Geochemical characterization of Lokoja-Basange Sandstone at Imiegba and Okpekpe areas, Benin flank of Anambra basin, Nigeria: implications for provenance, tectonic setting and source-rock weathering

  • Authors

    • Solomon Omale Obaje Adekunle Ajasin University Akungba-Akoko, Nigeria
    • Mr. Adekunle Ajasin University Akungba-Akoko, Nigeria
    2024-01-06
    https://doi.org/10.14419/gcmec839

  • Abstract

    This study investigates the geochemical attributes of the Lokoja-Basange Sandstone situated in Okpekpe and Imiegba areas of the Benin Flank of Anambra Basin, Nigeria. The aim of this study is to unveil its provenance, tectonic setting, and source rock weathering extent. Using energy dispersive x-ray fluorescence (EDXRF) "Minipal 4" spectrometer analysis, nine outcrop samples were examined for major oxide concentrations. The results show significant average SiO2 (77.09 wt. %), Al2O3 (12.10 wt. %), Fe2O3 (2.72 wt. %), Na2O (1.64 wt. %), K2O (2.41 wt. %), while TiO2, MnO, MgO, CaO, P2O5, LOI had average concentrations of less than 1.00 wt. %. Bivariate plots of log [Fe2O3/K2O] versus log [SiO2/Al2O3] indicate 77.80% litharenites and 22.20% arkose sediments. The [Al2O3]-[CaO+Na2O]-[K2O] ternary plot, the tectonic discriminant diagrams of [SiO2/20]-[K2O+Na2O]-[TiO2+Fe2O3+MgO], log [K2O/Na2O] versus SiO2, [SiO2/Al2O3] versus log [K2O/Na2O] and bivariate discriminant functions plot indicate that the sediments have felsic igneous provenance and quartzose sedimentary origin, within a passive margin tectonic setting and the source-area underwent moderate to near complete chemical weathering in semi-arid to humid climatic conditions with increasing chemical maturity. Conclusively, the chemical alteration index (CIA) ranges from 65.4% to 74.2%, averaging 70.70%; the chemical index of weathering (CIW) averages 82.37%; the plagioclase index of alteration (PIA) averages 78.88%; and the mineralogical index of alteration (MIA) averages 41.43%. These data signify extensive weathering of felsic igneous source rocks, highlighting mineralogical maturity of Lokoja-Basange Sandstone. In essence, this study enriches insights into the sandstone's origins, sedimentary context, and weathering history.

     

