Paul Désiré NDJIGUI

Paul Désiré NDJIGUI · UY1 Research Hub

2024Article de revueAccès ouvert

Potential engineering applications of volcanic scoria from Mount Cameroon area, Central Africa: evidence from petrography and geochemistry

Discover Civil Engineering

This study was initiated to explore the suitability of volcanic scoria from Mount Cameroon along the Cameroon Volcanic Line (CVL) in engineering applications. The mineral composition has been obtained through thin sections observation and XRD method. The XRF analytical methods have been used to determine major element composition. The studied rocks are dark gray to reddish in color with a vacuolar structure and porphyritic microlithic texture recalling the Strombolian dynamism. They are mainly made up of pyroxene, olivine, plagioclase, opaque minerals, quartz, magnetite and iddingsite. The presence of phenocrysts of olivine and clinopyroxene is due to mantle contamination. The main chemical components of scoria of Mount Cameroon are silica, alumina, iron and calcium oxides. The abundant vitreous phases are responsible for the acidic character revealed by high SiO 2 + Al 2 O 3 contents. Fe 2 O 3 , MnO and MgO are hosted by ferromagnesian minerals while SiO 2 , Al 2 O 3 , K 2 O, NaO and P 2 O 5 are found in acidic vitreous phases. The mineral and chemical composition of the scoria of Mount Cameroun is similar to those of scoria previously studied around the world. They can be used as absorbents for metals because of their high adsorption capacity and affinity for metals. The high SiO 2 + Al 2 O 3 + Fe 2 O 3 contents and low LOI values show that the scoria from Mount Cameroon are suitable to the use in cement and concretes. They can improve the resistance to sulfate, and chlorite and alkali silica reaction. According to the chemical composition, the rocks are conforming to French standard NFP18310. Their high CaO contents are favorable to improve the quality of scoria blended cements.

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2023Article de revue

Hydrogeochemical appraisal of groundwater quality in Ngoua watershed (Douala-Cameroon): Implication for domestic purposes

Pauline Totancine Ngo Billong, Roger Feumba, Paul‐Désiré Ndjigui

Scientific African

Groundwater has been used for many purposes like domestic, agriculture, and industrialization in many regions of the world. Assessing groundwater quality and identifying pollutant risks are essential for managing groundwater resources. Ngoua watershed is located in sedimentary coastal zone of Douala. Groundwater is the major source of water for domestic purposes. Thus, the objective of this work is to assess groundwater chemistry and identify hydrochemical processes affecting groundwater quality of Ngoua catchment and its implication for domestic use. 30 groundwater samples were collected (23 wells, 4 springs and 3 boreholes) and physical-chemical parameters were analysed (T°, pH, TDS, EC), cations (Na+, K+, Ca2+; Mg2+ NH4+) and anions (Cl−, HCO3−, SO42− NO3−, PO43−, and F−) and calculation of groundwater quality index (WQI). The pH indicates that the groundwater in the study area is acidic to neutral. The temperature is similar to the ambient temperature of the study area (27°C). The EC and TDS of the study area are average and the water are moderately mineralized. The order of mean abundance of the cation concentrations is as follows Ca2+ ˃Na+ ˃ Mg2+ ˃K+ ˃NH4+and the order of increasing classification of the anions is as follows NO3−˃Cl− ˃SO42- ˃HCO3− ˃PO43−˃F− The distribution of chemical facies of groundwater in the study area is as follows: 63.33% Ca-HCO3, 23.33% Ca-Mg-Cl and finally 13.33% Na-Cl. The factors controlling groundwater chemistry are rock-water interaction, cation exchange, dissolution and anthropogenic activities may affect groundwater chemistry. Water Quality Index on this study varies between 2.12-187.21 with average of 29.67 and the majority of groundwater in the study area is acceptable in quality and can be used for domestic purposes such as drinking and irrigation. Nitrate and sulfate are the main contaminants of groundwater in the area. However, the high concentrations of NO3− in groundwater suggests than human activities (industrial and domestic activities) is intense and responsible factors for groundwater pollution in study area. Results of this study indicate importance of preventive measures to control groundwater contamination in Ngoua watershed.

