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Gold Behavior in Weathering Products of Quartz Vein in Mintom Area South Cameroon(Central Africa)

International Journal of Geosciences 2013年第10期4卷 1401-1410页

作者： Aurelien Manfred Mbenoun Gilbert Francois Ngon Ngon elie constantin bayiga Rose Yongue Fouateu Paul Bilong Department of Earth Science Faculty of SciencesUniversity of DoualaDoualaCameroon Department of Earth Science Faculty of SciencesUniversity of YaoundeYaoundeCameroon

Gold mineralization in Mintom area, south Cameroon was studied in a tropical forest setting using X-ray diffraction, inductively coupled plasma-atomic emission spectrometry (ICP/AES) and inductively coupled plasma-mass spectrometry (ICP/MS) respectively for the mineralogical and chemical data. The mineralization occurs in quartz veins in the archean Ntem complex of the vast Congo Craton in Central Africa. Gold distribution patterns were vertically studied in the different horizons of the weathering profile and in the different grain-size fractions of the materials sampled in the pit on down slope of the interfluve where the mineralization exists. The weathering profile consists of an upper, thin loose sandy-clayey horizon (P6) covered by a light humic horizon, a nodular horizon with lateritic nodules or blocks (P5), a gravel horizon (P4), a thin spotted horizon (P3) and a saprolite (P2) up to 1.4 m thick. The specific geochemical signature of the bedrock is not recognized in each horizon of the weathering profile. Some groups of elements, e.g., high SiO2 and low REE characterize quartz vein while Cr-Ni characterizes a basic rock like gabbro. The residual gold is concentrated at the base of weathering profile. Its concentration increases from the saprolite up to the gravel horizon and decreases in the surface horizons. However, the evolution of visible Au distribution is not the same for all grain-size fractions: 1) in the finest fraction, the Au content is only regular in spotted and gravel horizons;2) in the medium size fractions, the Au is in high content and greatly decreases from saprolite up to the spotted horizon and disappears in the upper horizons;3) in the coarsest fraction, Au content is found in the saprolite and the maximum Au content of the weathering profile is found in this layer just above the mineralized quartz vein. This observation shows that the Mintom residual gold comes from the quartz vein.

关键词： Geochemical Gold Laterites Mintom Quartz Veins Weathering

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Ore Texture,Mineralogy and Whole Rock Geochemistry of the Iron Mineralization from Edea North Area,Nyong Complex,Southern Cameroon:Implication for Origin and Enrichment Process

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International Journal of Geosciences 2017年第5期8卷 659-677页

作者： Bravo Martin Mbang Bonda Jacques Etame Arnaud Patrice Kouske elie constantin bayiga Gilbert Francois Ngon Ngon Simon Joel Mbai Martine Gerard Department of Earth Sciences Faculty of ScienceUniversity of DoualaDoualaCameroon Department of Civil Engineering The University Institute of TechnologyUniversity of DoualaDoualaCameroon IRD UMR 161 CEREGEInstitut de mineralogie et physique des milieux condensesParisFrance

This study presents the ore texture, mineralogy and whole rock geochemistry of iron occurrence from the Edea North area located at the upper limit of the Nyong Unit, part of the Congo craton. This iron mineralization is of magnetite quartzite type enclosed by metamorphic rocks of the granulite facies. Two main facies have been identified over the study area including the banded and the massive facies. The mineralogical set of these facies is in majority represented by magnetite, quartz and pyroxene martite in addition to minor biotite, apatite, and amphibole. Magnetite presents as irregular and elongated minerals which can contain quartz inclusions of various shapes and sizes, as blasts clustering, around pyroxenes and isolated xenomorphic magnetite minerals in the silicate phases. Quartz varies from fine to coarse-grained and ribbon quartz. This indicates re-crystallization and deformation during metamorphism. Electron microprobe analysis on magnetite and martite show Fe2O3 contents that vary between 96.11 and 99.76. Whole rock chemical data showed that Fe-contents are as high as 62.9 wt%. The SiO2 content varies between 33.8 wt% and 51.2 wt%. Iron oxides and SiO2 are negatively correlated. Moreover, the low positive correlations between Al2O3 and HFSE, and LILE suggest a contribution of clastic materials in the protolith of studied materials. The samples show low contents of V, Cr, Ba, Zr with respect to igneous rocks. This may infer a sedimentary origin for the studied rocks;furthermore, these materials may have undergone hydrothermal alteration. The REE patterns reveal enrichment in LREE compared to HREE. Some samples show positive Eu (1.82) and other negative anomalies Eu (0.54 to 0.97). The lack of Ce anomalies suggests that the depositional environment of the Edea North iron occurrence was anoxic or suboxic. Overall, the Edea North iron occurrence may have undergone significant input from hydrothermal sources with imprints of the clastic during its deposition

