The Séguéla region, which constitutes the study area, is located in the northwestern part of Côte d’Ivoire, West Africa. Côte d’Ivoire, which lies within the West African Craton, is geologically dominated by two major domains: the Archean and the Paleoproterozoic. The study area belongs to the Archean-Proterozoic transition zone, situated to the east of the Archean Domain and the Sassandra Fault, and along the western margin of the Paleoproterozoic Domain ( Figure 1 ). The various lithologies observed in the area include tonalitic gneisses, migmatites, volcano-plutonic belts, granitoid plutons of diverse composition, and metasedimentary rocks intruded by plutons [1] . Previous works [2] - [5] have shown that this western part of the Archean domain in Côte d’Ivoire is composed of gray tonalitic and trondhjemitic gneisses, charnockites, greenstone rocks metamorphosed under granulite facies, magnetite-bearing banded quartzites, and biotite migmatites. These formations are intruded by pink granites and basic-ultrabasic complexes. This entire assemblage has been attributed to the Leonian (3.5 - 2.9 Ga) and Liberian (2.9 - 2.6 Ga) orogenic cycles by earlier authors [6] .

In Côte d’Ivoire, the crustal evolution experienced three major Precambrian orogenies: the Liberian, Leonian, and Eburnean. The resulting basement, older than 1.6 Ga, occupies almost the entire territory except for the extreme south, which is covered by the coastal basin [7] . The granitoids make up the majority of the outcrops of this Precambrian basement and are highly diverse, thus representing significant geological components of the country [8] . The granitoids of Côte d’Ivoire have been the subject of numerous lithostratigraphic and geochemical studies aimed at understanding their genesis [9] - [14] . Following in the footsteps of these earlier works, we have focused particular attention on the granitoids of the Séguéla region, which is known as a diamond-bearing zone. It is therefore necessary to undertake petrographic and geochemical studies to contribute to a better understanding of these rocks in this region.

Geologically, Côte d’Ivoire forms part of the West African Craton, more specifically within the Man-Leo Shield [6] . The country is predominantly underlain by a Precambrian basement (97.5%) and a younger sedimentary cover (2.5%). This basement, which includes the study area, is subdivided into two major domains: the Kenema-Man Domain to the west and the Baoulé-Mossi Domain to the east, separated by the major transcurrent Sassandra Fault. Previous studies [2] [4] [15] - [17] have shown that the Kenema-Man Domain is largely composed of Archean terrains made up of a granito-gneissic basement complex and supracrustal greenstone belts. These rocks were successively affected by the Leonian orogeny (3.4 - 3.0 Ga) [18] [19] and the Liberian orogeny (2.9 - 2.7 Ga) [2] [18] , and were later overprinted by the Eburnean orogeny [20] - [22] . In contrast, the Baoulé-Mossi Domain to the east is mainly composed of Paleoproterozoic formations deformed and metamorphosed during the Eburnean event [20] - [23] . The lithologies of the Kenema-Man Domain are predominantly TTG-type (tonalite-trondhjemite-granodiorite) suites, associated with kinzigitic metasediments, magnetite-bearing quartzites, and granulitic metabasalts [2] [4] [15] [21] [24] . Between the Archean and Paleoproterozoic domains sensu stricto lies a transition zone, bounded by the Sassandra Fault to the west and approximately longitude 6˚W to the east. This zone exhibits clear Archean inheritance, marked by crustal relics dated at about 3.2 Ga in the southern part of the SASCA Domain [4] [25] [26] .

Located in the west-central part of Côte d’Ivoire, the Séguéla region belongs to this Archean-Proterozoic transition zone, lying east of the Archean Domain and the Sassandra Fault, and along the western margin of the Paleoproterozoic Domain ( Figure 1(A) ). The region is well known for its diamondiferous field, fed by kimberlite and lamproite dykes ( Figure 1(A) ). These dykes intrude granite plutons separated by amphibolite panels belonging to the Birimian formations. The granites are monzonitic, containing biotite and hornblende, and display well-differentiated pegmatitic and aplitic cupolas, as well as porphyroid margins [1] ( Figure 1(B) ). Their N170˚ orientation is structurally controlled by the contact between the Archean and Paleoproterozoic lithospheres of the West African Craton.

