Tectonic Setting of the Syenite Around Igarra, Southwestern Nigeria: Constraints from Geochemistry

Syenites are relatively rare within the Nigerian Basement Complex. As a result of their rarity, these rocks have been given less research attention over time and consequently poorly understood. The syenitic at Igarra were studied to ascertain tectonic evolution using geochemistry. Sampling was carried out survey-type geological field mapping approach. A total 10 samples collected for laboratory analyses. Compositionally, intermediate with regards SiO2 content (58.02% – 60.58%), having Al2O3 alkali (Na2O + K2O) compositional ranges 15.34% 15.52% 8.99% 9.7% respectively. sampled similar consistent in trace earth elements concentrations (the only exception being Zr values ranging from 4 ppm 79 ppm). enriched Ba, K, TI, Sr but depleted Tc, Nb, U, Hf, Yb, Te Ta. syenites also show fairly high ratios Rb/Nb Rb/Sr mean 488.627 0.171 seen geochemical analyses, around high-K calcalkaline, alkalic alkalic-calcic. peraluminous character as shown by bivariate plot A/NK vs. A/CNK. Sedimentary protolith continental crustal parent magma is inferred rocks. similarity consistency trends major, indicative cogenetic origin geochemistry discrimination plots indicate geodynamic setting orogenic post-orogenic. volcanic arc geotectonic interpreted syenites, emplacement thought initiated during late stages Pan-African reactivation continued into post-orogenic times.