The goal of ths research is to use nobel gases to constrain thenature and origin of mantle heterogeneities. The controversy regarding the extent to which helium isotopes are decoupled from the other isotopic tracers by magma chamber proceses will be tested by measurements of He/(Th+U) ratios and by measurements of He,Sr,Nd, and Pb isotopes in the same samples. The research will help constrain the origin of the variability on different time and length scales, and also resolve some of the controversy regarding the interpretation of low 3He/4He ratios in oceanic rocks. New measurements will be made on samples from ocean islands and ridges that are geologically well constrained.