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2023Article de revue

Mapping geological configuration using geophysics data: an investigative approach in targeting iron ore, gold mineralization and other commodities, a case study of Toko-Nlokeng area (Nyong Greenstone Belt, SW Cameroon)

Yannick Saturnin Evina Aboula, Joseph Mvondo Ondoa, Paul‐Désiré Ndjigui

Applied Earth Science Transactions of the Institutions of Mining and Metallurgy

Regional geophysical data are important for detecting the presence of mineral deposits under cover. This study used geophysical data coupled with field geology of the Toko-Nlokeng area, Cameroon, to locate and map structures and lithologies as part of an exploration campaign for mineral deposits. The airborne geophysical survey in the Toko-Nlokeng area located in the Nyong complex revealed a predominantly EW striking highly folded series result of polyphase deformation of iron formations and host rocks divided into domains based on magnetic and radiometric character. The geophysical data indicate that major faults and shear zones strike NE-SW, with N–S striking units on the western margin and mainly E–W striking units in the rest of the area. These data suggest a major N–S thrust fault similar to the Borborema Province (NE Brazil) terrane marked by accretionary processes during the assembly of Western Gondwana. Several significant NE–SW striking shear zones are present. The data revealed many moderate to highly magnetic bodies that are interpreted as magnetite-bearing iron formation, mafic–ultramafic intrusions and flows, skarns, carbonatites and kimberlites. The magnetic and radiometric trends reveal the internal regional rock fabric and strike, and iron ore targets with magnetic anomaly up to 27,000 nT related to iron formations and other significant targets for gold, potassium (alteration) and uranium. The Toko-Nlokeng iron deposit is comprised of magnetite-bearing quartzite beds and is concordant with the surrounding host rocks and stands as one of a broad group of magnetite-dominated iron formations that occur throughout West and Central Africa. A new geological map was produced from mapped lithologies and microstructure characteristics of the iron formations, interpretations of the aeromagnetic data and structural features. The study results have important implications for regional exploration programs.

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2023Article de revue

Multi-method characterization of the recent sediment from the Dibi subsidence lake in the tropical Adamawa region (central Cameroon): Implications for the palaeoenvironmental reconstruction

Agathe Catherine N. Ngo Ndje, Chavom Bachirou Mfayakouo, Soureiyatou Fadil-Djenabou, Paul‐Désiré Ndjigui

