Geochemistry of Mafic Rocks from the Birimian Basement of Doropo (Northeast of Côte d’Ivoire): Petrogenetic and Geodynamic Implications

Abstract

The northeastern region of Côte d'Ivoire is characterised by a granitic basement mainly composed of biotite granite rocks. According to mapping work in the Gbabédjou and Doropo areas, these Birimian granitoids are cut by gabbro dykes and amphibolite enclaves, which are the subject of this study. In order to better understand the role and the implication of mafic rocks in the Doropo basement emplacement, a multidisciplinary methodology integrating microscopic observations and geochemical analyses of major and trace elements was carried out on 4 samples considered representative of the outcrops studied. Green hornblende, clinopyroxene, and accessory sphene minerals are found in mafic mineral phases, according to petrographic research. Whole-rock analyses reveal that mafic samples with TiO 2 contents < 2% are poor in Ti and have both calc-alkaline and tholeiitic rock affinities. They are metaluminous with A/CNK > 1.1 ratios giving them an orogenic granite nature (I-type). Their REE patterns are moderately fractionated (La/Sm) N = 2.66 -6.13 and (La/Yb) N = 11.17 -43.70) with a very negative Eu anomaly (Eu/Eu* = 0.75 -0.97). The multi-element diagrams are characterized by negative Nb-Ta anomalies and geotectonic studies have identified them as volcanic arc formations. All these characteristics allowed us to distinguish the Doropo mafic rocks as formations originating from the juvenile continental crust, emplaced under the Archean tectonics model with significant crustal contamination in the source. Magma driven by mantle diapir has been injected at the base of the continental crust and the heat induces the partial melting of the overlying How to cite this paper:

New lithostructural map of the Doropo region, northeast Côte d'Ivoire: Insight from structural and aeromagnetic data

“…Block et al (2015Block et al ( , 2016 suggest that these granitoid domains of northwest Ghana, precisely the granitoid domain of "Bole Boulenga", can be linked to those of Côte d'Ivoire (Nassian granitoid domain) and that both of these domains belong to the same geological province based on geochemical and geochronology data. This confirms the already published research works in the northeast of Côte d'Ivoire (Arnould, 1961;Delor et al, 1995;Hirdes et al, 1996;Lüdtke et al, 1998;Vidal et al, 2009;Baratoux et al, 2015;Block et al, 2015Block et al, , 2016Siagné et al, 2021;Digbeu et al, 2022). They represent a granito-gneissic basement intruded by various granites and granodiorites intersected by pegmatitic and doleritic dykes.…”

Pétrographie et géochimie des leucogranites de la région de Sassandra (Domaine Baoulé-Mossi au sud-ouest de la Côte d’Ivoire)

“…Nous avons utilisé les compositions chimiques en éléments majeurs de 3 échantillons de granites à deux micas (HH/63/66, BY/63/3028 et JPC/65/18) issus des travaux de Papon (1973) et la composition en éléments majeurs sur roche totale de 7 nouveaux échantillons de leucogranites à titre comparatif. Les éléments majeurs ont été dosés par Fluorescence de Rayons X (XRF) l'aide d'un appareil XRF-1500 selon la méthode analytique XF700 (Skursch et al, 2020) et (Digbeu et al, 2022). Ces nouvelles analyses ont été réalisées au laboratoire d'analyse minérale du Bureau Véritas Commodities Canada, Ltd.…”