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The Nigerian Younger Granite (NaYG) province is renowned for its world-class anorogenic alkaline ring granite complexes and has been recognized as a potential host for abundant Nb–Sn–W–Mo mineralization. In this study, a comprehensive investigation was conducted on the southernmost complex of the province, known as the Afu granite complex, encompassing petrography, zircon U–Pb dating and Lu–Hf isotopes, and whole-rock geochemical analyses. The dominant rocks within the Afu complex consist of biotite granite and albite biotite granite. Both rock units exhibit typical characteristics of A1-type granite, including elevated levels of alkali oxides (Na2O + K2O = 8.01–8.52 wt%) and high field strength elements (Zr + Nb + Ce + Y = 495–950 ppm), as well as high FeOT/(FeOT + MgO) and Ga/Al ratios, similar to other younger granites found in Nigeria. Bulk rock Sm–Nd and zircon Lu–Hf isotopic data (εNd(t) = −2.6 to 0.9; εHf(t) = −7.2 to −0.5) indicate a predominantly crustal material-dominated magma source, with some contribution from mantle-derived magma. The linear correlations observed between Rb/Sr and Nb/Ta ratios as well as Sr contents from biotite granite to albite biotite granite suggest the significant role played by magma differentiation. The elevated bulk Nb contents observed in all rocks, along with the presence of Sn–W-bearing quartz veins, contribute to the rare metal mineralization of the Afu complex and indicate a combination of magmatic and hydrothermal processes. Additionally, zircon U–Pb dating results from the Afu granites reveal their relatively young ages (149–148 Ma) compared to other NaYGs (263–151 Ma), suggesting the cessation of anorogenic alkaline magmatism within the NaYG province. [ABSTRACT FROM AUTHOR]

A less prominent N-S oriented continental-scale strike-slip shear zone occurs within the Babouri-Figuil Magmatic Complex (BFMC). Studies have shown that such shallow to middle crustal levels shear zones often display long-lasting deformation, physical expression of strain localization, and mineralization. However, until dates, deformation evolution and structural mineralization of this ~ 8 km long shear zone in Babouri-Figuil remain enigmatic, which prompted its investigation. A combined structural study supported by U-Pb zircon dating on the sheared granitoids is reported. Biotite granite sampled near Sorawel village yielded zircon U-Pb concordia age of 606 ± 6 Ma, whereas hornblende-biotite granite sampled at the western corner of the Ribao massif yielded zircon U-Pb concordia age of 601 ± 2 Ma. These granites were emplaced in a transpressive tectonic regime shortly after a regional thickening event < 620 Ma. The studied microstructures demonstrate a typical transition from protomylonite to extremely deformed mylonite marked with decreased mineral sizes. On thin sections, two main zones are identified: "zone A" (low-strain zone) and "zone B" (high-strain zone). Core-mantle K-feldspar porphyroclasts within the mylonite show dislocation creep deformation, whereas recrystallized to neocrystallized aggregates indicate plastic flow by viscous grain boundary sliding. Shear sense indicators revealed both early dextral and late sinistral shearing. In all, the results revealed that the Guider-Sorawel shear zone (GSSZ) experienced ductile deformation probably under medium to high temperature conditions. The double shearing is possible during the switch of the regional maximum principal stress from N-S (~ 585 Ma) to NW-SE (< 580 Ma). The obtained dates are syn-collisional and are consistent with D2 deformation phase in other parts of Cameroon. Also, the dates marked the final tectonic college between the north Cameroon domain and the southwest Chad domain, which probably might have induced the SZ. The construction of these adjacent domains probably resulted to a sort of increased temperature and strain localization that led to the initiation of a rheologically weaken mechanical zone via which the magma generated flows to near surface crustal level. [ABSTRACT FROM AUTHOR]

