Preliminary investigation of the rare earth element (REE) composition of the shale in the Oshosun Formation exposed at the Sagamu quarry, eastern Dahomey Basin, southwestern Nigeria

Abstract

Shales belonging to the Oshosun Formation exposed at the Sagamu quarry of the West African Portland Cement have been mapped and assessed for their abundances in rare earth elements (REE). The shale thickness, which measures approximately 15m and overlies the Ewekoro Formation is separated by a very thin bed of glauconite. The shales are grey to dark grey and well laminated.
Preliminary investigation of the rare earth elements of selected shale samples shows the average composition values: La (43.12), Ce (97.20), Nd (38.60), Sm (7.00), Eu (1.80), Tb (1.03), Yb (2.74), Lu (0.41). This result shows a slight enrichment in the light rare earth elements but a significant depletion of the heavy rare earth elements similar to the seawater derived shales. This signifies that the shale precursors are granitic rocks with large proportions of alkali feldspars and low contents of plagioclase feldspars.


Journal of Mining and Geology Vol. 43 (2) 2007: pp. 105-108