International Journal of Sediment Research

The evolution and functioning of various tropical ecosystems is poorly understood due to a lack of quantitative techniques to characterize the physicochemical composition of soils and sediment. Here, a detailed multi-method study of lithological changes is provided from a core taken from the silted-up Dibi subsidence lake (central Cameroon). To unravel the provenance of sediment, mineral constituents, and organic matter sources, an array of tools are applied including a spectrophotometer, a laser particle sizer, Rock-Eval pyrolysis, X-ray diffractometer (XRD), a portable X-ray fluorescence (XRF) spectrometry, and an inductively coupled plasma-atomic emission spectroscopy (ICP-AES) instruments. The studied core consists of light-colored deposits at the base (Unit 1) overlain by dark humic deposits (Unit 2). The sediment is very well graded (grading index Sd < 0.35Ф), indicative of bottom suspended to rolling transport. Unit 1 is characterized by relatively low values of total organic carbon (TOC: 2%–5%) whereas the dark Unit 2 has high contents of TOC (10%–33%). The core shows a high oxygen index (OI) value (average = 207 mg carbon dioxide (CO2)/g TOC) and a low hydrogen index (HI) value (average = 107 mg hydrocarbon (HC)/g TOC). This indicates highly altered organic matter (OM), likely from decomposed terrestrial plants. The chlorophyll-α fingerprint (peak around 675 nm) also reveals an autochtonous primary production of organic matter. The mineralogical assemblage of Unit 2 comprises kaolinite, quartz, feldspars, montmorillonite, ilmenite, siderite, gibbsite, rutile, and anatase whereas that of Unit 1 is similar but differs with the presence of illite and the absence of gibbsite. The high titanium dioxide (TiO2) and zirconium (Zr) contents confirm that the source rocks also are comprised of granites, and gneiss without volcanic rocks, such as basalts and trachytes. The source rocks have been intensively weathered using some parameters such as ln(Al2O3/Na2O), K2O/Rb, K/Al, and weathering indices, where Al2O3 denotes aluminum oxide, Na2O denotes sodium oxide, K2O denotes potassium oxide, Rb denotes rubidium, K denotes potassium, and Al denotes aluminum. The enrichment factors (EF) of redox-sensitive trace elements and their relation with TOC, the negative values of manganese/iron ratio (Mn∗) associated to three elemental ratios (cupper/zinc (Cu/Zn), thorium/uranium (Th/U), and vanadium/chromium (V/Cr)) attest to the predominance of sub-oxic to anoxic bottom waters in Dibi lake during sediment deposition. The data also show low primary productivity at the base of the core, followed by an increase towards the top, linked to the intensification of weathering and facilitated by humid climatic conditions, usually increase terrestrial input and palaeoproductivity. The petrological data show a generally warm and humid palaeoclimate. This climatic variation has contributed to the large spread of the savannah and disappearance of the forest. This study sheds light on the late Pleistocene to Holocene palaeoenvironment evolution of the Adamawa region which could be integrated into the context of the Pleistocene to Present regional evolution of the tropical palaeoenvironment.

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2023PrépublicationAccès ouvert

Partial melting of garnet bearing metabasite in the Nyong Complex (Southwestern Cameroon) records to the Eburnean/Trans-Amazonian orogenic: Evidence from field and petrological investigations

Eric José Messi Ottou, Yannick Saturnin Evina Aboula, Sylvestre Martial Ntomba, Paul‐Désiré Ndjigui, Joseph Mvondo Ondoa

Research Square

Abstract Field and petrographical inspections display that garnet bearing metabasite within Lolodorf area in the Nyong Complex was slightly melted during high P-T conditions of 9 to 11 kbar and 840 to 894 °C under very slightly wet melting conditions. Leucosome vein and pocket are present within garnet bearing metabasites. The leucosome veins within garnet bearing metabasites and garnet bearing leucogranite display the same peritectic minerals suggesting that they represent melt which compelled in the Nyong Complex. The garnet and clinopyroxene are inclusions rich which are interpreted as trapped melt, ribbon quartz within the leucosome body which represents injected melt combined with leucosome composed of peritectic products of garnet, clinopyroxene, (± amphibole) and the presence of coalesce garnet grains after dislocation of garnet necklace are consistent with anatexis. The metabasite of Lolodorf in the Nyong rocks archives the geodynamic of the of the Eburnean/Trans-Amazonian orogenic events. These field and petrographic observations are supported by chemical analyses, in which the enrichment of MB3 sample in K 2 O, Ba, LREE, Th, Hf, Zr, and P 2 O 5 than others garnet bearing metabasite samples. These results lead us to consider the Nyong Complex as a younger Complex resulted during Eburnean period. Partial melting of garnet bearing metabasite in the Nyong Complex highlights to stabilisation and differentiation of the Eburnean/Trans-Amazonian orogenic crust. Field and petrographical inspections display that garnet bearing metabasite within the Lolodorf area in the Nyong Complex was slightly melted during high P-T conditions of 9 to 11 kbar and 840 to 894 °C under very slightly wet melting conditions. Leucosome veins and pockets are present within garnet bearing metabasites. The leucosome veins within garnet bearing metabasites and garnet bearing leucogranite display the same peritectic minerals metabases suggesting that they represent melt which, compelled in the Nyong Complex. The garnet and clinopyroxene are rich inclusions which are interpreted as trapped melt, ribbon quartz within the leucosome body, which represents injected melt combined with the leucosome composed of peritectic products of garnet, clinopyroxene, (± amphibole) and the presence of coalesce garnet grains after dislocation of garnet necklace are consistent with anatexis. The metabasite of Lolodorf in the Nyong rocks geobics the geodynamics of the Eburnean/Trans-Amazonian orogenic events. These field and petrographic observations are supported by chemical analyses, in which the enrichment of MB3 samples in K 2 O, Ba, LREE, Th, Hf, Zr, and P 2 O 5 rather than other garnet bearing metabasite samples. These results lead us to consider the Nyong Complex as a younger Complex that resulted during the Eburnean period. Partial melting of garnet bearing metabasite in the Nyong Complex highlights to stabilisation and differentiation of the Eburnean/Trans-Amazonian orogenic crust.

