This proposal requests an Accomplishment Based Renewal for continued support of our application of the Re-Os isotope system to problems concerning the geochemical evolution of the solid Earth. We will focus on: 1) Delineation of the importance of mafic components (pyroxenites, eclogites) in the mantle sources of mid-ocean ridge basalts and mafic-potassic volcanism from Italy, the Colorado Plateau and southwestern Africa. 2) Re-Os age dating of sulfide inclusions in diamonds from the Slave craton and N.W. Australia. 3) Extend our studies of the Re-Os systematics of cratonic mantle peridotite xenoliths to China and west Africa. 4) Examine the Re-Os systematics of lower crustal garnet granulite xenoliths from Minas Gerais, Brazil to define the chronology of crust formation in this area. 5) Study the Re-Os system of the eclogitic and peridotitic rocks of the Dabie and Su-Lu terranes in eastern China to date the igneous formation of these materials and to examine the behavior of Re and Os during high-grade metamorphism. 6) Improve the understanding of the behavior of the platinum group elements (PGE's) during igneous differentiation by measuring whole rock PGE patterns by isotope dilution ICP-MS in most of the samples studied for Re-Os isotopic variation.
