African Fold Belt Research Articles

Source and age of the Ngaye banded iron formations, Adamawa Yadé Domain, Central Cameroon: Constraints from whole-rock geochemistry and U-Pb zircon geochronology

The Ngaye inlier of the Adamawa Yadé Domain is located in the Central African Fold Belt, adjacent to the Nyong Complex at the northern margin of the Congo craton, in central Cameroon. This area consists of metamorphosed granite-greenstone associations comprising amphibole- and pyroxene-rich banded iron formations (BIFs), amphibolites, and migmatitic gneisses. This study reports detailed petrographic, whole-rock geochemical, and LA-ICP-MS U-Pb zircon data for the Ngaye BIFs and associated amphibolites to better constrain their source, tectonic setting, and age. Amphibole-rich BIFs exhibit high REE-Y content and uncommon LREE-enriched patterns. In contrast, pyroxene-rich BIFs display combined low REE-Y content, seawater-like patterns, and positive Eu anomalies, suggesting a mixture of seawater and hydrothermal fluids during their deposition. The geochemical data of associated amphibolites suggest a back-arc setting for the Ngaye metavolcanosedimentary sequence, similar to that of the Nyong Complex. LA-ICP-MS U-Pb zircon dating of amphibole-rich BIFs indicate a maximum depositional age of ca. 2186 Ma and subsequent metamorphism at ca. 2038 Ma, overlapping with that of metavolcanosedimentary sequences from the Nyong Complex. Neoproterozoic age of ca. 598 Ma obtained for these BIFs is interpreted as the Pan-African metamorphic/hydrothermal imprint. This finding suggests that the post-depositional fluid overprint was probably related to the regional Pan-African tectono-thermal event.

Geochronology and geochemistry of a Neoproterozoic syn-tectonic granitic pluton in the Gari-Gombo area, East Cameroun: Implications for petrogenesis and tectonic evolution

Granites are widespread in many Precambrian orogenic belts worldwide; therefore, they can provide insights into orogenic processes and associated magmatism. Zircon UPb age, monazite Th-U-total Pb age and whole-rock geochemical data for a granite pluton from the Gari-Gombo area in the Adamawa-Yade domain of the Central African Fold Belt (CAFB) in East Cameroon are presented. The granite is composed dominantly of perthitic K-feldspars, quartz, plagioclase and minor biotite with accessory monazite, apatite and zircon. LA-ICP-MS zircon UPb dating yielded an age at ca 631–620 Ma, which is interpreted as age of emplacement that coincides with the onset of D2 Pan-African deformation. Monazite grains in Gari-Gombo granite follow strictly the huttonite substitution trend in Th + U vs Si coordinates. Monazites give consistent Neoproterozoic ages of 630 ± 4 Ma and 602 ± 4 Ma, indicating that growth history and crystallization age of monazites also correlate well with the Pan-African plutonism and granulite facies metamorphism (ca 614–600 Ma) in the Gari-Gombo area. The Gari-Gombo pluton samples show high-K calc-alkaline magnesian, slightly peraluminous signature, high SiO2 (70.16–78.80 wt%), K2O (4.39–5.38 wt%), and Rb (165–248 ppm), and low P2O5 ≤ 0.01 wt% and Sr (146–222 ppm) contents. They have highly-fractionated REE pattern ((La/Yb)N = 6.17–148.18), moderately Eu negative anomalies (Eu/Eu* = 0.53–0.93) and the obviously Nb and Ti negative anomalies. These geochemical features suggest that the Gari-Gombo pluton is a highly fractionated I-type granite generated by partial melting of older meta-igneous materials at middle to lower crustal levels. The 2.9 and 0.95 Ga inherited zircon grains identified within the studied granites further confirm the existence of ancient crust in this region.

