A long-lasting Archean deformation history in the Sangmelima terrane, NW Congo Craton, Southern Cameroon
Résumé
The Sangmelima granite-greenstone belt (SGB) belongs to the Ntem Complex (NW Congo craton), and is represented by granite-gneiss terranes, granite-greenstone associations, mafic-ultramafic complexes, and mafic dyke swarms. Here, we present a new tectonic evolution model based on an aeromagnetic map, structural analysis, and geochronological data. Regional strain D1 is characterized by the development of steep foliations, steeply plunging lineations occasionally associated with vertical stretching of granitic dykes. D1 shear sense is top-toNNE oblique normal motion, inferred from the S 1 mylonitic fabric and the finite strain suggested that the vertical flow component dominates at the regional scale compared to the horizontal motions (Akame et al., 2020b). Syn-D1 melts, mineral assemblages and microstructures indicate that D1 took place under high-grade metamorphic conditions. D2 comprises deformation associated with sinistral strike slip and granitic dyke extractions. The C 2 shear zones are locally clogged by granitic melt and epidote-chlorite-biotite mineral recrystallizations, showing that the D2 transpressive deformation occurred from ductile to brittle conditions. The basement has thus been affected by a progressive D1-D2 strains induced by the bulk EW sub-horizontal shortening associated with vertical stretching in a transpressive tectonic style