New lithostructural map of the Doropo region, northeast Côte d'Ivoire: Insight from structural and aeromagnetic data
Résumé
This study, performed in the Doropo region (northeastern Côte d'Ivoire) in the Paleoproterozoic domain (southern part of the WAC), aims to produce a detailed lithostructural map of this area. The geology of this region is less known due to the thick lateritic overburden and the scarcity of outcrops. Recent airborne geophysical data (aeromagnetic) integrated with field structural and lithological observations allowed to distinguish several lithologies including biotite granite, gneissic and migmatitic granite, granodiorite, tonalite, gabbro, amphibolite, rhyolite and dolerite. Filtering techniques of derivatives, upward continuation, tilt, analytical signal, spectral analysis and 3D Euler deconvolution showed the presence of faults, shear zones and intrusions. The structural analysis revealed four deformation events (D1-D4): (i) D1 is a N–S compression marked by E-W foliation (S1), conjugate NE-SW and NW-SE sinistral and dextral shears, respectively, as well as F1 folds with E-W axial planes; (ii) D2 is a major transpressive phase characterized by an intense NE-SW foliation (S2), E-W dextral shear zones, a weakly dipping stretching L2 lineation plunging N-E, and NE-SW faults; (iii) D3 is a NE-SW compressional phase generated NW-SE foliation (S3) with ∼E-W shears, and NW-SE axial plane F3 folds; (iv) D4 is a late, rather brittle phase characterized by brittle structures (faults, fractures, etc.) and the emplacement of NE-SW and NW-SE dolerite dykes. This tectonic evolution demonstrates that the Doropo region was subject to ductile and then brittle deformations. Furthermore, we suggest that the geodynamic model which could have prevailed in the Doropo region occurred in an oceanic arc collisional tectonic context.
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