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2023Autre

Petrology and Au-PGE investigation dataset of the recent alluvial sediments from the Ngaye River watershed, northern Cameroon

Paul‐Désiré Ndjigui, Estelle Huguette O. Ngono, Soureiyatou Fadil-Djenabou

Data in Brief

Petrological data of the recent alluvial sediments from the Ngaye River watershed in the Northern Cameroon were used in order to infer their origin with the probable source rocks as gneisses, amphibolites, and granites; and to investigate the occurrence of precious metals like Gold and Platinum Group Elements (Au-PGE). The Ngaye River watershed is located in the Adamawa plateau from the Adamawa-Yade Domain (AYD) in the Central Cameroon, Central Africa. This region is characterized by two contrasted seasons which induce a savanna vegetation cover with gallery forests along the rivers. The field works were done during the dry season. During this season, several whole fractions of sediments were sampled at six vertical lithological sequences along the right terrace of the Ngaye Rivers. The selection of samples was linked to their grain size and color. To better understand the origin of sediments, twenty-one rock samples (gneisses, amphibolites, and granites) were also collected. The grain size distribution was done using the Robinson's standard Pipetting Method. Thin sections were done for the determination of mineral assemblages and textural features of rocks using Leica DM 750P optic microscope. Mineralogical compositions of sediments were obtained using the X-ray diffraction (XRD) instrument. The major elements data were determined using the X-ray Fluorescence spectrometry (XRF). The Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) was used to obtain the concentrations of trace elements including rare earth elements and Au-PGE. The investigation of Au-PGE was done only in amphibolites as well as in the concentrate heavy minerals (160-100 µm) from sediments of lithological sequence A. Data of this paper are further presented and discussed in Ndjigui et al. [1].

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2023Article de revue

Petrology and geochemistry of metamorphosed rocks associated with iron formations of the Toko‐Nlokeng iron deposit, (Southern Cameroon): Implications for geodynamic evolution and mineralization