Mineralization of Zr-REE-Y in the Ngaoumbol iron formations, central Cameroon: Insights from petrography, mineral chemistry and whole rock geochemistry

The increasing importance of rare earth elements (REE) and critical metals in contemporary society has led us to investigate the mineral potential of the Ngaoumbol area, located within Cameroon's Central African Fold Belt (CAFB). In this study, we have conducted a comprehensive analysis that includes petrography, whole rock geochemistry, and mineral chemistry, along with the application of an outlook coefficient known as Koult, with the aim to evaluate the prospectivity of the Ngaoumbol iron formations as a potential source of REE-Y resources. This coefficient is defined as the ratio of the relative abundance of critical Rare Earth Elements to the relative abundance of excess REE. The iron formations in the Ngaoumbol area are fine-to medium-grained foliated rocks with alternating magnetite and actinolite bands and quartz bands, suggesting a sedimentary parentage. These rocks have an average REE-Y content of 1438.43 ppm and a Koult of 0.77, indicating their potential as raw sources for REE. Furthermore, the investigated samples exhibit high average Zr content (7748 ppm), suggesting that the rocks may host potentially economic Zr ore. The Zr-REE-Y mineralization in the Ngaoumbol area is hosted in detrital zircon, monazite and xenotime, probably deriving from the weathering of alkaline/subalkaline rocks surrounding the deposits. Our findings suggest that the Ngaoumbol area has promising REE and Zr resources. However, further exploration and evaluation are necessary to determine the extent and economic viability of these resources.

Petrogenesis of metaluminous and peraluminous granitoids from Garga-Sarali zone : evidence of I- and S-type sources (central African fold belt in Cameroon)

The Garga-Sarali granitoids outcrop from a metamorphic basement in the central-eastern part of the Central Cameroonian Domain of the Central African fold belt in Cameroon, and are petrographically very complex. They can be divided into two types : (1) Granodiorites of metaluminous type-I, with a fine-grained porphyritic variant texture, consisting of quartrz + orthoclase + microcline + plagioclase + biotite + zircon + oxides ± apatite; (2) and two-mica granites of hyper-aluminous type-S, with a grainy texture, consisting of the same quartzo + k-feldspars + biotite + cordierite ± apatite. These formations both belong to a calc-alkaline-subalkaline, hyper-potassic to shoshonitic signature, and to the tectonic domains of volcanic arc granites. Their emplacement is intimately linked to a crustal parent magma (metagrauwackes and metabsalt-tonalites) that imbibed through the openings in the post-orogenic pan-African lithospheric constraints. Their La/Yb ratio, with (La/Sm)n ranging from 2.18-5.75 ppm, reflects their richness in LREE, and the average Eu/Eu*=0.666 ppm suggests that the residual magma was supersaturated with silica.

Mapping and discrimination of the mineralization potential in granitoids from Banyo area (Adamawa, Cameroon), using Landsat 9 OLI, ASTER images and field observations

The Banyo area is situated in the west Cameroon domain of the Central African Fold Belt. In this study, field data and remote sensing conventional mapping techniques including Red-Green-Blue (RGB) colour combination, principal component analysis (PCA), Crosta-PCA, Band Ratios (BR), Constrained Energy Minimization (CEM), Minimum Noise Fraction (MNF), Spectral Angle Mapper (SAM) classification and Linear Spectral Unmixing (LSU) algorithms were used to process Landsat 9 OLI and ASTER data in order to discriminate various rock units such as biotite-amphibole granites, hornblende-biotite orthogneiss and map associated mineral deposits (e.g., iron-oxide, hydroxyl and corundum minerals). In addition, it was found that RGB combination (743) of OLI bands, PCA of OLI bands (PC123), BR of OLI bands (4/2, 6/7, 6/5), BR of ASTER (4/2, 7/6, 8/9), Crosta-PCA of OLI bands, MNF (123) of OLI bands, SAM, and LSU techniques applied to ASTER bands ascertain potential locations of granitoids and gneisses bearing iron and hydroxyl minerals. On the other hand, this study also revealed that corundum deposits are detected by applying the CEM method to OLI band ratio 6/7 highlighting red tones and processing SAM classification algorithm both using laboratory reference spectra. Automatic (using PCI Geomatica line tool) and manual extractions of lineaments revealed three major trends (N-S, E-W, and WNW-ESE to NW-SE) and an accessory trend (NE-SW to ENE-WSW) that surround hydrothermally altered rocks recognized as containing iron oxide, hydroxyl, and corundum mineral deposits. In the field, these lineaments may group to the tree deformation phases. The D1 phase (NW-SE); the D2 phase (NE-SW to ENE-WSW) and the D3 phase (N-S). Maximum Likelihood Calssification (MLC) and SAM classification methods showed to be more effective in discriminating rocks bearing Iron-oxide, hydroxyl and corundum minerals in the study area.This result permits to confirm that, the combination of remote sensing (Landsat 9 OLI and ASTER data in this case) and field data constitute a useful tool for mineral exploration in the shear zone. However, the accuracy assessment was relied on comparing the different maps produced from Landsat 9 OLI and ASTER data with the ground truth sample points and also, with the earliest geological map of Banyo area. Thus, quantitatively the results were accurate at 99%.

