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Published July 2008 | public
Journal Article

Oxygen isotopes in Samoan lavas: Confirmation of continent recycling

Abstract

Lavas from the Samoan volcanic chain show the most enriched geochemical signatures ever documented in oceanic lavas (^(87)Sr/^(86)Sr as high as 0.7205). In order to test the hypothesis that their source contains a component of recycled upper continental crust, we measured oxygen isotope compositions of olivine phenocrysts from these lavas. Correlations between δ^(18)O of olivines (5.11‰–5.70‰) and ^(87)Sr/^(86)Sr and ^(207)Pb/^(204)Pb of whole rocks, as well as Ce/Pb and Nb/Th ratios of whole rocks, indicate that (1) measured δ^(18)O are primary, mantle-derived values, and (2) the enriched mantle source of these lavas contains continental crust or its derivative sediments. The observed trend between δ^(18)O and ^(87)Sr/^(86)Sr can be fit using either clastic marine sediment or continental crust values of δ^(18)O, Sr concentration, and ^(87)Sr/^(86)Sr, but only those for clastic marine sediments are compatible with trace element modeling. We conclude that the enriched source for Samoan basalts was created by sedimentation of continent-derived material into a marine environment, followed by subduction and mixing with ambient mantle.

Additional Information

© 2008 The Geological Society of America. Manuscript received 7 November 2007. Revised manuscript received 1 April 2008. Manuscript accepted 4 April 2008. We thank Nami Kitchen for her skilled help on the laser fluorination apparatus. We also thank E. Widom, P. Castillo, and W. White for their thoughtful reviews of this manuscript. We gratefully acknowledge National Science Foundation grants OCE-9819038 and EAR-0125917 (to Hart).

Additional details

Created:
August 22, 2023
Modified:
October 20, 2023