Letter | Published:

Boron and oxygen isotope evidence for recycling of subducted components over the past 2.5 Gyr

Nature volume 447, pages 702705 (07 June 2007) | Download Citation

Abstract

Evidence for the deep recycling of surficial materials through the Earth’s mantle and their antiquity has long been sought to understand the role of subducting plates and plumes in mantle convection. Radiogenic isotope evidence for such recycling remains equivocal because the age and location of parent–daughter fractionation are not known. Conversely, while stable isotopes can provide irrefutable evidence for low-temperature fractionation, their range in most unaltered oceanic basalts is limited and the age of any variation is unconstrained. Here we show that δ18O ratios in basalts from the Azores are often lower than in pristine mantle. This, combined with increased Nb/B ratios and a large range in δ11B ratios, provides compelling evidence for the recycling of materials that had undergone fractionation near the Earth’s surface. Moreover, δ11B is negatively correlated with 187Os/188Os ratios, which extend to subchondritic values1, constraining the age of the high Nb/B, 11B-enriched endmember to be more than 2.5 billion years (Gyr) old. We infer this component to be melt- and fluid-depleted lithospheric mantle from a subducted oceanic plate, whereas other Azores basalts contain a contribution from 3-Gyr-old melt-enriched basalt2. We conclude that both components are most probably derived from an Archaean oceanic plate that was subducted, arguably into the deep mantle, where it was stored until thermal buoyancy caused it to rise beneath the Azores islands 3 Gyr later.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

References

  1. 1.

    , , , & Recycled Archaean oceanic mantle lithosphere in the Azores plume. Nature 420, 324–327 (2002)

  2. 2.

    , , , & The origin of enriched mantle beneath Sao Miguel, Azores. Geochim. Cosmochim. Acta 71, 219–240 (2007)

  3. 3.

    , , & Seismic detection of folded, subducted lithosphere at the core–mantle boundary. Nature 441, 333–336 (2006)

  4. 4.

    et al. Finite-frequency tomography reveals a variety of plumes in the mantle. Science 303, 338–343 (2004)

  5. 5.

    Mantle geochemistry: the message from oceanic volcanism. Nature 385, 219–229 (1997)

  6. 6.

    & Inferences about magma sources and mantle structure from variations in 143Nd/144Nd. Geophys. Res. Lett. 3, 743–746 (1976)

  7. 7.

    & Chemical and isotopic systematics of oceanic basalts. Geol. Soc. Spec. Publ. 42, 313–345 (1989)

  8. 8.

    , , & Lithium isotope evidence for subduction-enriched mantle in the source of mid-ocean-ridge basalts. Nature 443, 565–568 (2006)

  9. 9.

    Oxygen isotope variations of basaltic lavas and upper mantle rocks. Rev. Mineral. Geochem. 43, 319–364 (2001)

  10. 10.

    , , & Oxygen isotope evidence for the origin of enriched mantle beneath the mid-Atlantic ridge. Earth Planet. Sci. Lett. 220, 297–316 (2004)

  11. 11.

    & Boron content and isotopic composition of oceanic basalts: geochemical and cosmochemical implications. Earth Planet. Sci. Lett. 121, 277–291 (1994)

  12. 12.

    , , & Boron isotope compositions of South Atlantic MORB and mantle sources. Geochim. Cosmochim. Acta 69, abstr. A94 (2005)

  13. 13.

    & Primitive boron isotope composition of the mantle. Science 269, 383–386 (1995)

  14. 14.

    , , & Osmium isotopic compositions and Re-Os concentrations in sulfide globules from basaltic glasses. Earth Planet. Sci. Lett. 154, 331–347 (1998)

  15. 15.

    , , & U-Th isotope disequilibria and ocean island basalt generation in the Azores. Chem. Geol. 139, 145–164 (1997)

  16. 16.

    , & Partial melting and upwelling rates beneath the Azores from a U-series isotope perspective. Earth Planet. Sci. Lett. 239, 42–56 (2005)

  17. 17.

    , , , & UWG-2, a garnet standard for oxygen isotope ratio: strategies for high precision and accuracy with laser heating. Geochim. Cosmochim. Acta 59, 5223–5231 (1995)

  18. 18.

