Geochemistry of Magmatic Rocks of the Syama Belt, Southern Mali, West African Craton

Abstract

Within southern Mali, the Syama belt constitutes a linear major structure-oriented N-S, which host several gold deposits (e.g., Syama and Tabakoroni) and prospect areas (e.g. Tellem). The Syama Belt is formed by magmatic rocks (basalts, lamprophyres, andesites, dacites and microgranites); sedimentary rocks (shales) and volcano-sedimentary rocks (pyroclastics). The magmatic rocks are divided into two main volcanic series: tholeiitic affinity rocks (basalts and lamprophyres) and calc-alkaline affinity (andesites) that are the most evolved. The field relationships between rocks of these two series suggest that the calc-alkaline series are younger the tholeiitic series. These tholeiitic series present the Mid-Ocean Ridge Basalt (MORB) affinity whereas the calc-alkaline series would be linked to an island arc-type. This coexistence is not an isolated case within the West African Craton (WAC). Otherwise, the Syama belt has all the characteristics of other belts, within which a number of gold deposits are developed, in the WAC.