Oumarou Faarouk NKOUANDOU^1*, Aminatou MEFIRE FAGNY², Gabriel Ovidiu IANCU³ & Jacques-Marie BARDINTZEFF^4,5
1Faculty of Science, University of Ngaoundéré, P.o. Box. 454 Ngaoundéré-Cameroon, *Corresponding author address: ofaarouk@yahoo.fr
²Faculty of Science, University of Ngaoundéré, P.o. Box. 454 Ngaoundéré-Cameroon, afagny2002@yahoo.fr
³Faculty of Geography and Geology, University of Alexandru Ioan Cuza, Iaşi, Romania, 700505-RO, Iaşi, Bulevardul Carol I nr. 20A (ogiancu@yahoo.com)
^4,5University of Paris-Sud, Laboratoire IDES, UMR 8148, Bât. 504, F−91405 Orsay, France: email address: jacques-marie.bardintzeff@u-psud.fr Tel. (33) (1) 69 15 67 44

PETROLOGY AND GEOCHEMISTRY OF DOLERITIC DYKE OF LIKOK (CAMEROON, CENTRAL AFRICA)

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Dolerites dyke swarm trending N70, N135 and E-W transect the Pan-African granitic rocks of Likok area (Adamawa plateau-Cameroon) in Central Africa. Petrography, mineral chemistry and geochemical compositions of those rocks have been attempted for the first time. Dolerites exhibit a coarse-grained porphyroid and sub-ophitic doleritic texture. Microprobe analyses show that they are composed of diopside (Wo_49.27En_41.92Fs_8.81), subcalcic augite (Wo_{25.41−41.93} En_{42.34−46.61} Fs_{11.37−31.80}) and pigeonite clinopyroxene (Wo_18.64 En_46.12 Fs_35.24). Plagioclases are labrador (Ab_{34.74−46.25} An_{51.15−63.40}), andesine (Ab_{55.14−64.54} An_{35.12−44.96}), oligoclase (Ab_{76.97−85.96} An_1.27−22.61) and albite (Ab_{92.42−93.76} An_5.64−6.38). Alkali feldspar is dominantly orthoclase (Or_{72.97−97.97} Ab_1.83−25.73). Biotite, titanomagnetite, ilmenite, apatite and titanite are accessory phases. XRF whole-rock chemical analysis highlight two distinct dolerites of group I (Mg: 53.0%) and group II (Mg: 62.0−65.0%) compositions. All dolerites belong to low-Ti quartz-normative continental tholeiites, generated from the enriched sub-continental lithospheric mantle. The similar characteristics are displayed by the neighboring dyke swarm from Biden (Cameroon) and Obudu (Nigeria), arguing for a common early stage setting of Pan-African break-up, initiated in Late Jurassic-Early Cretaceous time.