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Journal of Earth Science 2024年第1期35卷 16-28页

作者： Landry Soh Tamehe Huan Li sylvestre ganno Zuxing Chen Yanick Brice Lemdjou Safiyanu Muhammad Elatikpo School of Geosciences and Info-Physics Central South UniversityChangsha 410083China Department of Earth Sciences University of Yaounde IYaounde 3412Cameroon Institute of Oceanology Chinese Academy of SciencesQingdao 266071China Department of Geology Ahmadu Bello University ZariaZaria 810107Nigeria

The Bipindi iron ore district is located in the central section of the Nyong Complex at the northwestern margin of the Congo Craton in Southwest *** iron district contains numerous iron mineralization hosted by the Mewongo,Bibole,Kouambo,and Zambi banded iron formations(BIFs).These BIFs contain magnetite as the main iron ore mineral associated with pyrite,and gangue minerals are quartz with minor chlorite and *** origin of iron ore from these BIFs was investigated using a combination of in-situ magnetite and whole-rock *** studied BIF ore samples have a narrow range of TFe between 30.90 wt.%and 43.20 wt.%,indicating a low-grade *** geochemical signatures of magnetite such as low contents of base metals(e.g.,Cu,Co,V,and Zn)and low Co/Zn ratios600 and>75,respectively),we suggest that magnetite was derived from a mixture of seawater and~0.1%low-temperature hydrothermal fluids in an oxidizing ***,low-temperature hydrothermal and later metamorphic fluids were necessary for the transformation of the protolith Nyong Complex BIFs to iron ore.

关键词： banded iron formations iron ore geochemistry Congo Craton trace element composition LA-ICP-MS

喀麦隆西南部Mamelles条带状铁建造元素地球化学特征

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海洋科学 2024年第7期48卷 47-56页

作者： SOH TAMEHE Landry ganno sylvestre 陈祖兴 ROSIÈRE Carlos Alberto 中国有色桂林矿产地质研究院有限公司广西桂林541004 Department of Earth Sciences University of Yaounde I812 YaoundeCameroon 中国科学院海洋研究所山东青岛266071 Department of Geology Universidade Federal de Minas Gerais31270-901 Belo HorizonteMinas GeraisBrazil

Mamelles铁矿床位于喀麦隆南部刚果克拉通西北缘,距离克里比地区东南方向约20km。该矿床由大规模、高品位磁铁矿矿体组成,赋存于Nyong杂岩体的条带状铁建造(BIF)中。该矿床中的BIF与角闪岩和片麻岩相伴生。在详细的野外调查基础上,我们... 详细信息

Mamelles铁矿床位于喀麦隆南部刚果克拉通西北缘,距离克里比地区东南方向约20km。该矿床由大规模、高品位磁铁矿矿体组成,赋存于Nyong杂岩体的条带状铁建造(BIF)中。该矿床中的BIF与角闪岩和片麻岩相伴生。在详细的野外调查基础上,我们获取了BIF的全岩地球化学数据,并用以约束它们的物质来源和沉积环境。弱正铕(Eu)异常(δEu=2.14~3.55)表明高温热液流体对MamellesBIF的贡献是通过海底火山岩蚀变作用的方式,并有少量碎屑物质输入。正铈(Ce)异常的缺失表明,这些BIF可能沉积在缺氧的深海环境中,如火山弧或弧后盆地深水区。

关键词：刚果克拉通喀麦隆 Mamelles铁矿条带状铁建造地球化学

Depositional age and tectonic environment of the Gouap banded iron formations from the Nyong group,SW Cameroon:Insights from isotopic,geochemical and geochronological studies of drillcore samples

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Geoscience Frontiers 2021年第2期12卷 549-572页

作者： Landry Soh Tamehe Chongtao Wei sylvestre ganno Carlos Alberto Rosiere Jean Paul Nzenti Chesther Gatse Ebotehouna Guanwen Lu Key Laboratory of CBM Resources and Reservoir Formation Process Chinese Ministry of EducationChina University of Mining and TechnologyXuzhouJiangsu221116China Department of Earth Sciences University of Yaounde IP.O.Box 812YaoundeCameroon Department of Geology Universidade Federal de Minas Gerais31270-901Belo HorizonteMinas GeraisBrazil School of Civil and Environmental Engineering University of Science and Technology BeijingBeijing 100083China

