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Geochemistry and Geochronology of Peraluminous High-K Granitic Leucosomes of YaoundéSeries (Cameroon): Evidence for a Unique Pan-African Magmatism and Melting Event in North Equatorial Fold Belt

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International Journal of Geosciences 2012年第3期3卷 525-548页

作者： Ngnotue Timoleon Ganno Sylvestre nzenti jean paul Schulz Bernhard Tchaptchet Tchato Depesquidoux I Suh Cheo Emmanuel Department of Earth Sciences University of Yaoundé I P.O. Box. 3412 Messa-Yaoundé Department of Geology University of Buea P.O. Box. 63 Buea-Cameroon Department of Geology University of Dschang P.O. Box. 67 Dschang-Cameroon Institut für Mineralogie TU Bergakademie Brennhausgasse 14 09596 Freiberg/Sachsen Germany

Geochemical and geochronological studies have been carry out on the leucosomes of Yaoundé series with the aims to identify the magma sources and to indicate their production periods and emplacement within the formations of the Pan-African North-Equatorial Fold Belt (PANEFB) in Cameroon. The Yaoundé series belongs to the Southern domain of the PANEFB and it is composed of migmatites in which two types of granitic leucosomes (in situ leucosomes and injected leucosomes) have been distinguished. These rocks display characteristic of calc-alkaline (in situ leucosomes) and high-K calc-alkaline to shoshonitic series (injected leucosomes). All the rocks are peraluminous with in situ leucosomes conform to S-type and injected leucosomes conform to I- and S-type granitoids. Major and trace elements composition reveal that in situ leucosomes derived from the partial melting of the host metapelite whereas injected leucosomes derived from the melting of metagreywacke. These sources are similar to those of granitoids from central and northern domains of the PANEFB. Th-U-Pb dating by electron microprobe (EMP) and LA-ICP-MS U-Pb dating on zircon have been used to constraints the melting event and emplacement of leucosomes in Yaoundé series. Th-U-Pb monazite dating, undertaken in two samples of leucosomes, gives two groups of monazite ages. The older group gives an age of 658 Ma whereas the age of younger group is 592 Ma. U-Pb dating of zircons from the leucosomes reveals a Pan-African age ranging from 626 to 654 Ma whereas zircons from metapelitic host rock reveal the overprinting of an early Pan-African event 911 - 1127 Ma on Palaeoproterozoic (2127 Ma) inheritance. These data clearly indicate that the host rocks of leucosomes of Yaoundé series have been firstly metamorphosed during Tonien-Stenien period (911 - 1127 Ma) and reveal the existence of extended unique melting event (592 and 658 Ma) in the Yaoundé series which is contemporaneous with the magmatism responsible for the emp

关键词： Pan-African North-Equatorial Fold Belt Yaoundé Series EMP Monazite Dating LA-ICP-MS U-Pb Dating Leucosomes Peraluminous Melting Event Magmatism

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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

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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

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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

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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

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On the Contribution of Wu Wen-Tsün to Algebraic Topology

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Journal of Systems Science & Complexity 2019年第1期32卷 3-36页

作者： BRASSELET jean-paul I2M (CNRS)-Aix-Marseille University

The aim of this article is to present the contribution of Wu Wen-Tsün to Algebraic Topology and more precisely to the theory of characteristic classes. Several papers provide complete and welldocumented biography and academic career of Wu Wen-Tsün, in particular, Hudecek, 2014; O'Connor and Robertson, 2006; Wen-Tsün Wu's Academic Career, 2006; Selected works of Wen-Tsun Wu, *** author does not repeat the details provided in these papers concerning the Wu Wen-Tsün's bibliography, we will just mention people involved in the Wu Wen-Tsün's period in *** addition to Wu Wen-Tsün's papers, the Dieudonné's book(Dieudonné, 1960) provides an excellent presentation of main results of Wu Wen-Tsün in Algebraic and Differential Topology. The author will use and abuse of this book(and refer to) when *** the introduction, the author recalls mainly historical facts concerning the contribution of Wu Wen-Tsün to Algebraic Topology. The second section shows speci?cally the contribution of Wu WenTsün to the Stiefel-Whitney classes and introduces the third section, dealing with the(real) Wu *** author provides de?nition, properties as well as further developments and generalizations of the Wu classes. The fourth and ?fth sections are devoted to recent applications: In Cobordism theory and in Mathematical Physics. The author notices that Wu classes have been used as well in other domains,in particular surgery theory(Madsen and Milgram, 1979). The last section concerns the complex Wu classes and shows that the more recent Mather classes coincide with the previously de?ned complex Wu classes, that is a result from Zhou(1994)(see also Liu, 1996).This article is devoted to the contribution of Wu Wen-Tsün to the theory of Characteristic Classes,which coincides with his "French period"(1947–1951). However, speaking of Algebraic Topology, it is worthwhile to mention the important contribution of Wu Wen-Tsün to the Theory of realization of complexes or manifolds in Eucl

