Mineralogical Characterisation and IUGS-SCMR Classification of Metasediments from Ikpeshi, Southern Nigeria: an XRD and Multivariate Statistical Approach
DOI:
https://doi.org/10.33003/fjs-2026-1020-6033Keywords:
Modal mineralogy, IUGS-SCMR classification, Ikpeshi schist, X-ray diffractionAbstract
Eight (8) samples (SL1–SL8) from a mapped metasedimentary outcrop at Ikpeshi, Southern Nigeria, were characterised using semi-quantitative X-ray diffraction (XRD) data and the modal-mineralogical principles of the IUGS Subcommission on the Systematics of Metamorphic Rocks (SCMR). The assemblage comprises quartz (22.8–82.6 wt. %), K-feldspar, albite, muscovite or phlogopite (up to 55.6 wt. %), and variable illite and montmorillonite. Pearson/Spearman correlation, principal component analysis (PCA), and Ward hierarchical clustering distinguish three mineralogical groups. Harker-type diagrams constructed from oxide compositions recalculated from XRD modes show inverse relationships between Al2O3 and K2O and SiO2 (r = −0.88 and −0.94), reflecting modal dilution by quartz rather than igneous differentiation. Following the SCMR structural criterion, six samples are classified as schists, SL5 as montmorillonite quartzite, and SL3 as orthoclase-quartz rich granofels because it falls below the 75% quartz threshold and the available mineralogical evidence does not demonstrate a schistose fabric. The classifications remain provisional because XRD values are semi-quantitative weight percentages, whereas SCMR thresholds are based on modal volume proportions, and only eight samples were examined.
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