Mantle-crust-interaction and subduction dynamics in Central Cameroon: Evidence from the Pan-African Linté microgranular magmatic enclaves (MMEs) and host syenite

The Central African Fold Belt (CAFB) in Cameroon is characterized by voluminous intrusive rocks hosting microgranular magmatic enclaves (MMEs) whose petrogenesis and tectonic implications remain unclear. Here, we present detailed geochronological and geochemical data of the host rocks and their MMEs from the Linté pluton in central Cameroon. The MMEs are finer-grained than their host syenite and both rocks are composed of alkali feldspar, plagioclase, biotite, amphibole and pyroxenes as main mineral phases. The enclaves show lower Mg#, total alkalis and transition elements contents, and are more HFSEs depleted than the host syenite. Both rocks are characterized by high-K, metaluminous I-type, alkaline to sub-alkaline and magnesian affinities. The Ti-in-zircon thermometer suggests crystallization temperatures of 615–1080 °C and 613–1008 °C for syenites and MMEs, respectively. Their zircon trace element distribution and patterns coupled with whole-rock geochemical features indicate that the Linté intrusive rocks were most likely originated from interaction of mantle-derived magma with crustal material. LA-ICP-MS UPb zircon analyses yield emplacement age of 599 ± 3 Ma and 597 ± 4 Ma for the host syenite and MMEs, respectively, indicating coeval crystallization date. Integrated whole rock geochemistry, UPb dating and Ti-in-zircon thermometry data indicate that the Linté syenite were probably formed from a mantle-derived ultrapotassic alkaline melt with significant crustal contribution, while MMEs are likely derived from a similar but separate melt with more fractionation and crustal contamination. The genesis of the host syenite and MMEs magmas started with break-off of the Congo plate after subduction and collision. This initiated an upwelling thermal pulse and underplating of mafic magma which led to partial melting of the Paleoproterozoic crust of the Central Cameroon.

Petrography and geochemistry of basic and intermediate plutonic suite of the Mayo Nielse and Mayo Balche areas, (Poli Group, Central Africa Fold Belt, Northern Cameroon): Post‐collisional mantle refertilization and magma genesis

