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The 60 km-long Pan-African Bape massif intruded in the Adamawa-Yade Archaean block is an excellent case for the study of subduction–collision-related magmatism, its origin by interaction among magmas from various sources, and its bearing on the evolution of the Pan-African orogenic belt in Cameroon. An integrated study including mapping, petrography and geochemistry was carried out on these Ba–Sr rich quartz monzonites, quartz monzodiorites, monzonites, granodiorites (adakites), syenites and micromonzogabbros. The rocks are dominated by plagioclase + alkali feldspars + amphibole + biotite + sphene + opaque minerals + apatite + zircon ± pyroxene ± quartz assemblage. They are I-type, ferroan, metaluminous and belong to high-K calc-alkaline, shoshonitic series. REE patterns form two sets of tight closed and of highly differentiated patterns. The spider diagrams display Th, U, Nb, Ta, Zr and Hf negative and Ba, K, Pb and Sr positive anomalies. High K2O, Ba–Sr and moderate SiO2 contents and the variation of canonical ratios such as Zr/Sm, Zr/Hf, La/Sm, and Sm/Yb, point to multiple origins for the Bape granitoids such as (i) melting of a dehydrated subducting crust (adakites) and/or the metasomatized heterogeneous mantle wedge (spinel– and phlogopite–amphibole–garnet lherzolite), or (ii) the mixing of these liquids (other granitoids). The U–Pb emplacement age (640–603 Ma), coeval with the subduction–collision between the West-African and the Congo cratons, the occurrence of adakites, combined with geophysical data, support that these granitoids are link to the southeast–northwest subduction of the hot Yaounde oceanic crust under the Adamawa-Yade craton, during the Neoproterozoic time.

South of Bafia (Cameroon), the Pan-African Yoro-Yangben massif is emplaced in the Adamawa-Yade block, an archaean-paleoprotrozoic micro-continent that detached from the Congo craton during the early Neoproterozoic. This emplacement within a micro-continent raises the problematic of its (i) origin either by the melting of a subducted slab and the mantle wedge, or by the melting of the base of a thick crust or both, and (ii) bearing on the evolution of the Pan-African orogeny in Cameroon. Granodiorites, quartz monzonites, quartz diorites and adamellites occur as massive bodies crosscut by dykes of gabbros and granites. The texture varies progressively from granular bands at the core of the massif to foliated texture towards the border. Mineralogical composition is constant in all the rock types (Am+Bt+Pl+Kfs+Qtz+Op+Sph+Zrn+Ap), except the adamellites which are amphibole-free. Chemically, these potassic rocks are either magnesian and metaluminous, or ferroan and peraluminous. Quartz diorites, granodiorites and granites are High-K calc-alkaline whereas quartz monzonites, adamellites and gabbros are shoshonitic. Most incompatible elements (e.g. Nb, Zr) show an erratic variation with increasing silica contents. Granites rare earth elements (REE) patterns are highly fractionated with a positive Eu anomaly (Eu/Eu* = 2.50–2.04) compared to less fractionated REE patterns of adamellites, quartz monzonites, and granodiorites. The negative anomalies in U, Nb, Ta and Ti shown by gabbros, quartz diorites, quartz monzonites and granodiorites spider diagrams as Th, K, Pb, Zr and Hf positive anomalies for the adamellites and granites patterns are consistent with magmas derived from a subduction setting. The low 87Sr/86Sr(600) initial ratio (0.697–0.706) and eNdi values (−0.82706- 1.03707) of the rocks plot in the mantle array. However, a wide variation of the 87Sr/86Sr ratio values with constant eNdi suggests an enrichment in radiogenic 87Sr likely from an old crust displaying high Rb/Sr ratio. The variations of the La/Yb, Y/Nb and Zr/Nb ratios preclude the fractional crystallization process. Moreover, these characteristics, combined with the erratic (Zr, Nb) suggest particular magmatic sources and complex fusion processes to the Yoro-Yangben heterogeneous granitoids. The lower range of Ba/Nb values (130–135) and the occurrence of shoshonitic magmas likely point to the melting of an oceanic slab; while the higher range (225–230) indicates a blend of melts from oceanic slab and the associated sediments. Granite compositions are similar to melting liquids of metagreywackes. La/Sm and Sm/Yb ratios in gabbros, quartz monzonites and quartz diorite indicate an origin by a batch melting of phlogopite-amphibole-garnet lherzolite, whereas granodiorites and adamellites parent magmas may have originated from a batch melting of a metasomatized spinel lherzolite. Whole rock Sm-Nd and Rb-Sr results yield a unique age of 600 Ma, assigned to the collision time between the West-African and the Congo cratons. Thus, the Yoro-Yangben intrusion is part of the numerous Pan-African granitoids in Cameroon, South of Chad and East of Nigeria.