An integrated study was carried out on four anorogenic syenite-granite complexes (i.e. Banke, Dutsen Wai, Guraka, and Zuku) from the Nigerian Younger Granite (NaYG) province, in a bid to constrain their magma sources, rare metal mineralization potentials, and tectonic implications. These four complexes primarily consist of quartz syenite, granite porphyry, arfvedsonite aegirine granite, and biotite granite. The studied rocks are chemically characterized by high alkalis, HFSEs, Ga/Al ratios, and zircon saturation temperature (776–1127°C, average = 932°C), typically of A1-type granites. The zircon εHf(t) values of the arfvedsonite aegirine granite (−6.0 to −0.79) are higher than those of the granite porphyry (−9.57 to −7.67) and biotite granite (−9.49 to −5.86) suggesting moderate crustal contamination of mantle-derived melts for the origin of the peralkaline granites. Generation of the biotite granite likely involved inputs of both crustal- and mantle-derived melts and is evidenced by the presence of inherited Pan-African (600–610 Ma) zircons and low whole rock Nb/U and Nb/Ta ratios. Furthermore, input of crustal material likely increased the metal budget of the residual melt and enhanced Nb, Sn, and sulphide mineralization in the Banke granite porphyry and biotite granite and Dutsen Wai biotite granite. Zircon U-Pb dating results constrain the emplacement ages to early Mesozoic era, from the Banke granite porphyry of 180 ± 1 Ma, Dutsen Wai biotite granite of 177 ± 3 Ma, Guraka arfvedsonite aegirine granite of 227 ± 2 Ma and Zuku arfvedsonite granite of 186 ± 2 Ma. These age data indicate a local E-W age migration pattern for the alkaline magma emplacement in northcentral NaYG province. Integrated with other geological evidence, we favour a formation model for the anorogenic NaYG province likely driven by the reactivation of ancient shear zones and structures. [ABSTRACT FROM AUTHOR]

The Nigerian alkaline ring complexes have long been regarded as typical anorogenic A-type granite. However, uncertainty still surrounds many aspects of their petrogenesis and tectonic implication. In this paper, a combined study of whole rock geochemistry, Nd-Pb isotope and zircon U-Pb dating was carried out on the Kudaru ring complex from north-central Nigeria. The complex consists of mildly alkaline fayalite granite porphyry, peralkaline arfvedsonite granite and metaluminous biotite granite, which were emplaced between 176.9 ± 2.5 and 180.55 ± 0.6 Ma. These rocks are characterized by variably high alkalis, HFSEs, Ga/Al ratios, and zircon saturation temperature, typically of A-type granites. Notably, the popular subdivision scheme of A-type granite permits the discrimination of the alkaline-peralkaline granites as typical "A1-type" granites and the metaluminous granite as "A2-type". These co-existing A1 and A2 granites show distinct isotopic compositions with less negative εNd (t) values and higher 206Pb/204Pb ratios for the former, indicating that the magma which gave rise to the A1 and A2 suites was derived from an enriched mantle source but modified to different extent during ascent. Notably, the coexistence of A1-A2 granites do not indicate discrete tectonic regimes (intraplate setting for A1 and post-orogenic setting for A2), but rather point to a significant role of crustal contamination, as seen also from the differences in Y/Nb ratios. [ABSTRACT FROM AUTHOR]

Spatially associated A- and I- type granites and mafic dyke rocks from the Jiuhuashan region (South China) have been geochemically studied with a special emphasis on their halogen (F, Cl, Br, I) contents to better understand the role of halogens during their genesis. The A-type granites and mafic dyke rocks (125–130 Ma) intruded later than the I-type rocks (140–143 Ma) and whole-rock Nb/Ta ratios increase from I-type granites (12–14) via A-type granites (14–18) to mafic dykes (19–20). The εNd(t) values for the two rock series are indistinguishable (about − 4 to − 8), whereas mafic dykes reach εNd(t) values of up to + 2. We suggest that I- and A-type granites generate from a common source dominated by lower crust, whereas the associated mafic dykes representing mantle-derived magma. We propose that the I-type rocks were emplaced during subduction of the paleo-Pacific slab, whereas subsequent tectonic extension triggered upwelling of mantle-derived magmas that provided sufficient heat to re-melt the residual lower crust, and crystallized to the A-type granites. Relative to I-type granites, the A-type rocks are F-rich (mean of 1230 ppm vs. 540 ppm) but poor in Cl (mean of 25 ppm vs. 50 ppm) and Br (mean of 130 ppb vs. 200 ppb), with indistinguishable I contents (from < 1 to 30 ppb). Apatite and biotite from the two rock series show very similar relationships in terms of their F and Cl contents. A potential role of F for the genesis of A-type rocks is indicated by positive correlations with whole-rock HFSE and HREE contents and many other trace elements (e.g., Ga, Tl, Rb, Be). Calculated F and Cl abundances for primary melts are much higher than the respective whole-rock F and Cl contents, supporting late-stage volatile release during magma evolution. We suggest that the elevated F contents in A-type granites may initially originate from a F-rich melt and further elevated during prolonged magma differentiation. [ABSTRACT FROM AUTHOR]