The study area is located in the Poli Group, Western Cameroon Domain of the Central African Fold Belt. It is constituted mainly of Pan‐African granitoids intruding Neoproterozoic volcano‐sedimentary rocks, schists and gneisses. The granitoids host dykes of gabbroic and dioritic rocks which are the focus of this study. Gabbroic and dioritic rocks are clinopyroxene‐hornblende gabbros, clinopyroxene‐hornblende melagabbro, clinopyroxene‐hornblende leucogabbro and quartz‐diorite. Geochemically, the rocks are characterized by: SiO2 (46.03–58.88 wt. %); Mg# (27.78–79.46); MgO (2.10–18.40 wt.%); total alkali (0.97–10.7 wt.%); Fe2O3 (8.42–13.19 wt.%); and CaO (4.90–16.57 wt. %), meanwhile all the rare earth elements are enriched with respect to chondrites. The rocks are mainly medium‐K calc‐alkaline with subordinate low‐K and alkaline samples. The ratios of La/Ta (4.0–76.0), La/Nb (0.8–9.88) and Zr/Ba (0.11–0.52) indicate that their source is both asthenospheric and lithospheric. This source has characteristics of NMORB to EMORB, overprinted by fluids‐enriched silicic and carbonatitic metasomes likely as a result of slab‐mantle interactions in a subduction environment. The weak to strong fractionation of La/Yb ratio (La/YbN = 0.9–13.51) and non‐fractionation of the Dy/Yb ratio (Dy/YbN = 0.6–1.5) together with the behaviour of the rocks in the La/Sm versus Sm/Yb modelization diagram are consistent with a polybaric melting which started in the asthenosphere at a small rate, yielding the limited volume of alkaline rocks. It then continued in the lithosphere where a more extensive degree of melting produced medium‐K calc‐alkaline rocks. The melting was likely induced by the adiabatic decompression of the metasomatized mantle during the post‐collisional relaxation closing the tectonic stage of the Pan‐African Orogeny in the Poli area. The magma generated was near‐primitive and evolved by assimilation‐fractional crystallization.

Structural and microstructural evolution of Etam Shear Zone in the Central African Fold Belt, SW-Cameroon: implication of hydrothermal syn-tectonic quartz vein formation

Structural and microstructural evolution of Etam Shear Zone in the Central African Fold Belt, SW-Cameroon: implication of hydrothermal syn-tectonic quartz vein formation

Tourmaline occurrence and gold mineralization at a granitoid-metasediment contact in the Upper Lom Basin, east Cameroon

Gold mineralization of the Upper Lom Basin in the eastern Cameroon goldfield is spatially associated with tourmaline. The goldfield belongs to the Adamawa-Yadé Domain of the Central African Fold Belt and is characterized by eluvial, alluvial and lode gold deposits of Pan-African age. This paper examines the chemistry and morphology of saprock gold and its link with tourmaline in the host rock. Tourmaline chemistry was obtained using the electron microprobe analysis (EMPA) technique while gold grains were examined for morphology and microchemistry using the EMPA equipped with scanning electron microscopy and energy dispersive spectrum instruments. The tourmaline compositional data plot in the dravite field, and belongs to the alkali group showing major element variations that are typical of tourmaline associated with granite-related orogenic gold deposits common along shear zones. Gold alloy composition (Ag, Cu) suggests multiple gold precipitation events due to episodic fluid influx, with a range of 572–1000 gold fineness. We infer that tourmaline development and gold deposition were coeval within the aureole around the pluton and involved reduced hydrothermal fluids with low salinity. The high δ11B in the tourmaline also points to fluid derivation from the Pan African granitic basement widely recognized to be fertile in gold in eastern Cameroon. Tourmaline textural-chemical features such as low Na content and gold microchemistry point to granite-related hydrothermal style of primary gold mineralization, and has implications for exploration as tourmaline-rich rocks in the vicinity of the felsic plutons in the Lom Basin would be optimal target areas for future exploration.

Structural and kinematic analysis of the Nkondjock shear zone, central Cameroon: implications on the geodynamic evolution of the Central African Fold Belt

Structural and kinematic analysis of the Nkondjock shear zone, central Cameroon: implications on the geodynamic evolution of the Central African Fold Belt

Petrography and geochemistry of the Letta Pan-African plutonic and metamorphic rocks in eastern part of the Central African Fold Belt in Cameroon

Petrography and geochemistry of the Letta Pan-African plutonic and metamorphic rocks in eastern part of the Central African Fold Belt in Cameroon

