9316255 Patchett This project will continue Hf and other isotopic research into problems of crustal and mantle chemical evolution, with two main thrusts: (1) to complete study of granitoids melted from different crustal sources, and (2) to undertake a new effort to definitively determine the depleted mantle source of new crust over geologic time. Terranes have been selected from Greenland, Australia, Africa, Canada, USA and Saudi Arabia as representing known or potential juvenile additions to the continents over 3.8-0.7 Ga. Other terranes and collaborations may become necessary to fully determine the depleted source evolution. This data should constitute a firm basis for modeling by the PIs and others of crust- mantle evolution 4.0 Ga to present.
