Isotope ratios and concentrations of silica, titanium, aluminium, calcium, sodium and iron are correlated in shield-stage basaltic lavas erupted over the past three million years From eight Hawaiian volcanoes. These correlations indicate the presence of a component beneath Hawaii with a bulk composition which is distinct from typical mantle peridotite. This material is most probably recycled oceanic crust distributed within the Hawaiian plume as segregations of quartz-bearing garnet pyroxenite or eclogite, which yield silica-rich (dacitic) magmas on partial melting.