HR: 0800h
AN: V51B-0553    [Abstracts]
TI: Geochemical Constraints on the Enriched End-member of the Hawaiian Plume: Temporal Geochemical Variation Within the Koolau Shield
AU: * Huang, S
EM: huangs@mit.edu
AF: Department of Earth, Atmospheric and Planetary Sciences, Massachusette Institute of Technology, 77 Mass Ave, Cambridge, MA 02139 United States
AU: Frey, F A
EM: fafrey@mit.edu
AF: Department of Earth, Atmospheric and Planetary Sciences, Massachusette Institute of Technology, 77 Mass Ave, Cambridge, MA 02139 United States
AB: The surface of Koolau volcano is composed of Makapuu-stage shield lavas which define the well known, distinctive endmember composition for Hawaiian shield lavas, known as the Koolau component. From $\sim$300 m to 470 m below this surface, drilling and coring by the Koolau Scientific Drilling Project shows that the Koolau shield lavas transitioned to a composition similar to Mauna Loa lavas; these Koolau lavas form the Kalihi-stage of the Koolau shield. Among all Koolau shield lavas and within the Makapuu- and Kalihi-stages, there are strong correlations between the compositional parameters, SiO$_{2}$ content (adjusted to be in equilibrium with Fo$_{90}$ olivine), Sr/Nb, La/Nb and Th/La, with radiogenic isotope ratios of Nd, Hf and Pb. These trends show that as the shield aged there was an increasing role for a marine sediment component accompanied by SiO$_{2}$-rich (dacite) melt. Therefore a recycled oceanic crust component was increasingly important as the Koolau shield moved away from the hotspot and encountered lower temperature.
DE: 1025 Composition of the mantle
DE: 1065 Trace elements (3670)
DE: 1000 GEOCHEMISTRY (New field, replaces Rock Chemistry)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting