Petrography And Geochemistry Of The Anyaboni Formation Of Kwahu Group, Voltaian Supergroup, Ghana: Implications For Provenance And Uranium Exploration

ABSTRACT An integrated petrographic and geochemical study of the Anyaboni Formation, Kwahu Group, Voltaian Supergroup in Ghana was carried out to infer the provenance, tectonic setting, paleoweathering and paleoclimate conditions and uranium mineralisation potential of the basin. Twenty representative rock samples were collected from the Anyaboni Formation in Asesewa and its surrounding areas for petrographic and whole rock geochemical studies. The major elements were analysed by ICP-OES and the trace elements/REEs by ICP-MS. Two main rock types were identified in the area based on field observations; feldspathic sandstones and quartz sandstones. The petrographic studies indicated that the sandstone type was quartz arenite with texturally and compositionally matured minerals. On the basis of petrography the provenance was defined as metamorphic source and the tectonic setting was revealed as that of craton interior (predominantly) and recycled orogen. The sedimentation also occurred in a low-relief and tropical (humid) climatic conditions. The geochemical studies indicated that the sandstone types are mainly subarkose with contributions of arkose, sublitharenite and quartz arenite. The parent lithology is a quartzose sedimentary igneous source with contributions from felsic source. The CIA and PIA values range from 66.05 to 80.77 and 66.67 to 98.34 respectively. These values indicate that the paleoweathering condition is moderate to high, leading to alteration of unstable minerals to stable, oxide/hydroxide and clay minerals. Tectonic setting discrimination diagrams based on the geochemistry confirmed a passive continental margin setting. Uranium concentration studied alongside with Th, Zr and V in the study area indicates generally low levels. However, there is a strong positive correlation between U and Th, Zr and V concentrations and can serve as pathfinders for U in the area.