Postcumulus processes in oceanic-type olivine-rich cumulates: The role of trapped melt crystallization versus melt/rock interaction

Combined microstructural and geochemical investigations on MORB-type primitive olivine-rich cumulates intruded in the Erro-Tobbio (ET) mantle peridotites (Voltri Massif, Ligurian Alps, Italy) revealed that significant chemical changes in minerals were caused by postcumulus crystallization. This is indicated by the occurrence of accessory interstitial minerals (Ti-pargasite, orthopyroxene and Fe-Ti oxides) and by systematic chemical zoning in intercumulus clinopyroxene, resulting in marked trace element (e.g. REE, Ti and Zr) enrichment at constant high Mg-numbers (0.88-0.91) and LREE depletion. Geochemical modelling shows that low trapped melt amounts (