Abstract
The Ajali Sandstone, South-western, Anambra Basin, was studied for Rare Earth Elements (REEs), using a Phillips 45 channel Inductively Coupled Plasma (ICP) Emission Spectrometer. The standard deviation of the REEs (Dy, Er, Eu, Y, Yb, La and Nd) averages 3.5 mg/L, 0.34 mg/L, 0.32 mg/L, 3.93 mg/L, 1.96 mg/L, 4.02 mg/L and 2.24 mg/L respectively for each of the sampled locations. The REEs concentrations showed both positive and negative concentration anomalies. The enrichment or depletion of the REEs is generally attributed to their tendency to be incorporated into plagioclase preferentially over other minerals. The Ajali Formation is predominantly sand/sandstone, with clay occurring only as intercalations/thin beds of clay drapes with the increasing particle size of the sand grains, makes the rate of adsorption and distribution of REEs in the soil low, and explains the low values of REEs concentration. Soil organic matter (SOC) plays an important role in the adsorption and migration of REEs in the Ecosystems. The SOC is linearly associated with REEs Concentration as it increases with increasing content of SOC. The Ajali Sandstone studied falls in the vicinity of abandoned cropland to cropland in a lower/gentle slope region, correspondingly low in soil organic matter content and as such slow rate of distribution and migration of REEs concentrations in the Ajali Sandstone. The sesquioxides such as Fe oxides increases as REEs contents increases. The 0.46 mean value of Fe2O3 in the Sandstone of the area studied implies a low REEs adsorption rate and subsequently the very low REEs concentrations of the soils. The istribution of REEs within the Ajali Formation soils were grossly affected by the factors that influenced the adsorption and migration rate of the minerals during magmatic fractionation process, hence the low REEs concentration of the Sediments.
 Keywords`: Sansdstone, Anambra Basin, Rare Earth Elements, Magmatic fractionation
Highlights
Location of Study Area: The study area and its environs are situated in Fugar, Ayogwuiri, Auchi and Uzebba all enclosed within the Ajali Formation
Sample Analysis: The samples were analysed for Rare Earth Elements (REEs) using a Phillips 45 channel Inductively Coupled Plasma (ICP) Emission Spectrometer by method described in Wash et al, (1981)
The rest of the magma will be depleted with the concentration of Eu, Er and Yb been lower than expected with respect to the other REEs in the magma. This explain the extremely low concentrations of Eu, Er, and Yb and the fairly high to high concentrations of Dy, Y, La as seen in the REE concentration plots (Figure 2-6). This REE concentration anomaly is an indication of the provenance of the Ajali Sandstone in the area studied is likely sourced from a mafic-igneous source
Summary
Goldschmidt (1954) suggested that during the processes of weathering soil formation and sedimentation, all REEs are concentrated in the hydrolysate minerals (clays, and shale components, bauxite minerals and oxidates of iron and manganese). This low solubility coupled with the very similar chemical properties of the REE and their resistance to fractionation in supercrustal environment (Nance and Taylor, 1977) has resulted in the use of the REE distribution patterns to identify parental materials of supercrustally altered rocks and sediments (Nance and Taylor, 1977; Taylor and Hallberg, 1977 and Willerman and Condie, 1973).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
