LA–ICP–MS zircon U Pb dating, Lu Hf, Sm Nd geochronology and tectonic setting of the Mesoarchean mafic and felsic magmatic rocks in the Sangmelima granite-greenstone terrane, Ntem Complex (South Cameroon)

Abstract

The Ntem Complex represents the northwestern margin of Congo Craton in southern Cameroon. It consists mainly of charnockites, TTG suites, potassic grantitoids, minor supracrustal and mafic rocks. The latter include gabbronorite enclave or sill, gabbro and dolerite dykes. The metagabbro are basaltic to andesitic in composition and show geochemical features of low-La Archean tholeiitic basalts, and LREE-depleted (La N /Sm N < 1) akin to modern N-MORB. The doleritic dykes show high TiO 2 /P 2 O 5 (7.50-11.47) and (La/Yb) N ratios, and low Nb\ \Ta values similar to modern intraplate continental basalts and intermediate-La Archean tholeiitic basalt, least affected by contamination from granitic continental crust. The partial melting of low-to high-K mafic rocks of oceanic and continental arc affinity generated the charnockites and low−/medium-pressure TTGs. The potassic granites were formed by partial melting of charnockite or TTG, and inherited many geochemical features of their sources. New LA-ICP-MS U\ \Pb zircon dates suggest that the charnockites and TTG suites formed at 3155-2850 Ma. The gabbro intrusion was dated at 2866 ± 6 Ma. Migmatisation of TTG-gneiss was coeval whit the regional high-grade metamorphism event at 2843 ± 7 Ma. The potassic granites were probably crystallized at~2758 Ma. The garnet-whole rock Sm\ \Nd age of 2744 ± 31 Ma may represent the age of the second anatexis event coeval with D2 deformation. Literature data indicate the disruption or open isotopic systems in the Ntem Complex around 2500-2600 Ma.

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 maximum age of the granitic intrusion can be limited by the zircons in granitic gneisses, which show an Archean age. This age is comparable to that stated in the Sangmelima granodiorites (2834 Ma), TTG magmatism (2850 Ma), and Ngoulemakong tonalites (2833 ± 15 Ma) (Akame et al, 2020; Pouclet et al, 2007). This trench and the migmatization of TTG are likewise contemporaneous (2843 Ma) with the emplacement of the granite dykes (monzogranites) at about 2840–2825 Ma (Akame et al, 2020).…”

“…This age is comparable to that stated in the Sangmelima granodiorites (2834 Ma), TTG magmatism (2850 Ma), and Ngoulemakong tonalites (2833 ± 15 Ma) (Akame et al, 2020; Pouclet et al, 2007). This trench and the migmatization of TTG are likewise contemporaneous (2843 Ma) with the emplacement of the granite dykes (monzogranites) at about 2840–2825 Ma (Akame et al, 2020). Archaean ages have also been discovered in the Pan‐African region in the Makénéné zone (3.0–2.5 Ga, Tchakounté et al, 2017) and Meiganga pyroxene and amphibole gneisses (2721–27 Ma; 2925 Ma; Ganwa et al, 2016).…”

“…Given that the geochemical profiles of our granitic gneisses and those of Mewengo and the garnet amphibolite gneisses of Kribi bear striking similarities, we hypothesize that these formations crystallized simultaneously. There- (Akame et al, 2020;Pouclet et al, 2007). This trench and the migmatization of TTG are likewise contemporaneous and is in good agreement with earlier investigations (Bouyo Houketchang et al, 2019;Kwamou et al, 2021;Loose & Schenk, 2018).…”

“…2843 Ma) with the emplacement of the granite dykes (monzogranites) at about 2840-2825 Ma(Akame et al, 2020). Archaean ages have also been discovered in the Pan-African region in the Makénéné zone (3.0-2.5 Ga,Tchakounté et al, 2017) and Meiganga pyroxene and amphibole gneisses(2721-27 Ma; 2925 Ma;Ganwa et al, 2016).…”

Contrasting Depositional Environment of Iron Formation at Endengue Area, NW Congo Craton, Southern Cameroon: New Insights from Trace and Rare Earth Elements Geochemistry

“…The Ntem complex represents the northwestern edge of the Congo craton in Central Africa and comprises the Archaean Ntem and Ayina groups and Archaean to Paleoproterozoic Nyong group (Figure 1(a) [37]. International Journal of Geosciences…”