HR: 0800h
AN: V51A-1469    [Abstracts]
TI: Volatiles in Hawaiian, Submarine Rejuvenated-Stage Lavas: Evidence for Metasomatism by Silicate and Carbonatitic Melts of the Mantle Surrounding the Hawaiian Plume
AU: * Dixon, J
EM: jdixon@rsmas.miami.edu
AF: Univ. of Miami/RSMAS, 4600 Rickenbacker Cswy., Miami, FL 33149 United States
AU: Clague, D
EM: clague@mbari.org
AF: MBARI, 7700 Sandholdt Road, Moss Landing, CA 95039 United States
AU: Cousens, B
EM: brian_cousens@carleton.ca
AF: Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6 Canada
AU: Monsalve, M L
EM: mmonsalve@rsmas.miami.edu
AF: Univ. of Miami/RSMAS, 4600 Rickenbacker Cswy., Miami, FL 33149 United States
AB: We present new volatile and trace element data for submarine rejuvenated-stage lavas erupted at various locations around Hawaii, including samples from the Hawaiian Arch south of Hawaii, the channel between Kauai and Oahu, and the northwest flank of Ni'ihau. These submarine lavas provide a unique opportunity to study temporal and spatial variations in magma generation processes associated with Hawaiian volcanism, particularly with respect to volatiles, which are partially to mostly retained in quenched glassy rinds. Submarine rejuvenated-stage lavas are characterized by variable H₂O /Ce ratios with values up to 700, significantly higher than values measured in MORB and other OIB glasses. These lavas, especially those from Ni'ihau, display trace element heterogeneity greater than that of shield lavas with enrichments in Ba and Sr, high and highly variable Ba/Th and Sr/Nd, and depletions in Zr, Hf, U, Nb, and Ta. Also, the largest Ba/Th and H₂O /Ce values are in alkali basalts with lesser enrichments observed in the basanites and nephelinites, implying that the greatest enrichments are associated with the largest extents of melting. These submarine rejuvenated-stage lavas are isotopically similar to the North Arch and Honolulu Series basalts, which have been modeled by melting of depleted lithosphere recently metasomatized by enriched incipient melt (<2% melting) from the Hawaiian plume (Yang et al., J. Petrol. 44, 603-627, 2003). The relative homogeneity of the radiogenic isotopic compositions combined with the highly variable Ba- and Sr-enrichment indicates that metasomatic components have variable trace element compositions and are derived from a single source, namely the Hawaiian plume. We suggest that these volatile, trace element, and radiogenic isotopic characteristics are best explained by the presence of carbonate in the Hawaiian plume and the occurrence of metasomatism of the mantle surrounding the plume by carbonatitic, as well as silicate, melts in the mantle source for rejuvenated-stage Hawaiian magmas.
DE: 1025 Composition of the mantle
DE: 1065 Major and trace element geochemistry
DE: 3037 Oceanic hotspots and intraplate volcanism
DE: 8427 Subaqueous volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005