Geochemical Affinity And Geotectonic Setting Of Palaeoproterozoic Amphibolites Within Granitic -Gneissic Basement Of The South Central Area Of Burkina Faso, West- Africa

Abstract

The south central part of the basement of Burkina Faso which lies within the west African craton, comprises of granitic- gneissic complex in close association with lenticular masses of amphibolites possibly of Archaean age. Petrographic analysis indicates that these rocks were products of contact metamorphism of early basic volcanic rocks induced by surrounding Eburnean granite intrusions. Their geochemical features are consistent with oceanic low K tholeiite, emplaced within a back- arc basin basalts (BABB) setting during Eburnean orogeny (2200-2000 Ma). Field and radiometric data (Pb/Pb, Rb/Sr) suggest that amphibolites (2180+- 90 Ma) are older than calc-alkaline granitic plutons and dykes (2007+-39, 1935+-27 Ma), both units being of Palaeoproterozoic age.

Keywords: Burkina Faso, amphibolites, tholeiite, Back- arc basin basalts, Palaeoproterozoic

Global Journal of Geological Sciences Vol. 6 (1) 2008: pp. 9-22