Cambrian mafic magmatism in the Kékem area, NW edge of the Adamawa-Yadé domain, Central African Fold Belt: Implications for Western Gondwana dynamics

The tectonic evolution of the Central African Fold Belt (CAFB) has been intensely studied, but the timing of the end of the Pan-African orogenic cycle is poorly constrained, leading to contrasting tectonic models. In order to address the nature of magmatic products associated with and the timing of the end Pan-African orogenic cycle, we use mineral chemistry, whole-rock geochemistry and Sr − Nd isotopes, and zircon trace element and U − Pb geochronology of northern and southern gabbro that cut the post-collisional Central Cameroon Shear Zone; results are discussed in the tectonic framework of the CAFB. Clinopyroxene and whole-rock chemistry show that the northern and southern gabbros are mainly subalkaline, with a tholeiitic/transitional affinity. Northern and southern gabbros have REE and trace element patterns, characterized by enrichment in LREE, and depletion in HREE, Th, U, Nb, Ta, and Pb. Their Sr − Nd isotope data show low (87Sr/86Sr)i of 0.703793–0.704608 and slightly negative ɛNd(t) values ranging from −3.20 to −0.66 with Paleoproterozoic Nd model ages of 2149–1612 Ma. Moreover, the northern and southern gabbros yield U − Pb zircon ages of 486 ± 15 Ma and 497 ± 13 Ma, respectively. Our combined data is consistent with the northern and southern gabbroic magma having originated at (or near) a deep, probably asthenospheric mantle source and may have interacted with Paleoproterozoic subduction metasomatized lithospheric mantle during ascent as a result of lithospheric extension associated with lithospheric scale shearing along the shear zone. In concert with previous studies, we suggest that the evolution of the CAFB was characterized by subduction and eventual collision at 660–600 Ma followed by a 600–570 Ma post-collisional stage and final extension from 560 − 486 Ma. The extensional regime was associated with mafic to felsic magmatism with geochemical signatures evolving towards a tholeiitic/transitional or alkaline affinity. Correlation of the CAFB with the Borborema Province of the Brasiliano fold belt suggests that both shared a similar tectonic evolution and orogenic cycle characterized by early crustal thickening followed by transcurrent tectonics and ultimate lithospheric extension.

Geochronology, geochemistry and Sr-Nd, Hf-O isotope systematics of the Linte massif, Adamawa - Yade domain, Cameroon: Implications on the evolution of the Central African Fold Belt

The Central African Fold Belt (CAFB) holds a key position in understanding the process and implications of the Pan-African orogeny in central Africa. However, it has not been fully understood as geological information on some vital domains is not yet available. The Linte massif in the Adamawa-Yade, one of the unrepresented terranes, was investigated and its whole rock geochemical, zircon U-Pb geochronology and Hf-O isotope characteristics and whole rock Sr-Nd data are presented and discussed here. The Linte massif is largely constituted of syenite and subordinate monzonite. The zircon U - Pb dating reveals three major ages at 660, 630 and 600 Ma, indicating a protracted magmatism which lasted at least 60 Ma, during the Neoproterozoic. The rocks are shoshonites, I-type and metaluminous. They have high LILEs (Cs, Rb, Ba and Sr), HFSEs (Th and U) and LREE contents. Their Nb/U, Ta/U, Ce/Pb, Th/La and Th/U ratios, δ18Ozrn (5.3–7.6‰) and zircon εHf(t) (−14.7 to +3.2), point toward predominantly crustal with or without a mantle component in the sources. The negative εNd(t) values (−8.1 to −10.0), Paleoproterozoic Nd-TDM model ages (ca. 1700–1900 Ma), Hf-TDM2 ages of ca. 1300–2400 Ma of zircon grains in Neoproterozoic rocks underline their derivation from Mesoproterozoic to Paleoproterozoic basement rocks.The lithospheric mantle-generated heat facilitated partial melting in the sources region, as inferred from the shoshonitic affinity and the subduction-related geochemical features (Nb, Ta and Ti depletion). A mainly crustal source with a minor mantle component is inferred for the 660 Ma magmatism and for the 630 Ma rocks emplaced during crustal thickening. On the other hand, the 600 Ma (youngest) magmatic rocks were derived from a crustal source. We infer a subduction-collision setting for the Linte massif during the 660–600 Ma interval. The 630–600 Ma interval of the culmination of collision is consistent with the timing of the main convergence of the Brasiliano Orogeny recorded in South America (∼630–600 Ma), suggesting continuation of tectonic features into the western Gondwana.

