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Xenoliths Evidence of Alkaline Magmatic Infiltrations Beneath Lake Nyos (Cameroon Volcanic Line, West Africa)

Open Journal of Geology 2022年第6期12卷 433-459页

作者： merlin isidore teitchou Joseph Legrand Tchop Michel Grégoire Pauline Wokwenmendam Nguet Eddy Ferdinand Mbossi Jacques Dili-Rake Joseph Victor Hell Institute for Geological and Mining Research Buea Cameroon Geosciences-Environnement Toulouse Toulouse France

Xenoliths enclosed in Lavas of the Nyos volcano (Cameroon Volcanic Line, continental sector) range from fertile lherzolites to harzburgites. One spinel-free wehrlite has been also sampled. The occurrence of phlogopites and pargasites in some harzburgites together with specific textural rock-type (lherzolites transitional porphyroclastic to equigranular), including major and trace element compositions both in peridotites bulk rocks and minerals point out interactions between the mantle and basaltic magmas responsible for the formation of wehrlites beneath the Nyos volcano. Hydrous minerals (phlogopites and pargasites) and metasomatic events are their main petrogeochemical signatures different from group 1 samples which are characterized by spoon-shaped REE patterns. Later on, hydrous phases, Ti-rich Cpx, CaO rich Ol, Ti, and V rich Ol wehrlite precipitated from melt enrichments due to the percolation of the mantle by basaltic magmas of alkaline affinity. The metasomatic liquid which percolates the Nyos mantle column was a dense alkaline silicate rich in volatile, displaying low HFSE abundances in the metasomatic hydrous melts compared to the LILE. It is suggested that Nyos mantle peridotites have experienced: 1) variable metasomatic events related to the percolating of the depleted mantle by a alkaline silicate liquid, 2) the spinel-free wehrlite is a group 2 sample corresponding to a cumulate of a similar melt, 3) amphibole may be a potassium-bearing mineral instead of or in addition to phlogopite at shallower levels of Nyos upper mantle and 4) transitional textural rock facies express also the fingerprint of rising mantle plume which were percolated by alkaline magma during their transit to the surface.

关键词： Nyos Wehrlites Hydrous Minerals Alkaline Silicate Melt Percolation

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Upper Mantle Dynamic and Evolution beneath Lake Nyos Volcano (Cameroon Volcanic Line), Documented by Peridotite Xenoliths Enclosed in Alkali Basalts

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International Journal of Geosciences 2022年第6期13卷 438-463页

作者： merlin isidore teitchou Joseph Legrand Tchop Michel Grégoire Eddy Ferdinand Mbossi Pauline Wokwenmendam Nguet Sahabo Aboubakar Abdoulaye Ateba Bekoa Institute for Geological and Mining Research Buea Cameroon Geosciences-Environnement Toulouse UMR Toulouse France

Volcanic deposits from the lake Nyos contain ultramafic xenoliths: lherzolites, harzburgites and wehrlites, sometimes containing amphiboles and phlogopites. The lithospheric mantle beneath Nyos, as inferred from chemical diagrams, has experienced partial melting and variably cryptic and modal metasomatism of the two groups of samples that have been distinguished: Group 1 samples are characterized by spoon-shaped REE patterns, and Group 2 samples show light (L) REE-enriched patterns. Metasomatic events were associated with pervasive infiltration of volatile (Ti, CO2, H2O) or alkali-rich small melts fractions and fluids. Later on, hydrous phases, Ti-rich Cpx, CaO-rich Ol, Ti-rich Ol, Cr poor and low values of NiO and FO (%) in wehrlite compared to other xenoliths, precipitated from alkali enrichments due to the percolation of the mantle by basaltic magmas. The metasomatic liquid which percolates the Nyos mantle column was a dense alkaline silicate rich in volatile, displaying low HFSE abundances in the metasomatic hydrous melts compared to the LILE. It is suggested that 1) cryptic metasomatism affected Group 1 samples, 2) the spinel-free wehrlite is a Group 2 sample corresponding to a cumulate of a similar melt and 3) amphibole may be a potassium-bearing mineral in addition to phlogopite at shallower levels of Nyos upper mantle. P-T estimated indicates that xenoliths were initially equilibrated in the garnet stability field, at depth of 85 Km, and then they were re-equilibrated in the spinel field owing to isobaric heating up to 1000℃. Adiabatic decompressions occur from 85 to 50 Km materialized by sample NK14 showing transitional porphyroclastic to equigranular texture and displaying pyroxene-Cr spinel symplectites, and from 50 to 30 Km corresponding to 8 - 18 Kbar, pressures in which most xenoliths were incorporated in the host lavas. Therefore, the presence of rising mantle plumes from 85 to 50 Km (sample NK14) and from 50 to 30 Km

