Synkinematic ferro-potassic cal-alkaline magmatism from the yoro-yangben massif, along the southern part of central domain of cameroon pan-african fold belt

In this study we examine the geological significance and petrogenesis of orogenic Pan-African high-K calc-alkaline magmas from the Yoro-Yangben area in southern part of central domain of the Pan-African, North-Equatorial Fold Belt in Cameroon. The objective is to constrain the source and the geotectonic setting of these magmas and therefore to understanding the geodynamic environment of the Yoro-Yangben massif in the Bafia series. 21 samples were analyzed by XRF and ICP-MS. The rock sequences consist of orthogneisses with abundant granodiorite, granite biotite and quartz monzonite composition associated to amphibolite and covers a range of about 46 to 76 wt.-% SiO2. Rocks are metaluminous and of I-type granitoids and characterized by variable LREE enrichment, moderate HREE fractionation with strong negative Eu anomalies. Trace element distribution patterns show that these rocks were derived from crustal protoliths. Sm-Nd and TDM ages point a heterogeneous source and the Nd values a major crustal component. The 87Sr/86Sr ratios indicate that the protolith had a short crustal history. Tectonic evolution is polyphase and monocyclic. Kinematic criteria (C-S fabrics, φ, δ, σ structures), magmatic and solid state deformation markers combine to the elongated shape of the plutons parallel to the Cameroon Central Shear Zone point to syntectonic (D2) magma emplacement compatible with a ductile shear zone which controls the plutonic rocks emplacement. These results resemble other Neoproterozoic high-K calc-alkaline granites of Cameroon and Central Africa Republic and also display strong similarities with high-K calc-alkaline plutons of eastern Nigeria and the Borborema Province in NE Brazil.