Field description and sampling along two pits, granulometry, Atterberg limits, mineralogical (XRD, FTIR, DSC & TGA) and geochemical analyses of the Balengou clays help to determine their characteristics and the genesis of the deposit. The mineralogical composition is comprised of halloysite–kaolinite, quartz, montmorillonite, hematite, anatase, feldspar, zircon, chromite, and apatite. Gibbsite and illite occur at the shallow and deep depth, respectively. Dikes of sand-poor clays contain also cristobalite and tridymite. Pairs of elements Rb–Ba, Rb–Sr, Nb–Ta, Ta–Zr, TiO2–Zr display good positive correlations (R2 > 0.85). REE patterns are highly fractionated (LaN up to 3312, LaN/YbN: 19–10) and are marked by deep Ce and Eu negative anomalies. Immobile element canonical ratios indicate that the protoliths were commendite/pantelerite, rhyolite and dacite, or their plutonic equivalents. Mineralogical and geochemical features lead to the suggestion that the clays derived from an advanced argillic hydrothermal alteration.

The Zindeng phonolitic flow forms a NW-SE elongated body located on the SE flank of Mount Bambouto (West-Cameroon), along the Cameroon Volcanic Line. It covers basalt emplaced on top of the Dschang biotite megacrystic granite. The magnitude of the magnetic susceptibility (Km) in the phonolitic lava flow varies between 196 μSI and 15769 μSI, indicating a dominantly ferromagnetic sensus lato behavior (Km > 1000 μSI; 89% of the stations) due to the presence of pseudo-single to multi-domain magnetite grains as deduced from hysteresis data. The low values of the degree of magnetic anisotropy, the dominantly oblate shape of the AMS ellipsoids and the concordance between lava plane and magnetic foliation point to flow-related magnetic fabrics. The pattern of the magnetic foliations and lineations indicate that the SE part of the phonolite was emplaced as a dome, whereas the NW part corresponds to a flow domain sensus stricto. It is suggested that the viscous phonolitic magma rose from a feeding conduit below the southeastern part of the lava flow and propagated laterally towards the NW.

The southern part of the Central African Fold Belt (CAFB) in Cameroon is a southward regional-scale nappe-stacking domain (the Yaounde Domain). It comprises the Neoproterozoic Yaounde Group, thrust onto the Congo craton, and the poorly known Bafia Group, which is classically assumed to be a (Palaeoproterozoic) tectonic slice of basement overthrusting the Yaounde Group to the north. New field observations, zircon U–Pb, and whole-rock and garnet Sm–Nd data allow a better understanding of the Bafia Group within the context of the CAFB. The Bafia Group is probably a Neoproterozoic metasedimentary sequence, comparable to those situated north of the Congo craton (Poli, Lom, and Yaounde). In addition to the Palaeoproterozoic to Archean source, the detrital zircons in the Bafia Group are inherited from 1617 ± 16 Ma granitoids. Our results also led us to discuss the source and provenance of the Bafia Group's gneiss protoliths, and the metamorphic evolution of this group.

TIMS-ID and SIMS U–Pb dating on zircons from metaplutonic rocks involved in the Pan-African nappe of southern Cameroon allow definition of three groups of subduction-related intrusions: group-I intrusions represented by the Masins metagabbro in the Lomie region yielded 666 ± 26 Ma; group-II intrusions represented by the Mamb metasyenogabbro and the Yaounde pyriclasite yielded ca. 620 Ma and are broadly coeval with the deposition of the Yaounde metasediments; group-III intrusions represented by the Elon augen metagranite and the Ngaa Mbappe metamonzodiorite yielded ca. 600 Ma. The onset of the nappe tectonics occurred under high-grade conditions in the range 616 to 610 Ma and continued around 600 Ma with the emplacement of the shallowest nappes. Finally, the construction of southern Cameroon proceeded by a multi-stage evolution characterized by a long-lived development of magmatic arcs associated with rapid opening and closure of sedimentary marginal basins in relation to a northward subduction.

Available isotopic and geochronological data, combined with new petrographic and structural observations in Cameroon, permit discussion of the nature and extension of the Paleoproterozoic West Central African Belt, which resulted from the Eburnean collision between the Congo and Sao Francisco cratons. The portion of the belt recognized in Cameroon is approximately oriented NNE-SSW and includes the Nyong series along the NW corner of the Congo craton and Paleoproterozoic remnants cropping out further north within the late Neoproterozoic Pan-African belt. The dominant rock units consist of migmatitic orthogneisses associated with amphibolites, felsic gneisses of volcanic to volcano-sedimentary origin, quartzites, and banded iron formations. Orthogneisses are mostly TTG compositions within the Nyong series and metadiorites to metagranodiorites to the north in the Pan-African belt. Paleoproterozoic evolution is characterized by the development of nappe tectonic structures, recognized in the Nyong series, and by high-grade, granulitic facies metamorphism that was associated with arrested charnockite formation. The Paleoproterozoic structures and mineral assemblages were subsequently reworked more severely in the Pan-African mobile belt than in the Nyong series, where they are locally well preserved. Broadly, the Nyong series may be ascribed to a proximal domain characterized by reworking and recycling of the adjacent Archean cratonic crust, while the occurrences farther north represent a more distal domain characterized by newly formed Paleoproterozoic (Birrimian) crust. This is consistent with the distribution of metamorphic ages, which display a polarity from the internal zones (ca. 2.1 Ga) to the external zones (ca. 2.03 Ga) and suggest origin of the metamorphic rocks in a modern-type collisional belt during the Paleoproterozoic (Eburnean).