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Skew of mantle upwelling beneath the East Pacific Rise governs segmentation

Nature volume 446, pages 409–414 (2007)Cite this article

Abstract

Mantle upwelling is essential to the generation of new oceanic crust at mid-ocean ridges, and it is generally assumed that such upwelling is symmetric beneath active ridges. Here, however, we use seismic imaging to show that the isotropic and anisotropic structure of the mantle is rotated beneath the East Pacific Rise. The isotropic structure defines the pattern of magma delivery from the mantle to the crust. We find that the segmentation of the rise crest between transform faults correlates well with the distribution of mantle melt. The azimuth of seismic anisotropy constrains the direction of mantle flow, which is rotated nearly 10° anticlockwise from the plate-spreading direction. The mismatch between the locus of mantle melt delivery and the morphologic ridge axis results in systematic differences between areas of on-axis and off-axis melt supply. We conclude that the skew of asthenospheric upwelling and transport governs segmentation of the East Pacific Rise and variations in the intensity of ridge crest processes.

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Figure 1: Location and geometry of the seismic experiment and tomographic image of the mantle low-velocity zone (MLVZ) and orientation of mantle anisotropy.
Figure 2: Map of the distribution of seismic ray paths and mean P n delay times versus azimuth and latitude.
Figure 3: Normalized data misfit following tomographic inversion versus azimuth of seismic anisotropy imposed on starting model.
Figure 4: Proposed model of segmentation beneath the East Pacific Rise.

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Acknowledgements

We thank the officers and crew of the RV Maurice Ewing and members of the scientific party for their assistance. D.R.T. thanks E. Hooft and E. Humphreys for numerous discussions and J. Karson, T. Durant and D. Villagomez for comments. Supported by the RIDGE and RIDGE 2000 Programs, Ocean Sciences Division, NSF.

Author Contributions All authors participated in the experimental design, the collection of the data and in several stages of data reduction and analysis. D.R.T. conducted the tomographic analysis and wrote the manuscript with comments from co-authors.

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Authors and Affiliations

  1. Department of Geological Sciences, University of Oregon, Eugene, Oregon 97403, USA,

    Douglas R. Toomey

  2. Nancy-Université, CRPG, 54501 Vandoeuvre les Nancy, France,

    David Jousselin

  3. Department of Geology and Geophysics, University of Hawaii-SOEST, Honolulu, Hawaii, 96822, USA,

    Robert A. Dunn

  4. School of Oceanography, University of Washington, Seattle, Washington 98195, USA,

    William S. D. Wilcock

  5. Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA,

    R. S. Detrick

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Correspondence to Douglas R. Toomey.

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Toomey, D., Jousselin, D., Dunn, R. et al. Skew of mantle upwelling beneath the East Pacific Rise governs segmentation. Nature 446, 409–414 (2007). https://doi.org/10.1038/nature05679

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