关键词： Algebraic topology characteristic class cobordism theory mathematical physics Wu Class

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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

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Microbiota-host interplay at the gut epithelial level,health and nutrition

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Journal of Animal Science and Biotechnology 2017年第2期8卷 327-334页

作者： jean-paul Lallès Division of Human Nutrition Division INRA Clermont-Ferrand France Human Nutrition Research Center-West Nantes France

Growing evidence suggests the implication of the gut microbiota in various facets of health and disease. In this review, the focus is put on microbiota-host molecular cross-talk at the gut epithelial level with special emphasis on two defense systems： intestinal alkaline phosphatase（IAP） and inducible heat shock proteins（iHSPs）. Both IAP and iHSPs are induced by various microbial structural components（e.g. lipopolysaccharide, flagellin, CpG DNA motifs）,metabolites（e.g. n-butyrate） or secreted signal molecules（e.g., toxins, various peptides, polyphosphate）. IAP is produced in the small intestine and secreted into the lumen and in the interior milieu. It detoxifies microbial components by dephosphorylation and, therefore, down-regulates microbe-induced inflammation mainly by inhibiting NF-κB pro-inflammatory pathway in enterocytes. IAP gene expression and enzyme activity are influenced by the gut microbiota. Conversely, IAP controls gut microbiota composition both directly, and indirectly though the detoxification of pro-inflammatory free luminal adenosine triphosphate and inflammation inhibition. Inducible HSPs are expressed by gut epithelial cells in proportion to the microbial load along the gastro-intestinal tract. They are also induced by various microbial components, metabolites and secreted molecules. Whether iHSPs contribute to shape the gut microbiota is presently unknown. Both systems display strong anti-inflammatory and anti-oxidant properties that are protective to the gut and the host. Importantly, epithelial gene expressions and protein concentrations of IAP and iHSPs can be stimulated by probiotics, prebiotics and a large variety of dietary components, including macronutrients（protein and amino acids, especially L-glutamine, fat, fiber）, and specific minerals（e.g. calcium）and vitamins（e.g. vitamins K1 and K2）. Some food components（e.g. lectins, soybean proteins, various polyphenols） may inhibit or disturb these systems. The general cel ular and molecula

关键词： Diet Gut Inducible heat shock protein Inflammation Intestinal alkaline phosphatase Microbiota

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Single-particle cryo-EM: beyond the resolution

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National Science Review 2019年第5期6卷 864-866页

作者： jean-paul Armache Yifan Cheng Department of Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences Pennsylvania State University Howard Hughes Medical Institute University of California San Francisco Department of Biochemistry and Biophysics University of California San Francisco

Structural biology aims to provide structural insights into our understandings of biological processes at the atomic *** structures of biological macromolecules are often determinedby one of the three major methods:Xr... 详细信息

关键词： Single-particle cryo-EM beyond the resolution

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G~n filling orbicular N-sided holes using periodic B-spline surfaces

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Science China(Information Sciences) 2011年第7期54卷 1383-1394页

作者： paul jean-Claude School of Software Tsinghua University Key Laboratory for Information System Security Ministry of Education of China Tsinghua National Laboratory for Information Science and Technology Institute National de Recherche en Informatique et en Automatique

The orbicular N -sided hole filling problem is usually introduced by filleting an end-point of a part with large *** existing methods based on quadrilateral partition or constrained-optimization can rarely generate high-order continuous blending surfaces under these *** paper first reparameterizes the boundary of the specified orbicular N -sided hole to ensure the compatibility of neighboring cross-boundary derivatives on the connecting points,preserving their G n *** we compute the control points of the periodic B-spline surface using the sufficient G n continuity condition on the pole and the algorithm of extending parametric *** method generates single blending surface,which can be converted into standard Bspline surface by adding knots without introducing *** only elevates the degree of the boundary by *** construction method is simple and efficient,without iteration nor large-scale matrix *** achieves G n continuity under compatible *** blending examples underline its feasibility and practicability.

关键词： CAD periodic B-spline surface polar coordinates N -sided hole filling G n continuity

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