Investigating the mineralogical and geochemical composition of fluvial sediments of Watari river system, Kano, Nigeria

Abstract

A key objective of this research is to conduct a mineralogical and geochemical screening of the fluvial sediments in Watari river. Data collected from this study can be used to further enhance scientific understanding of the fluvial processes in the Watari basin as well as the larger Hadejia-Jama' are basin. The geological data can also be used as input information for the prediction of sedimentation rates in the Watari dam, Kano. An intensive field was conducted to explore thebedforms (sand bars, ripples, and sand filled channel or dunes) of the proximal channel environments, platform geometry and sinuosity.X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses were used to study the mineralogy and chemical composition of the collected samples, respectively. The Watari river can be considered as braided due to the presence of smaller multi-threaded channels, braid or channel bars. The lithology of exposures observed at the river bank show a series of depositional cycles that comprise mudrocks (light and dark), sandstone, conglomerate and a basal quartzitic gravel deposit. The wacke and sub-litheranite rocks were sourced from mafic and intermediate igneous rocks. The relatively high La and Ce in the mudrocks can be attributed mainly to the adsorption of Ce onto Fe-oxides which are abundant in the fluvial sediments eroded from lateritic soils. From the bivariate plot of Al2O3/SiO2 against Fe2O3+MgO, the sandstone facies fall under the passive continental margin, while the quartzite and conglomerate facies are grouped under the foreland basin, and the light mudrock facies is classified under the continental island arc. In addition, the plot of Al2O3/(CaO + Na2O) against Fe2O3+MgO shows the sandstone and quartzite facies fall under the foreland basin. The relatively high concentration of feldspar and muscovite mica in the siliciclastic facies is indicative of close proximity to parent material, and low degree of weathering and diagenesis. The variability in the mineral composition points toward different cycles of fluvial sedimentation, diverse provenance, and wide range of source materials.The geochemical data further buttresses the variability in provenance, wider geographic area of the sediments or re-deposition and reworking by fluvial actions.