The discovery of the Gouap banded iron formations(BIFs)-hosted iron mineralization in the northwestern of the Nyong Group(Ntem Complex)in southwestern Cameroon provides unique insights into the geology of this *** this contribution,we firstly report detailed study of geochemistry,isotopic and geochronology of well preserved samples of the Gouap BIFs collected from diamond *** Gouap BIFs consist mainly of amphibole BIFs and amphibole-pyrite BIFs characterized by dominant Fe_(2)O_(3)+SiO_(2)contents and variable contents of CaO,MgO and SO_(3),consistent with the presence of amphibole,chlorite,epidote and pyrite,formed during amphibolite facies metamorphism and overprinted hydrothermal *** amphibole–pyrite BIFs are typically enriched in trace and rare earth elements(REE)compared to the amphibole BIFs,suggesting the influence of detrital materials as well as secondary hydrothermal *** Post Archean Australian Shale(PAAS)-normalized REE–Y profiles of the Gouap BIFs display positive La,Eu anomalies,weak negative Ce anomalies,indicating a mixture of low-temperature hydrothermal fluids and relatively oxic conditions probably under relative shallow *** present here the first isotopic data of BIFs within the Ntem ***δ^(30)Si_(NBS28)values of the quartz from the Gouap BIFs vary from-1.5‰to-0.3‰and from-0.8‰to-0.9‰for the amphibole BIFs and amphibole–pyrite BIFs,*** quartz hasδ^(18)OV-SMOW values of 6.8‰–9.5‰(amphibole BIFs)and 9.2‰–10.6‰(amphibole–pyrite BIFs).The magnetite from the Gouap BIFs showsδ^(18)O values ranging from-3.5‰to-1.8‰and from-3‰to-1.7‰for the amphibole BIFs and amphibole–pyrite BIFs,***,the pyrite grains in the amphibole–pyrite BIFs displayδ34S values of 1.1‰–1.8‰.All isotopic data of the Gouap BIFs confirm that they might have precipitated from low-temperature hydrothermal fluids with detrital input distant from the volcanic *** to their geochemical and isotop

关键词： Gouap Banded iron formations Isotope geochemistry Zircon geochronology Ryacian period Brasiliano-Congo orogeny

Petrogenesis, LA-ICP-MS zircon U-Pb geochronology and geodynamic implications of the Kribi metavolcanic rocks,Nyong Group, Congo craton

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Acta Geochimica 2022年第3期41卷 470-495页

作者： Hermine Mvodo sylvestre ganno Gus Djibril Kouankap Nono Donald Hermann Fossi Philomene Estelle Nga Essomba Marvine Nzepang Tankwa Jean Paul Nzenti Department of Earth Sciences University of YaoundéIP.O.Box 812YaoundeCameroon Department of Geology HTTCUniversity of BamendaP.O.Box 39BambiliBamendaCameroon Institute for Geological and Mining Research P.O.Box 4110YaoundéCameroon Faculty of Mines and Petroleum Industries University of MarouaKaélé08MarouaCameroon