We present major and trace elemental geochemical data, Sr–Nd–Hf isotopes and zircon U–Pb ages for igneous rocks of the Mufushan complex (~ 2400 km 2 outcrop area) in South China. The complex intruded episodically from late Jurassic (ca.154 Ma) to early Cretaceous (ca. 146 Ma) with a compositional evolution from diorite through granodiorite and biotite-bearing monzogranite to two-mica leucogranite and garnet-bearing leucogranite dykes. Diorites have high Mg# (up to 71), low SiO 2 and high siderophile elements (e.g. Cr, Ni and V) resembling sanukite or high-Mg diorite. They display isotopic characteristics similar to those of incident enriched mantle-derived mafic rocks, such as low I Sr (t) (0.7080–0.7085), high εNd(t) (− 4.3 to − 4.8) and εHf(t) (− 2.41 to 0.59). In contrast, felsic rocks show a common crustal signature with higher I Sr (t) (0.7115–0.7184), lower εNd(t) (− 7.9 to − 10.2) and εHf(t) values (− 7.73 to − 4.04). These felsic rocks display decreasing Al 2 O 3 , CaO, FeO tot , MgO contents and gradually enhanced depletions in Sr, Ba and Ti and Eu with increasing SiO 2 and decreasing zircon U–Pb age, which implies continuous magmatic evolution towards leucogranites dominated by fractional crystallization. The most evolved SiO 2 -rich rocks (two-mica leucogranites) are compositionally similar to the Himalaya leucogranites, indicating that prolonged fractional crystallization of metaluminous granitic magma is a feasible mechanism to form peraluminous leucogranitic magma. The differentiation process of the felsic magma lasted from 152 to 146 Ma as indicated by zircon U–Pb dating, which implies that magma differentiation, emplacement and subsequent solidification in giant batholiths may proceed on a timescale of several million years. [ABSTRACT FROM AUTHOR]

The Younger Granite province of Niger and Nigeria exemplifies a classical anorogenic alkaline ring granite belt with southward age migration from ca. 470 Ma to 140 Ma. However, the precise age transition from the older Nigerien Younger Granite (NrYG) to the younger Nigerian Younger Granite (NaYG) is poorly constrained. The Daura and Dutse complexes, located at the northernmost tip of the NaYG province, represent a temporal and spatial link between the NrYG and NaYG provinces. The Daura complex is composed of amphibole syenite and biotite granite, while the Dutse complex consists of fayalite syenite and arfvedsonite aegirine granite. Similar to other alkaline rocks of the NrYG and NaYG provinces, the Daura and Dutse samples all chemically show typical A 1 -type granite features, such as high alkalis (K 2 O + N 2 O = 8.33–11.27 wt%.), Ga/Al ratios, Zr + Nb + Ce + Y contents (527–2345 ppm) and FeOt/(FeOt+MgO) ratios (0.03–0.70) as well as elevated HFSEs. The Nd Hf and Pb isotopic systematics show that all the syenite-granites yield εNd (t) = −2.9 to +1.5, ɛHf (t) = −3.8 to +16.7, and 206Pb/204Pb = 17.818 to 19.555, suggestive of magmas derived from a slightly depleted mantle source with OIB imprints. A reduced to slightly oxidized redox state is invoked for the parental melt based on estimations from mineral chemistry. The Daura amphibole syenite is composed of >60% alkali feldspar, show high Eu/Eu* (>1), Ba/Zr (>3.5) values and cumulate textures, resembling an alkali feldspar cumulate rock. The other alkaline granitic rocks were likely generated from variable fractional crystallization of the residual melt with distinct crustal contaminations. Zircon U Pb dating reveal that the Daura amphibole syenite and biotite granite were emplaced at 324 ± 1 Ma and 321 ± 3 Ma, respectively, whereas the Dutse granitoids showed episodic intrusive periods of ca. 264 Ma and 232 Ma. All these results predate other anorogenic alkaline complexes of the NaYG and update the oldest age (ca. 214 Ma in previous references) recorded in the alkaline granite province. To the north, it connects well with ages from the Zinder complex (~330 Ma) in the southernmost NrYG province, reflecting a significant link between the NrYG and NaYG provinces. From a broad view, a linear age migration from north to south in the Niger-Nigeria Younger Granite province remains well preserved, although temporal and spatial intervals exist in local region. This emplacement pattern can be traced to the periodic and repeated reactivation of lithospheric shear zones and transcurrent faults. • The Daura syenite records onset of the alkaline magmatism in the NaYG province. • AFC process plays a key role in the diversity of the studied alkaline granitoids. • Reactivation of transcurrent faults accounts for age migration in the NaYG province. [ABSTRACT FROM AUTHOR]

