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Exploration of Potential Ore Deposits along the Cameroon Volcanic Line from Gravity and Magnetic Studies

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Open Journal of Geology 2020年第10期10卷 1009-1026页

作者： Fosso Téguia M. Estelle Eric Nana Gaelle Vanessa Lepatio Tchieg Sterve Alain Ntomb Biboum Edouard Olivier Eyike Yomba Albert Zanga Amougou Alain Atéba Bekoa Ntepe Nfomou Branch for Geophysical and Volcanological Research/Institute for Geological and Mining Research Buea Cameroon University of Douala Faculty of Science Department of Physics Douala Cameroon University of Yaounde 1 Faculty of Science Department of Physics Yaounde Cameroon National Institute of cartography Yaounde Cameroon

A gravity and magnetic study has been carried out along the continental part of the Cameroon Volcanic Line (CVL), with the aim to explore the possibility of ore’s presence into the basement of this region. Different processing techniques have been applied, including the isostatic residual, the analytic signal and the Euler deconvolution to compute the Bouguer and magnetic anomalies. Following Euler solutions (result of Euler deconvolution) and the analytic signal results, four profiles crossing main structures on the isostatic residual have been used to enhance the structure of intrusions in the studied area. Despite the lack of constraints in the studied region, the results show that the basement is intruded by bodies of different density (2.57 g/cm3 to 2.87 g/cm3), different size and shape, with depths between 1 and 10 kilometers. These bodies have been interpreted as old rocks then as potential reservoirs of rare ores. In addition, volcanic rocks modeled have constituted potential reserves of other ores like graphite, sulfur, copper, iron.

关键词： Ores Deposits Cameroon Volcanic Line (CVL) Gravity Magnetic

Evidence for the Upwelling of Mafic Bodies into the Upper Crust beneath the N40-50°E Branch of the Pan-African Central Cameroon Shear Zone from Gravity Studies

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Open Journal of Geology 2018年第3期8卷 278-297页

作者： Loudi Yap Robert Nouayou Depesquidoux Tchaptchet Tchato Joseph Kamguia Apollinaire Bouba department of Physics Faculty of Sciences University of Yaoundé 1 Yaoundé Cameroon Research Laboratory in Geodesy National Institute of Cartography Yaoundé Cameroon department of Earth Sciences Faculty of Sciences University of Yaoundé 1 Yaoundé Cameroon department of Physics Advanced Teacher’s Training College University of Maroua Maroua Cameroon

The existence of mafic bodies at mid crustal level beneath the Pan-African Central Cameroon Shear Zone is still a matter of debate. To provide additional constrains on this issue, the crust of the west region of Cameroon has been investigated using gravity data. Analyses of these data show N40-50°E oriented iso-anomal contours in the Bafoussam area, interpreted as the N40-50°E branch of the Central Cameroon Shear Zone. In addition, spectral analysis and 2.5D gravity modeling reveal intrusions of mafic bodies at depth between 3.2 and 14.2 km under N40-50°E aligned volcanic centers, namely Mt Bambouto and Mt Mbapit. The above observations suggest a structurally controlled emplacement of the mafic bodies. In the light of the recent geophysical data, the interaction between the NE-ward channel flow operating at the bottom of the lithosphere or the asthenosphere upwelling and the Cameroon Shear Zone could better explain the magma upwelling in the upper crust. This result is the novelty of the present work.

关键词： West Region Mafic Bodies Central Cameroon Shear Zone Gravity 2.5D Modelling

GEOENGINEERING FIELD TECHNIQUES FOR ROCK CHARACTERIZATION OF COASTAL PROTECTION STRUCTURES

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GEOENGINEERING FIELD TECHNIQUES FOR ROCK CHARACTERIZATION OF...

3D Modelling from New and Existing Gravity Data of an Intrusive Body in the Northern Part of Kribi-Campo Sub-Basin in Cameroon

2009 International Symposium on Rock Mechanics:"Rock Characterisation,Modelling and Engineering Design Methods"

作者： Ana Pires Helder I.Chaminé Laboratory of cartography and Applied Geology LABCARGADepartment of Geotechnical EngineeringInstitute of EngineeringPolytechnic of PortoPortugalGeoBioTec Centre(GeoresourcesGeotechnics and Geomaterials Research Group)University of AveiroPortugal