Metavolcanic rocks are well-exposed in the Kribi area within the Nyong Group, Congo craton, but their origin, age, and tectonic significance are poorly *** we report integrated field mapping and petrography,geochemistry, and LA-ICP-MS zircon U-Pb ages of these metavolcanic rocks to constrain their petrogenesis and geodynamic implications. The studied rocks consist of mafic granulite, garnet-amphibole gneiss, and garnet-biotite gneiss, and occur interbanded with sharp contact and intruded by syenite dyke. These metavolcanic rocks are classified as MORB-like tholeiitic to calc-alkaline basalts,basaltic andesite, and rhyodacite rocks with within-plate setting geochemical signatures. The metabasite rocks(basalt to basaltic andesite protolith) are likely the equivalent of a spinel peridotite product representing ~ 2–5 %partial melting of metasomatized mantle source, while the metarhyodacite rocks are derived from the fractional crystallization of the same parental magma. Zircon U-Pb data revealed that the rhyodacite rocks initially formed at2671 ± 51 Ma and underwent later metamorphism at2065 ± 55 Ma. The Neoarchean protolith age is comparable to the ca. 2628 Ma tholeiitic magmatism and ca.2666 Ma high-K granites, suggesting bimodal Neoarchean magmatic event within the Ntem Complex, while the metamorphic ages fall within the ca. 2100–2000 Ma highgrade tectono-metamorphic event attributed to Eburnean/Trans-Amazonian orogeny. At the regional scale,metavolcanic rocks with similar origins and ages are documented in the Sa o Francisco Craton in Brazil, suggesting comparable geodynamic evolution on both sides of the south Atlantic during the Paleoproterozoic.

关键词： Metavolcanic rocks MORB Within plate volcanic zone Mantle source Fractional crystallization Congo craton Cameroon

Geochemical constraints on the origin and tectonic setting of the serpentinized peridotites from the Paleoproterozoic Nyong series,Eseka area,SW Cameroon

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Acta Geochimica 2020年第3期39卷 404-422页

作者： Philomene Nga Essomba Tsoungui sylvestre ganno Evine Laure Tanko Njiosseu Jean Lavenir Ndema Mbongue Brice Kamguia Woguia Landry Soh Tamehe Jonas Didero Takodjou Wambo Jean Paul Nzenti Department of Earth Sciences University of Yaounde IP.O.Box 3412MessaYaoundeCameroon Department of Earth Sciences University of DschangP.O.Box.67DschangCameroon Key Laboratory of CBM Resources and Reservoir Formation Process Chinese Ministry of EducationChina University of Mining and TechnologyXuzhou 221116JiangsuChina

Serpentinized rocks closely associated with Paleoproterozoic eclogitic metabasites were recently discovered at Eseka area in the northwestern edge of the Congo craton in southern ***,we present new field data,petrography,and first comprehensible wholerock geochemistry data and discuss the protolith and tectonic significance of these serpentinites in the *** studied rock samples are characterized by pseudomorphic textures,including mesh microstructure formed by serpentine intergrowths with cores of olivine,bastites after *** constitutes almost the whole bulk of the rocks and is associated(to the less amount)with tremolite,talc,spinel,and ***-rock chemistry of the Eseka serpentinites led to the distinction of two *** 1 has high MgO(>40 wt%)content and high Mg#values(88.80)whereas Type 2 serpentinite samples display relatively low MgO concentration and Mg#values(50 ppm).This similarity,associated with the high Cr contents,spinel-peridotite protolith compositions and Mg/Si and Al/Si ratios imply that the studied serpentinites were formed in a subductionrelated *** U-shaped chondrite normalizedREE patterns of serpentinized peridotites,coupled with similar enrichments in LREE and HFSE,suggest the refertilized nature due to melt/rock interaction prior to *** on the results,we suggest that the Eseka serpentinized peridotites are mantle residues that suffered a high degree of partial melting in a subductionrelated environment,especially in Supra Subduction Zone *** new findings suggest that the Nyong series in Cameroon rep

关键词： Serpentinites Mantle peridotites Melt/rock interaction Paleoproterozoic suture zone Eseka area Nyong series Congo/Sao Francisco cratons

Geophysical and Geotechnical Investigations of a Landslide in Kekem Area, Western Cameroon

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International Journal of Geosciences 2012年第4期3卷 780-789页

作者： Pouyon Dieudonné Epada ganno sylvestre Tabod Charles Tabod University of Yaoundé I University of Yaounde I National Civil Engineering Laboratory

