Geochemical Characterization and Provenance Studies of Gombe Formation, Gongola Sub-Basin, Northern Benue Trough, Nigeria

Abstract

Major element geochemical analyses of the Gombe Formation in the Gongola Sub
basin, Northern Benue Trough, were conducted to determine the provenance, 
weathering intensity, compositional maturity, and tectonic setting of the sediments. 
The study was based on outcrop samples collected within Latitude 9°00′00″
10°30′00″N and Longitude 10°00′00″–11°30′00″E. A total of thirty-one (31) 
representative samples were collected and analyzed using X-ray Fluorescence (XRF) 
to determine the major oxide composition of the sediments. The XRF results 
identified SiO₂, Fe₂O₃, Al₂O₃, K₂O, TiO₂, MgO, P₂O₅, MnO, CaO, and NiO as the 
dominant major oxides. Binary geochemical discrimination diagrams based on the 
major oxide data were employed to classify the sandstones. The average Chemical 
Index of Alteration (CIA), Plagioclase Index of Alteration (PIA), and Chemical 
Index of Weathering (CIW) values of 79.76%, 64.81%, and 94.03%, respectively, 
indicate moderate to intense chemical weathering of the source rocks and/or 
weathering during sediment transport prior to deposition. The Index of 
Compositional Variability (ICV) values range from 0.32 to 33.47, with an average of 
5.67, suggesting that the sediments are compositionally and chemically immature. 
Based on the log(Fe₂O₃/K₂O) versus log(SiO₂/Al₂O₃) discrimination plot, the 
sandstones were classified as wackes, arkose, lithic arenite, and sub-arkose, with 
minor iron-rich shale. Provenance discrimination diagrams indicate derivation 
predominantly from felsic and intermediate igneous provenances. Furthermore, the 
SiO₂ versus (Al₂O₃ + K₂O + Na₂O) plot suggests deposition under predominantly 
semi-arid to arid climatic conditions, reflecting the prevailing palaeoclimatic regime 
during sediment accumulation.