关键词： Nyos Xenoliths Metasomatism P-T Estimated Mantle Diapirs Rift-Zones

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Magmatism of the Beka Volcanic Massifs (Cameroon Volcanic Line, West-Central Africa): New Petrographical and Mineralogical Data

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Journal of Geoscience and Environment Protection 2022年第7期10卷 198-228页

作者： Jacques Dili-Rake Sahabo Aboubakar Abdoulaye Joseph Legrand Tchop merlin isidore teitchou Christian Mana Bouba Oumarou Faarouk Nkouandou Daouda Dawaï Eddy Ferdinand Mbossi Research Centre for Geophysics and Volcanology Institute of Geological and Mining Research Buea Cameroon Faculty of Sciences University of Maroua Maroua Cameroon Centrer for geological and Mining Research Institute of Geological and Mining Research Garoua Cameroon Faculty of Sciences University of Ngaoundere Ngaoundere Cameroon

The Beka volcanic massifs are located northeast of Ngaoundere region, within the Adamawa plateau. It consists mainly of basanites, trachytes and phonolites. The petrographic study shows that all the basanite lavas have porphyritic microlitic textures with a more pronounced magmatic fluidity than the felsic lavas displaying trachytic textures. The lavas are composed of phenocrysts, microlites and microphenocrysts of olivine, clinopyroxene, plagioclase and iron-titanium oxides for the basanites and of greenish clinopyroxene, alkali feldspar, and titanomagnetite for the felsic lavas. Chemical microprobe analysis indicates that the olivine crystals are magnesian (Fo73-78). Clinopyroxene crystals have a composition of diopside (Wo47-) in the basaltic lavas and diopside near the hedenbergite pole in the trachytes phonoliths and titanomagnetite (TiO2: 21.13% - 22.36% and FeO: 68% - 68%). Chemical analyses on whole rocks show that all the lavas belong to the same series and the felsic lavas come from the differentiation of basanite lavas by fractional crystallization of the minerals therein. The basanites originate from a low rate of partial melting of an OIB-type mantle. Contamination and mixing processes are suspected. Lavas of similar composition are found in other volcanic centres of the Adamawa plateau and the continental and oceanic sectors of the Cameroon Volcanic Line, in particular the Kapsiki plateau, Mounts Cameroon and Bamenda.

关键词： Cameroon Volcanic Line Adamawa Plateau Beka Volcanic Massif Fractional Crystallization OIB-Type Mantle

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New Data on the Genesis and Evolution of the Primitive Magmas of Mount Cameroon: Contribution of Melt Inclusions

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Journal of Geological Research 2020年第4期2卷 46-61页

作者： Legrand Joseph Tchop Pauline Wokwenmendam Nguet Benjamin Ntieche Victor Metang Jacques Dili Rake merlin isidore teitchou Jacqueline Vander Auwera Georges Emmanuel Ekodeck Charles Nkoumbou Department of Earth Sciences Faculty of SciencesUniversity of YaoundéIPO Box 812 YaoundéCameroon Geophysical and Volcanological Research Unit Institute of Geological and Mining ResearchPO Box 370 BueaCameroon Higher Teacher Training College University of Yaounde1 PO Box 812 YaoundéCameroon Deparement de Geology University of Liège B-4000 Sart-TilmanBelgium

Mount Cameroon is a Plio-Quaternary volcanic massif, without a centralcrater, made up of more than 140 pyroclastic cones. It is one of theactive volcanoes of the Cameroon Volcanic Line. Mount Cameroon meltinclusions are found in microdroplets trapped in the early minerals (olivines)from the pyroclastic products. The analysis of these melt inclusions allowedus to find primitive liquids compared to lavas. Major elements study ofthe magmatic inclusions, trapped in the most magnesian olivines (Mg#84-86) of Mount Cameroon revealed “primitive” liquids of basanite and alkalibasalt type with variable composition compared to the much more uniformbasalts of the magmatic series of Mount Cameroon. The study of thesetrapped liquids shows that: (1) the original primitive lavas did not undergothe process of evolution by FC, but rather underwent fundamentally (orexclusively) the process of partial melting;(2) the emitted lavas, evolvedessentially by FC;(3) the variations in the trace element contents of theprimitive liquids directly reflect a variation in the rate of partial melting ofa homogeneous mantelic source. The very high La/Yb ratios of the MountCameroon melt inclusions (> 20) characterize a garnet lherzolite *** of the melt inclusions show a negative anomaly or depletion in K,Rb and Ba as those of HIMU. The “primitive” liquids and lavas of MountCameroon represent a co-genetic sequence formed by varying degrees ofpartial melting of a source considered as homogeneous.