The coastal human population has been growing in many countries around the *** is currently estimated that about half of the globe population lives in coastal zones,although there is large variation among *** several countries,coasts currently face severe sea-level rise problems as a consequence of tectonic and anthropogenically induced *** coastal systems should be considered vulnerable to changes in climate,given increasing population density in coastal zones,long lead times for implementation of many adaptation measures,and institutional,financial and technological *** long as population grows,maintenance of existing revetments and other shoreline structures is becoming more *** a result,inspection,repair,and rehabilitation of existing structures represent a large part of a coastal work.A regular structural and environmental forcing monitoring programme enables structures to be evaluated for safety,condition and functionality,as the cost of maintaining this existing coastal infrastructure is high,there are being developed and employed new methods to reduce *** rock and concrete armoured structures need ongoing maintenance to ensure they continue to perform acceptably. In Portugal there are about 290 coastal protection structures along the coastline and it is of vital national interest to study its stability and *** 70%percent of these structures are groins and *** project aims to be a contribution to its geoengineering,by developing new methodologies for the rock material evaluation since its origin (quarry) until the project.A case study of the coastal protection structures from Espinho region(NW Portugal,Iberian Peninsula) is presented,which includes a GIS-based recognition and characterization of armourstone quarries. This study was carried out to improve diagnosis and prediction of geomaterials status from coastal protection *** addition the importance of coastal geoengineering

关键词： coastal geoengineering geomaterials GIS mapping rock evaluation deterioration level

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International Journal of Geosciences 2017年第8期8卷 984-1003页

作者： Kue Petou Rokis Malquaire Owona Angue Marie Louise Njingti Nfor Manguelle-Dicoum Eliezer National Institute of cartography Yaoundé Cameroon Postgraduate School of Sciences Technologies & Geosciences University of Yaoundé I Yaoundé Cameroon department of Physics Advanced Teacher Training College University of Yaoundé I Yaoundé Cameroon department of Physics Faculty of Science University of Yaoundé I Yaoundé Cameroon

A new gravity survey was carried out in the northern part of the onshore Kribi- Campo sub-basin in Cameroon. The data were incorporated to the existing ones and then analyzed and modeled in order to elucidate the subsurface structure of the area. The area is characterized in its north-western part by considerably high positive anomalies indicative of the presence of a dense intrusive body. We find, 1) from the analysis of the gravity residual anomaly map, the high positive anomalies observed are the signature of a shallow dense structure;2) from the multi-scale analysis of the maxima of the horizontal gradient, the structure is confined between depths of 0.5 km and 5 km;3) from the quantitative interpretation of residual anomalies by spectral analysis, the depth to the upper surface of the intrusive body is not uniform, the average depth of the bottom is h1 = 3.6 km and the depths to particular sections of the roof of the intrusion are h2 = 1.6 km and h3 = 0.5 km;4) and the 3D modeling gives results that are suggestive of the presence of contacts between rocks of different densities at different depths and a dense intrusive igneous body in the upper crust of the Kribi zone. From the 3D model the dense intrusive igneous block is surrounded by sedimentary formations to the south-west and metamorphic formations to the north-east. Both formations have a density of about 2.74 g/cm3. The near surface portions of this igneous block lie at a depth range of 0.5 km to 1.5 km while its lower surface has a depth range of 3.6 km to 5.2 km. The shape of the edges and the bottom of the intrusive body are suggestive of the fact that it forms part of a broader structure underlying the Kribi-Campo sub-basin with a great influence on the sedimentary cover.

关键词： Kribi-Campo Sub-Basin Gravity Data 3D Modelling Spectral Analysis Residual Anomaly

Estimation of Evapotranspiration Using SEBAL Algorithm and Landsat-8 Data--A Case Study： Tatra Mountains Region

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Journal of Geological Resource and Engineering 2016年第6期4卷 257-270页

作者： Ayad Ali Faris Beg Ahmed H. Al-Sulttani Adrian Ochtyra Anna Jarocinska Adriana Marcinkowska department of Geography College of Education University of Mustansiriyah Baghdad Iraq department of Regional Planning College of Physical Planning University of Kufa Najaf Iraq department of Geoinformatics Cartography and Remote Sensing Faculty of Geography and Regional Studies University ofWarsaw Warsaw Poland College of Inter-Faculty Individual Studies in Mathematics and Natural Sciences University of Warsaw Warsaw Poland

ET （Evapotranspiration） is one of the climate elements, which plays an important role in water balance, and effects on the ecosystem of any region. Therefore, many mathematical equations and algorithms have been found and designed to calculate and estimate values of evapotranspiration. Calculation methods are either based on data from meteorological stations or using other sources of data where the area is lacking from meteorological stations. Remote sensing data are one of the important sources and techniques to estimate many climate elements including evapotranspiration. The selected study area is located in Tatra Mountains on the borders between Poland and Slovakia. Tatra Mountains are the most valuable areas in Poland and Slovakia. The main objective of current study is to estimate the spatial variation of ET using SEBAL algorithm and Landsat-8 imagery. The analysis is carried out using Landsat-8 （OLI/TIRS） data, ASTER GDEM and reference weather parameters. Sixteen ERDAS models are prepared to calculate the various parameters related to solar radiation. The models are prepared to calculate the values of surface radiance surface reflectance, surface albedo, NDVI, LAI, surface emissivity, surface temperature, net radiation, soil heat flux, sensible heat flux, latent heat flux, which are consequently used to calculate the hourly and daily evapotranspiration in study area. Results ofpixel wise calculations show the values of surface temperature which are varied from 6.2℃ at mountain shadow areas to 34.6 ℃ at bare rocks and bare land area, while the spatial variation of ET at different land covers shows the hourly ET ranged from 0 to 0.72 mm/hr, while the daily ET varied from 0.0 to 17.0 mm/day. Results show clear relation between land use/land cover and solar radiation parameters and impact of vegetation cover on the ET values in pixel wise domain.