Source-depleted granites were rarely reported in South China. Hereby we identified such a granitic pluton, the Tiandong pluton, at Northeastern Guangdong province in Southeastern (SE) China. Whole-rock Sr-Nd and zircon Hf isotopes of the Tiandong granites both revealed obviously depleted source signatures, with initial isotopic values of initial 87 Sr/ 86 Sr = 0.7032–0.7040, ε Nd ( t ) = 1.1–1.5, and ε Hf ( t ) = 6–13, respectively. Zircon U-Pb dating implied the granite was intruded in Early Jurassic (188 Ma). The dominant minerals of the Tiandong granite consist of K-feldspar, plagioclase, quartz and biotite, with accessory mineral assemblage of apatite + zircon + magnetite. Based on the mineralogy and the depleted isotopic signature, the granites chemically show I-type affinity such as low Zr + Nb + Ce + Y (131.6 to 212.2), 10 4 × Ga/Al (2.12–2.27), A/CNK values < 1.1 (0.97–1.03), corundum molecule < 1 (0–0.55) and extremely low P 2 O 5 contents (0.05 wt%). The one-stage and two-stage depleted mantle Nd model ages (T DM = 0.89 to 0.84 Ga, T 2DM = 0.88 to 0.85 Ga) are consistent. T DM (Hf) values of 0.31–0.63 Ga are also indistinguishable from T 2DM (Hf) values of 0.35–0.75 Ga. The Nd and Hf isotopic compositions confirm that the Tiandong granites are juvenile crustal accretion but decoupled Nd-Hf isotopic systems. The juvenile crust is likely to originate from a mixed source of the primary asthenospheric mantle and the subordinate EMII. Combined with early studies of adjacent rocks, we propose that the early Jurassic (~ 200–175 Ma) magmatism as evidenced by the Tiandong granites might be driven by upwelling of asthenosphere and subsequent underplating of mafic melts in an intra-plate extensional setting as a response to far-field stress during early stage subduction of the paleo-pacific plate. [ABSTRACT FROM AUTHOR]

The Babouri–Figuil Magmatic Complex (BFMC, adjacent to the central-south Chad domain) is located on the southern flank of the Saharan Metacraton. It is amongst the least geologically studied regions in Cameroon; only a few key research papers on geochronology and isotopes have been completed. The emplacement of granitic bodies is poorly constrained between the early and late–Neoproterozoic with inherited zircons of older Paleoproterozoic–Neoproterozoic ages. In this study, undeformed biotite granite massifs (Lombel and Badesi) were studied, and their geochronologic, geochemical and mineral chemical data, including Nd–Sr–Hf isotopes, are presented. The massifs are enriched in pink K-feldspar (orthoclase and microcline; 60–65 wt%) and plagioclase (8–10 wt%) anastomosing to intergranular quartz (18–20 wt%) and biotite (3–5 wt%) crystals. The Lombel massif yielded a Concordia age of 566 ± 2.5 Ma (MSWD = 1.6, zircon U–Pb), slightly older than the Concordia age of 556 ± 2.7 Ma (MSWD = 2.1, zircon U–Pb) obtained for the Badesi massif. These are interpreted as emplacement ages, which post–date arc magmatism by ∼ 45 Ma. The geochemistry of the massifs showed sub- to mid–alkaline, high–K alkali–calcic, and weakly peraluminous compositional characteristics. The calculated biotite temperatures ranged from 613 to 647 °C, pressures from 100 to 300 MPa, and H 2 O from 3.0 to 3.5 wt%. Whole–rock composition geothermobarometry revealed low pressure of 100–500 MPa, depths of 3.5–18 km and low oxygen fugacity (ΔQFM = −0.6), indicating reducing crystallization conditions. The estimated radiogenic isotopic values are similar for both massifs, falling in the range from initial ε Hf (t) = +2.6 to +8.4 and initial ε Nd (t) = +1.3 to +2.1, with a corresponding average initial Sr of 0.70212–0.70458. These radiogenic isotope values suggest a mantle–derived origin for this granite or the melting of a juvenile mafic crustal protolith, as confirmed by the two–stage model age obtained (TDM 2 = ∼ 1.2 Ga). Given that biotite is interstitial in alkali feldspar and plagioclase in both massifs, this suggests that biotite chemistry records conditions of magma evolution. Overall, these results confirm that the studied massifs are post–collisional products emplaced at shallow crustal levels under evolved magmatic conditions. They are coeval with a few post–magmatic intrusions in the central–south Chad and emplaced after the Sao–Francisco Congo Craton collided with the Saharan Metacraton. The ages obtained enabled a possible correlation with several Neoproterozoic post–collisional granites in Cameroon, south-central Chad, Central African Republic and Borborema Province of Brazil. The ages also revealed that continental assembly coupled with regional late–magmatism occurred during the Proterozoic. • Post-collisional A-type granite intrudes the Babouri-Figuil Complex. • They are emplaced between 566 ± 2.5 Ma and 555 ± 2.7 Ma, after orogeny. • They are peraluminous, alkali-calcic and sub-to mid-alkaline granites. • All authors contributed in this research. [ABSTRACT FROM AUTHOR]

