High-K to shoshonitic magmatism across the northern Archean Kéména Man Margin (Guinea): implications for the Eburnean orogenic gold mineralizations

The Baoulé-Mossi Paleoproterozoic domain is known for its world-class orogenic gold deposits formed during the Eburnean orogeny between ca. 2.15 and 2.07 Ga. As part of the orogenic cycle, a suite of mafic and felsic potassic intrusive rocks was emplaced between ca. 2.10 to 2.08 Ga along the Paleoproterozoic margin of the Archean Kéména Man craton in Guinea. These high-K to shoshonitic intrusive rocks are characterized by (i) enrichment in LILE and LREE, (ii) strong Pb spikes and (iii) depletion in Ta-Nb-Ti. These features could suggest that the mantle source was metasomatized by Pre-Eburnean subduction. Two different Hf model ages were obtained for these Paleo-proterozoic shoshonitic rocks suggesting two distinct sources involving crust extraction from the depleted mantle at ca. 2.7-2.4 Ga and at ca. 3.7-3.2 Ga. We envisage that these shoshonitic magmas derived by partial melting of metasomatized lithospheric mantle in response to lithospheric delamination after the Paleo-proterozoic Baoulé-Mossi/Archean Kéména Man collision during the late Eburnean orogeny. We propose that this reworking magmatic event at ca. 2.10-2.08 Ga could have remelted residual Au-rich cumulates left in the deep lithosphere by arc magmatism and be respon-sible for large-scale fluid migration related to late orogenic gold mineralizations in the Baoulé-Mossi domain.