Rare Earth Element Geochemistry and Abundances in Syenites and Charnockitic Rocks of Selected Locations within Southwestern Nigeria

Rare earth elements (REE) are critical metals widely used in modern technology. There is an increased demand for these elements which has necessitated additional exploration. The REE geochemistry of syenites and charnockitic rocks from selected locations within southwestern Nigeria were studied to determine their concentrations, distribution patterns, and mineralisation potential to deduce if they can be economically exploited. Mineralogical studies were carried out using scanning electron microscopy (SEM). Ten rock samples including five syenites and five charnockites were analysed for their elemental composition using inductively coupled plasma – mass spectrometry (ICP-MS). The REE-bearing minerals identified from the SEM analysis include apatite and monazite. The fractionation ratio (La/Yb)_N ranged from 29.36 to 48.75 for the syenites and from 24.43 to 48.29 for the charnockites, indicating magmatic differentiation. Total REE (∑REE) in the syenites (342–675 ppm) and charnockites (220–802 ppm) suggests that they are enriched with respect to REE but the REE concentration in the rocks of the study area had very low ∑REE compared to the REE contents of the rocks where they have been mined and may therefore not be economically viable.