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Helium and lead isotopes reveal the geochemical geometry of the Samoan plume

Jackson, M. G. and Hart, S. R. and Konter, J. G. and Kurz, M. D. and Blusztajn, J. and Farley, K. A. (2014) Helium and lead isotopes reveal the geochemical geometry of the Samoan plume. Nature, 514 . pp. 355-358. ISSN 0028-0836. doi:10.1038/nature13794.

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Hotspot lavas erupted at ocean islands exhibit tremendous isotopic variability, indicating that there are numerous mantle components1, 2 hosted in upwelling mantle plumes that generate volcanism at hotspots like Hawaii and Samoa3. However, it is not known how the surface expression of the various geochemical components observed in hotspot volcanoes relates to their spatial distribution within the plume4, 5, 6, 7, 8, 9, 10. Here we present a relationship between He and Pb isotopes in Samoan lavas that places severe constraints on the distribution of geochemical species within the plume. The Pb-isotopic compositions of the Samoan lavas reveal several distinct geochemical groups, each corresponding to a different geographic lineament of volcanoes. Each group has a signature associated with one of four mantle endmembers with low 3He/4He: EMII (enriched mantle 2), EMI (enriched mantle 1), HIMU (high µ = 238U/204Pb) and DM (depleted mantle). Critically, these four geochemical groups trend towards a common region of Pb-isotopic space with high 3He/4He. This observation is consistent with several low-3He/4He components in the plume mixing with a common high-3He/4He component, but not mixing much with each other. The mixing relationships inferred from the new He and Pb isotopic data provide the clearest picture yet of the geochemical geometry of a mantle plume, and are best explained by a high-3He/4He plume matrix that hosts, and mixes with, several distinct low-3He/4He components.

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URLURL TypeDescription information ReadCube access
Kurz, M. D.0000-0003-1745-2356
Blusztajn, J.0000-0002-5475-1948
Farley, K. A.0000-0002-7846-7546
Additional Information:©2014 Macmillan Publishers Limited. Received 01 February 2014. Accepted 15 August 2014. Published online 15 October 2014. We thank J. Natland, P. Hall and M. Regelous for discussions, and R. Carlson for access to analytical facilities. Comments from B. Hanan and K. Harpp improved the manuscript. M.G.J. acknowledges grants from the NSF that funded this research: OCE-1061134, OCE-1153894, EAR-1348082 and EAR-1145202. Online Content Methods, along with any additional Extended Data display items and Source Data, are available in the online version of the paper; references unique to these sections appear only in the online paper.
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Subject Keywords:Geochemistry, Geodynamics, Volcanology
Record Number:CaltechAUTHORS:20140820-091223045
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:48716
Deposited By: George Porter
Deposited On:29 Oct 2014 18:00
Last Modified:10 Nov 2021 18:34

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