HR: 0800h
AN: V41C-1470    [Abstracts]
TI: Recycled Component in the Canary Plume: Constraints From Olivine Phenocryst Composition and Radiogenic Isotopes in the Shield Stage Lavas From the Canary Islands
AU: * Gurenko, A
EM: agurenko@mpch-mainz.mpg.de
AF: Max Planck Institute for Chemistry, Geochemistry, P.O. Box 3060, Mainz, 55020 Germany
AU: Sobolev, A
EM: asobolev@mpch-mainz.mpg.de
AF: Max Planck Institute for Chemistry, Geochemistry, P.O. Box 3060, Mainz, 55020 Germany
AU: Sobolev, A
EM: asobolev@mpch-mainz.mpg.de
AF: Vernadsky Institute of Geochemistry and Analytical Chemistry, Kosigin Str. 19, Moscow, 117975 Russian Federation
AU: Hoernle, K
EM: khoernle@ifm-geomar.de
AF: IfM-GEOMAR, Wischhofstr. 1-3, Kiel, 24148 Germany
AU: Schmincke, H
EM: hschmincke@ifm-geomar.de
AF: IfM-GEOMAR, Wischhofstr. 1-3, Kiel, 24148 Germany
AB: One of the major geochemical challenges in understanding the dynamics of mantle melting is to identify the components involved in magma genesis. A contribution from recycled lithosphere is commonly proposed but still the subject of considerable debate. The Canary plume is one of the few plumes that can be traced all the way to the core-mantle boundary with seismic tomography [1], making it an excellent location for studying the deep crustal recycling. Trace element and isotopic signatures of the mafic magmas erupted on the Canary Islands require partial melting of a time-integrated high U/Pb (HIMU)-type mantle source, whose origin is attributed to the recycling of less than 2 Ga old oceanic crust [1,2]. We studied the most primitive picritic through alkali basaltic to basanitic subaerial lavas from Gran Canaria, Tenerife, La Gomera and La Palma shield stages, as well as submarine basaltic hyaloclastites drilled during ODP Leg 157 in the submarine clastic apron of Gran Canaria. In accordance with the experimental results [3], these volcanic rocks could be formed by the greatest degree of partial melting of the source rocks. The lavas are moderately enriched in light rare earth elements, Nb, Ta, and depleted in K and Pb, resembling HIMU-type magmas from ocean islands such as Mangaia and St. Helena. The Sr-Nd-Pb isotope data (87Sr/86Sr = 0.7030-0.7033, 143Nd/144Nd = 0.51288-0.51293, 206Pb/204Pb = 19.49-20.27, 207Pb/204Pb = 15.59-15.66, 208Pb/204Pb = 39.21-39.81) and the relationship between Sr isotopes in whole rocks and O isotopes in olivine phenocrysts (delta-18O = 4.3-5.8+/-0.3 permil) rule out extensive magma contamination within the crust [4]. Variations of Ni concentrations in early crystallized olivine phenocrysts and coexisting melts [5] were used to quantify the amount of recycled material involved in the Canary plume. The observed large, systematic inter- and intra-island variations of Ni in Ol phenocrysts exceeding the obtained 2-sigma analytical error of +/-0.01 wt.% NiO cannot be explained by olivine fractionation. Furthermore, strong positive correlation of Ni/MgO with 87Sr/86Sr (R = 0.86) and negative correlation with 206Pb/204Pb isotopic ratios (R = 0.61) suggest that significant amounts of a recycled component appear to be involved in partial melting of the Canary plume increasing from Tenerife through La Gomera and La Palma to Gran Canaria. The largest amount of the recycled component was found in the ODP Leg 157 hyaloclastites. References: [1] Montelli et al. (2004) Science 303, 338-343; [2] Hoernle et al. (1991) EPSL 106, 44-63; [3] Wyllie (1988) JGR 93, 4171-4181; [4] Gurenko et al. (2005) GCA, submitted manuscript; [5] Sobolev et al. (2005) Nature 434, 590-597.
DE: 1025 Composition of the mantle
DE: 1040 Radiogenic isotope geochemistry
DE: 1065 Major and trace element geochemistry
DE: 3630 Experimental mineralogy and petrology
DE: 3640 Igneous petrology
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005