The objective of this proposal is to apply the Re/Os system to problems in mantle evolution and the nature of mantle magma sources using the decay of 187Re to 187Os as the natural tracer. This study will focus on 1) comparing the 187Os/186Os ratios of mid-ocean ridge basalts with those of ocean island basalts; 2) the coupled use of 187Os/186Os and 3He/4He variations in basalts elucidating magma sources; 3) a systematic study of carefully documented samples of the Mesozoic Appalachian tholeiite province of eastern North AMerica will determine the controls on Re and Os abundances during generation and evolution of mantle-derived magmas on long-term Re/Os systematics of lithosphere mantle. The samples will be analyzed for 187Os/186Os by negative ion thermal ionization mass spectrometry (NTIMS). Re concentrations will continue to be determined by SIMS. This work should provide a broader understanding of the origin of mantle magmas.