    Author Biography

    • Mr., Adekunle Ajasin University Akungba-Akoko, Nigeria

      Research Fellow

  • References

    1. M. Duze, A. Ojo, McMillan Senior School Atlas. McMillan Education Limited, 1977, 21.
    2. C.M. Fedo, H.W. Nesbitt, G.M. Young, Unraveling the effects of potassium metamorphism in sedimentary rocks and paleosols, with im-plications for paleoweathering conditions and provenance. Geology 23 (1995) 921-924. https://doi.org/10.1130/0091-7613(1995)023<0921:UTEOPM>2.3.CO;2.
    3. C.M. Fedo, K.A. Eriksson, E.J. Krogstad, Geochemistry of shales from the Archean (̴ 3.0 Ga) Buhwa Greenstone Belt, Zimbabwe: Im-plications for provenance and source-area weathering. Cosmochimica Acta 60 (1996) 1751-1763. https://doi.org/10.1016/0016-7037(96)00058-0.
    4. X.X. Gu, J.M. Liu, M.H. Zheng, J.X. Tang, L. Qt, Provenance and tectonic setting of the Proterozoic turbidites in Hunan, South China: Geochemical evidence. Journal of Sedimentary Research 72 (2002) 393-407. https://doi.org/10.1306/081601720393.
    5. L. Harnois, The CIW index: Anew chemical index of weathering. Sedimentary Geology 55 (1988) 319-322. https://doi.org/10.1016/0037-0738(88)90137-6.
    6. Heron, M. M. 1988. Geochemical classification of terrigenous sands and shales from core or log data. J Sed Res 58(5): 820-829. https://doi.org/10.1306/212F8E77-2B24-11D7-8648000102C1865D.
    7. S.B. Kroonenberg, Effect of provenance, sorting and weathering on the geochemistry of fluvial sands from different tectonic and climat-ic environments. Proceedings of 29th International Geological Congress, Part A (1994) 69-81.
    8. J.B. Maynard, R. Valloni, H.S. Yu, Composition of modern deep-sea sands from arc related basin. In: J.K. Leggett (ed.). Trench Forearc Geology: Sedimentation and tectonics on modern and ancient active plate margins. Geological Society of London Special Publication 10 (1982) 551-561. https://doi.org/10.1144/GSL.SP.1982.010.01.36.
    9. H.W. Nesbitt, G.M. Young, Early Proterozoic climates and plate motions inferred from major element chemistry of lutites. Nature 299 (1982) 715-717. https://doi.org/10.1038/299715a0.
    10. C.S. Nwajide, T.J.A. Reijers, Geology of the Southern Anambra Basin. In: T.J.A. Reijers (ed.), Selected Chapters on Geology, Warri, SPDC, 1996; 133-148.
    11. C.S. Nwajide, Geology of Nigeria’s Sedimentary Basins. CSS Bookshops Limited, Lagos, 2013; 1-548.
    12. S.O. Obaje, R. Ahmed, Palynomorphs Content of Mamu Formation in Okpekpe-1, Benin Flank of Anambra Basin, Nigeria. Journal of Research in Environmental and Earth Sciences 8(7) (2022) 57-63.
    13. S.O. Obaje, O. Akinyele, R. Ahmed, B. Alli, A. Adefemisoye, Palynomorphs Content of Mamu Formation in Okpekpe-1, Imiegba-1 and Imiegba-2, Benin Flank of Anambra Basin, Nigeria. Journal of Applied Sciences and Environmental 26(9) (2022) 1545-1552. https://doi.org/10.4314/jasem.v26i9.13.
    14. S.O. Obaje, B. Alli, Trace Element Geochemical Analysis and Depositional Environment of Lokoja-Basange Sandstone at Imiegba Area, Southwestern Nigeria. In: Attila Çiner et al. (Eds.). Chapter 21: Advances in Science, Technology and Innovation: Recent Research on Sedimentology, Stratigraphy, Paleontology, Tectonics, Geochemistry, Volcanology and Petroleum Geology Proceedings of the First Mediterranean Geosciences Union Annual Conference Istanbul 2021 (volume 2), 2023; 95-99. https://doi.org/10.1007/978-3-031-43222-4_21.
    15. B. Roser, R. Korsch, Determination of tectonic setting of sandstone-mudstone suites using content and ratio. Journal of Geology 94(5) (1986) 635-650. https://doi.org/10.1086/629071.
    16. L.J. Suttner, P.K. Dutta, Alluvial sandstone composition and paleoclimate; I, framework mineralogy. Journal of Sedimentary Research 56(3) (1986) 329-345. https://doi.org/10.1306/212F8909-2B24-11D7-8648000102C1865D.
    17. G. Voicu, M. Bardoux, L. Harnois, R. Crepeau, Lithological and geochemical features of igneous and sedimentary rocks at Omai gold mine, Guyana, South America. Exploration and Mining Geology 2(6) (1997) 153-170.

  • Downloads

  • How to Cite

    Omale Obaje , S., & Adekunle Adefemisoye , A. (2024). Geochemical characterization of Lokoja-Basange Sandstone at Imiegba and Okpekpe areas, Benin flank of Anambra basin, Nigeria: implications for provenance, tectonic setting and source-rock weathering. International Journal of Advanced Geosciences, 12(1), 1-6. https://doi.org/10.14419/gcmec839