Re-fertilization of the Lithospheric Mantle
The composition of the lithospheric mantle has been debated for the last 30 years. Most massif peridotites have very high proportion of fertile peridotite, which has been interpreted as sections of unmelted depleted upper mantle. Correlation between the proportion of mafic layers and the fertility of the host peridotite has been the first indication that fertile mantle could be the product of re-fertilization of a previously ultra-depleted residual peridotite, after the formation of the oceanic crust, by reaction processes during percolation of basaltic melts. We are using Re-Os, U-Pb, Sm-Nd, Lu-Hf and Rb-Sr isotopes, Platinum Group Elements, and trace and major elements to test the re-fertilization hypothesis of the lithospheric mantle. The supra-chondritic Re/Os, Pd/Os and Pt/Os ratios supports the re-fertilization hypothesis.
Saal, A.E., Takazawa, E., Frey, F.A., Shimizu, N. and Hart, S.R. - (2001) - Re-Os isotopes in the Horoman peridotite: Evidence for refertilization? Journal of Petrology 42, (1), 25-37.
Takazawa, E., Frey, F.A., Shimizu, N., Saal, A.E. and Obata, M. - (1999) - Polybaric petrogenesis of mafic layers in the Horoman peridotite complex, Japan. Journal of Petrology, 40, (12), 1827-1851. 
Other project collaborators:
E. Takazawa (Niigate University); F. Frey (MIT); N. Shimizu and S. Hart (WHOI)