Decoding Sediment Provenance and Tectonic Setting through Integrated Heavy Mineral and XRD analyses: Insights from the Imiegba Sedimentary Deposit, Southern Nigeria

Abstract

Understanding sediment provenance is key to reconstructing basin evolution, tectonic and climatic conditions in continental margins. While the Anambra Basin and the basins surrounding it have been extensively investigated, the Imiegba deposits on the Benin flank remain poorly understood. This study adopts X-ray diffraction (XRD) and heavy mineral analyses to deduce the provenance, mineralogical maturity and tectonic setting of the Imiegba sediments in southern Nigeria. Ten representative samples were analysed for heavy mineral composition through bromoform separation and petrographic analysis, while seven pulverised samples were examined using XRD (Cu-kα radiation, 5° - 70° 2θ range). The heavy mineral composition includes zircon, tourmaline, rutile, garnet, kyanite, sillimanite, epidote, hornblende, biotite, and andesine with a ZTR index ranging from 3.3% to 20.45%, suggesting moderate mineralogical maturity and polycyclic derivation. XRD analysis reflected dominant phases of quartz, feldspars (orthoclase, sanidine), muscovite, and kaolinite, accompanied by accessory minerals such as glauconite, moganite, berlinite, omphacite and wurtzite. The unified mineralogical evidence suggests a mixed provenance, derived primarily from felsic igneous and high-grade metamorphic sources, with secondary contributions from volcanism. Kaolinite abundance indicates intense tropical weathering. Glauconite suggests marine influence and low-energy depositional conditions. The occurrence of high-pressure minerals such as omphacite and wurtzite indicates tectonically active source terrains. Collectively, the data indicate Imiegba sediments were deposited in an active continental margin, influenced by both cratonic and uplifted metamorphic sources. This study demonstrates the strength of integrating XRD and heavy mineral analysis in provenance deduction and contributes to a broader understanding of polycyclic sedimentary systems and basin evolution.