This article is a contribution to the understanding of the structuration of the West African Craton (WAC) through an integrated analysis of geophysical and petro-structural data from the Daloa region in west-central C？te d’Ivoire. Airborne magnetic data were used for mapping a regional structure, as this is a forested region. Fourier domain processing (Reduce To Equator, Analytical Signal, and Tilt derivative) was used to produce maps highlighting the main regional structures, which were then confirmed in the field. This method made it possible to define the geometry of the different massifs and the contacts between the different lithological units. The Daloa region is made up of calc-alkaline granitoids (granites and migmatites) and schists elongated in directions ranging from N20？E to N60？E, with subvertical dips (60？SE to 80？SE). The massifs are traversed by a network of fractures oriented E-W, NW-SE, NE-SW, which correspond to the direction of the numerous aplite, pegmatite, tourmalinite, and quartz veins observed there. Brittle deformation is characterized by the formation of vein structures or strike-slip faults. These directions are consistent with the lineament directions observed on geophysical maps. The structuring of this region occurred in four main phases recognized at the scale of the West African Craton: a NNW-SSE synmagmatic compression phase (D1), followed by an early NE-SW extensional phase (D2) during a period when the massifs still retained some ductility. Next comes a N-S compression phase (D3) responsible for numerous shears, and finally a late tensile phase (D4) leading to the reactivation of the faults from phase D2.
References
[1]
Menchikoff, N. (1949) Quelques traits de l’histoire geologique du Sahara occidental. Livre jubilaire Charles Jacob. Annales Hebat et Haug, 7, 303-325.
[2]
Morel, S.W. (1979) The Geology and Mineral Resources of Sierra Leone. Economic Geology, 74, 1563-1576. https://doi.org/10.2113/gsecongeo.74.7.1563
[3]
Thiéblemont, D., Delor, C., Cocherie, A., Lafon, J.M., Goujou, J.C., Baldé, A., Bah, M., Sané, H. and Fanning, C.M. (2001) A 3.5 Ga Granite-Gneiss Basement in Guinea: Further Evidence for Early Archean Accretion within the West African Craton. Precambrian Research, 108, 179-194. https://doi.org/10.1016/s0301-9268(00)00160-1
[4]
Egal, E., Thiéblemont, D., Lahondère, D., Guerrot, C., Costea, C.A., Iliescu, D., et al. (2002) Late Eburnean Granitization and Tectonics along the Western and Northwestern Margin of the Archean Kénéma-Man Domain (Guinea, West African Craton). Precambrian Research, 117, 57-84. https://doi.org/10.1016/s0301-9268(02)00060-8
[5]
Caen Vachette, M. (1986) Apport de la géochronologie isotopique à la connaissance du Protérozo？que inférieur de l’Afrique de l’Ouest. Publication CIFEG, 10, 17-23.
[6]
Feybesse, J., Billa, M., Guerrot, C., Duguey, E., Lescuyer, J., Milesi, J., et al. (2006) The Paleoproterozoic Ghanaian Province: Geodynamic Model and Ore Controls, Including Regional Stress Modeling. Precambrian Research, 149, 149-196. https://doi.org/10.1016/j.precamres.2006.06.003
[7]
Grenholm, M., Jessell, M. and Thébaud, N. (2019) A Geodynamic Model for the Paleoproterozoic (ca. 2.27-1.96 Ga) Birimian Orogen of the Southern West African Craton: Insights into an Evolving Accretionary-Collisional Orogenic System. Earth Science Reviews, 192, 138-193.
[8]
Milési, J.P., Feybesse, J.L., Pinna, P., Deschamps, Y., Kampunzu, H., Muhongo, S., et al. (2004) Geological Map of Africa 1:10,000,000, SIGAfrique Project. 20th Conference of African Geology (CAG20), Orléans.
[9]
Allou, B.A., Lu, H.Z., Guha, J., Carignan, J., Naho, J., Pothin, K. and Yobou, R. (2005) Une Correlation Genetique entre les Roches Granitiques, et les Depots Eluvionnaires, Colluvionnaires et Alluvionnaires de Columbo-Tantalite d’Issia, Centre-Ouest de la Cote d’Ivoire. Exploration and Mining Geology, 14, 61-77. https://doi.org/10.2113/gsemg.14.1-4.61
[10]
Dago, A.G.B., Coulibaly, Y. and Ouattara, Z. (2019) Typologie pétrographique et géochimique des granito？des de la région de Daloa au Centre Ouest de la C？te d’Ivoire. Afrique Science, 15, 208-221.
[11]
Dobrin, M.B. (1976) Magnetic Prospecting: Fundamental Principles and Instruments. In: Dobrin, M.B., Introduction to Geophysical Prospecting (3rd Edition), McGraw-Hill, 476-518.
