PETROGENESIS, MAJOR OXIDES AND TRACE ELEMENTS GEOCHEMISTRY OF MIGMATITE IN AJUBA, KWARA STATE, NIGERIA

Abstract

Petrogenesis, major oxides and trace elements geochemical study was carried out on migmatite in Ajuba. The study area is located on Latitudes 8° 05'N and 8°13'N and Longitudes 5°23'E and 5°30'E. Five rock samples were taken from the migmatite outcrops and used for petrographic and geochemical analyses. The geochemical analysis was done using X-ray Fluorescence Spectrometer technique. The dominant rock type is migmatite; gneiss and granite outcrops were also found in sparse distribution. Ptygmatic folds, which constitute the palaeosome, is the common structure observed on the migmatite rock. The petrographic analysis shows that the migmatite consists of quartz, biotite, plagioclase, hornblende and microcline. The major oxides analysis indicates SiO2 as the dominant oxide with concentration range values (70.71 wt. % - 79.32 wt. %) and average of 74.80 wt. %. Al2O3 (14.98 wt. % - 16.44 wt. %, average: 15.70 wt. %) and Fe2O3 (9.10 wt. % - 15.41 wt. %, average: 12.39 wt. %), K2O (6.67 wt. % - 8.86 wt. %, average: 7.50 wt. %) and CaO (0.49 Wt. % - 4.64 wt. %. average: 2.73 wt. %). P2O5, MnO and TiO2 are less than 1.0 wt. %. The trace elements analysis indicates the concentration distributions: Rb (0.11-0.15 ppm, average 0.13 ppm), Co (0.04-0.17 ppm, average 0.10 ppm). Trace elements ˂ 0.10 ppm are Zn, W, Ni, Cu, V and Pb. From the petrographic and geochemical assessment, the petrogenesis of the migmatite has silica-rich igneous parentage. Moreover, the plots of SiO2-CaO and K2O-SiO2 placed the migmatite on the “upper boundary field of Francisian Greywacke” protolith and Shoshonite series, respectively.