关键词： Primitive magma Partial melting Fractional crystallization Alkali basalt Mount Cameroon Active volcano

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REDISSE in Benin and Lessons Learned for the Management of Public Health Emergencies after Five Years of Implementation

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Open Journal of Epidemiology 2024年第3期14卷 493-507页

作者： Fidelia Hinson Arthur Dagan Dorine Laura Danmitondé Blaise Hounyo isidore Domanou David Houéto REDISSE Project Cotonou Benin School of Public Health University of Parakou Parakou Benin

Introduction: Benin was embarked on phase 3 of the REDISSE Benin project (Regional Disease Surveillance Systems Enhancement) which began in 2018. The objectives were in five key components namely, Surveillance and health information;Laboratory capacity building;Emergency preparedness and response;Human resources management for effective disease surveillance and epidemic preparedness;and Institutional Capacity Building, Project Management, Coordination and Advocacy. After five years of implementation, this study aimed at the documentation of lessons learned and best practices. Methods: A descriptive cross-sectional study. Apart from individual semi-structured interviews, a thematic workshops bringing together the project’s main stakeholders recruited on an exhaustive way by component to identify and validate lessons learned, good practices and propose improvement mechanisms to be taken into account by the sector. Criteria were set up and used to validate best practices and lessons learned. Results: A total 54 (Surveillance workshop), 47 (Preparedness & response workshop), 53 (Human Resources workshop), 26 (Laboratories workshop) participated to the thematic workshops, and five interviews. The good practices (33: 9 for animal health, 7 for human health and 17 crosscutting) and lessons learned (10: 3 for animal health and 7 for human health) have been identified and have been the subject, depending on the case, of proposals for improvement or conditions necessary for their maintenance. Discussion: The richness of a project lies not only in the immediate achievement of its results, but also and above all, in its usefulness for similar interventions, whether in the local, regional, national or international context. It is in this context that the REDISSE project has set out to make public the various lessons learned and best practices from the implementation of its activities over a period of some five consecutive years.

关键词： Public Health Emergency Events Preparedness and Response Capitalization REDISSE Benin

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Successful Laparoscopic Management of a Migrated Intrauterine Contraceptive Device in the Pelvic Cavity: A Case Report

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Open Journal of Obstetrics and Gynecology 2024年第1期14卷 36-43页

作者： Tompeen isidore Inna Rakya Tchounzou Robert Neng Humphry Mangala Georges Tchenté Charlotte Mboudou Emile Department of Gynecology and Obstetrics Faculty of Medicine and Biomedical Sciences The University of Yaoundé I Yaoundé Cameroon Department of Gynecology and Obstetrics Faculty of Medicine and Biomedical Sciences The University of Garoua Garoua Cameroon Department of Gynecology and Obstetrics Faculty of Health Sciences The University of Buea Buea Cameroon Department of Gynecology and Obstetrics Faculty of Medicine and Pharmaceutical Sciences The University of Douala Douala Cameroon

Background: An Intrauterine device (IUD) is a long-acting reversible contraceptive commonly used in clinical practice. Its insertion in the uterus is simple and safe. But sometimes, complications can occur. Case Report: Herein, we report a case of successful laparoscopic removal of a missing IUD Copper-T, mis-inserted in a 32-year-old woman, 4 months after she delivered by caesarian section, and presented persistent lower abdominal pain lasting 6 months. Uterine ultrasound was unremarkable, but a plain abdominopelvic X-ray confirmed the presence of the Copper-T inside the abdominal cavity. Conclusion: Insertion of IUD is simple and safe. When the diagnosis of uterine perforation following its insertion is clinically suspected and radiologically confirmed, laparoscopy, when available, remains one of the best options for removal.

