Paleoarchaean charnockite in the Ntem Complex, Congo Craton, Cameroon: insights from SHRIMP zircon U-Pb ages

Abstract

SHRIMP U-Pb analysis of zircon from charnockites and granite of the Archaean Ntem Complex, southern Cameroon was conducted to clarify the magmatic evolution of the northern part of Congo craton. Zircon morphologies and bulk chemistry are consistent with a magmatic origin for the charnockites. Zircons collected from two charnockites in the southern part of the complex yield differing magmatic ages of 3266 ± 5 Ma and 2883 ± 11 Ma. A xenocrystic zircon in a granite collected from the northern part of the complex gives a single grain 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. In addition, an inherited magmatic age of 3399 ± 6 Ma was obtained from the ~ 2883 Ma charnockite. The present data provide evidence of early Paleoarchaean magmatic activity, including charnockitic plutonism in the Congo craton.