Le paléovolcanisme de la bordure occidentale de la boutonnière de Kédougou, Paléoprotérozoïque du sénégal oriental: incidences géotectoniques

Abstract

The main petrographical and geochemical patterns (major, trace and rare earth elements) of the epimetamorphosed volcanic rocks from the Mako Supergroup (Birimian) from the central and southern part of the western border of the Kedougou-Kenieba Inlier (Palæoproterozoic) are presented. The petrographic patterns indicate a predominance of tholeiites with the middle and upper parts of the lithological sequence containing scarce andesite, rhyodacite and rhyolitic end members of calc-alkaline affinity. The observed geochemical trend is compared with the patterns from other Palæoproterozoic areas of the West African Craton, as well as recent volcanic rocks, whose geotectonic setting is well constrained. The evolution of the Kedougou Inlier corresponds to an ocean island-arc environment, in agreement with previous research on epimetamorphic volcanodetrital and sedimentary formations, and Birimian granitoids. This research underlines the importance of island-arc accretions in crust generation during Palæoproterozoic times in West Africa.