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The geological evolution of the Central African Fold Belt (CAFB) remains debated. The granitoids, orthogneisses and granitic veins from the Goa-Mandja area (Adamawa-Yade domain) are considered to constrain this belt. These rocks are consistent with late-D 2 regional emplacement and synchronous with the magmatism at ~600 Ma within the CAFB in Cameroon and its extension into northeastern Brazil, as the zircon U Pb dating points to 603–598 Ma crystallization ages. Analytical data reveal slightly elevated δ18O zrn (6.45–7.17‰) and δ18O WR (8.20–8.61‰), moderate to high SiO 2 (59.70–77.23 wt%), low MgO (0.07–2.77 wt%), Cr (0.29–55.12 ppm), Ni (0.45–33.6 ppm), V (1.52–116.62 ppm) and Mg# (0.02–0.36) contents, indicating crustal origin. The low to medium 87Sr/86Sr i (0.703328–0.722670) and positive to negative ε Nd(t) (+5.7 to −9.9), coupled with the diversity of Nd model ages (T DM2) support the heterogeneity of crustal protoliths. The high positive ε Nd(t) (+5.7) of the granitic vein indicates derivation from juvenile Neoproterozoic (Nd-T DM2 at 854 Ma) crustal protolith. T DM2(Nd) and T DM2(Hf) ages of 1188–2120 Ma and 2173–2480 Ma also suggest the involvement of Mesoproterozoic to Paleoproterozoic crustal protoliths. Samples show metaluminous to weakly peraluminous, high-K calc-alkaline to shoshonitic and I-type granitoid features and are similar with crustal rocks in regard to LILE (Rb, K) and LREE enrichments and HFSE (Nb, Ta, Ti) depletions. These combined features indicate slab subduction related setting for the magma generation. Slab subduction may have generated the heat necessary to provoke partial melting at the lower crustal level. Considering their position close to the Tchollire-Banyo Fault corridor, at the transition between the Adamawa-Yade and northern domains, the subduction derived features shown by the Goa-Mandja I-type granitoids could be related to the subduction of an old plate boundary during amalgamation of Gondwana. Therefore, the Goa-Mandja area records dominant magmatic accretion along the northern margin of the Congo craton (active margin) associated with a possible northwestern subduction. • The Goa-Mandja granitoids formed at 603–598 Ma. • Variable types of granitoids are identified in the Goa-Mandja area. • They were originated from heterogeneous crustal protoliths. • They are related to the subduction of an old plate boundary during Gondwana assembly. [ABSTRACT FROM AUTHOR]

It is debated whether global-scale tectono-magmatic quiescence prevails on the Earth during the early Paleoproterozoic. The early Paleoproterozoic meta-mafic and intermediate rocks in the southwestern Yangtze Block of South China could provide an opportunity to constrain not only the tectonic evolution of the Yangtze Block itself but also augment our understanding of the global tectono-magmatic lull during the early Paleoproterozoic. Zircon U Pb geochronological study indicates that the meta-mafic rocks were emplaced at ca. 2.32 Ga, whereas the intermediate rocks were emplaced at ca. 2.35 Ga. These two lithologies are characterized by subduction-related whole-rock geochemical (such as depleted Nb, Ta and enriched Rb, K, Pb) and unradiogenic Nd Hf isotopic signatures (ε Hf (t) < 0, ε Nd (t) < 0), implying a derivation from a geochemically enriched lithospheric mantle modified by ancient subduction. Thermodynamic modeling further suggests that the intermediate rocks are products of the AFC process between mantle-derived basaltic magma and TTG-like basement rocks at shallow crustal levels. We interpret this as occurring within a post-orogenic extensional setting. Integrated with the published work, we further posit that the Yangtze Block experienced a tectonic regime transition from compressive orogenesis to post-orogenic extension during the early Paleoproterozoic, and the magmatic activities in several crustal blocks are still active until ~2.3 Ga and therefore places important constraints on the beginning of the tectono-magmatic lull. [Display omitted] • 2.35–2.32 Ga mafic-intermediate magmatism is identified in the SW Yangtze Block. • Mafic-intermediate rocks in this study were derived from the lithospheric mantle. • Tectonic transition from orogeny to post-orogenic extension at ~2.35 Ga in Yangtze. [ABSTRACT FROM AUTHOR]

• Protolith of Nkondjock orthogneisses crystallized at 607 ± 4, 624.4 ± 3.5 and 621 ± 9.1 Ma. • The Nkondjock orthogneisses show geochemical affinity of S- and I-type granitoids. • They were derived from thickened low crust and mature continental crust. • They were formed during the collision between the Congo and West African craton. The Nkondjock area located in Western Cameroon is part of the Neoproterozoic Central African orogenic belt, at the northern border of the Congo craton. Rocks of the Nkondjock area are: two-mica orthogneisses, two-pyroxene orthogneisses and mylonitic orthogneisses. The protolith of two-mica, two-pyroxene and mylonitic orthogneisses crystallized at 607 ± 4, 624.4 ± 3.5 and 621 ± 9.1 Ma, respectively, and are thus consistent with the Central African Orogenic belt. Inherited zircons (2043 ± 27 Ma) of mylonitic orthogneisses are interpreted as an inherited age of the metacratonization of the northern border of the Congo craton. S-type affinity of two-mica orthogneisses together with two-pyroxene orthogneisses (Mabombé) display geochemical affinities typical of adakite, including high La/Yb N (29.7–55.6) and low Y (3.43–6.69 ppm) with low Mg# (30.8–55), εNd(t) (−8.6 to −6.5), high 87Sr/86Sri (0.70684–0.71063) and positive εHf(t) (+3 to +4.9), similar to those adakites formed by partial melting of thickened lower crust with some mantle input. Two-pyroxene orthogneisses (Ndogboni) and mylonitic orthogneisses display I-type granitoids affinity with A/CNK (0.93–1.06) and are depleted in Nb, Ta, Sr, P, Ti and enriched in Rb, Th, and Pb. They also have low εNd(t) (−10.3 to −11), high 87Sr/86Sr i (0.71017–0.71063) and negative εHf(t) (−19.1 to −1) similar to melts derived from mature continental crust. Sr-Nd-Hf isotopes confirm heterogeneous source for these orthogneisses with bimodal distribution on εHf(t) and εNd(t) values, suggesting mixing between juvenile mafic melt and a mature continental crust during the evolution of the Central African Orogenic belt. We suggest that the protolith of these orthogneisses (S- and I-type granitoids) were formed during syn -collisional setting between the Congo and the West African craton which followed a subduction through partial melting of a thickened lower continental crust due to a thermal anomaly induced by upwelling of asthenosphere through slab break-off. [ABSTRACT FROM AUTHOR]