The relation between Li, V, P2O5, and Al2O3 contents in marls and mudstones as indicators of environment of deposition

The contents of Li, V, P2O5, and Al2O3 in marls and mudstones collected from three different formations, cropping out in northern Iraq, showed that the ratios of Li/Al2O3, V/Al2O3, and P2O5/Al2O3 in these rocks can be used to discriminate environments of deposition of these formations. Relatively high values of the above ratios characterize the deep marine Shiranish environment while lowest values characterize freshwater environment of deposition of the Injana rocks. Despite that marls of the Fatha formation were deposited in marine lagoonal environment, the ratios P2O5/Al2O3 and V/Al2O3 could not be discriminated from the freshwater Injana mudstones. The well-known phenomenon that marine surface water and down to a depth of 50 m almost lacks soluble P explain this behavior. In such water, almost all the soluble P is consumed by surface organism rendering it unavailable for adsorption by the sediments. The high salinity of the lagoonal environment prevented adsorption of soluble V on clay minerals because of its inability to compete with other species of much higher concentrations.