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.