关键词： Landsat-8 remote sensing evapotranspiration solar radiation SEBAL NDVI.

Application of Coefficient of Anisotropy to the Geophysical Prospecting of Campo—Ma’an Area of the Ntem Complex in Cameroon

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Open Journal of Geology 2017年第12期7卷 1801-1818页

作者： Njingti-Nfor Owona Angue Marie Louise Kue Petou Rokis Malquaire Bisso Dieudonné Lando Tsakou Julyo Achille Postgraduate School of Sciences Technologies & Geosciences University of Yaoundé I Yaoundé Cameroon department of Physics Advanced Teacher Training College University of Yaoundé I Yaoundé Cameroon National Institute of cartography Yaoundé Cameroon School of Geosciences China University of Petroleum Qingdao China

Audiomagnetotelluric data were acquired for 10 sounding stations in open fields and roads along the main highways from Campo to Ma’an in Cameroon. An application of the coefficients of anisotropy was used to determine the tectonic settings and the nature of the contacts between the sedimentary formation of the Kribi-Campo basin and the cratonic Ntem Complex. The results of this study show that apart from the sedimentary formation, the metamorphic formation in this area comprises two metamorphic blocks: a regional metamorphic block which might be igneous or granitic in nature and composition and seem to be Precambrian and plutonic in origin and a contact or transitional metamorphic block, which might represent schist or gneiss rocks. The contact or transitional metamorphic block might be as a result of a long period of contact between regional metamorphic rocks and rocks of sedimentary formation. These contact/transitional metamorphic rocks which are found sandwiched between rocks of sedimentary formation and rocks of the regional metamorphic block and at varied depths confirm the existence of vertical and sub-vertical contacts between the Kribi-Campo basin and the cratonic Ntem complex. Two types of rock contacts have been identified: a sedimentary-schist contact which is found at the boundary between the sedimentary formation and the transitional metamorphic block and a schist-granite contact between the transitional and regional metamorphic blocks. Two main formations: a sedimentary formation, which is found in the Kribi-Campo sub-basin and the Ntem River bed and its flood plains and the metamorphic formation which includes both the transitional and regional metamorphic rocks have also been identified in the area of study. Subsurface rocks and rock materials have been observed to be highly resistive and occupying almost the entire subsurface in the area of study confirming the high vertical tectonic stability of the Ntem Complex even at contact with the sedimentar

关键词： Anisotropy Telluric Geo-Electric Subsidence Isotropic Vertical Faults Tectonics

An Integrated Remote Sensing and GIS in Monitoring Landuse and Land Cover Change in Egbeda Local Government Area, Oyo State, Nigeria

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Journal of Geoscience and Environment Protection 2022年第7期10卷 1-14页

作者： Adewale Olusola Akingbade Michael Ajide Oyinloye Sharafdeen Bolaji Olatunji department of cartography African Regional Institute for Geospatial Information Science and Technology (AFRIGIST) Ile-Ife Nigeria department of Urban and Regional Planning Federal University of Technology Akure Nigeria Cooperative Information Network (COPINE) Advance Space Technology Application Laboratory (South West) Obafemi Awolowo University Ile-Ife Nigeria

Effective planning relies on accurate and up-to-date information on existing land use and land cover. The timely detection of trends in land use and land cover change and a quantification of such trends are of specific interest to planners and decision makers. The aim of this research is to use remote sensing and GIS to monitor landuse and land cover change in Egbeda Local Government Area, Oyo State with a view to determining how useful such information can be to planners and decision makers for effective urban management. The research was conducted using remote sensing and Geographical information System at determining the trend and extent of land use and land cover change and its driving force in Egbeda Local Government Area, Oyo State. The methods used include: digitization, digital image processing and spatial analysis using an inverse distance weighted (IDW) technique, Maximum likelihood supervised classification and post classification change detection techniques were applied to Landsat imageries acquired in 1984, 2006 and 2018. Imageries were classified into built-up area, vegetation, bare surface, cultivation and water body. The results of the analysis obtained showed drastic change in built-up area which rose to 32.8% from 25.4% between 1984 and 2018 periods. To reduce the effect of land use expansion in the study areas, policy measures were recommended which include proper inventory of land use and land cover, regular monitoring of urban areas spread of development and regional development programs. These will enable the government, stakeholders, policy makers and planners to make informed decisions provided by these technologies to attain and sustain future urban development.

