Geology, Types and Implication of Leucosomes in Migmatite at Lauki, Sheet 148, Toro SE, Bauchi State; Nigeria

S.D. Abegunde; A.I. Haruna; U.S. Umar; A.I. Jibrin; B.I. Gani; P. Lila; A.S.; Abdullahi; K. Musa; W. Musa; M.A. Hassan; J.K. Ayeni

doi:10.56201/ijaes.vol.12.no8.2026.pg43.60

Geology, Types and Implication of Leucosomes in Migmatite at Lauki, Sheet 148, Toro SE, Bauchi State; Nigeria

S.D. Abegunde, A.I. Haruna, U.S. Umar, A.I. Jibrin, B.I. Gani, P. Lila, A.S., Abdullahi, K. Musa, W. Musa, M.A. Hassan, J.K. Ayeni

Abstract

This study investigates the geology, types and implication of leucosomes in migmatite of Lauki and environs, Sheet 148, Toro Southeast, Bauchi State, Nigeria, Geological mapping identified the principal lithologies as stromatic metatexites, leucosomes, quartzite, dolerite trachy- andesite and pegmatite. Field relationships indicate that the leucosomes in contact with the metatexites formed by localized partial melting, whereas the leucosome without any visible contact with metatexite represent mobilized felsic melts emplaced along structural pathways. Petrographic evidence, including biotite depletion, quartz–feldspar assemblages, myrmekitic textures, and recrystallization features, supports an anatectic origin indicating likely occurrence of insitu and insourced leucosomes. The close overlap of the stromatic metatexite and leucosomes on the TAS, Harker, A/CNK–A/NK and REE plots demonstrates that they are chemically indistinguishable and therefore represent products of the same melt generation event. The R1-R2 Batchelor + Bowden plot indicates anorogenic while melt was generated during an orogeny this is because during anatexis, the melt preferentially incorporates K- feldspar, quartz, and Na-rich plagioclase. This produces felsic, alkali-rich composition- the felsic melt is extracted while biotite and ferromagnesian minerals remain in the residue and this changes the major-element ratios (R1 and R2), causing the leucosomes and host stromatic metatexite to plot toward the anorogenic field. Whole-rock geochemical analyses reveal that light rare earth elements (La, Ce, and Nd) are preferentially retained within the stromatic metatexites, whereas Dy is relatively enriched in the insitu and insourced leucosomes. This distribution suggests incomplete dissolution of LREE-bearing accessory minerals, likely monazite, during partial melting, resulting in the retention of LREEs within the source rocks while selective transfer of HREEs occurred into the anatectic melt. Conversely, the insitu and insourced leucosomes record melt segregation, migration, and crystallization during the Pan- African high-grade metamorphic event which resulted in their mode of occurrence in the field. The study concludes that the Lauki migmatite terrain preserves an integrated record of crustal anatexis, melt evolution, and selective REE partitioning, providing new insights into the petrogenesis of leucosomes and highlighting the exploration significance of the metatexites for rare earth element mineralization within the Nigerian Basement Complex.

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Geology, Types and Implication of Leucosomes in Migmatite at Lauki, Sheet 148, Toro SE, Bauchi State; Nigeria

Abstract

References

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