The study area is located in the central part of the Archean-Proterozoic transition zone defined by [4] [26] , where Archean relics have been identified within the juvenile Birimian formations. The kimberlitic dykes of the Séguéla region crosscut two granite plutons separated by small amphibolite panels belonging to the Paleoproterozoic Birimian formations of the West African Craton. These are biotite- and hornblende-bearing monzonitic granites, exhibiting differentiated pegmatitic and aplitic cupolas as well as porphyroid margins [1] . They have been Pb/Pb dated at 3132 ± 9 Ma to 3141 ± 2 Ma [4] . The kimberlitic structures do not crop out naturally, as they are covered by several meters of colluvium. The granitoids belong to the granito-gneissic complexes of the Séguéla region. Our study confirms the presence of granites, granodiorites, and migmatites. Petrographically, these rocks are dominated by quartz and feldspars, with microcline more abundant than plagioclase, which is often sericitized and occurs as myrmekite. This mineral is considered metasomatic, associated with tectonic activity [35] .

Metasomatism has been suggested [11] as responsible for microclination of feldspars in Eburnean granitoids, resulting in increased potassium content. This phenomenon is also observed in Archean formations and can be attributed to varying degrees of crustal recycling within the West African Craton during the Eburnean [17] [25] [36] - [38] . The migmatitic nature of the studied granitoids suggests a crustal anatectic origin, supported by field observations of magmatic banding, reflecting segregation between granite neosome and granodiorite paleosome [39] .

Geochemically, the Séguéla granitoids exhibit a metaluminous to slightly peraluminous character and a calc-alkaline to shoshonitic trend, marked by K₂O enrichment. This potassium enrichment is accompanied by an increase in SiO₂, as shown in the Harker diagrams [32] ( Figure 4 ). According to [40] , peraluminous characteristics indicate a crustal affinity, whereas metaluminous signatures suggest a mantle contribution, implying a dual origin for the Séguéla granitoids. This aligns with previous studies [13] [41] reporting dual origins for Ivorian granitoids. According to [42] [43] , A/CNK ratios between 1 and 1.1 correspond to granitoid generations of I- and S-type, indicating a possible mixture of metaluminous magmas with more differentiated crustal assimilation. The opposite trends observed in the Harker binary diagrams of Al₂O₃/SiO₂ and K₂O/SiO₂, as well as the negative Sr and Eu anomalies and positive Eu anomalies in the granites, reflect the mixing of two chemically distinct sources or magmatic assimilation. The similar patterns of multi-element and rare earth element (REE) spectra for the granitoids and migmatites may suggest a common origin for the formation of these rocks.

The potassic nature of these granitoids can also be explained by rock evolution: more differentiated rocks tend to be richer in potassium [10] . However, potassium and biotite enrichment may also reflect crustal metasomatism. For instance, [44] studying Ouahigouya granitoids (Burkina Faso) attributes high potassium to the progressive breakdown of ferromagnesian minerals, particularly biotite, which releases potassium into the evolving rock.

The similarities in REE and multi-element patterns among granites, granodiorites, and migmatites suggest a common magmatic source. Positive Eu anomalies in granites versus negative anomalies in granodiorites and migmatites indicate that granites likely formed by partial melting of a moderately differentiated crustal protolith, and enriched in residual plagioclase. Overall, the granitoids and migmatites were likely generated in subduction-related zones, akin to Archean TTGs [45] . Subduction-induced fluid release facilitated the formation of K-rich pink granites.

This study provides a petrographic and geochemical characterization of the Séguéla granitoids.

Petrographically, the rocks are predominantly quartz-feldspar, with main ferromagnesians being green-brown biotite and green hornblende. The dominance of microcline likely reflects metasomatism linked to Eburnean tectonics, affecting much of the West African Craton.

Geochemically, the analyzed rocks define a calc-alkaline to slightly shoshonitic chemistry for migmatites. Both granitoids and migmatites are metaluminous to peraluminous, with strong LILE enrichment (Cs, Ba, Rb, K) and pronounced Nb-Ta depletion, indicating a subduction-related environment (or remelting of a subduction-derived source). The REE patterns are consistent with this geodynamic setting, resembling Archean TTGs, suggesting formation through subduction-related melting of mafic and ultramafic rocks transformed into eclogite, followed by crustal recycling. Indeed, these rocks exhibit high (La/Yb)_N fractionation rates ranging from 12.79 to 59.29 and heavy rare earth element (HREE) depletion with (Gd/Yb)_N ratios ranging from 1.92 to 3.56.

Future work should include geochronological studies (trace elements and isotopes) to determine the ages of these granitoids and migmatites, identify their protoliths, and perform structural analyses to evaluate the tectonic relationships within the study area and better define their Archean character.

I would like to express my sincere gratitude to PASRES (Strategic Support Program for Scientific Research) and to the T2GEM project (Geophysical and Geochemical Technologies for Mining Exploration) for funding this research.