Letter | Published:

Mantle upwellings above slab graveyards linked to the global geoid lows

Nature Geoscience volume 3, pages 435438 (2010) | Download Citation

Abstract

The global geoid is characterized by a semi-continuous belt of lows that surround the Pacific Ocean, including isolated minima in the Indian Ocean, Ross Sea and northeast Pacific and west Atlantic oceans. These geoid lows have been attributed to Mesozoic subduction1,2. Geodynamic models that include slab graveyards in the lower mantle as inferred from seismic topography or from plate reconstructions correctly predict the general trend of geoid minima3,4. However, these models fail to accurately reproduce localized geoid lows in the Indian Ocean, Ross Sea and northeast Pacific Ocean. Here we show that the geoid lows are correlated with high-velocity anomalies near the base of the mantle and low-velocity anomalies in the mid-to-upper mantle. Our mantle flow models reproduce the geoid minima if the mid-to-upper mantle upwellings are positioned above the inferred locations of ancient subducted slabs. We find that the long-wavelength trough in the geoid is linked to high-density slab graveyards in the lower mantle, whereas upwelling regions in the mantle above 1,000 km depth cause discrete lows within the larger trough. We suggest that this mode of upwelling in the mid-to-upper mantle is caused by buoyant hydrated mantle that was created by processes around and above subducted slabs.

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Acknowledgements

We thank R. Moucha for helpful comments on an earlier version of the letter. This work was supported through Caltech Tectonics Observatory (by the Gordon and Betty Moore Foundation), the National Science Foundation (EAR-0609707 and EAR-0810303), the New Zealand Foundation for Research Science and Technology, and StatoilHydro. The original CitcomS software was obtained from CIG, Computational Infrastructure for Geodynamics (http://geodynamics.org). This is Contribution Number 10034 of the Division of Geological and Planetary Sciences and Number 217 of the Tectonics Observatory, Caltech.

Author information

Affiliations

  1. Seismological Laboratory, California Institute of Technology, Pasadena, California 91125, USA

    • Sonja Spasojevic
    •  & Michael Gurnis
  2. GNS Science, PO Box 30368, Lower Hutt 5040, New Zealand

    • Rupert Sutherland

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Contributions

S.S. carried out analysis and mantle convection modelling, and all authors participated in the modelling strategy, interpretation of results and preparing the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Sonja Spasojevic.

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DOI

https://doi.org/10.1038/ngeo855

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