Composición y evolución de las lavas de la isla de Branco (Cabo Verde)

• Autores: José Luis Brandle Matesanz
• Localización: Geogaceta, ISSN 0213-683X, Nº. 40, 2006, págs. 91-94
• Idioma: español
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• Resumen

  • 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 (Fo 84-76 olivine, En 44-36 diopside, An 83-31 plagioclase) showing geochemical affinity of typical ocean island basalts. The scarce most evolved members are mugearites (olivine absent, En 41-31 clinopyroxene, An 51-26 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).