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The bafoussam volcanic series:origin and evolution of the volcanism along the Cameroon volcanic line

Acta Geochimica 2022年第6期41卷 1049-1068页

作者： Philippe Essomba Gilles Chazot Nicaise Blaise Tchuimegnie Ngongang Arnaud Agranier Pierre Kamgang HervéBellon Philippe Nonnotte Pierre Wotchoko Innocent Badriyo Département Des Sciences de La Terre FacultéDes SciencesUniversitéde YaoundéIB.P.812YaoundéCameroun Geo-Ocean CNRSIfremerUMR6538Univ Brest29280PlouzaneFrance Département Des Sciences de La Terre FacultéDes SciencesUniversitéde DoualaDoualaCameroun Department of Geology Higher Teacher Training CollegeUniversity of BamendaBambiliBamendaCameroon Département de Séismologie et Géologie Observatoire Volcanologique de Goma-RDCGomaRépublique Démocratique du Congo

The bafoussam area in western Cameroon is part of the central Cameroon Volcanic Ligne(CVL).This study presents the mineralogy,major and trace element compositions,Sr-Pb-Hf isotopes,and new K-Ar geochronological data about mafic and felsic volcanic *** rocks belong to two different series:A transitional series made of basalts,basaltic andesite,and trachytes and an alkaline mafic series with basalts,hawaiites,and *** age data show that the transitional series belongs to the oldest part of the CVL and was emplaced between 47 and 35 *** alkaline volcanism is younger,with ages ranging from10 to 4.5 *** evolution in both series is accomplished through a fractional crystallization process,with the removal of olivine and clinopyroxene,while plagioclase does not seem to be a major crystallizing *** the samples are enriched in incompatible trace elements,but the rocks from the alkaline series have more fractionated REE patterns and high Nb content compared to the transitional mafic *** lavas have lower initial^(87)Sr/^(86)Sr and higher^(176)Hf/^(177)Hf and Pb isotopic ratios than the transitional *** La/Nb and high^(87)Sr/^(86)Sriratio are among chemical characteristics that show that some samples from the transitional series have interacted with a crustal component during their evolution in the *** cannot be used for discussing the mantle source of the volcanic rocks from this *** elements show that primary magmas for both series formed in a garnet-bearing mantle source,with higher partial melting degrees(3-5%)for the transitional magmas than for the alkaline magmas(bafoussam lavas formed from two different mantle *** magmas formed from a pyroxenite-bearing enriched mantle with low Pb isotopic *** mantle source is present in all the oldest lavas from the *** magmas formed from an HIMU-like mantle sourc

关键词： Cameroon Volcanic Line bafoussam Mafic volcanic rocks Felsic volcanic rocks Mantle source

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Petrochemical Characterization of Two Distinct Types of Dolerites from bafoussam Area, West Cameroon

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International Journal of Geosciences 2013年第8期4卷 1131-1144页

作者： Gus Djibril Kouankap Nono Pierre Wotchoko Sylvestre Ganno Divine Ngong Njinchuki Jean Paul Nzenti 1Department of Geology HTTC University of Bamenda Bamenda Cameroon 2Laboratory of Petrology and Structural Geology Faculty of Science University of Yaoundé I Yaoundé Cameroon Department of Geology HTTC University of Bamenda Bamenda Cameroon Economic Geology Unit Department of Geology University of Buea Buea Cameroon Laboratory of Petrology and Structural Geology Faculty of Science University of Yaoundé I Yaoundé Cameroon

Two petrochemical types of doleritic dykes have been distinguished in bafoussam area: 1) the olivine-bearing dolerites which are the most representative are dark green, showing characteristics of alkaline basalts and, 2) the calcite-bearing dolerites are grayish green, showing characteristics of tholeiitic basalts. The studied dolerites are less differentiated (1 FeOt/MgO 2);they present the evolution of a subalkaline magma following a calc-alkaline series (alkaline dolerites) and the tholeiitic series (tholeitiic dolerite). The chondrite normalized multielement spider diagrams of all the dolerites show a pronounced depletion in Ba, Th, and enrichment in Rb. Their geotectonic context is inferred to be intraplate and the contrast between the two types is probably due to a diverse source: crustal source for calcite-bearing dolerites and mantle source for olivine-bearing dolerites.

关键词： Doleritic Dyke Petrochemical Alkaline Tholeiitic Intraplaque bafoussam

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Hydrogeochemical Model and Water Quality of Groundwater in the Granito-Basaltic Fractured Rock Aquiferous Formations in bafoussam, West Region-Cameroon

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Journal of Water Resource and Protection 2018年第11期10卷 1148-1174页

作者： R. A. Akoachere T. A. Eyong M. O. Eduvie S. E. Egbe O. O. Yaya M. O. Nwude Department of Geology University of Buea Buea Cameroon National Water Resources Institute Kaduna Nigeria

This study determined the hydrogeochemical model of groundwater and groundwater domestic-agro-industrial quality in bafoussam using hydrogeochemical tools and physicochemical parameters: Ionic ratios, Gibbs diagrams, Piper diagrams, Durov diagrams and water quality indices. From physicochemical parameters;pH ranged from, 4.47 - 7.84;EC, 10 - 820 μS/cm;Temperature, 22.3°C - 29.5°C and TDS, 6.7 - 549.4 mg/L. The major ions fell below WHO acceptable limits. The sequences of major ionic abundance are: Ca2+ > Mg2+ > K+ > Na+ > NH+4, HCO-3 > Cl- > SO2-4 > NO3 > HPO2-4. Recharge by atmospheric precipitation, ion-exchange and simple dissolution processes are responsible for groundwater character, ionic content resulted from ion exchange and rock-weathering. Water types are Ca-HCO3 and Ca-Cl Hydrogeochemical facies are Ca-Mg-Cl-SO4 and Ca-Mg-HCO3. Domestic water quality was determined by use of pH, electrical Conductivity EC, total dissolved solids TDS, total Hardness HT and water quality index WQI. WQI values ranged from 0 - 42.09 and HT 67.89 - 339.01 indicating that water is of good domestic quality. Agro-industrial suitability of groundwater was determined using, sodium adsorption ratio SAR, permeability index PI, Magnesium adsorption ratio MAR, percent sodium %Na, Kelly’s ratio KR and Residual sodium carbonate RSC and Wilcox diagram;From irrigational water suitability parameters, SAR values ranged from 0.01 - 0 05;%Na 3.69 - 15.50;KR 0.005 - 0.023;PI 1.04 - 67.98;MAR 2.89 - 55.27;RSC -5.22 to -0.44 and Wilcox diagram indicate that inorganic groundwater content in the study area is excellent-good for irrigation;this is of significance since bafoussam a major agroindustrial zone in Cameroon and Central Africa is in the process of developing large scaled irrigation based agricultural projects dependent on use of surface and groundwater. Recharge from precipitation exchanges ions with the weathered country rocks and mixes with regional flow in a generally south-east north-w

关键词： Hydrogeochemical-Model Water-Quality Fractured-Rock-Aquifer bafoussam Cameroon

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