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Long-term preservation of slab signatures in the mantle inferred from hydrogen isotopes

Shaw, AM; Hauri, EH; Behn, MD; Hilton, DR; Macpherson, CG; Sinton, JM

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Authors

AM Shaw

EH Hauri

MD Behn

DR Hilton

JM Sinton



Abstract

Seismic tomographic images indicate that subducted lithosphere is transported into the deep mantle. Petrologic modelling shows that water contained in subducted slabs can be carried to depths of at least 200 km (ref. 2); however, whether the hydrated slab signature is preserved at greater depths depends on diffusion rates. Experimental studies give conflicting results on the question of hydrogen preservation. On a small scale, hydrogen equilibration with ambient mantle should be rapid, implying that the slab hydrogen signature may not be preserved in the deep mantle. However, on large scales the time required for diffusive equilibration is longer and hydrogen anomalies may persist. Here we present hydrogen and boron data from submarine volcanic glasses erupted in the Manus back-arc basin, southwestern Pacific Ocean. We find that samples with low hydrogen-isotope values also exhibit the geochemical signature of dehydrated, subducted lithosphere. Combined with additional geochemical and geophysical data, we interpret this as direct evidence for the preservation of hydrogen anomalies in an ancient slab in the mantle. Our geochemical data are consistent with experimental estimates of diffusion for the upper mantle and transition zone. We conclude that hydrogen anomalies can persist in the mantle without suffering complete diffusive equilibration over timescales of up to a billion years.

Citation

Shaw, A., Hauri, E., Behn, M., Hilton, D., Macpherson, C., & Sinton, J. (2012). Long-term preservation of slab signatures in the mantle inferred from hydrogen isotopes. Nature Geoscience, 5(3), 224-228. https://doi.org/10.1038/ngeo1406

Journal Article Type Article
Publication Date Mar 1, 2012
Deposit Date Nov 27, 2012
Publicly Available Date Mar 29, 2024
Journal Nature Geoscience
Print ISSN 1752-0894
Electronic ISSN 1752-0908
Publisher Nature Research
Peer Reviewed Peer Reviewed
Volume 5
Issue 3
Pages 224-228
DOI https://doi.org/10.1038/ngeo1406
Keywords Geochemistry, Structural geology, Tectonics and geodynamics, Volcanology, mineralogy and petrology.

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