Mineralogical and geochemical evaluations of Quaternary sedimentary clay formation, Niger Delta Basin, Nigeria: Depositional environments, provenance and paleoclimatic outcomes in Umukwata and its environs case study

Abstract

Abstract: This study involves an exploratory series of sedimentary clay deposits specifically selected to examine sedimentological characteristics using field studies, mineralogical composition, X-ray diffraction (XRD) and major oxides and traces using inductively coupled plasma-mass spectrometry (ICP-MS). This study aims to determine the influence of the mineralogical composition, major oxides and trace elements of clay minerals on the provenance, depositional environment and paleoclimate of Quaternary sedimentary clay deposits in the Niger Delta Basin, Nigeria. The average compositions of nonclay silicate minerals in the study area are quartz 55.0%, orthoclase 17.0%, albite 21.0% and muscovite 7.0%. The major oxides >1 recorded in the study area are SiO₂ = 79.340%, Fe₂O₃ = 2.555%, MgO  = 3.010%, CaO  = 1.617%, Al₂O₃  = 10.259% and TiO₂  = 1.051%. The trace elements >1 recorded are O 50.370%, Mg 1.815%, Al 5.430%, Si 37.087%, Ca 1.155%, and Fe 1.578%. Ba/Co 5.00, Ni/Co 0.20, Ti/Zr 7.41, Mg/Ca 1.57 and Si/Al 6.83. Field studies revealed that the clay formation in the study area comprises laminated, burrow clay facies, laminated nonburrow clay facies, and white-brown clay facies. The identified facies and SiO₂/Al₂O₃ and TiO₂/Al₂O₃ ratios indicated a continental depositional environment. The presence and high concentrations of non-clay-based minerals such as quartz, orthoclase, albites and muscovite and the complete absence of illite and montmorillonite clay minerals represent deposition under a continental environment from granitic rocks. The lower values of muscovite, albite, and orthoclase reflect deposition under humid paleoclimatic conditions with relatively low pH values. The high concentration of muscovite suggests that the clay sediments in the study area have undergone intense chemical weathering. This results in residual minerals within the studied clay formation. The cross plot of TiO₂ vs Al₂O₃, the high Ba/Co, Ni/Co, Ti/Zr, Mg/Ca and Si/Al ratios confirmed a mature felsic provenance with minor contributions from the mafic region.