Petrographic and Optical Cathodoluminescence Study of Detrital Quartz: Provenance Indicator for the Sediments of the Campanian Lokoja-Basange Formation, Anambra Basin, Nigeria.

Over the years, very few studies have been carried out on the Lokoja-Basange Formation, the most recent being the research on the implication of the geochemistry and mineralogy of the formation on provenance, tectonic setting and paleo-redox condition carried out by Akinyemi et al. in 2014. However, there is no recorded account of the application of cathodoluminescence microscopy as a provenance tool to study the Lokoja-Basange Formation. This drove the decision to carry out this research. The aim of this research was to unravel the provenance of the Campanian quartz arenitic sediments of the Lokoja-Basange Formation using integrated optical Cathodoluminescence and Petrographic characteristics approach.Fourteen sandstone samples recovered at one meter interval from outcrop section were used for the study. Thin sections were prepared from all the fourteen samples while four samples selected at targeted intervals were subjected to cathodolominescence analysis. Results of the cathodoluminescence analysis showed the presence, in abundance, of detrital quartz with characteristic dull red to violet CL colour and mottled texture. The common occurrence of compactional features such as Boehme Lamella, and micro fracturing within individual quartz grains, but without corresponding compressional features at the grain to grain boundaries suggested complex diagenetic history for the sandstones of Lokoja-Basange Formation. These features were indication of quartz derived from low grade metamorphic rocks which had undergone multiple reworking before final deposition. The sediments of the formation were texturally immatured and mineralogically matured, suggesting a high degree of chemical weathering. In conclusion,the sandstones of the Lokoja-Basange Formation are mineralogically matured but texturally immatured. These indicate the dominance of chemical weathering of the parent rocks from where the different aggregates of the rocks were formed and transported. Quartz cathodoluminescence of the sediment shows the dominance of grains from low grade metamorphic sources. The detrital quartz grains were not only subjected to metamorphism/stresses that altered their internal textures, but also subsequent external influences that slightly altered grain exteriors (chemical alteration and/or corrosion).