Abstract
The sedimentology and geochemistry of the major oxides and trace elements of DF-2 well, Onshore, Niger Delta, are presented in this study. The study is aimed at describing the sedimentological characteristics as well as using the major oxides and trace elements to investigate the provenance, tectonic history and palaeo-depositional conditions of the well. Selected samples were investigated with fused bead X-Ray Fluorescence (XRF) spectrometry to determine their major oxides and fused bead laser ablation inductively couple plasma mass spectroscopy (LA-ICP-MS) for their trace elements. Sedimentological analysis from the well shows that the lithology ranged from shaly sand, sandy shale, sandstone and shale. The results show the dominance of silicon oxide (SiO2) contents which ranges from 81.1 to 91.4 wt. % (average of 87.1 wt. %). The low average concentration of Cr<150 ppm and Ni <100 ppm, the ratios of Th/Sc, Th/Co, Th/Cr, Cr/Th, La/Sc, as well as the plots of Th/Co versus La/Sc and TiO2 versus Zr, all infer a felsic source rock. The discrimination plots of ratioK2O/Na2O against SiO2 and Log K2O/Na2O against Log SiO2/Al2O3 indicated passive continental margin. Various chemical classifications of the sediments show that the sandstone facies plotted mainly in quartzarenite, sublitharenite and Fe-rich sand domains. The samples were deposited under oxic environment based on the average values of U/Th (0.26 ppm), Ni/Co (2.79 ppm) and Cu/Zn (1.81ppm) and bivariate plot of Ni/Co versus V/Cr. However, the bivariate plot of Ni/Co versus V/ (V+Ni) specifies oxic to anoxic conditions and V/Vi + Ni ratios indicate oxic, suboxic to euxinicpalaeode positional environments for the sediments. Geochemical characterization illustrates mixed marine and terrigenous source input, deposited mainly in semi humid/humid climate. The positive values attained from ratios of Al2O3/(CaO+MgO+Na2O+K2O) infers mineralogical maturity based on stable mobile oxides content in the studied samples.
 Keywords: Felsic Rock, Quartzarenite, Litharenite, Passive Margin, Mobile Oxide, Mature Sediments.
Highlights
The Niger Delta is situated on the Gulf of Guinea on the west coast of central Africa and extends throughout the Niger Delta Province as defined by Klett et al, (1997)
Major oxides were determined by X-Ray Fluorescence Spectrometry on oven dry temperature of 1050C
The results of the major oxides are described as oxides percent by weight and trace elements quantified in ppm as shown in Tables 1 and 2
Summary
The Niger Delta is situated on the Gulf of Guinea on the west coast of central Africa and extends throughout the Niger Delta Province as defined by Klett et al, (1997) It is one of the world’s largest, deltas, with the sub aerial portion covering about 75,000 km and extending more than 300 km from apex to the mouth (Doust and Omatsola, 1990).From the Eocene to the present, the delta has prograded southwestward, forming depobelts that represent the most active portion of the delta at each stage of its development (Doust and Omatsola, 1990, Fig. 1b). The composition of siliciclasticfacies depends on the principal chemical composition of the source rock area and the tectonic history of the depositional basins (Das and Haake, (2003); Jin et al, (2006).
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