Fractionation of Pleistocene alkali-basalts from the northern Golan Heights, Israel

The Pleistocene volcanic rocks of the Ortal and Golan formations, which cover the northern Golan, consist of flows and scoria cones of basanites, hawaiites, and alkali-basalts. Geochemical and mineralogical characterization of the two formations show general similarity. However, the Golan Formation is characterized by higher olivine phenocrysts contents, higher MgO concentrations, higher Mg numbers, and lower Al₂O₃ concentrations compared with the Ortal Formation. The magmas of both formations suffered up to 30 wt% fractionation of clinopyroxene and olivine, other phases being minor. The similarity in mineral chemistry of the phenocrysts of both formations suggests that the two stages in the evolution of Ortal basalts occurred at mantle depth. -from Authors