U-Pb Geochronology of the Jebba Granitic Gneiss and Its Implications for the Paleoproterozoic Evolution of Jebba Area, Southwestern Nigeria

Abstract

Jebba area southwestern Nigeria forms part of the Nigerian basement complex which lies in the Neoproterozoic PanAfrican mobile belt. It is underlain by several lithological units among which is a polydeformed granitic gneiss. This rock has been dated by LA-ICP-MS yielding a concordant U-Pb zircon age of 2207 ± 20 Ma indicating the crystallization age of the granite protolith. This early Rhyacian age and its affinity with within-plate granites indicates emplacement during crustal extension and rifting preceding the main phase of the Eburnean orogeny. The strong, early, shear fabric, S 1 , in the rock is interpreted to be also of Paleoproterozoic age i.e. imprinted during the Eburnean orogeny. The Jebba granitic gneiss is thus correlatable with the widely abundant Paleoproterozoic granitic magmatism now represented by many orthogneisses and documented in other parts of southwestern Nigeria, the West African craton, the Borborema Province, the Gurupi Belt, Sao Luis craton and Sao Francisco craton in Brazil.

Quantification of elemental composition of Granite Gneiss collected from Neelum Valley using calibration free laser-induced breakdown and energy-dispersive X-ray spectroscopy

“…Relative weight percentage of each of oxides of these elements is different in Granite Gneiss samples extracted from different geological locations. According to literature, after SiO 2 most abundant oxides are Al 2 O 3 , Fe 2 O 3 , and K 2 O (Odunyemi & Olufemi, 2011;Okonkwo & Ganev, 2012;Rutland & Sutherland, 1967).…”

Structural Geology of the Basement Complex Rocks in Iwaraja Area, Southwestern Nigeria

“…[5][6][7][8] have shown that the Nigerian Basement Complex comprises Archean and Proterozoic rocks and bears the imprints of the Liberian (2700 ± 200 Ma), Eburnean (2000 ± 200 Ma) orogenic events. This basement was a zone of reactivation and orogenesis during the PanAfrican (600 ± 150 Ma) event [9,10].…”

Geochemistry and geochronology of orthogneisses in Bode Saadu area, southwestern Nigeria and their implications for the Palaeoproterozoic evolution of the area

“…Similar Palaeoproterozoic orthogneisses have been documented from other parts of southwestern sector of the Nigerian basement complex (Fig. 1c) e.g., Ibadan granitic gneiss (Grant, 1970), Igbeti augen gneiss (Rahaman et al, 1983), Itakpe Hill migmatitic gneiss (Caen-Vachette and Umeji, 1987), Kabba Granodioritic Gneiss (Annor 1995), Jebba Granitic Gneiss (Okonkwo and Ganev 2012). These data indicate that the Palaeoproterozoic was an important period of crustal growth in southwestern Nigeria and confirm that the Eburnean orogeny affected this sector of the Nigerian Basement complex.…”

“…They include migmatites, orthogneisses, paragneisses as well as metabasic rocks which have attained amphibolites facies metamorphic conditions and in a few places the granulite facies conditions. Geochronological data from gneisses in southwestern Nigeria include late Archean and Paleoproterozoic ages (Oversby, 1975;Pidgeon et al, 1976;Rahaman et al, 1983;Caen-Vachette and Umeji, 1987;Rahaman, 1988;Annor 1995;Okonkwo and Ganev 2012).…”