Hf isotope evidence for pelagic sediments in the source of Hawaiian basalts

Lead, oxygen, and osmium isotopic ratios measured on Hawaiian basalts can b e matched with the isotopic ratios inferred for recycled ancient oceanic cr ust. High-precision hafnium isotopic data for lavas from several Hawaiian v olcanoes identify old pelagic sediments in their source. These observations support the recycling hypothesis, whereby the mantle source of ocean islan d basalts includes ancient subducted oceanic crust. Hyperbolic lead-hafnium isotopic relations among Hawaiian basalts further indicate that upper mant le material is not involved in the production of hot spot basalts.