The tectonics of the Central Africa Orogenic Belt (CAOB, in Cameroon, Chad, and the Central Africa Republic) is poorly constrained. For this reason, a study was carried out at the Cameroon-Chad border from biotite granite and hornblende-biotite massifs that intruded a gneiss-amphibolites basement of the NW Cameroon domain. Together, we report data on the whole-rock major and trace element compositions, mineral chemistry, and zircon U/Pb ages, supported by Nd-Sr-Hf isotopes. Both rocks are calc-alkaline, except for one sample with a Rittmann Serial Index (σ) > 3.5 (alkaline), high-K, and marginally peraluminous. The biotite granite is alkalic-calcic, whereas hornblende-biotite granite is alkalic. These rocks are characterized by high contents in SiO 2 (> 69.85 wt%), Fe-number [FeOt/(FeOt+MgO)] (ferroan), TiO 2 /MgO, and low CaO, MgO, and P 2 O 5 contents. Their petrological and geochemical features, such as early formed sodic and iron-rich amphibole, late crystallized biotite, and high Ga/Al ratios, are consistent with A-type granite formed from F and Cl enriched melts. Biotites compositions are close to those of annite, and amphiboles to ferro-amphibole, ferro-edenite, and ferro-gedrite types. The correlation for some major elements against SiO 2 is consistent with fractionation of K-feldspar, plagioclase, apatite, amphibole, biotite, Fe Ti oxides, and MnO-rich phases under 882 to 967 °C, < 5 kb, and low ƒO 2 (∆QFM = −0.55) at shallow crustal levels between <1 and 7 Km. Zircon U/Pb geochronology indicates two magmatic episodes for the biotite granite (RBO-27 and SMO-8) 602 ± 1.6 Ma, 602 ± 1.8 Ma, and (DBE-9) 707 ± 2.5, whereas hornblende-biotite granite (HRI-23) yielded 604 ± 1.0 Ma, respectively. The younger group yielded moderately to notably depleted initial Hf and Nd values [εHf(t) = − 3.4 to +1.8, av. = − 1.80; εNd(t) = − 2.46 to - 0.95, at 1.34 to 1.51 Ga], and low to moderate calculated initial Sr values (87Sr/86Sr(i) = 0.66781–0.70287). The older A-type granite yielded highly depleted initial Hf values (εHf(t) = + 7.74 to +9.30). The strong positive Pb anomaly for these granites indicates involvement of either crustal component or melt from the subducted slab. Given that the obtained initial Hf and Nd values are enriched relative to the depleted mantle (εHf(t) ~ +14; εNd(t) ~ +6.5), it therefore, suggest that these granites could be derived from low-degree partial melting of a juvenile crust extracted from the mantle. • The Babouri-Figuil granitoids show two magmatic episodes of ~700 Ma and ~ 600 Ma. • The ages indicate that they belong to pre-, syn - to late-collisional granites. • Nd-Sr-Hf data suggest mantle derived with various degree of crustal contamination. [ABSTRACT FROM AUTHOR]