This study has two main goals: 1) Determination of the age of Hf-depletions in peridotites. A systematic study of western US peridotites is the focus of the proposed peridotite study which will further constrain the existence through time of this Hf depleted component. 2) Estimation of the degree and depth of melting using the combined Nd and Hf-isotope systematics. Initial results show that melt parameters vary consistently with major element variations. This study will further examine the relationships between the isotopic melt parameters and the major element variations. It will be shown that Hf and Nd isotopes can thus be used to distinguish between models for melt generation and magma extraction.
