PRE-LEONIAN RELICS (3.15 GA) INVOLVED IN THE JUVENILE BIRIMIAN TERRAINS (2.1 GA) OF THE IVORY-COAST, WEST-AFRICAN CRATON

Relies of Archean gneiss are found within the juvenile Birimian magmat ic domain of the Ivory Coast (San Pedro area, Sasca zone). The tonalit ic gneisses studied here yield single-grain zircon ages (up to 3 141 /- 2 Ma), that are significantly older than the emplacement of grey gn eiss precursors (3 048 +/- 8 Ma) within the Archean Domain of the Man Rise, which points to a pre-Leonian crustal history. The presence of A rchean relies, inherited zircons and negative epsilon(Nd) values at 2. 1 Ga in the Birimian domain indicate some interaction between the Arch aean crust and the newly formed mantle-derived magmas. Consequently, s ome geographical link may have existed between the Archaean basement t errains and the juvenile magmatic belt that existed in the Birimian Do main 2.2-2.1 Ga ago.