Abstract
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.
Highlights
The magnetotelluric prospection method has been widely used in Cameroon as a reconnaissance method for geophysical investigations and 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 [1] [2] [3] [4]
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 present study is aimed at employing the magnetotelluric method to provide evidence on tectonic dislocations which might have led to the presence of plutonic intrusions in the cratonic structure of the Ntem Complex in Cameroon as reported by several authors amongst whom are: [5] [6] [7] [8]; as well as determining the nature of the contact between the sedimentary Campo Basin and the metamorphic cratonic Ntem Complex
Summary
The magnetotelluric prospection method has been widely used in Cameroon as a reconnaissance method for geophysical investigations and 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 [1] [2] [3] [4]. The entire African continent underwent a major phase of basement re-activation in the Late Precambrian, which resulted in the structural differentiation of the continent into stable cratonic nuclei, surrounded by mobile belts [9] [10] This event has controlled the subsequent tectonic history that has affected the whole continent with the most recent events being the East African rift that was initiated some 30 Ma to 40 Ma [11]. Studies of absolute plate motion show that at present, the African plate is almost stationary and this may be the reason why some of the most recent tectonic movements in the continent have been dominated by vertical and oscillatory motions which have led to either intrusions from the underlying substratum or subductions of near-surface materials into the architectural settings of subsurface formations [5] [6]
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