Polyphase deformation and evidence for transpressive tectonics in the Kimbi area, northwestern Cameroon Pan-African fold belt

Ganno Sylvestre¹, Nzenti Jean Paul¹*, Ngnotue Timoléon^1,2, Kankeu Boniface^1,3 and Kouankap Nono Gus Djibril¹

¹Université de Yaoundé I, Département des Sciences de la Terre, Laboratoire de Pétrologie et Géologie Structurale; B.P. 3412 Messa-Yaoundé - Cameroun.

²Université de Dschang, Département de Géologie, B. P. 67 Dschang - Cameroun.

³Institut de Recherches Géologique et Minière (IRGM), B. P. 4110 Yaoundé, Cameroun.

*Corresponding author. E-mail: jnzenti@yahoo.com. Tel: +237 94 85 64 73.

Accepted 29 January, 2010

   Abstract

The structures of the Pan-African fold belt in North-western Cameroon (Kimbi area) are the result of a succession of several events. Petrographic description and detailed kinematical analysis of the various structures with emphasis on superposed folds discovered in the metamorphic and plutonic complex of Kimbi area provided detailed information on the structures and the relative timing of deformation, which are as follows: (1) an early Pan-African stage (D₁) of tangential movement immediately followed by (2) two stages (D₂ and D₃). D₂ phase is heterogeneous simple shear in dextral transpressive context. D₃ tectonic phase, also marked by dextral transpressional movements, is the phase of superposed folding with a NNE-SSW kinematics direction. D₂ and D₃ are associated with medium-grade amphibolites facies metamorphism. (3) A brittle stage (D₄) responsible for the emplacement of granitic veins, faults and joints. The similarities of these last phases with the central Cameroon shear-zone suggest that the D₃ and D₄ stage are controlled by transcurrents tectonics. Transpressive tectonic seem to be the main deformation style in major shear zones of Central Africa and NE Brazil.

Key words: Transpressive tectonic, Pan-African, tangential movement, transcurrent tectonics, Cameroon.