HR: 14:10h
AN: V52D-03    [PDF]
TI: Depleted Components Within the Hawaiian Plume
AU: * Frey, F A
EM: fafrey@mit.edu
AF: Dept of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 United States
AU: Huang, S
EM: huangs@mit.edu
AF: Dept of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 United States
AU: Blichert-Toft, J
EM: jblicher@ens-lyon.fr
AF: Laboratoire des Sciences de la Terre, Ecole Normale Superieure de Lyon, 46, Allee d'Italie, Lyon Cedex, 69364 France
AU: Regelous, M
EM: M.Regelous@bristol.ac.uk
AF: Dept of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol, BS8 1RJ United Kingdom
AU: Lassiter, J C
EM: lassiter@mpch-mainz.mpg.de
AF: Max-Planck Institute fur Chemie, Postfach 3060, Mainz, 55020 Germany
AB: The rejuvenated-stage (post-erosional) lavas of volcanoes forming Hawaiian islands are alkalic and rich in incompatible elements, but among Hawaiian lavas they have the lowest $^{87}$Sr/$^{86}$Sr and highest $^{143}$Nd/$^{144}$Nd. The submarine North Arch lavas north of Oahu have similar geochemical characteristics. Although MORB-related lithosphere or asthenosphere has been inferred to be an important source component for these lavas, in detail their isotopic systematics deviate from the fields defined by most MORB. Specifically, at a given $^{143}$Nd/$^{144}$Nd these Hawaiian lavas are offset to high $^{87}$Sr/$^{86}$Sr relative to the field for MORB. They also have high $\epsilon_{Hf}$ relative to the $\epsilon_{Hf}-\epsilon_{Nd}$ trend of Hawaiian shield lavas, and they trend to lower $^{206}$Pb/$^{204}$Pb (less than 18) than most MORB. Surprisingly, tholeiitic lavas at Detroit Seamount, a 75-81 My volcanic edifice in the Emperor Seamount Chain, also have these isotopic characteristics. Unaltered glasses from Detroit Seamount and rejuvenated-stage lavas also have the distinctive high Ba/Th that distinguishes all Hawaiian lavas from MORB. We suggest that these geochemical similarities are not a coincidence. Although we cannot conclusively dismiss the hypothesis that the depleted component in these lavas originates from MORB-related lithosphere or asthenosphere, we propose the alternative hypothesis that the same depleted plume component has contributed to relatively young rejuvenated-stage alkalic lavas and old tholeiitic basalt from Detroit Seamount. How can this depleted component be expressed in such compositionally different lavas? Detroit Seamount formed on young and thin oceanic crust lithosphere thereby enabling sampling of a depleted plume component by relatively high extents of melting in a long melting column (Regelous et al., 2003). In contrast this depleted component is expressed in rejuvenated-stage lavas because these magmas may form from second-stage melting of a double-melting zone (Ribe and Christensen, 1999).
DE: 1000 GEOCHEMISTRY (New field, replaces Rock Chemistry)
DE: 1025 Composition of the mantle
DE: 1040 Isotopic composition/chemistry
DE: 1749 Volcanology, geochemistry, and petrology
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting