GEOCHEMISTRY, CLASSIFICATION AND MATURITY OF THE EOCENE NANKA FORMATION SOUTH EAST, NIGERIA

Abstract: The geochemistry, classification and maturity of the Eocene Nanka Formation were investigated. The sandstones are non-calcareous, ferromagnesian potassic sandstones composed of sublitharenites and quartz arenites. Plot of SiO₂/Al₂O₃ against quartz / (feldspar + lithic fragments) indicates compositional maturity. SiO₂/Al₂O₃ and Fe₂O₃/K₂O values are high, implying mineralogical maturity and low degree of clayness and presence of stable mobile oxides. The minute alkali content indicates the near absence of feldspar and high chemical maturity. The ZTR values suggests that the sediments are mineralogically immature to sub mature, however, the mineralogical maturity index classifies the Nanka sandstone as mature to super mature. A decrease in the abundance of TiO₂, Fe₂O₃, CaO, Na₂O, MgO, MnO, K₂O, and Al₂O₃ as SiO₂ increases is due to chemical weathering and removal of these elements. There is no correlation between K₂O and TiO₂ suggesting a loss of K₂O and an indication of diagenetic alteration of feldspars. There is no correlation with Na; the extrapolated regression equation did not pass through the origin, suggesting minimal Na₂O contribution from the clay minerals. There is no correlation between TiO₂ and Al₂O₃ due to depositional process and granulometry; indicating that TiO₂ is not associated with phyllosilicates. TiO₂/Al₂O₃ ratio is low indicating that the sandstone matrix is composed of clay minerals. There is no correlation between K₂O and Al₂O₃ due to changes in the quartz-matrix proportions reflecting the grading. The Al—Ti—Zr ternary plot and the wide range of TiO₂/Zr variations, indicates compositional maturity, good sorting trend, rapid deposition and low to medium Zr concentration

Keywords: Eocene, mineralogical maturity index, quartz, sandstones, ZTR index.

Title: GEOCHEMISTRY, CLASSIFICATION AND MATURITY OF THE EOCENE NANKA FORMATION SOUTH EAST, NIGERIA

Author: Henry Y. Madukwe, Matthew A. Adeniran, Paulinus N. Nnabo

International Journal of Recent Research in Interdisciplinary Sciences (IJRRIS)

ISSN 2350-1049

Vol. 10, Issue 2, April 2023 - June 2023

Page No: 41-57

Paper Publications

Website: www.paperpublications.org

Published Date: 02-June-2023

DOI: https://doi.org/10.5281/zenodo.7997489

Paper Download Link (Source)

https://www.paperpublications.org/upload/book/GEOCHEMISTRY,%20CLASSIFICATION-02062023-4.pdf