The first data about the composition of lava flows from Branco Island (Cabo Verde) are presented in this
work. Most lava flows in the sequence are alkali basalts (Fo84-76 olivine, En44-36 diopside, An83-31 plagioclase)
showing geochemical affinity of typical ocean island basalts. The scarce most evolved members are
mugearites (olivine absent, En41-31 clinopyroxene, An51-26 plagioclase, and kaersutite). The compositional
variations between both the types are explained by crystal fractionation and extraction of pyroxene (up to
29%) and lesser proportions of olivine and Fe and Ti oxides (Cpx: 75; Ol: 21; OxFeTi: 4). The transition to
mugearites from the most evolved basalts would mainly be due to extraction of pyroxene (24%) and Fe
and Ti oxides (Cpx: 68; Ol: 3; Plag: 5; OxFeTi: 30)