Neoproterozoic High-K Calc-Alkaline Granitoids from Bapa-Batie, North Equatorial Fold Belt, Central Cameroon: Petrogenesis and Geodynamic Significance

ABSTRACT

Neoproterozoic granitoids of the Bapa-Batie area crop out within the Central Cameroon Shear Zone (CCSZ). They comprise four rocks: (i) granodiorite, (ii) biotite-granite, (iii) biotite-amphibole-granite, and (iv) granitic dyke. The elongated shape of the plutons and foliation striking parallel to the CCSZ point to syntectonic magma emplacement. The rocks are metaluminous, weakly peraluminous, high-K, and calc-alkaline to shoshonitic ferro-potassic, with mineralogical and geochemical characteristics of I-type granitoids. The rocks are characterized by high Ba, Sr, Zr, Rb, Sr, low Ni and Cr contents, and by variable LREE enrichment, moderate HREE fractionation with strong negative to moderate Eu anomalies (in granodiorite, biotite-granite and biotite-amphibole-granite) and moderate to significant positive Eu anomalies (in granitic enclaves). Trace element distribution patterns show that all these rocks are distinctively depleted in Nb, P, Sr and Ti relative to other trace elements and indicate that these rocks were derived from crustal protoliths. Magmatic zircon grains in these granites yielded LA-ICP-MS U-Pb ages of 600 ± 3.7 Ma and 619 ± 29 Ma. The plutonic rocks of Bapa- Batie area resemble other Neoproterozoic high-K calc-alkaline granites of Cameroon and also display strong similarities with high-K calc-alkaline plutons of eastern Nigeria and the Borborema Province in NE Brazil.