New U–Pb zircon ages of Nyong Complex meta‐plutonites: Implications for the Eburnean/Trans‐Amazonian Orogeny in southwestern Cameroon (Central Africa)

Abstract

ICP-MS U-Pb zircon ages from the Nyong Complex of southwestern Cameroona part of the West Central African Fold Belt-trace Late Mesoarchean (2,850 Ma), Middle Palaeoproterozoic (2,080 Ma), and Neoproterozoic (605 Ma) events: Two meta-syenites and the protolith of an amphibolite are Late Mesoarchean; two meta-granodiorites are Middle Palaeoproterozoic; the amphibolite may have recrystallized in the Middle Palaeoproterozoic; all rocks are overprinted by the Neoproterozoic event. Integration with published data shows that our amphibolite sample has one of the oldest amphiboliteprotolith ages (2,810 Ma) reported so far. It shares the Middle Palaeoproterozoic metamorphism/recrystallization with other, previously dated amphibolites. An earlier reported metamorphic zircon age (2,090 Ma) from eclogite is somewhat older than the regional Middle Palaeoproterozoic metamorphism/recrystallization ages (2,040 Ma) reported from amphibolites. Thus, the eclogite-amphibolite ages may date an exhumation process. A published charnockite age, interpreted as an Early Mesoarchean crystallization age, is older than the Late Mesoarchean meta-syenite and amphibolite-protolith dates; its Middle Palaeoproterozoic metamorphism/recrystallization age, however, is identical with the metagranodiorites and amphibolites. The Neoproterozoic ages demonstrate the regional overprint of the Nyong Complex during this period. Integration of the Nyong Complex ages with published ones from the entire West Central African Fold Belt, and comparison with those from West Africa and South America, support their common origin from the Palaeoproterozoic collision between the Archean Congo and São Francisco shields.

Petrology and geochemistry of metamorphosed rocks associated with iron formations of the Toko‐Nlokeng iron deposit, (Southern Cameroon): Implications for geodynamic evolution and mineralization

“…The ages of the metamorphic zircons in the Mewengo garnet amphibole gneisses are equivalent, 2050 to 45 Ma (Kwamou et al, 2021); this is explained by the age of metamorphism in the Mewongo and Toko‐Nlokeng iron deposits. Owona, Ratschbacher, et al (2020) reporting that the oldest amphibolites‐protolith ages in the Nyong Complex is compatible with the few ages of 2800 Ma that have been published. Numerous studies conducted inside the Nyong Complex demonstrate that the calculated age (2050 ± 45 Ma) is comparable with ages determined for the regional metamorphism of Palaeoproterozoic granulite‐facies rocks (2.05 Ga; Toteu et al, 1994), eclogite (2.9 Ga; Loose & Schenk, 2018), and serpentinite (2.8 Ga; Nga Essomba et al, 2020).…”

“…This can be used to explain the greater endowment of iron deposits within the upper craton in the Nyong Complex. Djoukouo et al, 2021;Loose & Schenk, 2018;Nga Essomba et al, 2020;Owona et al, 2022;Owona, Ratschbacher, et al, 2020;Soh et al, 2021;Soh Tamehe et al, 2022) eny (e.g., Bouyo Houketchang et al, 2019;Djoukouo et al, 2021;Fuanya et al, 2019;Kamguia Woguia et al, 2022;Loose & Schenk, 2018;Moudioh et al, 2020;Owona et al, 2021;Owona et al, 2022;Owona, Ratschbacher, et al, 2020;Soh et al, 2021). Continental arcs have an extensive range of compositions, from silica-poor stages associated with the early stages of development of convergent plate margins to highly evolved magmas marking the end of subduction (Santos et al, 2021).…”

“…The Precambrian basement of the Ntem Complex (Figure 1c) consists of three major structural units, including (1) the Congo Craton, locally called the Ntem Complex, consisting of Archean cratonic geological formations (e.g., Akame et al, 2021; Maurizot et al, 1986; Pouclet et al, 2007; Tchameni et al, 2010) in the south; (2) the Palaeoproterozoic Nyong Complex (e.g., Bouyo Houketchang et al, 2019; Loose & Schenk, 2018; Soh et al, 2021; Toteu et al, 1994) to the NW of the Congo Craton; and (3) the Neoproterozoic Yaoundé Group (e.g., Kamani et al, 2021; Nzenti et al, 1988; Toteu et al, 2022) representing the southern part of the Central African Pan‐African Range that resulted from the convergence and continental collision at ca. 600 Ma (Figure 1a,b) (e.g., Kamani et al, 2021; Ledru et al, 1994; Owona, Ratschbacher, et al, 2020). In these areas, low to ultra‐high‐pressure mafic‐ultramafic rocks that have the most data indicate HP granulite facies assemblages (e.g., Lerouge et al, 2006; Loose & Schenk, 2018; Penaye et al, 2004).…”

“…In these areas, low to ultra‐high‐pressure mafic‐ultramafic rocks that have the most data indicate HP granulite facies assemblages (e.g., Lerouge et al, 2006; Loose & Schenk, 2018; Penaye et al, 2004). Consequently, the tectonic‐metamorphic evolution is characterized by the development of sheet tectonic structures and high‐grade granulite metamorphism associated with charnockitization, migmatization, and serpentinization during the Eburnean‐Amazonian collision from 2100 to 2000 Ma between the Congo and São Francisco cratons (e.g., Lerouge et al, 2006; Owona, Ratschbacher, et al, 2020; Soh et al, 2021). The Nyong Complex represents a belt approximately 240 km long and 160 km wide, oriented NNE–SSW (e.g., Bouyo Houketchang et al, 2019; Soh et al, 2021).…”

The Western Cameroon Highland margin: Is there any geomorphometric evidence of active tectonics?

“…The NyC is the Cameroonian part of the West Central African fold belt associated with the collision between Congo and São Francisco shields during the Eburnean/Trans Amazonian orogeny (Figure 1c; Feybesse et al, 1998;Lerouge et al, 2006;Maurizot et al, 1986;Neves et al, 2006;Owona et al, 2020Owona et al, , 2021. In the Western Cameroon highlands, it includes migmatitic gneisses and granulites with Archean nucleus made up of gneiss of TTG composition similar to those of the Archean Congo Craton (Pénaye, Toteu, Michard, Bertrand, & Dautel, 1989).…”