Major and trace element geochemistry of the shales of Sekuliye Formation, Yola Sub-Basin, Northern Benue Trough, Nigeria: implications for provenance, weathering intensity, and tectonic setting

The shales of Sekuliye Formation were investigated to interpret their provenance history, weathering, and tectonic setting based on major and trace element geochemistry. The major and trace element geochemistry revealed derivation of the shales from felsic igneous rocks with little influence from intermediate igneous rocks and quartzose sedimentary rocks. Weathering proxies such as plagioclase index of alteration (PIA), chemical index of alteration (CIA), index of chemical variability (ICV) and Rb/Sr ratios show that the source rock undergoes high degree of chemical weathering activities. Also, the plot CIA vs. ICV shows that all the studied shales were plotted below Post Archean Australian Shale. The ICV value of 0.85 also indicates high intensity of weathering activities in the provenance area. The paleoclimatic indicators (C values and Sr/Cu) and some trace elements ratios (Ni/Co and Cu/Zn) displayed deposition under humid conditions and oxic depositional environment, respectively. The Sr/Ba ratios revealed high salinity during the deposition of the studied shale, reflecting a marine depositional environment. Through geochemical studies, these sediments were classified as shales that are texturally immature and compositionally matured. The geochemical data plotted on tectonic setting discriminant function diagrams suggested a continental rift of passive margin settings. Accordingly, the inferred tectonic settings are comparable to the accepted model on the origin and evolution of the Benue Trough.

Automated summary

Analyzing the shales of the Sekuliye Formation using major and trace element geochemistry revealed their origin from felsic igneous rocks, high degree of chemical weathering, and a tectonic setting associated with continental rift or passive margin environments.