Geochemical characterisation of the < 2 μm fractions of cretaceous-tertiary kaolins from eastern dahomey and Niger delta basins, Nigeria: Implications on paleoenvironment, provenance, and tectonic settings

摘要

The geochemistry of the 2 mu m fractions of Cretaceous-Tertiary Kaolins from Eastern Dahomey and Niger Delta Basins, Nigeria was investigated to infer their paleoenvironment, provenance, and tectonic settings using major, trace, and rare earth elements (REE). Twenty-eight (28) samples comprising of fifteen (15) Cretaceous and thirteen (13) Tertiary kaolins, respectively, were collected. Geochemical compositions of the 2 mu m fractions were obtained using X-ray fluorescence (XRF) Spectrometry and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) analytical methods. Weathering indices such as chemical index of alteration (CIA, 96.98-99.39) and chemical index of weathering (CIW, 98.95-99.89) suggested intense chemical weathering under a wet tropical climatic condition. Ni/Co, V/Ni ratios and bivariate plot of V versus Ni indicated that they were deposited under marine oxygen-poor environment which is consistent with the horst and graben structural framework model of the Eastern Dahomey and Niger Delta Basins. The major, trace and REE data suggest that these deposits were derived from predominantly felsic source rocks with contributions from intermediate source rocks. The geochemical discrimination plots showed that the Cretaceous and Tertiary kaolins have been deposited in passive margin tectonic settings.