Host: Japan Association of Mineralogical Sciences
We have dated various granitoids from the Archaean Ntem complex, southern Cameroon by the SHRIMP zircon U-Pb method to define the magmatic evolution in the northwestern part of Congo craton. CL imageries of zircon grains collected from charnockites together with their Th-U composition and thin section observations clearly vindicate their magmatic origin. These zircons yielded magmatic ages of 3382 ±21Ma, 3266 ±5 Ma and 3062 ±15 Ma. Our data clearly suggest that the charnockite magmatism in the Ntem complex started earlier than ca. 2900 Ga as proposed previously. On another hand, xenocrystic zircon from a granite collected from the northern zone of the complex exhibit an early Mesoarchaean inherited age of 3477 ±16 Ma, the oldest age ever reported from the Congo craton, while majority of zircons in the same rock yield magmatic age of 2853 ±12 Ma. These features collectively support the existence of an early Mesoarchaean crust in the Congo craton.
