospheric mantle. The isotopic data of the dykes studied with hybrid magma composition are characterized by more radiogenic 87Sr/86Sr, 143Nd/144Nd and 206Pb/204Pb isotopic ratios with a dominant mixing of depleted MORB mantle (DMM)–enriched mantle 1 (EM1)–enriched mantle 2 (EM2), like those of other mafic dykes of the CL. [ABSTRACT FROM AUTHOR]

Using a multidisciplinary approach to understand the subsurface processes behind the formation of maar‐diatreme volcanoes is of growing interest. While geophysical characterization can visualize the diatreme and the feeding dike system beneath the volcano at a reasonable scale, such data are rare and generally unavailable. Stratigraphic‐controlled sampling and geochemical analysis of pyroclasts within the ejecta ring can, however, provide substantial information on dike evolution and the influence of the magmatic plumbing system on the growth of these volcanoes. Such investigation is presented here for the Barombi Mbo Maar (BMM), a complex maar of the Cameroon Volcanic Line (CVL) composed of a pile of tephra units linked to multiple explosive phases that were grouped into three eruptive episodes. Major and trace element compositions of lavas collected from the different eruptive units indicate that the erupted magmas at BMM consist mainly of basalt, trachybasalt and basanite, with Oceanic Island Basalts (OIB) and high μ (μ = 238U/204Pb) (HIMU) signatures. Compositional modelling suggests that partial melting occurred at different degrees in the garnet‐to‐spinel transition zone from one episode to another. The repetition of eruptions with big gaps between them, the presence of another large adjacent old maar crater next to the 2.5 km crater of the BMM, and the overall similarity in geochemical compositions from one eruption to another suggest a deep high‐productive zone in the mantle beneath the BMM. The latter productive zone was capable of generating magma batches episodically to fuel several individual monogenetic eruptions at the same location. [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 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]

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]

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]

As in other parts of the world, air pollution over West and Central Africa has major health and meteorological impacts. Air quality assessment and its possible sanitary impact have become essential even in medium-sized towns, therefore amplifying the need for easy-to-implement monitoring methods with low environmental impact. We present here the potential of magnetic methods to monitor air quality at street level in the medium-sized city of Maroua (northern Cameroon) affected by dust-laden desert winds. More than five hundred (544) samples of bark and leaves taken from Neem trees in Maroua were analyzed. Magnetic susceptibility, saturation remanence, and S-ratio were found to determine the concentration and nature of magnetic particles. They are dominated by magnetite-like particle signals as a part of particulate emissions due to urban activities, including both traffic, composed of a substantial proportion of motorcycles, and wood burning for food preparation. We show that both bark and leaves from Neem trees are adequate passive bio-recorders. The use of both enables different times and heights to be sampled, allowing for the high-resolution monitoring, in terms of spatialization, of various urban environments. Particle emissions require assessment and screening that could be carried out rapidly and efficiently by magnetic methods on bio-recorders, even in cities impacted by dust-laden wind. [ABSTRACT FROM AUTHOR]