Geochemistry and mineralogy of the Duwi black shale, along Nile Valley district have been studied to infer their economic importance and environmental impact. XRD and SEM revealed the dominance of smectite and kaolinite clay mineral phases. The loss on ignition “LOI” values (av. 22.03 %), reflect elevated content of organic matter. LOI displays a positive correlation with K2O and Al2O3 contents, confirming the dominance of organic matter rich clay minerals. Duwi black shales contain considerable concentrations of redox sensitive metals (e.g. V, U, Mo, Ni) and other economic elements (Cu, Pb, Zn). The enrichment of black shale with Zn, V, Cu and Cr was confirmed by the very high CF values (>6). PLI values are less than one, which indicate that the shale is not polluted. The Duwi black shales are classified generally as uncontaminated to moderately contaminated (0≤ Igeo <1). This is attributed to the natural weathering of the source rocks rather than artificial input. The organic richness of the studied samples ranges from fair to very good petroleum potential which can be considered promising oil shales. The HI and OI values of all the analyzed samples, indicating gas-oil-prone organic matter and kerogen type III.

Black shale; Duwi; Nile Valley; Economy; Environmental impact