Volcano-stratigraphy and petrography of bimodal volcanic rocks suites of Mekane Selam area, northwestern Ethiopian volcanic plateau

The volcanic stratigraphy and petrography of compositionally bimodal volcanic rocks in the Mekane Selam area were characterized by detailed field investigation, spatial and systematic sampling, and petrographic analysis. Three successions of basaltic rocks with rhyolitic and trachytic rock units at the top with a substantial volume of felsic pyroclastic deposits were categorized as the typical lithological formations in the study area. Volcanic rock types present in the study area include plagioclase phyric basalt, plagioclase-pyroxene phyric basalt, pyroxene-plagioclase phyric basalt, pyroxene-olivine phyric basalt, pyroxene phyric basalt, olivine phyric basalt, rhyolite, and trachyte from bottom to top. The basaltic rocks are composed of plagioclase, clinopyroxene, and olivine phenocrysts with minor Fe-Ti oxides (ilmenite and magnetites). The common phenocrysts of trachyte rocks are sanidine, plagioclase, Fe-Ti oxides, and minor hornblende and green pyroxenes (aegirine). Rhyolites contain quartz and sanidine phenocrysts.