HR: 11:25h
AN: T31H-05    [PDF]
TI: HFSE-REE systematics of Neogene IBM lavas
AU: Prinkey, D
EM: dprinkey@es.ucsc.edu
AF: UC Santa Cruz, Earth Sciences Department, Santa Cruz, CA 95064 United States
AU: * Gill, J
EM: jgill@es.ucsc.edu
AF: UC Santa Cruz, Earth Sciences Department, Santa Cruz, CA 95064 United States
AU: Williams, R W
EM: williams141@llnl.gov
AF: Lawrence Livermore National Laboratory, Analytical and Nuclear Chemistry Division, Livermore, CA 94551 United States
AB: Hf-Nd isotope ratios and REE+Hf concentrations have been measured for representative lavas from the Izu and Mariana arc, and can be compared with similar results for Mariana Trough basalts. Isotopes for all three suites define a trend parallel to the Terrestrial Array but displaced to its high-Hf side, as for Indian Ocean MORB. The Izu arc volcanic front lies at the most depleted end of the array whereas the Izu rear arc overlaps the Mariana volcanic front. The overall isotopic pattern is qualitatively consistent with arc and back arc magmas being mixtures of Indian-type mantle plus small amounts of subducted sediment. However, the slope of the isotope correlation requires a mantle-like Nd/Hf ratio for the sediment component that is much lower than in most IBM sediment. Izu rear arc lavas also lack the expected negative Ce and Hf concentration anomalies. Together the data indicate substantial intrinsic isotopic heterogeneity in the IBM mantle wedge, and small amounts of LREE$>$Hf addition from the slab, least at the Izu volcanic front.
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8125 Evolution of the Earth
DE: 8158 Plate motions--present and recent (3040)
DE: 8429 Lava rheology and morphology
SC: Tectonophysics [T]
MN: 2003 Fall Meeting