Tene Djoukam Joëlle Flore^1,, Fontem Kibong Nicoline², Wotchoko Pierre³, Chenyi Vohnyui Marie-Louise⁴, Kouankap Nono Gus Djibril³

The Nkor Noni area is located in Mount Oku, the fourth largest volcanic massif of the tertiary Cameroon Volcanic Line (CVL). The basement formation of the area is made up of Pan-African granitoids, crosscut by numerous basaltic dykes. Within the central domain of Pan-African Fold Belt in Cameroon, many basaltic dykes were subjected to detailed studies; but their sources and tectonic setting are still controversial. The basaltic dykes of Nkor Noni area are sub-vertical and strike N077°E to N085°E. They exhibit a microlitic/porphyritic texture made up of olivine, pyroxene, plagioclase and opaque minerals. Geochemically, the basaltic dykes of Nkor Noni area have a SiO2 content of 44.72 - 45.68 wt%, low MgO of 5.90 - 6.22 wt%, Fe2O3 of 12.55 - 13.22 wt.%, low Mg#= (31.7-32.9%), relatively high TiO2 (2.54 - 2.63 wt%) indicating a more evolved magma, with an alkaline affinity similar to some basalts outcropping along the CVL. Primitive mantle normalized rare earth element (REE) patterns display a slight enrichment in Light Rare Earth Elements (LREE) over Heavy Rare Earth Elements (HREE) with LaN/YbN values of 7.5 - 8.7, and Eu/Eu* of 0.979 to 1.012, demonstrating a null or none Eu anomaly. The Nkor Noni basaltic dykes were generated from 15% partial melting of a source rock having a spinel-garnet lherzolite composition, with very slight crustal input. They show a subduction-to collision-related magmatism and Within Plate geotectonic setting. Their rare earth element patterns are similar to those of the Manjo, Dschang, Maham and Kedem basaltic dykes outcropping along the CVL, suggesting the same mantle source with variable degrees of crustal contamination.

Nkor Noni, Basaltic dykes, alkaline, Within Plate, Cameroon Volcanic Line