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Open Journal of Geology 2019年第4期9卷 226-244页

作者： Elad Mkoumbe Fosso Téguia M. Estelle Eric eyike yomba albert Njandjock Nouck Philippe Tabod Charles Tabod Department of Physics Faculty of Science University of Douala Douala Cameroon Branch for Geophysical and Volcanological Research/Institute of Geological and Mining Research Buea Cameroon Department of Physics Faculty of Science University of Yaoundé I Yaoundé Cameroon

A three-dimensional model of the Logone Birni Basin (LBB) is presented by combining gravity and magnetic data and constrained by broad seismic profiles. The 3-D model has revealed the distribution of the stratigraphic formations as well as the top basement variation. Detailed structure of different stratigraphic sequences is presented for the first time for this basin and some of the sequences correlate with established sequences of the neighboring basins. The sediments pill consists of six sedimentary units dating from the Neocomian to the Quartenary. The Makary subbasin or Northern Logone Birni Basin (NLBB) is the deepest part of the basin and may hold good prospect for hydrocarbon generation and accumulation. However, the limited presence of faults and intrusive bodies decreases the possibility of thermal degeneration, contrary to the Central Logone Birni Basin (CLBB) where conditions seem to be fulfilled for possible hydrocarbon generation and maturity. The complexity of the structural pattern of the model is further enhanced by the presences of volcanic bodies, some of which lay directly on basement or interbedded with the sediments layers mainly in the CLBB.

关键词： Gravity/Magnetic Anomalies Stratigraphic Sequences Sediment Thickness Logone Birini Basin 3D-Model

Magnetic Anomaly Interpretation of the Northern Congo Craton Boundary: Results from Depth Estimation and 2.5D Modeling

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Journal of Geoscience and Environment Protection 2017年第12期5卷 90-101页

作者： Basseka Charles Antoine eyike yomba albert Kenfack Jean Victor Njiteu Tchoukeu Cyrille Donald Som Mbang Constantin Mathieu Shandini Njankouo Yves University of Douala Faculty of Science Department of Earth Science Douala Cameroon University of Douala Faculty of Science Department of Physics Douala Cameroon University of Dschang Faculty of Science Department of Earth Science Dschang Cameroon University of Yaoundé I Faculty of Science Department of Physics Yaoundé Cameroon

A magnetic-based geophysical study was performed across the southern part of Cameroon to investigate the boundary between the Archean Congo craton and the Pan-African metamorphic belt. Magnetic gradient techniques including Euler deconvolution and Tilt derivative have been applied to an aeromagnetic data profile to determine the depth of sources and their lateral extension. 2.5D magnetic modeling shows that the prominent magnetic positive anomalies observed on total magnetic map of south Cameroon are produced by deep and strongly magnetic bodies under the Pan-African formations mainly an important dyke formation structure with a high susceptibility of 0.041 (SI units), at an average depth of 4148 m and with a lateral extension of about 10 km. These bodies are interpreted to have emplaced at high crustal levels in a continental collision zone and were subsequently metamorphosed at granulite grade conditions, during the Pan-African orogeny about 620 Ma ago.

关键词： Congo Craton Magnetic Anomalies Euler Deconvolution Tilt Derivative 2.5D Modeling

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

2.5-D Earth Crust Density Structure Modeling of the Central Part of Cameroon Using Gravity Data

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Open Journal of Earthquake Research 2020年第3期9卷 289-306页

作者： Francoise Martine Enyegue a Nyam albert eyike yomba Alain Rodrigue Nzeuga Alix Stanislas Soh Department of Physics Faculty of ScienceUniversity of Yaounde IYaoundeCameroon Faculty of Science University of Douala Head of the Watch Technologic Unit Ministry of Scientific Research and InnovationYaoundeCameroon

The knowledge of areas of high and low geophysical densities is of paramount importance to better understand the geodynamic, tectonic and geomorphologic evolution of the earth. Several geophysical methods have been developed to achieve this, including a 2.5 D modeling from gravity data, which is the approach used in this work and whose aim is to highlight the causative geological structures of these contrasts in the central part of Cameroon. This zone extends between latitudes 3° and 7° North and longitudes 11° and 16° East. Several filters were applied to the gravimetric and topographic data using the Oasis Montaj software from geosoft in order to develop the different anomaly maps and Grav2dc in order to develop the different geological models of the subsoil. In the final analysis, it appears that this part of Cameroon suggests the presence of granitic rocks and sedimentary rocks whose density contrasts vary between -0.19 and -0.205 g/cm3 observed in the localities of Banyo, Ngaoundere and Abong-Mbang. We also observe the presence of gneiss and volcanic rocks of contrast density varying between 0.0522 to 0.0534 g/cm3 in the locality of Tibati, and granitic intrusions in addition to basic rocks of contrast density varying between 0.285 at 0.29 g/cm3 in the localities of Yoko, Bertoua and Belabo.

