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The Sanaga iron ore prospect is a recent discovery in the Nyong Series with a resource estimated at 82.9 Mt at 32.1% Fe and whose origin remains debatable. The mineralization occurs as NE-SW oriented discontinuous lenticular bodies of magnetite-bearing pyroxene-gneisses (MPG) hosted by ortho-derived gneisses. Rare amphibolites are observed. The MPG mineral assemblage consists of quartz-magnetite-orthopyroxene-garnet-tremolite/actinolite exhibiting a granoblastic texture, which is characteristic of granulite facies metamorphism. The granodioritic gneisses show compositional features of the tonalite-trondhjemite-granodiorite association. Their trace and REE element geochemistry indicate their protolith melt resulted from the partial melting of a subducted oceanic slab, with interaction with the overlying mantle wedge during ascent. The amphibolites show enrichment in LILE with negative Ta–Nb and Zr–Hf indicating arc-related magmas generated by partial melting of a sub-continental lithospheric mantle source with metasomatism by subduction-related fluids. The MPG exhibits oxidation-exsolution features characterized by ilmenite lamellae, with hematite fracture-filling in magnetite, and lacks features characteristic of typical BIF such as LREE depletion relative to HREE, positive Eu, La, and Y anomalies. Based on the results of this study, we interpret the Sanaga MPG as a possible skarn-type mineralization formed by the metamorphism/metasomatism of a possible BIF protolith. The results of this study compare with similar magnetite-rich mineralization in the São Francisco craton in northeastern Brazil and enhance the correlation of pre-drift reconstructions of the São Francisco–Congo Cratons. [ABSTRACT FROM AUTHOR]

Biotite granites and K-feldspar granites are the dominant intrusive rock types of the Colomine gold district in the Neoproterozoic terrain of SE Cameroon. The silica contents of these granitoids range from 68.93–75.39 wt% and Au contents from 0.6 to 32 ppb. They are weakly peraluminous (ASI = 1.0–1.2) I-type granitoids with high-K calc-alkaline to shoshonitic character, emplaced within a syn -collisional arc setting. They have fractionated trace element patterns (LaN/YbN: ~ 11–331) with enrichment in LREE compared to HREE and weak to strong negative Ba, Nb, Sr, P, Ti, Lu, and Eu (Eu/Eu* = 0.12–0.52) anomalies. The geochemical characteristics suggest that the granitoids formed by partial melting of crustal source rocks with some input from greywackes. Differentiation of the hydrous parent magma was characterized by fractionation of muscovite, biotite, hornblende, plagioclase, and K-feldspar with minor zircon, apatite and Fe-Ti oxide. Mafic garnet-bearing inclusions represent an early crystallization phase that was incorporated in the later felsic melt. The granitoids became emplaced into Proterozoic schist belts. Along the contacts, they became brecciated, sheared, foliated and sericitized. These "contact granites" have higher gold contents (5–32 ppb) than the fresh granitoids (0.6–3 ppb). Remobilisation of gold from early magmatic sulfide minerals by post-magmatic hydrothermal fluids enriched the shear-related granitoids. Hydrothermal alteration results to enrichment in Cu, Ni, Cr, Mo, Ga, V, Tl, and Au and depletion in LREE (e.g., La, Ce, Pr). Micro-shear and fault zones in the vicinity of the granitoids constitute favourable sites for exploration. • Biotite and K-feldspar granites are the dominant rocks in the Colomine area, SE Cameroon. • They are weakly peraluminous, high-K calc-alkaline to shoshonitic, I-type granitoids derived from partial melting of crustal material. • These granitoids were emplaced into Proterozoic schist belts and became brecciated, sheared, foliated and sericitized along the contacts. • The fresh granitoids have relatively low Au values compared to areas of the pluton affected by post magmatic hydrothermal alterations. [ABSTRACT FROM AUTHOR]

The textural characteristics of felsic lavas and ignimbrites in the Sabga area along the continental segment of the Cameroon Volcanic Line (CVL) are documented in this study. Two rhyolitic lava flows separated by mafic and rhyodacitic lava flows were dated by zircon LA-ICP-MS technique in order to constrain the timescales of successive flow emplacement as well as magma chamber processes in this volcanic field. The studied samples have rheomorphic characteristics such as eutaxitic textures defined by elongated fiamme as well as deformed and welded glass shards. They exhibit flow banding and contain spherulitic groundmass. Rhyolitic autobreccias and ignimbrites are widespread in the Sabga area, are peralkaline in nature and their ages are broadly similar at ~23.0 ± 0.3 Ma (23.34 ± 0.34 Ma for the ignimbrite and 22.98 ± 0.28 Ma for the rhyolitic autobreccia unit). These ages suggest rapid recharge of magma into a periodically replenished and open chamber. The felsic rocks in the Sabga area and around the Bamenda Highlands are also younger compared to other felsic units along the CVL (29 Ma to 69.4 ± 0.4 Ma). [ABSTRACT FROM AUTHOR]

The Neoproterozoic Pan-African Orogeny in the Adamawa-Yadé domain (AYD) of Cameroon is characterized by intense magmatism of metaluminous to weakly peraluminous I-type granites spatially associated with transcurrent shear zones. This domain provides a critical geological record that is important for unravelling the regional tectonic evolution and geodynamic setting. We present new zircon U-Pb ages and Lu-Hf isotope data from pre-collisional biotite granite and porphyritic K-feldspar granite of the gold-producing Colomine district. Zircon U-Pb ages of biotite granite samples suggest emplacement at 727 ± 8 Ma and at 671 ± 6 for the porphyritic K-feldspar granite. Metamorphic-hydrothermal events between 600 and 550 Ma resulted in Pb-loss of most dated zircons. Lu-Hf isotope data of zircon grains form the porphyritic K-feldspar granite with ϵHf (t) values of −28.7 to −22.6 and T DM c ages of 2.4–2.1 Ga overlap with those of the biotite granite (ϵHf (t) values of −29.4 to −19.6; T DM c ages of 2.5–1.9 Ga). Depleted mantle model ages and ϵHf (t) values suggest that the granites were derived from crustal reworking of older Archean to Paleoproterozoic crust with minor mixing from a juvenile component during the Pan-African. The formation of these pre-collisional granites is interpreted as related to accretion tectonics that started around 750 Ma and incorporating tectonic domains of the Central African Fold belt, namely, the NW Cameroon domain, Mayo-Kebbi domain and the Adamawa-Yade domain. • U–Pb, Lu–Hf isotope data from Colomine zircons presented. • Biotite granites and porphyritic K-feldspar granite were emplacement at ca. 727 ± 8 Ma and ca. 671 ± 6, respectively. • Model Hf ages for the zircons grains ranges from 2.5 to 1.9 Ga. • The granites were derived from crustal reworking of older Paleoproterozoic crust with mixing from a juvenile component. • Accretion tectonics started around 750 Ma incorporating tectonic domains of the Central African Fold belt. [ABSTRACT FROM AUTHOR]