Petrovolcanic stratigraphy of Jita River section in the Northeastern sector of the Ethiopian Flood basalt province

Abstract

The Jita River volcanic series is situated in the northeastern Ethiopian volcanic province; the area provides a well-preserved stratigraphic sequence from lower basalt formation to upper lava flow termination. The main objective of the study is to establish the petrostratigraphy of the area and use these observations for the reconstruction of magmatic conditions along a well-exposed volcanic section. The major volcanic units of the Jita section from bottom to top are aphyric-intergranular basalt, aphyric-trachy basalt flow, augite cumulophyric basalt, olivine-augite phyric basalt, kfs vitrophyric rhyolite, augite phyric basalt, aphyric columnar basalt, moderately welded tuff, kfs phyric rhyolitic-ignimbrite, kfs phyric rhyolite, columnar-aphyric basalt, and slightly vesicular aphyric basalt. Petrographically, these volcanic rocks have different modal mineralogy and textures, revealing that there is a variation in the depth of mineral fractionation and magma flux in the stratigraphy. The flows clearly showed a broad change in modal mineralogy and eruptive cyclicity, and these constraints were that they were pulsed with a fluctuating magmatic influx along the complex plumbing systems and over time fed by shallower magmatic plumbing reservoirs. Overall, this stratigraphic study provides a new insight into the magmatic evolution of the northeastern Ethiopian volcanic provinces.