Petrogenesis and tectonic implication of Neoproterozoic I-Type Granitoids and orthogneisses in the Goa-Mandja area, Central African Fold Belt (Cameroon)

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-D2 regional emplacement and synchronous with the magmatism at ~600 Ma within the CAFB in Cameroon and its extension into northeastern Brazil, as the zircon UPb dating points to 603–598 Ma crystallization ages. Analytical data reveal slightly elevated δ18Ozrn (6.45–7.17‰) and δ18OWR (8.20–8.61‰), moderate to high SiO2 (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/86Sri (0.703328–0.722670) and positive to negative εNd(t) (+5.7 to −9.9), coupled with the diversity of Nd model ages (TDM2) support the heterogeneity of crustal protoliths. The high positive εNd(t) (+5.7) of the granitic vein indicates derivation from juvenile Neoproterozoic (Nd-TDM2 at 854 Ma) crustal protolith. TDM2(Nd) and TDM2(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.

Geochronology and correlations in the Central African Fold Belt along the northern edge of the Congo Craton: New insights from U-Pb dating of zircons from Cameroon, Central African Republic, and south-western Chad

The Central African Fold Belt (CAFB) is the least well-known of all major Pan African belts. Here, we present new geochronologic work carried out in several critical areas of western Central African Republic, the region standing between northern Cameroon and southwestern Chad, and southern Cameroon. Our results allow us to: (1) clarify the regional extension of the Congo Craton in SE Cameroon and in the SW Central African Republic; (2) demonstrate that the units thrust along the northern edge of the Congo Craton from Cameroon to the Central African Republic are comparable in nature and in age; (3) better constrain the limits and described better the role of the Adamawa-Yadé crustal block during the Pan-African pre-collisional and collisional events in relation to the Congo Craton and the Yaoundé-Yangana nappe units to the South, and to the Poli-Leré magmatic arc to the North and; (4) clarify some of the elements of correlation with NE Brazil. Overall, a model involving two subduction zones is proposed to explain the evolution of the Pan-African belt north of the Congo Craton. The main steps include; (1) break-up and basin development from the early Tonian to at least 620 Ma on the northern edge of the Congo Craton, and on both the southern and the northern edges of the Adamawa-Yadé Block, concomitantly with the development of the Poli-Leré arc in northern Cameroon and Chad; (2) pre-tectonic plutonism in all domains since c. 800 Ma with culmination between 650 and 620 Ma; (3) collisional events starting around 620 Ma with metamorphism reaching the granulite facies at c. 600 Ma in all the domains; (4) nappe tectonics with thrusting of the Yaoundé-Yangana units onto the Congo Craton, accretion of the Poli-Leré arc to Adamawa-Yadé Block, and widespread syntectonic magmatism (600–580 Ma) with emplacement partly controlled by transcurrent regional shear zones, and emplacement of post-tectonic granitoids (c. 550 Ma) in both Adamawa-Yadé block and Poli-Leré magmatic arc. Collisional and post-collisional (620–550 Ma) events were synchronous along the entire belt from Central Africa to Brazil.