[12]
Finlay, C.C., Maus, S., Beggan, C.D., Bondar, T.N., Chambodut, A., Chernova, T.A., et al. (2010) International Geomagnetic Reference Field: The Eleventh Generation. Geophysical Journal International, 183, 1216-1230. https://doi.org/10.1111/j.1365-246x.2010.04804.x
[13]
Blakely, R.J. (1995) Potential Theory in Gravity and Magnetic Applications. Cambridge University Press. https://doi.org/10.1017/cbo9780511549816
[14]
Bérubé, C.L. and Gagnon, J.L. (2024) Aniso Polarization Modeling with Neural Networks and Effective Medium Theory. Geophysics.
[15]
Baranov, V. (1957) A New Method for Interpretation of Aeromagnetic Maps; Pseudo-Gravimetric Anomalies. Geophysics, 22, 359-382. https://doi.org/10.1190/1.1438369
[16]
Baranov, V. and Naudy, H. (1964) Numerical Calculation of the Formula of Reduction to the Magnetic Pole. Geophysics, 29, 67-79. https://doi.org/10.1190/1.1439334
[17]
Nabighian, M.N. (1972) The Analytic Signal of Two-Dimensional Magnetic Bodies with Polygonal Cross-Section; Its Properties and Use for Automated Anomaly Interpretation. Geophysics, 37, 507-517. https://doi.org/10.1190/1.1440276
[18]
Nabighian, M.N. (1974) Additional Comments on the Analytic Signal of Two-Dimensional Magnetic Bodies with Polygonal Cross-Section. Geophysics, 39, 85-92. https://doi.org/10.1190/1.1440416
[19]
Bouiflane, M. (2008). Cartographies aéromagnétique et magnétique multi échelles: étude structurale d’une région du Fossé rhénan. Ph.D. Thesis, Université Louis Pasteur.
[20]
Roest, W.R., Verhoef, J. and Pilkington, M. (1992) Magnetic Interpretation Using the 3-D Analytic Signal. Geophysics, 57, 116-125. https://doi.org/10.1190/1.1443174
[21]
Salem, A., Williams, S., Fairhead, J.D., Ravat, D. and Smith, R. (2007) Tilt-Depth Method: A Simple Depth Estimation Method Using First-Order Magnetic Derivatives. The Leading Edge, 26, 1502-1505. https://doi.org/10.1190/1.2821934
[22]
Chardon, D., Jayananda, M., Chetty, T.R.K. and Peucat, J. (2008) Precambrian Continental Strain and Shear Zone Patterns: South Indian Case. Journal of Geophysical Research: Solid Earth, 113, B08402. https://doi.org/10.1029/2007jb005299
[23]
Baptiste, J., Martelet, G., Faure, M., Beccaletto, L., Reninger, P., Perrin, J., et al. (2016) Mapping of a Buried Basement Combining Aeromagnetic, Gravity and Petrophysical Data: The Substratum of Southwest Paris Basin, France. Tectonophysics, 683, 333-348. https://doi.org/10.1016/j.tecto.2016.05.049
[24]
Miller, H.G. and Singh, V. (1994) Potential Field Tilt—A New Concept for Location of Potential Field Sources. Journal of Applied Geophysics, 32, 213-217. https://doi.org/10.1016/0926-9851(94)90022-1
[25]
Verduzco, B., Fairhead, J.D., Green, C.M. and MacKenzie, C. (2004) New Insights into Magnetic Derivatives for Structural Mapping. The Leading Edge, 23, 116-119. https://doi.org/10.1190/1.1651454
[26]
Djro, S.C. (1998) évolution tectono métamorphiques des gneiss granulitiques archéens du secteur de Biankouma (Nord Ouest C？te d’Ivoire). Thèse de doctorat, Université d’Abidjan, 171 p.
[27]
Arnould, M. (1961) étude géologique des migmatites et des granites précambriens du Nord-Est de la C？te d’Ivoire et de la Haute-Volta méridionale. Université Clermont Auvergne, 174 p.
[28]
Casanova, R. (1973) Géochimie et minéralogie des granito？des éburnéens de C？te d’Ivoire. Thèse de Doctorat d’état ès Sciences, Université de Nice, 327 p.
[29]
Pouclet, A., Doumbia, S. and Vidal, M. (2006) Geodynamic Setting of the Birimian Volcanism in Central Ivory Coast (Western Africa) and Its Place in the Palaeoproterozoic Evolution of the Man Shield. Bulletin dela Société Géologique de France, 177, 105-121. https://doi.org/10.2113/gssgfbull.177.2.105
[30]
K？íbek, B., Sykorová, I., Machovi？, V. and Laufek, F. (2008) Graphitization of Organic Matter and Fluid-Deposited Graphite in Palaeoproterozoic (Birimian) Black Shales of the Kaya-Goren Greenstone Belt (Burkina Faso, West Africa). Journal of Metamorphic Geology, 26, 937-958. https://doi.org/10.1111/j.1525-1314.2008.00796.x
[31]
Pouclet, A., Prost, A.E., Ama-Salah, I. and Lapierre, H. (1990) Les ceintures birimiennes du Niger occidental (Protérozo？que inférieur), nouvelles données pétrologiques et structurales des formations métavolcaniques. Comptes Rendus de l’Académie des Sciences, 311, 333-340.
