0000000000594005
AUTHOR
Barth N. Ekwueme
Single zircon ages of migmatitic gneisses and granulites in the Obudu Plateau: Timing of granulite-facies metamorphism in southeastern Nigeria
Abstract A single zircon geochronological study of gneisses from the Obudu Plateau of southeastern Nigeria, using the evaporation technique, indicates that zircons recorded several Precambrian high-grade metamorphic events (Eburnean and Pan-African). Igneous and multifaceted metamorphic zircons yielded 207 Pb/ 206 Pb ages of 2062.4 ± 0.4 Ma, 1803.8 ± 0.4 Ma and 574 ± 10 Ma, respectively and confirm for the first time that granulite-facies metamorphism affected the basement of southeastern Nigeria, resulting in the formation of charnockites and granulitic gneisses. The Pan-African high-grade event was coeval with the formation of granulites in Cameroon, Togo and Ghana and resulted from colli…
Single zircon evaporation ages from the Oban Massif, southeastern Nigeria
Abstract A single zircon geochronological study in the Oban Massif of southeastern Nigeria, using the evaporation technique, provides evidence for the existence of Palaeoproterozoic crustal components in the area. The banded gneiss in the Oban village yielded a 207 Pb 206 Pb age of 1931.9±0.8 Ma, whilst charnockites associated with this gneiss provided an emplacement age of 584.5 ± 1.0 Ma. The volumetrically most important intrusive unit in the Oban area is a granodiorite that yielded a zircon age of 616.9 ± 1 Ma. These ages suggest that the banded gneiss is the oldest rock in the Oban Massif and that the emplacement of granodiorite and the formation of charnockites took place during the Pa…