Tarkwaian Deposits of the Birimian Belt of Houndé: Petrological, Structural and Geochemical Study (Burkina-Faso, West Africa)

Abstract

The Tarkwaian deposits of the Birimian belt of Houndé are located in the Baoule-Mossi Paleoproterozoic area of the West African Craton. The sedimentary units consist of sandstone heterometric pelitic feldspthic sandstone with locally interbedded breccias, puddings and polygenic conglomerates. Lithic pebbles and macroscopic fragments that are similar to vein type originated quart castings and andesitic-dacitic projections, felsic sub-volcanic rocks evolving from microdioritic to microgranite composition are detected in terrigenous sediments. The volcanic packages form a linear strip composed of basic to intermediate rocks and andesitic to dacitic volcaniclastites. The contacts between these units are not clearly exposed but the different facies between the polygenic conglomerates and sandstones show discordant tectonic contacts with the Tarkwaian and the Birimian. The geochemical nature of these Tarkwaian formations is strongly influenced by the relative decline of the dominant quartz of feldspars and phyllites. The improperly classified and immature feldspathic sandstones show context affinities of island arc probably dictated by Birimian lithic products. Sedimentologically, the cross-bedded stratification and the predominance of sandstone terrigenous lands indicate a deposition in a fluvio-deltaic hydrodynamic setting along intermontane Birimian rift. The similarities between these Tarkwaian formations and the typical Tarkwaian of the Tarkwa basin in Ghana are probably limited to petrographic and not stratigraphic aspects, which lead to likening them to flyschoïd or molassic tardi Birimian deposits.