Magnetic Characterization of Amphibolites from the Fomopéa Pluton(West Cameroon):Their Implication in the Pan-African Deformation of the Central African Fold Belt

摘要

The Fomopea granitic pluton is emplaced in gnessic and amphibolitic basement.These gneissic and amphibolitic basement rocks are represented in the pluton's body as sub-rounded,elongated or stretched xenoliths.Amphibolitic xenoliths display testimonies of two main tectonic events namely:(i) E1 flattening deformation event characterized by a NW-SE to E-W foliation with a best pole at 246/57 and a mineral stretched lineation with a best line at 293/47;and(ii) E2 compressive event typified by(1) N-S to NNE-SSW steeply dipping foliation;(2) S-type flexion-fold indicating a sinistral shear movement.These amphibolite rocks indicate a magnetic susceptibility magnitude(Km) range from 418 μSI to 90092 μSI for 87% of the stations showing a ferromagnetic behavior.K-T curves reveal the presence of Ti-poor magnetite as susceptibility mineral carrier.Magnetic foliation and lineation suggest that the N-S strike direction observed in the Bamendou amphibolite is,as pointed out elsewhere in the Central African Fold Belt,of paramount importance in the tectonic evaluation of the Fomopea area,since it has most likely acted as major deformation phase in the second tectonic event in the belt.