A comprehensive documentation and study of 176Hf/177Hf isotope ratio variation of mid-ocean ridge basalt (MORB) glasses from the URI dredge rock collection will be conducted. The collection focuses on unusually elevated mid-ocean ridge segments affected by nearby hotspots and underlying mantle plumes. About 300-400 samples from some 300 different sampling localities will be studied. Possible correlations, or decoupling, will be sought between the radiogenic Lu-Hf isotope system with that of Pb, Sr, Nd, and He isotope systems, and other geochemical parameters previously established on the very same basalt glasses. The study should provide new constraints on the depth and mode of melting and extent of garnet involvement beneath mid-ocean ridge segments affected by hotspots such as Jan Mayen, Iceland, Azores, Sierra Leone, St Helena and Tristan da Cuhna in the Atlantic, the Galaggos and Easter in the Pacific, and the Afar in the Gulf of Aden-Red Sea region. Greater insights should also be gained on suboceanic mantle geochemistry, length scales of heterogeneities, and mantle dynamics. The study will be done in collaboration with Dr. Janne Blichert-Toft and Dr. Francis Albarede, from the Ecole Superieure de Lyon, France, where the 176Hf/177Hf ratio measurements will be made by plasma source multi-collector mass spectrometry, after Hf has been separated at URI.