Yannick Saturnin Evina Aboula, Paul‐Désiré Ndjigui, Joseph Mvondo Ondoa

Geological Journal

Detailed petrographic, lithostratigraphic, and geochemical data of metamorphosed orthogneisses and mafic‐ultramafic metavolcanic rocks intruded into the greenstone belt of the Toko‐Nlokeng iron deposit have enabled the reconstruction of the tectonic and geodynamic setting and crustal evolution of the Nyong Complex. Samples were collected from the drill holes TNF11_01 and TNF11_02 from 17.16 m to 335.85 m depth. The lithostratigraphy supported by field and petrographic observations outlines two main lithologies: Iron formations (IFs) and metamorphosed host rocks. The IFs (granular iron formations (GIF) and banded iron formations (BIF)) are intercalated with host rocks consisting of orthogneisses and mafic‐ultramafic rocks. New and published geochemical data of metamorphosed associated IFs from Anyouzok (TNF08 prospect) of the Toko‐Nlokeng iron deposit, Mewengo iron deposit, Bipindi, and Kribi metavolcanic rocks in the Nyong Complex, suggest that these rocks were formed by material from intrusive and extrusive magmatic episodes with mid‐ocean ridge basalts (MORB) contaminated by either subduction or crustal components. CaO/Al 2 O 3 and (Gd/Yb) N ratios >1 and positive Nb anomalies in ultramafic rocks indicate a mantle plume source contaminated by metasomatized subduction mantle lithosphere. These data also show that the mafic‐ultramafic metavolcanic rocks derive from magma of basaltic and basaltic andesite compositions, with a tholeiitic to calc‐alkaline tendency characteristic of the upper mantle. These data reveal that gneisses derive from granite and diorite subalkaline, peraluminous, and ferroan to magnesian compatible with Cordilleran magmas and island arcs with polygenetic crustal signatures. All samples of mafic granulites, garnet‐amphibolite, metabasites, and ultramafic granulites in the Nyong Complex reveal no residual garnet and predominantly show ca. 4% partial melting of an amphibole‐spinel‐peridotite source in the Dy/Yb versus La/Yb. Otherwise, hornblendites of Toko‐Nlokeng display ca. 5% partial melting of an amphibole‐garnet‐peridotite source, average (Gd/Yb) CN ratio of the hornblendites is (Gd/Yb) CN = 7.56 > 2. This result suggests these hornblendites do not have the same magmatic source as other mafic‐ultramafic rocks of the Nyong Complex. Mafic‐ultramafic host rock protoliths are classified as E‐MORB, P‐MORB, and G‐MORB (hornblendites) compositional types and arc, back‐arc ‘B’ in subduction unrelated, rifted margin setting with minor crustal contamination. The tholeiitic to calc‐alkaline and peraluminous affinity of these rocks indicate a mature arc and thickened crust during the Eburnean Trans‐Amazonian orogenic belts of the Congo Craton. This study shows that the host rocks were emplaced in a convergent tectonic setting and affected by a syn‐collisional episode where melts were derived from the partial melting of thick basaltic crust into amphibolite–eclogite facies in the subduction zone. The geochemical signatures of the mafic‐ultramafic rocks support the tectonic accretionary of the Palaeoproterozoic plume arc in Nyong Complex. Furthermore, the resulting hydrothermal alteration process was accompanied by an increase in Fe; particularly under conditions dominated by seawater, the origin and source of iron and silica in the Toko‐Nlokeng deposit.

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2021Article de revueAccès ouvert

DMSO Deintercalation in Kaolinite–DMSO Intercalate: Influence of Solution Polarity on Removal

Berenger ZOGO MFEGUE, Jean Aimé Mbey, Sandotin Lassina Coulıbaly, Vincent Laurent Onana, Paul‐Désiré Ndjigui

Journal of Composites Science

This study focused on the deintercalation of dimethyl sulfoxide (DMSO) from a kaolinite–DMSO complex in various solvents. The use of kaolinite as filler in polymer–clay composite generally faced the difficulty of kaolinite dispersion due to its high cohesion. For improved dispersion of kaolinite within a given matrix, previous intercalation of small polar molecules is usually done prior to its displacement during composite-making. The influence of the solvent polarity on the deintercalation in analyzed here to understand its role during the deintercalation process. The intercalation of the DMSO was done by solution-mixing and its displacement was done in distilled water, ethyl acetate, and acetone. The products of deintercalation were analyzed using Fourier transform infra-red (FTIR), powder X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The weakening of the kaolinite cohesion after DMSO intercalation is demonstrated through the broadening of the diffraction peak associated with the kaolinite on XRD patterns. From FTIR spectra, the weakening is associated with the displacement to low wavenumbers of the Si–O or Al–O vibration bands within the kaolinite–DMSO complex. The kaolinite dehydroxylation temperatures from DSC show that the rate of DMSO displacement affects the ordering of the recovered kaolinite. The crystallite size of the kaolinite is reduced from the raw to the recovered kaolinite after DMSO displacement, indicating an exfoliation of the kaolinite. From these results, it is found that the removal of the DMSO from the kaolinite–DMSO complex is influenced by solvent polarity. The higher the polarity, the greater the removal of the DMSO from the complex. Solvent polarity affects the rate of DMSO displacement, which influences the ordering of the recovered kaolinite. It is suggested that solvent polarity can be used to control the removal rate of DMSO, which may be key to the dispersion of the kaolinite platelets.

