The Re-Os isotope system has unique potential to contribute to geochemical studies of the earth because information provided by this system will be complementary to that currently available from other isotope systems and should provide new insight on the geochemical evolution of the mantle, formation of the core and creation of continental crust. This project will determine an accurate Os isotope growth curve for the mantle, estimate the crustal residence time of the parents of 3.6 Ga craton core rocks, better understand the behavior of Re and Os in igneous systems and estimate the Os isotope heterogeneity of the present mantle. Techniques will be based on the ongoing work at the National Bureau of Standards (NBS) of J. Fassett and DTM Research Associate R. J. Walker. Funds will be used primarily to pay Walker's salary and to build a chemical facility at DTM for the separation of Re and Os. Initially, analyses will be performed by laser resonance ionization mass spectrometry (RIMS) on the Fassett-Walker 6" RIMS machine at NBS. Later, an improved 9" mass spectrometer, presently under construction at DTM, will be used.
