Geochemistry of Sandstones of AWI Formation, South-eastern Nigeria: Implication for Weathering, Provenance and Tectonic Settings

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Author(s) Okon E E | Essien N U | Adeyemi G O
Pages 742-755
Volume 6
Issue 4
Date April, 2017
Keywords Sandstone Geochemistry, Provenance, Tectonic Setting, Awi Formation
Abstract

The geochemistry of sandstones of Awi Formation have been examined in order to infer paleoweathering, provenance and tectonics settings. 10 samples were collected and subjected to whole rock geochemistry (major oxides, trace and rare earth elements). The results show large variation in the major oxides of the sandstones from Awi formation. High SiO2 and Al2O3 and low values for Fe2O3, TiO2 and MgO compared with the Post Archean Australian Shale (PAAS) values. Relatively high Chemical Index of Alteration values (CIA, 63.78 – 91.77; mean: 83.70), Chemical Index of Weathering (CIW, 81.78 – 99.69; mean:93.88), Mineralogical Index of Alteration (MIA, 27.56 – 83.53; mean:67.40) and Index of Compositional Variation (ICV, 0.21 – 1.17; mean 0.53) suggesting intensive weathering at the source area. There is positive correlation between Al2O3 and K2O and Na2O suggesting abundant clay mineral contribution to major oxides during weathering process. Enriched High field strength elements (Zr:225.71; Nb:11.62; Hf:6.15; Th: 16.81 and U:3.48) and bivariate plots of TiO2 against Ni reflects contributions from more felsic provenance for the sediments, with few contributions from mafic source. Tectonic setting discrimination based upon major oxides and rare earth elements suggest deposition in a passive continental margin setting. The characteristics of these sediments reflects fluvial conditions. The geochemical characteristics of the sediments strongly suggest deposition in a humid, non-marine environment.

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