The return of subducted continental crust in Samoan lavas

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Date
2007-08-04Author
Jackson, Matthew G.
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Hart, Stanley R.
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Koppers, Anthony A. P.
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Staudigel, Hubert
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Konter, Jasper G.
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Blusztajn, Jerzy S.
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Kurz, Mark D.
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Russell, Jamie A.
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https://hdl.handle.net/1912/2075As published
https://doi.org/10.1038/nature06048Abstract
Substantial quantities of terrigenous sediments are known to enter the
mantle at subduction zones, but little is known about their fate in the mantle.
Subducted sediment may be entrained in buoyantly upwelling plumes and returned
to the earth’s surface at hotspots, but the proportion of recycled sediment in the
mantle is small and clear examples of recycled sediment in hotspot lavas are rare.
We report here remarkably enriched 87Sr/86Sr and 143Nd/144Nd isotope signatures
(up to 0.720830 and 0.512285, respectively) in Samoan lavas from three dredge
locations on the underwater flanks of Savai’i island, Western Samoa. The
submarine Savai’i lavas represent the most extreme 87Sr/86Sr isotope compositions
reported for ocean island basalts (OIBs) to date. The data are consistent with the
presence of a recycled sediment component (with a composition similar to upper
continental crust, or UCC) in the Samoan mantle. Trace element data show similar
affinities with UCC—including exceptionally low Ce/Pb and Nb/U ratios—that
complement the enriched 87Sr/86Sr and 143Nd/144Nd isotope signatures. The
geochemical evidence from the new Samoan lavas radically redefines the
composition of the EM2 (enriched mantle 2) mantle endmember, and points to the
presence of an ancient recycled UCC component in the Samoan plume.
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Author Posting. © Nature Publishing Group, 2007. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature 448 (2007): 684-687, doi:10.1038/nature06048.