关键词： Magnetite Texture Edea North Nyong Complex Southern Cameroon

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Lixiviation of Open-Coast Dumping Site and Pollution of Water and Soils of Edea Industrial Zone（Littoral-Cameroon）

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Journal of Environmental Science and Engineering(B) 2013年第5期2卷 289-298页

作者： Noa Tang Sylvie Nguene Feudoung Daniel Etame Jacques bayiga elie constantin Bilong Paul Department of Earth Sciences Faculty of Sciences University of Douala Douala 24157 Cameroon Department of Earth Sciences Faculty of Sciences University of Yaounde I Yaounde 812 Cameroon

The nexus between water, food and energy is one of the most fundamental relationships and challenges for society. Indeed, seepage of wastes stored into dumping sites of Edea township, favor their lixiviation. Soluble components of matter are slowly dissolves, drained by meteoric water and flowed into tail bay vicinity. Knowledge of trace and toxic metal concentrations in the biotic matrices is important for assessing the effects of pollutants and the risk of exposure. In this study, A1, Mn, Cd, Cr, Cu, Pb and Zn were quantified respectively in 33 samples of soil and water, using ICP-MS （Inductively Coupled Plasma Mass Spectrometry）, Pb were found between 1.38-88.28 mg/L. Higher concentrations of Al were found in Alucam industrial wastes （315,502.33 mg/kg）, and in Hysacam domestic wastes （54,126.93 mg/kg）. Concentrations of Cd （1.955 mg/kg）, Pb （469.00 mg/kg） and Zn （853.00 rng/kg） are higher in domestic wastes. The ones of Mn （696.96 mg/kg） and Cu （1,320.10 mg/kg） are higher in industrial wastes. Higher concentrations of Pb and Cu let assume that it is a risk of poisoning relative to these elements around this area. These findings illustrate that lixiviation of dumping wastes has great influence on water and soils pollutions of the study ecosystem.

关键词： Dumping site lixiviation metallic trace elements pollution chemical intoxications

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Morpho-Structural Mapping Constraints from Geophysical and Test Pit Investigations: Case Study of the Bomkoul Locality in Douala Sedimentary Basin, Cameroon, Central Africa

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Journal of Geoscience and Environment Protection 2019年第10期7卷 136-153页

作者： Michel Bertrand Mbog Jean Victor Kenfack Gilbert François Ngon Ngon Bernard Tassongwa elie Constant bayiga Jacques Etame Department of Earth Science Faculty of ScienceUniversity of DschangDschangCameroon Department of Earth Science Faculty of ScienceUniversity of DoualaDoualaCameroon

A survey using the electrical resistivity and test pit methods is carried out in the Douala subbasin in order to investigate the sub-surface layering and evaluate the thickness of each layer through the variation of the resistivity with the depth. Applying the Schumberger array, a total of 48 vertical electrical sounding is conducted along 8 profiles directed W-E and using traditional method, 25 test pits with depth between 15 and 19 meters are done. Qualitative interpretation is carried out through the resistivity and test pit maps. The test pit maps reveal the presence of the following layers: The first layer of thickness varies from 0.2 to 2.0 m (average of 1.9 m). The thickness of the second layer varies between 0.2 and 4.0 m with an average of 2.8 m. The thickness of the third layer is between 2.0 and 4.0 m with an average of 3.8 m. That of the fourth and fifth layers ranges respectively between 4.0 and 6.0 m (average of 5.4 m) and between 2.0 and 6.0 m with an average of 4.4 m. Isoresistivities maps from resistivities computed for different AB/2 values (1.5;4.4;13.5;19;27.5;58 m) are generally characterized by the apparent resistivities which define many domains in function of the AB/2 values. The superficial layer is characterized by electric resistivity values ranging from 720 to 2073 Ωm for AB/2 = 1.5 m and probably represents pedologic materials. For other values of AB/2, resistivity varies from 253 to 32,381 Ωm (AB/2 = 4.4 m), 0.1 to 1838 (AB/2 = 13.2 m) with an average of 341 Ωm, 0.3 to 1608 Ωm (AB/2 = 19 m) with an average of 279 Ωm, 6.4 to 1427 Ωm (AB/2 = 27.5 m) with an average 291 Ωm, and 19.7 to 3555 Ωm (AB/2 = 58 m) with an average of 850 Ωm. These different values of resistivity represent the sedimentary materials.

关键词： Douala Sub-Basin Isoresistivity Map Test Pit Sedimentary Materials Thickness

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