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2021Article de revue

Petrological features of volcanic scoriae from the southern part of the Cameroon Volcanic Line and their supplementary cementations application

Estelle Huguette Ngono Onana, Fuh Calistus Gentry, Paul‐Désiré Ndjigui

Heliyon

Volcanic scoriae from the southern part of the Cameroon Volcanic Line (Limbé, Loum-Tombel, Yamba, Doupé, Njinkouo, Foumbot, Manjo-manengollé, Galim and Djoungo) were investigated in order to determine their chemical and mineralogical composition, to deduce their origin and to identify their natural characteristics which may be useful to the cement industry. The mineralogical composition was determined by X-ray Diffractometer (XRD); X-ray Fluorescence (XRF) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) instruments provided geochemical data. In order to establish the relationship between the natural characteristics of volcanic scoriae and the properties of cements, the amount of amorphous phases was determined by dissolution using sodium hydroxide solution and the pozzolanic activity by thermogravimetric analysis. Field observations show that these rocks are basalts, basanites, hawaiites and picrobasalts. Their mineralogical composition includes augite, olivine, plagioclase, enstatite, feldspars, ettringite, portlandite and Fe–Ti minerals. Overall, they are characterized by high MgO, Fe 2 O 3 , CaO, and TiO 2 contents. The behavior of major and trace elements suggests that volcanic scoriae have an evolution dominated by partial melting. Besides, high chondrite normalized La/Yb (8–22), Tb/Yb (>1.9) and Dy/Yb (>2) values suggest that the melting corresponds to the garnet lherzolite stability field. The scoriae exhibit good pozzolanic reactivity after 28 days according to their considerable amount of amorphous phases, low CaO contents and their large specific surface area. According to ASTM C618 standard, the sum of SiO 2 , Al 2 O 3 and Fe 2 O 3 (SAI = 65.96–76.34 wt.%); LOI (-0.1–16.99 wt.%), and of CaO, Fe 2 O 3 and MgO (CIM = 23.43–34.06 wt.%) suggest that those less weathered materials seem appropriate as an additive in cement manufacture. The suitable use of volcanic scoriae in the cement industry closely depends on the petrological features of amorphous phases.

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2021Article de revue

Petrology of weathering materials developed on granites in Biou area, North-Cameroon: implication for rare-earth elements (REE) exploration in semi-arid regions

