GRANULOMETRIC AND GEOCHEMICAL ASSESSMENT OF AJALI SANDSTONE IN FUGAR AREA IN BENIN FLANK OF ANAMBRA BASIN, NIGERIA

Abstract

The aim of this study is to carry out granulometric and geochemical assessment of Ajali Sandstone outcrops in Fugar area in Benin Flank of Anambra Basin, Nigeria using results from grain size, major oxide and trace elements analyses. The study area lies between longitudes 06o 35’ 04” E and 06o 35’ 56” E and latitudes 07o 05’ and 21” N 07o 05’ 52” N. Five samples were collected from the study area for the analyses. Automated sieve shaking machine and Epsilon-5 x-ray fluorescence pAnalytical model were used. The sediments are fine-grained to coarse-grained poorly sorted to very well sorted. The sediments are strongly fine skewed to strongly coarse skewed. The sedimentary structures and the bimodal distribution of the grain size parameters pointed to intertidal environment of deposition for the sediments. SiO2 has the average concentration of 81.78 wt. % with range of 81.6 – 82.0 wt. %. It is followed by Al2O3 with average concentration of 9.41 wt. %. Fe2O3 has average concentration of 5.61 wt. %. Zr has average concentration of 1,500 ppm followed by Ba with mean concentration values of 1,290 ppm. Cu has an average concentration of 280.5 ppm. Conversely, U, Th, Co, Ni, As, Au and Pb have low concentration in the analysed samples. The sandstone samples are highly ferruginised because of their high Fe2O3 contents. The presence of ferromagnesian trace elements such as Cr, V and Co enrichment and the high weight percentages of SiO2 in the sandstone samples indicated origin from source rocks such as granites and migmatites. The sandstones from the study area are suitable raw materials for construction because of the negligible contents and non-pollution level of the radioactive elements in them.