This is a proposal to perform a thorough study on lava flows from two important intra-plate volcanic chains: Samoa and Guadalupe. Those localities were selected because they have extraordinary Sr-Nd-Pb isotopic compositions, suggesting they retain an unusually recognizable record of the processes responsible for mantle heterogeneity. Limited analyses demonstrate that these two localities are equally distinctive wit respect to helium: Samoa and Guadalupe have, respectively the highest and the lowest 3He/3He ratios found in mantle derived rocks. Excellent samples from both Samoa and Guadalupe have been obtained specifically for this work. In collaboration with several other investigators, the most important of these will be thoroughly studied. This includes petrographic and petrologic characterization, measurements of Sr, Nd, Pb, and He isotopes, and a limited number of Ar age determinations. The proposed work is new because it involves a very complete study of He systematics on well-controlled samples.