关键词： IUD Ectopic Migration Contraception Laparoscopy

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Epidemiologic, Diagnostic, and Therapeutic Features of Urinary Stone Disease in Northern Benin from 2018 to 2023

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Open Journal of Urology 2024年第2期14卷 128-137页

作者： Gandaho isidore Sossa Jean Toré Sanni Rafiou Dènon Emmanuel Allodé Alexandre Avakoudjo Déjinnin Josué Georges Département de Chirurgie et Spécialités Chirurgicales Université de Parakou Parakou Bénin Faculté des Sciences de la Santé Université d’Abomey-Calavi Abomey-Calavi Bénin

Objective: To determine the epidemiologic, diagnostic, and therapeutic features of urinary in northern Benin from 2018 to 2023. Patients and Method: The study was an observational and descriptive one. We exhaustively and retrospectively collected data from the medical records of the patients that were managed from February 1, 2018 to February 1, 2023 at the Department of Surgery of “Centre Hospitalier Universitaire Départmental Borgou-Alibori or CHUD-BA”. Results: Among the 4522 patients managed, 75% or 1.7% had urinary stone disease. Their mean age was 41 years. The sex ratio was 2.75, the males being predominantly affected. Of the 75 cases of urinary stone disease, 30.7% (n = 23) were renal, 46.7% (n = 35) were ureteral, and 22.7% (n = 17) were vesical. The patients came from variable geographical areas, ethnic groups, and professional sectors. Their main complaints were pain (57.3%), hematuria (14.7%), dysuria (12%), and fever (5.3%). 15 (20%) patients, i.e., 7 renal stone and 8 ureteral stone patients, had an obstructive renal failure. The imaging tools available were ultrasonography, tomography and computed tomographic scan. 11 of the bladder stone cases (64.7%) were associated with a bladder outlet obstruction. Overall, 38.7% of the patients had either diabetes mellitus (6.7%), hypertension or high blood pressure (6.7%), benign prostate hyperplasia (8%), urinary schistosomiasis (6.7%), ureteral pelvic junction obstruction (2.7%), and prostate cancer (1.3%). Of the 19 patients whose dietary behavior was investigated 15 (79%), 11 (57.9%) et 11 (57.9%) demonstrated a diet which was respectively rich in milk, fromage and meat. 100% of bladder stones were removed through cystolithotomy. Renal stones were removed by pyelolithtomy (52.2%) and nephrolithotomy (21.7%). Ureteral stones were removed through ureterolithotomy (40%), expelled by means of alpha-blockers (40%) or managed with ureteral pigtail stent (20%). Conclusion: The hospital prevalence of urinary stone d

关键词： Urinary Stone Epidemiologic Diagnostic Therapeutic

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Endometriosis beyond the Pelvis: A Case Series of Cutaneous Endometriosis and Literature Review

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Open Journal of Obstetrics and Gynecology 2024年第1期14卷 77-88页

作者： Tompeen isidore Nkoro Ombédé G. Anita Mendouga Menye Coralie Belinga Etienne Noa Ndoua Cyrille Foumane Pascal Department of Gynecology and Obstetrics Faculty of Medicine and Biomedical Sciences The University of Yaoundé I Yaounde Cameroon Department of Internal Medicine and Specialities Faculty of Medicine and Biomedical Sciences The University of Yaoundé I Yaounde Cameroon Department of Morphologic Sciences and Anatomopatology Faculty of Medicine and Biomedical Sciences The University of Yaoundé I Yaounde Cameroon Department of Clinical Sciences Faculty of Medicine and Pharmaceutical Sciences The University of Ebolowa Ebolowa Cameroon

Introduction: Cutaneous endometriosis is an uncommon but well-known skin disorder that represents about 0.5% to 1% of all endometriosis. The objective of this case series is to report clinical presentation, diagnosis, and management of various forms of cutaneous endometriosis. Material and Methods: It was an observational, retrospective and descriptive review of cases presenting with cutaneous endometriosis among Cameroonian women managed at the gynaecological outpatient department of Yaounde Gynaeco-Obstetric and Pediatric Hospital. All the following parameters were analysed: age, parity, previous pelvic surgery, presenting symptoms and duration, associated symptoms, localizations, imaging, size of the lesion, other localization of endometriosis, management and histopathological results. Results: we reported 4 cases of cutaneous endometriosis, with 3 umbilical endometriosis and 1 abdominal scar endometriosis. Patient age ranged from 28 to 39 years with an average of 33 years. All patients described infertility (two primary and two secondary) and two had a history of abdominal surgery. All patients presented local cyclical signs such as pain, swelling, color change and bleeding. The duration of symptoms varied from 2 to 3 years and the size of lesions ranged from 2 to 3.5 cm for umbilical lesions and was 9 cm for abdominal scar endometriosis. In all cases, no imaging was required for the diagnosis, which was suspected on the basis of patient’s history and the cyclical nature of local signs, followed by wide surgical excision and confirmation on histopathology. Conclusion: Cutaneaous endometriosis is a rare benign condition. Umbilical endometriosis seems to be the main cutaneous localization and can be described as primary or secondary. Even if its diagnosis must be confirmed by histopathology, it should be considered in patient with cutaneous cyclic signs such as pain, swelling or bleeding with or without history of abdominal surgery.