关键词： Landuse Land Cover Urban Management Remote Sensing GIS Satellite Imageries

Revisiting the determination of Mount Olympus Height(Greece)

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Journal of Mountain Science 2023年第4期20卷 1026-1034页

作者： Dimitrios AMPATZIDIS Georgios MOSCHOPOULOS Antonios MOURATIDIS Michael STYLLAS Alexandros TSIMERIKAS Vasileios-Klearchos DELIGIANNIS Nikolaos VOUTSIS Triantafyllia-Maria PERIVOLIOTI Georgios S.VERGOS Alexandra PLACHTOVA Genie Lab Department of Surveying and Geoinformatics EngineeringInternational Hellenic UniversityTerma Magnisias62124SerresGreece EO.Lab department of Physical&Environmental Geography Aristotle University54124ThessalonikiGreece Geoservice LTD Eirinis 14 Str55236ThessalonikiGreece Nomotechniki Pierias Dim.Dimadi 560100KateriniGreece Paths of Greece Karneadou 34-36Athens10676Greece Laboratory of Gravity Field Research and Applications-GravLab Aristotle University of Thessaloniki University Box 44054124ThessalonikiGreece Faculty of Science department of Applied Geoinformatics and cartography Charles UniversityAlbertov 612843Praha 2Czechia Balkan Center Center for Interdisciplinary Research and Innovation(CIRI-AUTH)AUTH Campus54124ThessalonikiGreece

The present study deals with the determination of Mount Olympus summit(Mytikas),exploiting modern observations such as Global Navigation Satellite Systems(GNSS)and existing geodetic *** last official Olympus height determination goes back 102 years by the Swiss surveyor *** then,only unofficial measurement campaigns have taken *** is a variety of released heights,which range from 2917 to 2919 *** September and October of 2022,we conducted a GNSS campaign,focusing on the area of highest Olympus *** precise GNSS measurements(accuracy of 1-3 cm),in conjunction with height information from Greece’s National Triangulation Network(5-10 cm accuracy)and an appropriate,recent geoid model(5-6 cm accuracy),we estimate through the so-called GNSS-levelling,the height of Olympus to 2917.727 m with respect to Greece’s officially accepted mean sea level and 2918.390 m with respect to the global vertical *** estimation of Olympus highest peak shows remarkable consistency at the level of 12.8 cm to that of *** in 1921.

关键词： Olympus Greece Mountain height determination GNSS leveling Surveying

Magnetotelluric Investigation of the Geo-Tectonic Stability of Campo-Ma’an Area in South Cameroon

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International Journal of Geosciences 2017年第12期8卷 1427-1441页

作者： Njingti-Nfor Owona Angue Marie Louise Clotilde Kue Petou Rokis Malquaire Bisso Dieudonne Piameu Kwagag Joel Postgraduate School of Sciences Technologies&GeosciencesUniversity of Yaounde IYaoundeCameroon department of Physics Advanced Teacher Training CollegeUniversity of Yaounde IYaoundeCameroon National Institute of cartography YaoundeCameroon School of Geosciences China University of PetroleumQingdaoChina

The magnetotelluric prospection method has been widely used in Cameroon not only as a reconnaissance method for geophysical investigations but also to determine the nature of the subsurface and the structural settings of the various geological formations in the country that resulted from the global geo-tectonic movements. The present study is aimed at employing the magnetotelluric method to provide evidence on major tectonic dislocations which might have led to the presence of plutonic intrusions in the cratonic structure of the Ntem Complex as well as determining the nature of the contact between the sedimentary Campo Basin and the metamorphic cratonic Ntem Complex. The analyses and interpretations of iso-resistivity maps and geoelectric sections from magnetotelluric data has enabled us to show that tectonic forces at contact between the sedimentary Campo Basin and the metamorphic Ntem Complex were of three different categories: gravity gliding, magmatic upwelling and lateral compressions. The results of the action of these forces were the development of vertical and sub-vertical faulting systems at Craton-Sedimentary Basin contact and subsidence of overburden that appears to have also paved the way for the setting-up of the Ntem River bed and its flood plains. This river bed and its flood plains have been characterized as having a sedimentary deposit depth of 500 m and width of 20 km. Meanwhile, the deep-seated contact faulting systems within the two identified formations have varied fault magnitudes with a maximum of 60 km. The relatively high apparently resistivity values (up to1.0 kΩ•m) for the sedimentary and the very high values for the metamorphic formations (up to and above 10.0 kΩ•m) suggest that the whole area is at present relatively geo-tectonically stable.

关键词： Magnetotelluric Tectonics Intrusions Gravity-Gliding Upwelling Compression