GEODYNAMIC EVOLUTION OF THE WEST-AFRICA B ETWEEN 2.2 AND 2 GA - THE ARCHEAN STYLE OF THE BIRIMIAN GREENSTONE BELTS AND THE SEDIMENTARY BASINS IN NORTHEASTERN IVORY-COAST

The lithostructural features of Palaeoproterozoic terrains of northeas tern Ivory-Coast, greenstones belts and then sedimentary basin (Birimi an), are similar to those of Archaean terrains. Their early deformatio n is only volumic deformation due to granitoid intrusions, mainly betw een 2.2 and 2.16 Ga. The shortening deformation (main deformation) is expressed by right folds and transcurrent shear zones ca 2.1 Ga. Neith er thrust deformation nor high pressure metamorphic assemblages are kn own. This pattern of flexible and hot crust, at least between 2.2 and 2.16 Ga, is pole apart to a collisional pattern, proposed for West Afr ican Craton by some authors. The Archaran/Palaeoproterozoic boundary w ould not represent a drastic change of the geodynamic evolution of the crust.