Quantitative Interpretation of Gravity Anomalies in the Kribi-Campo Sedimentary Basin (South Cameroon) Based on Spectral Analysis and 2.5D Modelling: Structural Implications

Kue Petou Rokis Malquaire,Manguelle-Dicoum Eliezer,Mioumnde Arthur Paterne,Kue Negham Martine Clémence,Njingti Nfor,Weiqi Song,Owona Angue Marie Louise Clotilde,Eloundou Essama Lionel

doi:10.4236/ojer.2020.93014

Kue Petou Rokis Malquaire, Manguelle-Dicoum Eliezer + Show 6 more

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https://doi.org/10.4236/ojer.2020.93014

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Abstract

Ground gravity survey was recently carried out in the Lolabe-Campo area, which constitutes the southern onshore portion of the Kribi-Campo sub-basin in South Cameroon. The obtained gravity data were processed and interpreted in order to elucidate the subsurface geology of the area in which preliminary studies highlighted the presence of an intrusive igneous body. In order to determine the nature and the characteristics of this body, spectral analysis, ideal body solution and 2.5D modelling methods were applied to the gravity data. The results suggest that the emplacement, breaking up and separation of the intrusive igneous body were the outcome of two tectonic events corresponding to an upward vertical translational tectonic movement followed by an anticlockwise rotational faulting tectonic movement. From a density contrast of 0.13 g&#183cm&#453, the two isolated bodies have an estimated density of 2.80 g&#183cm&#453 which is comparatively higher than the average density of 2.67 g&#183cm&#453 of the autochthonous rocks. These two blocks are completely surrounded by both sedimentary and metamorphic formations and are confined between the depths of 0.6 km and 3.5 km. The highly dense nature of the rocks and their location around the Atlantic Ocean led to the conclusion that the two intrusive bodies are composed principally of gabbro. The disposition and shape of the open zone resulting from the separation of the blocks are suggestive of a trap for the accumulation of hydrocarbons and mineral resources.

Highlights

The area under study is situated in the southern part of Cameroon (Central Africa), and constitutes part of the onshore domain of the Kribi-Campo sub-basin located between latitudes 2 ̊20'N and 3 ̊20'N and longitudes 9 ̊15'E - 10 ̊00'E
The results suggest that the emplacement, breaking up and separation of the intrusive igneous body were the outcome of two tectonic events corresponding to an upward vertical translational tectonic movement followed by an anticlockwise rotational faulting tectonic movement
In order to provide more detailed information on the nature and the characteristics of this intrusion, after a brief analysis and interpretation of the gravity anomaly map for the study area, this work consists of combining the indirect method, the inverse method and the direct method (2.5D modelling) to analyze and interpret the new gravity data collected in this region

Summary

Introduction

The area under study is situated in the southern part of Cameroon (Central Africa), and constitutes part of the onshore domain of the Kribi-Campo sub-basin located between latitudes 2 ̊20'N and 3 ̊20'N and longitudes 9 ̊15'E - 10 ̊00'E It is situated at the junction between three main structures: 1) the sedimentary Kribi-Campo sub-basin; 2) the southern edge of the Kribi-Campo fault and 3) the metamorphic cratonic Ntem Complex. This area was affected by a series of tectonic activities due to the collision between the Pan-African belt and the Congo craton that formed the structural features of Southern Cameroon [1] [2]. The main aim is to present the extensional and longitudinal dimensions of the Lolabe-Campo subsurface structure in general and to locate the gravity intrusion identified in the area

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