首页|Petrology of lherzolite xenoliths of Hosséré Sédé volcano(Adamawa plateau,Ngaoundéré area,Cameroon)
Petrology of lherzolite xenoliths of Hosséré Sédé volcano(Adamawa plateau,Ngaoundéré area,Cameroon)
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Numerous mantle xenoliths 6-12 cm in size and sub-angular to rounded in shape occur within Mio-Pliocene basanite lavas of the monogenic volcano of Hosséré Sédé in the Adamawa plateau.Xenoliths of spinel lherzolite exhibit protogranular,equigranular or porphyroclastic texture.Microprobe chemical analyses show that olivine is highly magnesian(Fo88-90),clinopyroxene crystals are diopside and augite(Wo41.6-49.6 En45.3-53.7 Fs4.2-6.2),orthopyroxene crystals are enstatite(Wo1.4-1.5 En88.6-89.0 Fs9.6-9.9)and spinel crystals are mainly Al-spinel associ-ated to minor Cr-spinel.Estimated temperatures and pressures through empirical formulas show that Hosséré Sédé xenoliths have equilibrated between 1085 and 1204 ° C and 1.08 to 1.57 GPa,corresponding to sampling depths of 36 and 52 km.Detailed petrographical and mineral chemistry of Hosséré Sédé xenoliths evidences the com-plex nature and composition of the subcontinental lithosphere under the Adamawa plateau.This may involve a probable uplift of the whole area after a limited exten-sional event,possible metasomatism through melt infiltration during shearing of the lithospheric mantle along the Pan African strike-slip fault system.
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