Petrogenesis, tectonic setting and geodynamic implications of Ouaden, Doumba Bello, and Ngoura granitic plutons (Eastern Cameroon): Constraints from elemental and Sr−Nd−Hf isotopic data and zircon U−Pb ages

The Ouaden, Doumba Bello, and Ngoura granitic plutons, eastern Cameroon, comprise segments of the Central African Fold Belt (CAFB) situated along the northern edge of the Congo craton. A geochemical, isotopic and geochronological study was carried out on these three plutons to determine their petrogenesis and tectonic environment of formation. Granodiorites and granites (SiO2 of 65–73 wt%, Mg# of 14–46) of these plutons are potassic and weakly peraluminous with A/CNK ratios of 0.99–1.10. On primitive-mantle normalized trace element diagrams, all intrusives are depleted in Nb, Ta, and Ti. LA-ICP-MS zircon U − Pb dating indicate that the Ouaden, Doumba Bello and Ngoura granitic plutons were emplaced coevally at 640 ± 3 Ma, 641 ± 3 Ma, and 638 ± 4 Ma, respectively. The granodiorites and granites have variable 87Sr/86Sr(i) ratios of 0.71117–0.71831, relatively unradiogenic whole-rock εNd(t) values of −9.6 to −6.3, and zircon εHf(t) values ranging from −10.1 to −2.1; the occurrence of mafic microgranular enclaves suggests mixing with mantle-derived magmas, and such mixing possibly resulted in the scattering of zircon Hf data. Two-stage Nd-Hf model ages of 2115–1856 Ma and 2218–1708 Ma, and ΔFMQ of +5.3 − +2.1 indicate that the studied granitoids were derived from partial melting of Paleoproterozoic crust under variable oxidizing conditions. All granitoids yield inherited zircon ages (736–685 Ma), indicating contamination of Early Neoproterozoic crust during ascent. A combined examination of the geological record, bulk rock chemistry and isotope signatures suggests that the granodiorites and granites formed by mixing of mantle-and crust-derived melts during a late-subduction early-collision setting between the Metacraton and the Congo craton.

The I- and -S type granites from the Shissa pluton, Central African Fold Belt in Cameroon: petrogenesis and geodynamic implication

The I- and -S type granites from the Shissa pluton, Central African Fold Belt in Cameroon: petrogenesis and geodynamic implication

Arc magmatism in the Nkoula granitoid suites, Central African Fold belt in Cameroon: evidence of a metasomatized high oxidized S- and I- type magma

Arc magmatism in the Nkoula granitoid suites, Central African Fold belt in Cameroon: evidence of a metasomatized high oxidized S- and I- type magma

Petrogenesis and tectonic setting of the Pan-African Deng-Deng intrusive complex in the Lom series, Eastern Cameroon

The Deng-Deng intrusive complex belongs to the Central African Fold Belt (CAFB) in eastern Cameroon and includes granodiorite and diorite. Both rocks are classified as metaluminous to slightly peraluminous, high-K calc-alkaline, and I-type granitoids (A/CNK <1.1). Primitive mantle-normalized trace-element patterns display large-ion lithophile elements (LILE) enrichment, such as Rb, Cs, Ba and K, and depletion in high-field-strength elements (HFSEs), such as Nb, Ti, Ta and P. The studied rocks are enriched in LREEs relative to HREEs and exhibit weak negative Eu anomalies (Eu/Eu* = 0.61–0.92 and 0.59–0.67 for the granodiorite and diorite, respectively), suggesting active continental margin arc affinity. The emplacement temperatures of these granitoids are estimated between 775 and 806 °C. Combined with their diagnostic ratios (e.g., Th/Ta, Rb/Sr, Nb/La, and La/Sm), we propose that the Deng-Deng granitoids were sourced by mixing between mafic magma derived from the lithospheric mantle and felsic magma derived from partial melting of a lower crust in a convergent margin setting.

Crustal modelling from Pan-African granites of the Colomine Gold District, SE Cameroon: Insights from zircon U-Pb dating and Lu-Hf isotope systematics

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 TDMc ages of 2.4–2.1 Ga overlap with those of the biotite granite (ϵHf(t) values of −29.4 to −19.6; TDMc 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.