U-Pb Pan-African ages of two charnockite-granite associations from Southwestern Nigeria

U-Pb dating of zircons from two separate charnockite granite associations from S.W. Nigeria, previously considered to be of Kibaran or Archean age, yield PanAfrican emplacement ages of 631±18 Ma and 586±5 Ma respectively when all the data points of each association are regressed together. These U-Pb data on zircons do not permit a confirmation of the field-established sequence of rock emplacement within each charnockite-granite association; thus synchronous ages of 620±20 Ma (charnockite NIG 4), 634±21 Ma (charnockite NIG 7) and 621±10 Ma (granite NIG 12) are obtained for the three analyzed rocks of the Akure-Ikerre-Ado Ekiti association while those of the Idanre association yield younger but synchronous ages of 580±10 Ma (charnockite NIG 2), 593±13 Ma (charnockite NIG 3) and 587±10 Ma (granite NIG 11). The ages obtained for the rocks of the Akure-Ikerre-Ado Ekiti association very well fit the existing data on the tectonic evolution of the basement complex of Nigeria, whereas those from the Idanre area are difficult to reconcile with the current interpretation of tectonic data in this area.