Investigations géophysiques dans la région de Loum-Minta par la méthode aeromagnétique : Implications structurales et géothermiques

Abstract

A geophysical study based on the aeromagnetic method is being carried out in the Loum-Minta region of central-eastern Cameroon, at the pan-African margin of the transition zone resulting from the pan-African chain -Craton of the Congo. The study area extends from South to North between latitudes 4 ° 00’ and 5°00 'N and from West to East between longitudes 12°00’ and 13°00' E. Data from the aeromagnetic surveys conducted in 1970 by the Canadian company SURVAIR on behalf of the Canadian International Development Agency (CIDA) were the key to this work. The purpose of this study was to determine the geological and tectonic structures of the subsoil of the study area and to analyse its current thermal state and possible geodynamic implications for the lithospheric structure. The simple methodological approach, based on the transformation of aeromagnetic data by means of several mathematical filters, has made it possible to identify zones of major contacts interpreted either as faults or as intrusive structures. An interpretive structural map based on the set of results has been constructed. The analysis of this map highlights known lineaments and highlights new as yet uncharted accidents, organized in the directions: E-W, ENE-WSW, NE-SW WNW-ESE and NW-SE. The dominant directions of the lineaments here are E-W, ENE-WSW, NE-SW. These different structural directions probably derive from the collision between the North-Equatorial chain and the Congo Craton and confirm that the area has been the scene of several tectonic tensions. The study on the present thermal state of Loum-Minta and possible Geodynamic implications for the lithospheric structure have been studied based on the estimation of the depths of the Curie point from the 2D spectral analysis of the magnetic data.The analysis shows that the Loum-Minta zone is characterized by shallow depths of the Curie point, averaging 9.09 km. There is also a geothermal gradient and a heat flow of average values of 72.24 °C/km and 180.59 mW respectively., well above average values observed in the continental lithosphere. These anomalous values of heat flow and geothermal gradient in the study area indicate a high thermal regime of the lithosphere, probably due to its rejuvenation during the Pan-African episode and the Pan-African craton continental collision of the Congo. The study area would thus present possible geothermal resources. To this end, the results obtained from this study can be very important for geothermal exploration.