This is a study of the rare gas isotope systematics of residual xenoliths from three islands within the Samoan hotspot chain. The xenoliths occur in post-erosional volcanics and are apparently the residual mantle remaining after extraction of the basaltic lava which formed the Samoan shield volcanoes. Rare gases (He, Ne, Ar and Xe) will be used to determine the evolution of the mantle source for Samoa and the processes occurring during melt formation and segregation. Rare gas analysis of individual mineral phases, plus interstitial glass will employ a variety of extraction techniques, including vacuum crushing, fusion by conventional step-heating, and laser fusion of individual mineral grains. The Samoan xenoliths are extremely gas-rich, and accurate He and Ar isotopic analysis can be obtained on single crystals of < 5 mg. The study should lead to a better understanding of the processes involved in the extraction of volatiles from mantle peridotites during the formation of a basaltic melt.