Wehrlite xenoliths and petrogenetic implications, Hosséré Do Guessa volcano, Adamawa plateau, Cameroon

Abstract Peridotite xenoliths of wehrlite composition, scarcely known in Adamawa plateau, Cameroon, were sampled by Mio-Pliocene basanites from Hosséré Do Guessa volcano. Their origins are discussed and elucidated trough petrography mineral chemistry. Studied wehrlites exhibit poikilitic or protogranular textures composed four main mantle phases (high Mg-olivine, augite, enstatite Al-spinel). Petrographic microprobe (Camebax SX100) chemical data (Fo90.8-91.4 olivine, Wo39.4-42.0 En90.5-91.1 Al-spinel) suggest a origin for the wehrlites. Hence, these rocks could not be considered cumulate. They have been equilibrated between 1,140 1,220°C, at pressures 1.5–2.0 GPa, 50–66 km deep, below crust-mantle boundary. Wehrlites might result reactions with carbonate/carbonatite melt, accompanying CO 2 degassing metasomatism fluid phases. suffered transpressional tectonics, during movement Tertiary times Pan-African strike-slip-faults, after solid-state tectonic relaxation.