关键词： Endometriosis Cutaneous Endometriosis Umbilical Endometriosis Cyclic Umbilical Swelling Cameroon

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Cameroon Climate Predictions Using the SARIMA-LSTM Machine Learning Model: Adjustment of a Climate Model for the Sudano-Sahelian Zone of Cameroon

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Open Journal of Statistics 2024年第3期14卷 394-411页

作者： Joseph Armathé Amougou isidore Séraphin Ngongo Patrick Forghab Mbomba Romain Armand Soleil Batha Paul Ghislain Poum Bimbar Dpartement de Gographie Universit de Yaound 1 Yaound Cameroon Observatoire National sur les Changements Climatiques (ONACC) Yaound Cameroon Laboratoire dAnalyse et Modlisation Multidisciplinaire Statistique (SAMM) Universit de Paris 1 Panthon Sorbonne Paris France Ecole Nationale Suprieure Polytechnique de Yaound 1 Yaound Cameroon Dpartement de Mathmatiques Ecole Normale Suprieure de Yaound Yaound Cameroon Dpartement dInformatique Universit de Yaound 1 Yaound Cameroon

It is acknowledged today within the scientific community that two types of actions must be considered to limit global warming: mitigation actions by reducing GHG emissions, to contain the rate of global warming, and adaptation actions to adapt societies to Climate Change, to limit losses and damages [1] [2]. As far as adaptation actions are concerned, numerical simulation, due to its results, its costs which require less investment than tests carried out on complex mechanical structures, and its implementation facilities, appears to be a major step in the design and prediction of complex mechanical systems. However, despite the quality of the results obtained, biases and inaccuracies related to the structure of the models do exist. Therefore, there is a need to validate the results of this SARIMA-LSTM-digital learning model adjusted by a matching approach, “calculating-test”, in order to assess the quality of the results and the performance of the model. The methodology consists of exploiting two climatic databases (temperature and precipitation), one of which is in-situ and the other spatial, all derived from grid points. Data from the dot grids are processed and stored in specific formats and, through machine learning approaches, complex mathematical equations are worked out and interconnections within the climate system established. Through this mathematical approach, it is possible to predict the future climate of the Sudano-Sahelian zone of Cameroon and to propose adaptation strategies.

关键词： Adjustment Calibration Climate Sudano-Sahelian Zone Numerical Model

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A Review on Technologies for the Use of CO2 as a Working Fluid in Refrigeration and Power Cycles

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Energy and Power Engineering 2024年第6期16卷 217-256页

作者： Orelien T. Boupda Hyacinthe D. Tessemo isidore B. Nkounda Fongang Francklin G. Nyami Frederic Lontsi Thomas Djiako Laboratory of Energy Higher National Polytechnic School of Douala University of Douala Douala Cameroon Institut Ucac-Icam Douala Cameroon Department of Energy and Mechanical Engineering ISTA-IUG University of Ngaoundere Ngaoundere Cameroon

The use of carbon dioxide as a working fluid has been the subject of extensive studies in recent years, particularly in the field of refrigeration where it is at the heart of research to replace CFC and HCFC. Its thermodynamic properties make it a fluid of choice in the efficient use of energy at low and medium temperatures in engine cycles. However, the performance of transcritical CO2 cycles weakens under high temperature and pressure conditions, especially in refrigeration systems;On the other hand, this disadvantage becomes rather interesting in engine cycles where CO2 can be used as an alternative to the organic working fluid in small and medium-sized electrical systems for low quality or waste heat sources. In order to improve the performance of systems operating with CO2 in the field of refrigeration and electricity production, research has made it possible to develop several concepts, of which this article deals with a review of the state of the art, followed by analyzes in-depth and critical of the various developments to the most recent modifications in these fields. Detailed discussions on the performance and technical characteristics of the different evolutions are also highlighted as well as the factors affecting the overall performance of the systems studied. Finally, perspectives on the future development of the use of CO2 in these different cycles are presented.

关键词： Refrigeration Cycle Power Cycle System Performance Transcritical CO2 Cycles Working Fluid

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