Elisé Sababa, Lionel G. Essomba Owona, Jean Pierre Temga, Paul‐Désiré Ndjigui

Heliyon

Due to the increasing demand resulting from the use of REE in many fields of human life, a weathering profile developed on granites in the semi-arid region of Biou area (North-Cameroon) has been characterized for rare-earth elements (REE) exploration. The mineralogical compositions of weathered materials were revealed by X-ray diffraction (XRD). X-ray Fluorescence (XRF) and Inductively Coupled Plasmas-Mass Spectrometry (ICP-MS) have been used to determine the geochemical composition of granites and the overlying weathered materials. The S-type and peraluminous granites are constituted by quartz, orthoclase, microcline, plagioclase, biotite, muscovite, pyroxene and opaque minerals. Accessory minerals are probably responsible for the interesting contents in REE + Y and some trace elements (e.g., Zr, Zn, Ba, Rb). The weathering profile show from the bottom to the top: (i) saprolitic horizons; (ii) lower loose clayey horizon; (iii) iron duricrust horizon; (iv) upper loose clayey horizon; (v) and organo-mineral horizon. Some weathered rock fragments remain in the loose clayey and organo-mineral horizons. The mineralogical composition of the weathering materials is dominated by illite, muscovite and feldspar. The low weathering degree of the materials is justified by the climatic and reducing conditions. The large ion lithophiles and ferromagnesian elements (Mg, Fe, V, Cu, Co, Cs Cr, Ni, Sc and Li) which are supposed to be mobile are so much accumulated in the weathering materials. REE show very low degree of fractionation in weathering profile due probably to the lack of good drainage. The whole weathering materials shows high REE + Y contents as its parent rock. Geochemical mass balance and enrichment factor reveal that REE, especially light REE, are so much enriched in the iron duricrust horizon (ion-adsorption REE deposit type). Some heavy REE are also enriched in the lower loose clayey horizon. This first survey has revealed that the weathering materials developed on granites in Biou area are favorable for further REE exploration.

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2021Article de revue

Provenance, nature, and U–Pb zircon geochronology of Ngaye rocks ( Adamawa‐Yadé Shield, Central Cameroon): New insights into the evolution of Archean crust within the Pan‐African belt

Gaëlle Sandra Assomo Ngono, Alembert Alexandre Ganwa, Sylvestre Martial Ntomba, Paul‐Désiré Ndjigui

Geological Journal

Petrographical, geochemical, and geochronological data obtained from Ngaye high‐grade metasedimentary rocks have contributed to determine the provenance, nature, and evolutionary history of the Adamawa‐Yadé Domain from the Archean to Pan‐African events. The rocks are migmatites formed after TTG and granitic crusts were reworked by partial melting at T = 683–994°C. Geochemical features, for example, low Rb/Sr ratio (0.03–0.53), high Cr/V, and Cr/Th ratios (9.91–100.75; 28.41–686.15), respectively, indicate that these samples were derived predominantly from a mafic crust source. The primordial mantle‐normalized spidergrams are characterized by negative Nb‐Ta anomalies, suggesting melting of crustal rocks. REE fractionation shown (La/Yb) N = 8.48–197.89) indicate melting of crustal source rocks (meta‐TTGs). Low Hf and Zr contents (0.95–5.65 ppm and 23–262.85 ppm, respectively), low Sr/Y ratios (9.17–200.65), and a positive correlation between Th/Sc and Zr/Sc, point to crustal reworking. U–Pb ages on detrital zircon in tonalitic and granodioritic gneisses indicate contribution of Mesoarchean and Paleoproterozoic sources and suggest a maximum deposition age during the Early Paleoproterozoic for their magmatic protoliths. Magmatic zircon grains of granodiorite, with a round shape, Th/U ratio values ranging from 0.02 to 1.23, and an oscillatory zonation yield post emplacement metamorphic ages at 2,077 Ma. The lower intercept ages obtained in this study, match the tectonic reworking of the crust during the Pan‐African event associated with partial melting due probably to regional‐scale shear zone activities and magmatic accretion of juvenile magmas.

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2021Article de revueAccès ouvert

Water Quality Assessment in the Bamoun Plateau, Western-Cameroon: Hydrogeochemical Modelling and Multivariate Statistical Analysis Approach

Zakari Mfonka, Amidou Kpoumié, Abdou Nasser Ngouh, Oumar Farouk Mouncherou, Daouda Nsangou, Felaniaina Rakotondrabe et 4 autre(s)

