Provenance and tectonic setting of Leuma Field sediments, Coastal Swamp Depobelt, Niger Delta Basin, Nigeria

Abstract

Geochemical analysis of sediments recovered from NS-1 well and NS-2 well, Leuma Field, Coastal Swamp Depobelt, Niger Delta Basin was done to establish tectonic setting and provenance. Data for ten major elements and forty-three trace elements were obtained from two boreholes. The geochemical signals display systematic  stratigraphic trends in the two wells that depict one source terrain. To determine the provenance of NS-1 well and NS-2 well sediments, Th/Co vs La/Sc plot was utilized which inferred that the sediments from NS-1 and NS-2 wells were derived from felsic source rocks. TiO₂ versus Ni bivariate plot was also used to establish the provenance and it revealed that the source of the sediments penetrated by NS-1 and NS-2 wells is predominantly acidic in nature. The provenance of NS-1 and NS-2 wells sediments was further confirmed by considering the ratios of Thorium/Scandium (Th/Sc), Thorium/Cobalt (Th/Co), Chromium/Thorium (Cr/Th) and Lanthanum/Scandium (La/Sc). For NS-1 well, Thorium/Scandium (Th/Sc) range from 1.12-2.01, Thorium/Cobalt (Th/Co) range from 0.91-1.66, Chromium/Thorium (Cr/Th) range from 4.21-16.04 and Lanthanum/Scandium (La/Sc) range from 3.69-8.78. For NS-2 well, Thorium/Scandium (Th/Sc) range from 0.95-2.05, Thorium/Cobalt (Thko/Co) range from 0.94-1.91, Chromium/Thorium (Th/Cr) range from 4.32-15.43 and Lanthanum/Scandium (La/Sc) range from 2.58-6.66. These values inferred that the sediments recovered from NS-1 and NS-2 wells were transported from felsic source rocks.
Inorganic geochemical results infer that the tectonic setting for NS-1 and NS-2 wells facies is passive continental margin.