TITLE:
Geochemical Discriminant for Provenance Characterization and Palaeogeography of Shales from Dahomey Embayment, Southwestern Nigeria
AUTHORS:
O. Innocent Ejeh
KEYWORDS:
Geochemistry, Shale, Provenance, Paleogeography, Dahomey Embayment
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.4 No.6,
June
14,
2016
ABSTRACT: The
geochemical compositions [major, trace and Rare Earth Elements (REE)] of
Cretaceous-Tertiary shales from
Gbekebo-1 well were used to characterize provenance, paleogeography, source
area weathering and tectonic setting of the study area located in the
southwestern part of the Dahomey Embayment, Nigeria. Core samples (eight) of
shales were obtained and analyzed geochemically using the combined methods of
major elements Fusion Inductively Coupled Plasma (FUS-ICP) and trace elements
Fusion Inductively Coupled Plasma Emission/Mass Spectrometry (FUS-ICP/MS). An
A-CN-K (Al2O3-CaO + Na2O-K2O)
ternary plot, geochemical discriminant function of major elements and chondrite
normalized plots of REE suggest an upper continental crust provenance of felsic
to intermediate or mixed igneous rocks of tonalite to granodiorite composition.
High values of chemical index of alteration (CIA, 82.22 - 96.39) and chemical
index of weathering (CIW, 88.10 - 99.17) indicated a palaeogeographic condition
marked by wet tropical climate where intense chemical weathering and erosion
prevailed. The Cretaceous-Tertiary shales from Gbekebo-1 well are inferred to
have been deposited in passive margin setting based on various geochemical
tectonic setting discrimination diagrams.