Compositional Characteristics in Relation to the Evolution of Granite Suites in Guguruji Area, Parts of Ayetoro (Sheet 226 NW and NE) and Kagara, Tegina (Sheet 142 SE), North-Central, Nigeria

The area of study lies within the Nigerian Basement Complex, largely of sutured low-grade assemblages of Proterozoic rocks. The major rock units in Guguruji area are schists, granites, gneisses and amphibolites, where the granitic intrusives are traversed by pegmatite and quartz veins. The major rock units in Kagara area are migmatitic gneiss, banded gneiss, granitic gneiss, meta-arkosic rock, amphibolite, talcose rock, phyllite, granodiorite, porphyritic granite, fine-medium grained granite, and pegmatite. Geochemically, granites from both locations are characterized by high SiO2 (65.42-72.11 wt. %), high total alkali concentrations displaying the predominance of K2O over Na2O. The negative correlation of SiO2 with Al2O3, Fe2O3 , CaO, TiO2 , and P2O5 and positive correlation with K2O and Na2O indicate fractionation nature of these granites. The granites are also enriched in Zr, Ba, K, Th and depleted in Nb suggesting the interaction with the crustal materials. The enrichment of large ion lithophile elements, depletion of high field strength elements are pointer to partial melting and crustal contamination of magma above subduction zones or volcanic arc and syn- to post-collisional granitoids. The granites are I-type, enriched in light rare earth elements relative to heavy rare earth elements and may have fractionated rare earth element patterns (La/Yb). The negative anomalies of Dy, Yb and Eu indicate magmatic related origin. However, I-type granitoids may also result from a contaminated mantle - derived magmas by a partial melting of crustal materials.