Journal of Water Resource and Protection

This study focuses on the geochemical and bacteriological investigation of surface and ground water in the Bamoun plateau (Western-Cameroon). During the period from September 2013 to August 2014, 71 samples were collected from two springs, one borehole, four wells and the Nchi stream for analysis of major elements. In order to obtain the characteristics of the various species of bacteria, 7 samples were selected. The analytical method adopted for this study is the conventional hydrochemical technic and multivariate statistical analysis, coupled with the hydrogeochemical modelling. The results revealed that, water from the zone under study are acidic to basic, very weakly to weakly mineralized. Four types of water were identified: 1) CaMg-HCO3; 2) CaMg-Cl-SO4; 3) NaCl-SO4 and 4) NaK-HCO3. The major elements were all listed in the World Health Organization guidelines for drinking water quality, except for nitrates which was found at a concentration > 50 mg /l NO-3 in the borehole F401. As for the hydrobiological aspect, the entire sample contained all the bacteriological species except for spring S301 and well P401. According to the hydrogeochemical modelling, the Gibbs model and multivariate statistical tests, the quality of surface and ground water of the Foumban locality is influenced by two important factors: 1) the natural factors characterized by the water-rock interaction, evapotranspiration/crystallization, 2) the anthropogenic factors such as: uncontrolled discharges of liquid and solid effluents of all kinds and without any prior treatment within the ground and the strong urbanization accompanied by lack of sanitation and insufficient care.

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2020Article de revue

TiO 2 –Zr–Th–Y–rare‐earth elements ore deposit in unconsolidated fine‐grained sediments from Tongo Gandima in the Bétaré Oya Gold district, Eastern Cameroon

Paul‐Désiré Ndjigui, Paola Raissa Bassanak Ongboye, François Ndong Bidzang

Geological Journal

Tongo Gandima is an area located in the southeastern part of the Bétaré Oya Gold district (Eastern Cameroon). Geochemical investigations on rare metals (TiO 2 , Th, Y, and rare‐earth elements [REE]) were carried out on sample types (source rocks, unconsolidated fine‐grained sediments, and concentrated sediments) using X‐ray diffraction (XRD), X‐ray fluorescence (XRF), inductively coupled plasma‐mass spectrometry (ICP‐MS), and scanning electron microscope equipped with EDAX spectrometer (SEM‐EDS) methods. In this study, five layers of river terraces were selected (organic matter layer, clayey layer, fine sandy layer, coarse sandy layer, and gravel layer). One of them, the gravel layer, is mineralized. TiO 2 , Zr, and REE are more enriched in monzonites than in granites. Unconsolidated sediments derive mainly from the erosion of weathered materials developed on monzonites and granites. The mineral assemblage of fine‐grained sediments from the gravel layer is muscovite, kaolinite, quartz, rutile, smectite, and others, and the average concentrations in Th, Zr, and Y are high. Fifty concentrated fractions from the same samples were analysed separately and their mineralogy is smectite, kaolinite, gibbsite, muscovite, quartz, rutile, anatase, zircon, titanomagnetite, and ilmenite. The heavy mineral fractions are opaque minerals, biotite, zircon, rutile, tourmaline, garnet, diopside, zoisite, and kyanite. TiO 2 , Zr, Th, Y, and REE contents are high. The REE oxides (REO) total grade ranges from 0.0088 to 15.66 wt%, marked by LREO‐abundance, especially in La 2 O 3 , Ce 2 O 3 , Pr 2 O 3 , and Nd 2 O 3 . The Tongo Gandima REO deposit was classified as LREO‐dominated type. The chondrite‐normalized REE patterns exhibit strong negative Eu anomalies; their V‐shaped patterns are typical of ore varieties. The abundant TiO 2 , Zr, Y, Th, and REE might have been influenced by surface processes (peneplanation and chemical weathering) and variations in sediment grain size. SEM‐EDS data reveal that apatite with Ce‐ and La‐dominant, monazite‐(Ce), and Ce‐Mn‐bearing ilmenite are rare metal‐bearing minerals. This study demonstrates that the economic importance of the alluvial‐fluvial placers from Tongo Gandima results from their high Ti, Zr, Th, Y, and REE contents.

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Paul Désiré NDJIGUI

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