Add to ORKGInternational audienceMelt inclusions are minute melts trapped during crystal growth [e.g., 1]. When trapped in euhedral olivine they are believed to represent the melt in which olivine grew[1], despite some post-entrapment modifications [e.g., 2, 3]. In this study, we analysed olivine hosted melt inclusions (OHMIs) in Mid-Ocean Ridge Basalts (MORBs) from two different locations on the Mid-Atlantic Ridge: FAMOUS and the 14° MAR triple junction (respectively Normal-MORB and Enriched-MORB).Silicon, as oxygen,is a major element inolivines and it diffusesslowly in dry basaltic melt [4]. Both isotope systems (O and Si) do not fractionate during melting [e.g., 5]. The isotopic ranges reported for bulk MORBs are narrow(<0.5‰)[e.g.,...