    & Oxygen isotope signatures in olivines from Sao Miguel (Azores) basalts: implications for crustal and mantle processes. Chem. Geol. 193, 237–255 (2003)

  19. 19.

    Ancient mantle in a modern plume. Nature 420, 281–282 (2002)

  20. 20.

    , , & Precise boron isotopic analysis of aqueous samples: ion exchange extraction and mass spectrometry. Geochim. Cosmochim. Acta 55, 3901–3907 (1991)

  21. 21.

    , & Precise boron isotopic analysis of complex silicate (rock) samples using alkali carbonate fusion and ion exchange separation. Chem. Geol. 142, 129–137 (1997)

  22. 22.

    , , & The boron systematics of intraplate lavlas: implications for crust and mantle evolution. Geochim. Cosmochim. Acta 60, 415–422 (1996)

  23. 23.

    et al. Behaviour of boron, beryllium and lithium during partial melting and crystallization: constraints from mineral-melt partitioning experiments. Geochim. Cosmochim. Acta 62, 2129–2141 (1998)

  24. 24.

    , & The role of aqueous fluids in the slab-to-mantle transfer of boron, beryllium, and lithium during subduction: experiments and models. Geochim. Cosmochim. Acta 62, 3337–3347 (1998)

  25. 25.

    & Composition of the depleted mantle. Geochem. Geophys. Geosyst. 5 doi: 10.1029/2003GC000597 (2004)

  26. 26.

    & boron isotope geochemistry of the oceanic crust from DSDP/ODP hole 504B. Geochim. Cosmochim. Acta 56, 1633–1639 (1992)

  27. 27.

    , , & Boron and lithium isotopic variations in a hot subduction zone—the southern Washington Cascades. Chem. Geol. 212, 101–124 (2004)

  28. 28.

    & The source regions of ocean island basalts. J. Petrol. 36, 133–160 (1995)

  29. 29.

    , & Mantle mixing: the generation, preservation and destruction of chemical heterogeneity. Annu. Rev. Earth Planet. Sci. 30, 493–525 (2002)

  30. 30.

    & Boron content and isotopic composition of oceanic basalts: geochemical and cosmochemical implications. Earth Planet. Sci. Lett. 121, 277–291 (1994)

  31. 31.

    & Boron isotope geochemistry of metasedimentary rocks and tourmalines in a subduction zone metamorphic suite. Phys. Earth Planet. Inter. 127, 233–252 (2001)

Download references

Acknowledgements

We are grateful to N. Rogers, K. Martyn and D. McKenzie, who originally supplied us with the samples analysed in this study, and also to T. Plank for the high-precision Nb concentration data. J. Valley provided access to his O isotope facility. We thank B. Bourdon, J. Gill, M. Reagan and A. Lini for discussions. A review by E. Hauri helped to improve the manuscript. S. Turner is funded by an ARC Federation Fellowship. This is GEMOC publication 466.

Author information

Author notes

    • Ilya Bindeman

    Present address: Department of Geological Sciences, 1272 University of Oregon, Eugene, Oregon 97403, USA.

Affiliations

  1. GEMOC, Department of Earth and Planetary Sciences, Macquarie University, Sydney, New South Wales 2109, Australia

    • Simon Turner
  2. Istituto di Geoscienze e Georisorse, Via Moruzzi 1, 56147 Pisa, Italy

    • Sonia Tonarini
  3. Department of Geology and Geophysics, University of Wisconsin, 1215 West Dayton Street, Madison, Wisconsin 53706, USA

    • Ilya Bindeman
  4. National Science Foundation, 4201 Wilson Blvd, Arlington, Virginia 22230, USA

    • William P. Leeman
  5. School of Geosciences, Monash University, PO Box 28E, Clayton, Victoria 3800, Australia

    • Bruce F. Schaefer

Authors

  1. Search for Simon Turner in:

  2. Search for Sonia Tonarini in:

  3. Search for Ilya Bindeman in:

  4. Search for William P. Leeman in:

  5. Search for Bruce F. Schaefer in:

Competing interests

Reprints and permissions information is available at www.nature.com/reprints. The authors declare no competing financial interests.

Corresponding author

Correspondence to Simon Turner.

About this article

Publication history

Received

Accepted

Published

DOI

https://doi.org/10.1038/nature05898

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.