Geophysical and geotechnical surveys were conducted in the Western Cameroon (Kekem area) following a landslide on argillaceous material in order to understand the triggering processes and mechanisms of this landslide and to assess the stability of the slope. The geophysical soundings consisting of vertical electrical soundings with the Schlumberger electrode array configuration were carried out to monitor the behaviour of electrical resistivity in the landslide. Geoelectrical data showed a zone of low resistivity values identified as a clayey sand-filled aquifer. This aquifer played an important role in the triggering process of the landslide. Geotechnical soundings showed that the aquifer had a thickness of 7.0 m. The depth from the landslide crest level to the failure surface reached 3.0 m and 20.6 m. Laboratory tests were then carried out in order to evaluate the cohesion of the soil and the angle of internal friction, and to calculate the safety factor in view of making a stability analysis. The laboratory results exhibited a soil with low consistency, almost doughy. The mean value of the safety factor (1.4) been lower than the slope stability coefficient (1.5), revealed that the slope is unstable, likely to know at any moment a reactivation of the slide. This study showed that electrical soundings coupled with geotechnical surveys are useful tools for the characterization of landslides.

关键词： Landslide Resistivity Argillaceous Material Basal Undercutting Kekem Cameroon

Origin and intraplate tectonic setting of mafic magmatic enclaves from the Ngaoundal area,Adamawa-Cameroon:Insights from petrography and geochemistry

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China Geology 2022年第4期5卷 579-594页

作者： Aliou Mamouda sylvestre ganno Guy Tchoupe Takam Bertin Arnold Mbita Motto Steven Hermann Donald Fossi Jean Paul Nzenti Joseph Mvondo Ondoa Department of Earth Sciences University of YaoundéIYaoundéCameroon Institute for Geological and Mining Research(IRGM) YaoundéCameroon

In this contribution,detailed field descriptions together with petrographic and bulk-rock major,trace and rare earth elements(REE)data are used to constrain the origin and geodynamic setting of the mafic magmatic enclaves(MMEs)recently discovered within the Pan-African Ngaoundal pluton,Adamawa area,central *** investigated MMEs are dark-colored with chilled margins,and display medium to coarse-grain igneous *** mineral assemblage is either dominated by K-feldspar and carbonate(group Ⅰ),or by amphibole and plagioclase(group Ⅱ),though the overall mineral phases made of amphibole,plagioclase,K-feldspar,and biotite are similar to that of their host syenite but in different *** MMEs in Ngaoundal area are foid-gabbro in composition with SiO_(2) contents ranging between 41.52% and 43.74% and are contiguous with their host granitoids of intermediate composition(SiO_(2)=57.52% to 58.98%).The host granitoid rocks are metaluminous,and belong to the shoshonitic *** and geochemical data have revealed that the Ngaoundal MMEs derived from rapid cooling of hot injected lithospheric mantle-derived magma within cooler host granitoids magma and were emplaced in the intraplate geodynamic setting.

关键词： Mafic magmatic enclaves(MMEs) Granitoids Lithospheric mantle REE Intraplate Adamawa-Cameroon

Geochemistry and zircon U–Pb ages of the Paleoproterozoic ultramafic rocks of the Mbi Valley, Boali area, Central African Republic

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Acta Geochimica 2022年第3期41卷 515-535页

作者： Evine Laure Njiosseu Tanko Prince Emilien Danguene Philomene Nga Essomba Tsoungui sylvestre ganno Jonas Didero Takodjou Wambo Bertin Guy Takam Tchoupe Gus Djibril Kouankap Nono Timoleon Ngnotue Boniface Kankeu Jean Biandja Jean Paul Nzenti Department of Earth Sciences University of DschangP.O.Box 67DschangCameroon Department of Earth Sciences University of BanguiP.O.Box 908BanguiCentral African Republic Department of Mining Engineering and Mineral Processing School of Mines and Petroleum IndustriesUniversity of MarouaP.O.Box 08Kaélé-MarouaCameroon Department of Earth Sciences University of YaoundéIP.O.Box 812YaoundéCameroon Department of Geology HTTCUniversity of BamendaP.O.Box 39BambiliBamendaCameroon Institute for Geological and Mining Researches(IGMR) P.O.Box 4110YaoundéCameroon

