THE SCALE OF SOURCE HETEROGENEITY BENEATH THE EASTERN NEOVOLCANIC ZONE, ICELAND

Geochemical characteristics of Icelandic basalts require mixing of sev eral sources: depleted asthenosphere, a plume (presumably heterogeneou s), and an enriched component (e.g. hydrothermally altered crust). We use lava compositions and Sr-Nd-Pb isotopic ratios from neighbouring c oeval volcanic centres to define spatial variations in source componen ts beneath the neovolcanic zones. Within the Eastern Volcanic Zone, ba salt compositions vary systematically from tholeiitic near central Ice land (Veidivotn, Grimsvotn) to Fe-Ti tholeiites at Hekla and Katla, to alkaline in Vestmannaeyjar. Each volcanic centre has distinctive geoc hemical characteristics that require differences in source components and proportions on the scale of 10-20 km.