Structure, Sr–Nd isotope geochemistry and zircon U–Pb geochronology of the granitoids of the Dabakala area (Côte d’Ivoire): evidence for a 2.3 Ga crustal growth event in the Palaeoproterozoic of West Africa?

Structural, mineralogical and chemical studies show that the rocks from the Dabakala area, previously reported as gneisses and migmatites, are in fact syntectonic granitoid bodies. Three chemical associations are distinguished: (i) trondhjemitic (Dabakala tonalites and granodiorites), calc-alkaline (Finéssigué granodiorites and undifferentiated biotite granodiorites and granites) and peraluminous (Sarala hololeucocratic granites and Kowara muscovite trondhjemites). Most granitoids display deformation patterns typical of an interference between pluton emplacement and transpressional tectonics induced by a NNW-SSE to NW-SE compression which led to three major NS sinistral shear zones (N’Zi, Katidougou, Ouango-Fitini). Geochronological data (U–Pb ID-TIMS and SIMS zircon ages) yielded 2312±17 Ma for the zircon cores from the Dabakala tonalite, 2154±1 Ma for the zircon rims of the same tonalite, 2162±32 Ma for Sarala, 2118±2 Ma for Kowara, and 2103±1 Ma for Finéssigué. Sr–Nd isotopic data further indicate that all these rocks are isotopically primitive ( 0.7000< 87 Sr/ 86 Sr