This paper investigates the geochemistry of bulk rock and infers the petrogenesis of ultramafic rocks in the Boali Precambrian terrane in Mbi Valley,in the North of the Central African Republic(CAR).The studied rocks comprise coarse primary olivine and orthopyroxene relics(dominant phase),magnesio-hornblende,magnetite,and ***-rock analysis indicates low SiO_(2)(average of 43.14 wt%)and high MgO(19.84–26.98 wt%)contents and their Mg number(Mg#)ranges from 74 to ***(526–865 ppm),Cr(1500–3680 ppm)***(Na_(2)O-K_(2)O)-FeO-MgO)and ACM(Al_(2)O_(3)-CaO-MgO)ternary diagrams have revealed that the studied samples correspond to arc-related ultramafic ***-normalized REE plots display an increasing trend from La to Sm(CeN/SmN:0.74–1.81),weak negative to no Eu(Eu/Eu*=0.72–1.05)and strong negative Ce(Ce/Ce*=0.33–0.98)*** mantle normalized of multi-element diagrams exhibit LREE enrichment and large ion lithophile elements(LILE)relative to high field strength elements(HFSE),and notable negative anomalies in *** suggests the generation of the parent melt by slab dehydration and wedge melting *** addition,incompatible trace element composition and ratios assumed that the source magma had an enhanced mantle source associated with a prominent influence of continental *** of mantle wedge by plate-dehydrated,LILE-rich fluids and the incorporation of sediments derived from subduction explain the enhancement of the *** major and trace element compositions jointly with the tectonic reconstruction of this region and LA-ICP-MS U–Pb data on zircon constrain the emplacement age at ca.2099 Ma in a continental margin arc setting involving subduction of an oceanic plate beneath the continental lithosphere,dehydration of the slab and mantle wedge *** result intimate that the remnants of Paleoproterozoic oceanic crust or subduction event and subsequent basins closure extended from

关键词： Atlantic supercontinent Central African Republic Ultramafic cumulate LILE-enriched fluids Arc setting

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

Contrasting Depositional Environment of Iron Formation at Endengue Area, NW Congo Craton, Southern Cameroon: New Insights from Trace and Rare Earth Elements Geochemistry

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International Journal of Geosciences 2021年第3期12卷 280-306页

作者： Robinson Tchatchueng Timoléon Ngnotué Evine Laure Tanko Njiosseu sylvestre ganno Hervé Wabo Jean Paul Nzenti Department of Earth Sciences University of Dschang Dschang Cameroon Department of Earth Sciences University of Yaoundé Yaoundé Cameroon Department of Geology University of Johannesburg Auckland Park South Africa

The Endengue Banded Iron Formation (BIF) is located in the northwestern edge of the Congo craton in Cameroon. Here, we report geochemical data of trace and rare earth elements (REE) of the Endengue BIF samples from the Archean Ntem complex and investigate their environmental setting. Two types of BIF occur at Endengue area, both containing minimal contamination from terrestrial material. Total REE (ΣREE) contents in the Type 1 BIF are extremely low, ranging from 0.34 to 1.83 ppm, similarly to pure chemical sediments while Type 2 BIF displays ΣREE contents ranging from 2.98 to 24.26 ppm. The PAAS-normalized REE + Y patterns of the two BIF types display LREE enrichment relative to HREE and weak positive Eu anomaly, most likely suggesting that the source of iron and siliceous of the Endengue BIFs is mainly from the contribution of low-temperature hydrothermal alteration of the crust. Type 1 BIF shows very low Nd content (* and positive Ce anomalies which suggests suboxic or anoxic seawater similar to the depositional environment of Elom BIF in Archean Ntem complex. In contrast, Type 2 BIF displays low to moderate Nd contents (1 and 100 ppm with the exception of sample LBR65) with negative correlation between Nd and Ce/Ce* and negative Ce anomalies. These features indicate precipa

关键词： Endengue BIFs Suboxic or Anoxic Oxic Depositional Environment Ntem Complex