Abstract : The Ain Sedma volcanic complex is part of Collo massif located in the northeastern Algeria. These rocks host iron mineralization and consist predominantly of Miocene calc-alkaline rhyolites, highly altered. Textural and mineralogical compositions of host rock and ores were determined using optical and SEM imaging. Ore chemistry was determined using ME-XRF and EDS analysis. The host rock is made up mainly of quartz, k-feldspar, and plagioclase. Associated mineralization is represented predominantly by magnetite, hematite, pyrite, limonite, and quartz as gangue mineral. magnetite microstructure includes mainly massive and disseminated textures. XRF and EDS results show that this mineralization contains high grade Fe (>60%) ore. Other major elements are Si, Al and Mn. Usual associated trace elements such as Ni, Cu, V contents are rather insignificant ranging from 10 to 20 ppm, 10 to 30 ppm and 10 to 30 ppm respectively. Our results combined with previous works suggest that magnetite formed from magmatic exsolved fluids after the emplacement of host rock. This volcanic episode was most likely followed by an H2S-rich fumarolic episode during which magnetite has been partly replaced by pyrite. Hematite and limonite occurred later as a product of weathering processes.