New insight into the origin of the low δ^(18)O magmas in Iceland

Iceland contains abundant low δ^(18)O volcanic rocks, reflecting ^(18)O-depleted sources and/or crustal contamination by assimilation and/or mixing with crustal melts. Previous attempts to distinguish among these mechanisms have been based principally on oxygen isotope measurements of whole-rocks, glasses, or mixed populations of phenocrysts. Here we add further constraints from micro-analyses of individual phenocrysts and xenocrysts.