Geological interpretation of the rifian foreland gravity anomalies and 3D modeling of their Hercynian granites (Northeastern Morocco)

• Published in: Journal of African earth sciences (1994) 2019-02, Vol.150, p.584-594
• Main Authors: El Azzab, Driss, Ghfir, Younès, Miftah, Abdelhalim
• Format: Article
• Language: English
• Subjects: 3D modeling; Granites; Gravity; Hercynian; Northeastern Morocco; Residual field
• ISSN: 1464-343X; 1879-1956
• DOI: 10.1016/j.jafrearsci.2018.09.013

Gravimetric data analysis and processing in the Guercif-Debdou-Mekkam regions representing the main domain of rifain foreland (Northeastern Morocco), enable to clarify the structure of the basement and identify areas of density contrast. The calculation of residual gravimetric (Rs) map shows the close relationship between the positive anomalies in the North of the Mekkam and Debdou areas and the uprising of the basement. However, the negatives anomalies are generated by the Hercynian granitic plutons formed by the interference of two anomalies with a maximum axis oriented NNE-SSW. At the border of the Southern one, the Soulouina granite outcrop in a small area, compared to the size of the attributed anomaly, which leads to the presence of a large, deep and thick granitic body. The keen analysis of the Rs map indicates that the buried granitic massifs extend over about 30 Km to the NNE under the Meso-Cenozoic cover. This result is confirmed by the presence of a metamorphic aureole close to the anomaly. A trial 3D modeling of gravity structures, using the USGS PFGRV3D program, shows a strong thickness of two granitic massifs. The SSW massif has a thickness of about 11 Km, while the NNE one is about 8 Km. The negative anomaly located at Mhirija village is correlated with the granitic apex of Alouana, generated by two granitic massifs buried at depth. It has the same contrast of density, age, and petrologic characteristics compared to than Soulouina, which indicates that they have the same behavior. In order to establish a new structural map of the study area, the horizontal gradient combined with lambertian reflectance applied to the Rs map was performed to delineate gravity inflection points, which overlaps with the vertical or the very steep-sided faults or any other surface limiting two compartments of different densities. The suggested faults reflect clearly the influence of Hercynian structural style. Last but not least, in this paper we propose a synthetic map displaying the lateral extension of Hercynian granites and the possible buried faults or non-mapped ones. Our final map represents an efficient and effective tool to help decision makers during mining exploration. •Analysis and processing of high gravimetric data of Guercif-Debdou-Mekkam regions.•Very fine interpretation of the different gravimetric anomalies.•Structural cartography of unmapped faults and their relation to geodynamic context.•3D modeling of the negative anomaly located in the Mekk