Geochemical Characteristics of Porphyritic Granites around Lanlate, Southwestern Nigeria
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The study was carried out to delineate the petrogenesis, geochemical features and mineralization index of PanAfrican granite around Lanlate area in the Nigerian Basement Complex. Geological mapping on a scale of 1:25,000 was carried out and Six (6) samples of granites were subjected to geochemical analysis using the Inductively Coupled Plasma-Mass Spectrometry (ICPMS). Mineralogically, the porphyritic granite is composed of phenocrysts of albite in groundmass of biotite, quartz, feldspar and muscovite. Geochemical analysis results revealed concentration (%) of 65.92 - 68.30, 14.45 - 15.10, 3.98 - 5.27, 1.70 - 2.07, 2.92 - 3.03, and 4.97 – 5.31 for SiO Al O Fe O , CaO, Na O and 2, 2 3, 2 3 2 K O, respectively. Trace elemental concentration (ppm) ranges as follows: 15.33 – 22.64, 5.49 – 6.81 and 101.3 – 2 128.4 for Cu, Pb, Zn and Ni respectively; and 6-5 – 6.8, 1.1 to 2.1, 6 – 10.7, 21 – 29, 127 – 174 and 101 – 143 for Co, Th, Sr, V, Ba and Rb respectively. For Rare Earth Elements (REE), concentration of La, Ce, Pr and Nd ranged 82- 109, 197 – 260, 23 – 31 and 88 – 121ppm, respectively. Values of (La/Yb) and (La/Sm) which are fractionation indices of N N Light REE/Heavy REE, ranged from 34.59 – 57.24 and 3.77 – 4.26, respectively. Classification plots reveal that the granites are perluminous, Calc-alkaline, with high potassium content emplaced in a VAG-WPG-Syn collisional setting. Rare metal and precious metal concentration are low and this implies that the granites are not mineralized. The granites are characterized by higher LREE concentrations when compared with granites of China where REEs exploration is ongoing thus this study area may be a place of interest in understanding Nigeria's economic potential of REE.
Publication Info:
Author: Olisa, O.G. , Mustapha-Aminu, S.O. , Ogunleye, S.O. and Omotoso, D.A.
Volume: 60
Issue: September
Published By: Journal of Mining and Geology Vol. 60(2) 2024. pp. 241 - 253 © Nigerian Mining and Geosciences Society, 2024-09-01