关键词： Gravity Anomaly Modeling Volcanic Intrusions

Topography of the Moho Undulation in Cameroon from Gravity Data:Preliminary Insights into the Origin,the Age and the Structure of the Crust and the Upper Mantle across Cameroon and Adjacent Areas

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Open Journal of Geology 2018年第1期8卷 65-85页

作者： albert eyike Francoise Enyegue A.Nyam Charles Antoine Basseka Department of Physics Faculty of ScienceUniversity of DoualaDoualaCameroon Department of Physics Faculty of ScienceUniversity of Yaounde IYaoundéCameroon Department of Earth Science Faculty of ScienceUniversity of DoualaDoualaCameroon

In this paper, the complete Bouguer anomaly data from Cameroon and part of the neighboring countries has been examined to compute the topography of the Moho undulations. This work is based on an improved filtering technique and an appropriate density contrast between the crust and the upper mantle. Comparison with seismic data shows that our Moho map defines better the continuity and morphology of the crust-mantle interface than the scattered seismic data in Cameroon. The present relief map, although may not give real depths at some areas provides a better surface correlation with the surface geology better than seismic techniques. Comparison between the Moho undulations and the topography maps reveals that the crust in Cameroon seems to not be in isostatic equilibrium. The Moho in the Central African Shear Zone (CASZ) must be linked with different dextral movements during the opening of the south Atlantic in the Cretaceous time. In the Chad basin, the Moho is associated to the opening of the central and south Atlantic ~130 Ma. In the case of the Congo basin, the Moho undulations are related to the post rift subsidence. The correlation between the Moho undulations map with the surface geology indicates that the actual morphology of the crust mantle interface in Cameroon can be related to the build-up of the West and Central African rift system dating back to the Early Cretaceous to Palaeogene, where the presence of intraplate tensional stresses reactivated previous shear zones of lithospheric weakness during the break up of Gondwana.

关键词： Crustal Instabilities Gravity Anomaly Moho Undulations Cameroon

Understanding the Meaning of the Positive Bouguer Anomaly of Waza (Northernmost Cameroon, Central Africa)

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Journal of Geoscience and Environment Protection 2019年第6期7卷 55-65页

作者： eyike albert Basseka Charles Antoine Lordon Djieto Anatole Eugene Nguimbous-Kouoh Jean Jacques Zanga-Amougou Alain Tabod Charles Tabod Department of Physics Faculty of Science University of Douala Douala Cameroon Department of Earth Science Faculty of Science University of Douala Douala Cameroon Department of Geology Faculty of Science University of Buea Buea Cameroon Department of Gas and Petroleum Exploration Institute of Mines and Petroleum Industries University of Maroua Maroua Cameroon Department of Physics Faculty of Science University of Yaoundé 1 Yaoundé Cameroon

Gravity and magnetic data were analyzed in conjunction with available geological data to determine the origin of observed positive gravity anomaly at Waza and its possible relationship to mafic intrusions. The data analysis includes the construction of a Bouguer gravity anomaly, isostatic residual gravity anomaly, total magnetic gradient and Euler solutions maps, and two and one-half dimensional gravity models. A positive gravity anomaly that occurs in Waza has amplitude of 35 mGal and can be separated into two parts. The top of the disturbing body causing the anomaly cannot be deeper than 4 km. We believe the anomaly is probably caused by a body of basaltic rocks lying at the upper surface of the Precambrian basement and originate from a self-propagating disturbance of magmatic loads on a pre-existing zone of lithospheric weakness. Melt migration might have been aided by tectonic and flexural stresses, such that the intrusion is limited in extent to the melting region of the plume and did not reach the surface. The model calculated to satisfy the observed anomaly consists of a 2.5 Km-thick slab underlain by a 10.5 km deep column. This model is interpreted to represent a sheet or saucer-like mafic intrusion that has a thick deep feeder. Detailed geophysical studies would be necessary to locate any possible economic occurrences.

关键词： Northern Cameroon Waza Bouguer High Total Magnetic Gradient Basaltic Intrusion