Geochemical Assessment of Sandstone of Dumbulwa Member of the Pindiga Formation Exposed at Ashaka Quarry, Gongola Basin, Ne Nigera

Detailed geological mapping coupled with sample collection of sandstone of Dumbulwa Member was carried out at the Ashaka Quarry in the Gongola Basin. The geological mapping showed that the dominant rocks outcropping within the study area are sandstone of the Dumbulwa and shale of the Kanawa Member. Geochemical analysis of sandstone oxides using X-ray Fluorescence (XRF) was carried out using six (6) samples and the investigation reveals the following results; SiO2 range from 30.04% to 87.67% with an average of 57.80%, Al2O3 range from 2.50% to 28.50% with an average of 14.76%, Fe2O3 range from 0.48% 63.67% with an average of 19.03%, CaO range from 0.26% to 1.39% with an average of 0.88%, K2O range from 0.15% to 10.79% with an average of 3.83%, P2O5 range from 0.325% to 0.725% with an average of 0.53%, MgO range from 0.00% to 1.20% with an average of 0.31% and MnO range from 0.02% to 1.67% with an average of 0.33%, Na2O range from 0.00% to 0.00% with an average of 0.00%, TiO2 range from 0.13% to 2.28% with an average of 1.09%, and lastly SO3 range from 0.20% to 0.48% with an average of 0.36%. Enrichment of silica (quartz)- SiO2 over Al2O3 (log SiO2/ Al2O3˂1.5) is a reflection of the duration and intensity of weathering and destruction of other minerals during transportation. This indicates that the sandstone samples of the study area have undergone long period of transportation and have been subjected to intense weathering resulting in the destruction of low temperature minerals like plagioclase and potassium feldspars during the phase of sedimentary cycle. The overall results showed that silica (SiO2) enrichment over Al2O3 by chemical and mechanical processes indicates sandstones maturity. Lack of abundance Na2O and K2O characterized immature sandstones such as arkoses and greywackes. Fe2O3 and MgO enrichment and concentration is a net result of provenance and processes that concentrate and preserved detrital ferromagnesian minerals and their alteration products.