Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

Geophysical evidence from the MELT area for compositional controls on oceanic plates

Nature volume 437, pages 249–252 (2005)Cite this article

Abstract

Magnetotelluric and seismic data, collected during the MELT experiment at the southern East Pacific Rise1,2, constrain the distribution of melt beneath this mid-ocean-ridge spreading centre and also the evolution of the oceanic lithosphere during its early cooling history. Here we focus on structures imaged at distances ∼100 to 350 km east of the ridge crest, corresponding to seafloor ages of ∼1.3 to 4.5 million years (Myr), where the seismic and electrical conductivity structure is nearly constant and independent of age. Beginning at a depth of about 60 km, we image a large increase in electrical conductivity and a change from isotropic to transversely anisotropic electrical structure, with higher conductivity in the direction of fast propagation for seismic waves. Conductive cooling models predict structure that increases in depth with age, extending to about 30 km at 4.5 Myr ago. We infer, however, that the structure of young oceanic plates is instead controlled by a decrease in water content above a depth of 60 km induced by the melting process beneath the spreading centre3.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Two model cross-sections of conductivity through the region 70–350 km east of the southern East Pacific Rise in the MELT area.
Figure 2
Figure 3: Average one-dimensional profiles through our conductivity model and theoretical curves based on laboratory data.

Similar content being viewed by others

References

  1. MELT Seismic Team, Imaging the deep seismic structure beneath a mid-ocean ridge: the MELT experiment. Science 280, 1215–1218 (1998)

    Article  ADS  Google Scholar 

  2. Evans, R. L. et al. Asymmetric electrical structure in the mantle beneath the East Pacific Rise at 17°S. Science 286, 756–759 (1999)

    Article  Google Scholar 

  3. Hirth, G. & Kohlstedt, D. L. Water in the oceanic upper mantle: implications for rheology, melt extraction and the evolution of the lithosphere. Earth Planet. Sci. Lett. 144, 93–108 (1996)

    Article  ADS  CAS  Google Scholar 

  4. Wolfe, C. J. & Solomon, S. C. Shear-wave splitting and implications for mantle flow beneath the MELT region of the East Pacific Rise. Science 280, 1230–1232 (1998)

    Article  ADS  CAS  Google Scholar 

  5. Rodi, W. & Mackie, R. L. Nonlinear conjugate gradients algorithm for 2-D magnetotelluric inversion. Geophysics 66, 174–187 (2001)

    Article  ADS  Google Scholar 

  6. Baba, K., Chave, A., Evans, R. L., Hirth, G. & Mackie, R. Mantle dynamics beneath the East Pacific Rise at 17°S: Insights from the MELT EM data. J. Geophys. Res. (submitted)

  7. Parsons, B. & Sclater, J. Variation of ocean floor bathymetry and heat flow with age. J. Geophys. Res. 82, 803–827 (1977)

    Article  ADS  Google Scholar 

  8. Conder, J. A., Forsyth, D. W. & Parmentier, E. M. Asthenospheric flow and the asymmetry of the East Pacific Rise, MELT area. J. Geophys. Res. 107(B12), 2344, doi:1029/2001JB000807 (2002)

    Article  ADS  Google Scholar 

  9. Dunn, R. A. & Forsyth, D. W. Imaging the transition between the region of mantle melt generation and the crustal magma chamber with short-period Love wave propagation along the southern East Pacific Rise. J. Geophys. Res. 108(B7), 2352, doi:10.1029/2002JB002217 (2003)

    Article  ADS  Google Scholar 

  10. Nishimura, C. & Forsyth, D. W. The anisotropic structure of the upper mantle in the Pacific. Geophys. J. R. Astron. Soc. 96, 203–229 (1989)

    Article  Google Scholar 

  11. Forsyth, D. W., Webb, S. C., Dorman, L. M. & Shen, Y. Phase velocities of Rayleigh waves in the MELT experiment on the East Pacific Rise. Science 280, 1235–1238 (1998)

    Article  ADS  CAS  Google Scholar 

  12. Forsyth, D. W. & Li, A. Array-analysis of two-dimensional variations in surface wave velocity and azimuthal anisotropy in the presence of multipathing interference. In Seismic Data Analysis and Imaging with Global and Local Arrays (eds Levander, A. & Nolet, G.) (AGU Geophys. Monogr., in the press)

  13. Xu, Y. S., Shankland, T. J. & Poe, B. T. Laboratory-based electrical conductivity in the Earth's mantle. J. Geophys. Res. 105, 27865–27875 (2000)

    Article  ADS  CAS  Google Scholar 

  14. Xu, Y. S., Shankland, T. J. & Duba, A. G. Pressure effect on electrical conductivity of mantle olivine. Phys. Earth Planet. Inter. 118, 149–161 (2000)

    Article  ADS  CAS  Google Scholar 

  15. Karato, S. The role of hydrogen in the electrical conductivity of the upper mantle. Nature 347, 272–273 (1990)

    Article  ADS  CAS  Google Scholar 

  16. Kohlstedt, D. L. & Mackwell, S. J. Diffusion of hydrogen and intrinsic point defects in olivine. Z. Phys. Chem. 207, 147–162 (1998)

    Article  CAS  Google Scholar 

  17. Kohlstedt, D. & Mackwell, S. J. in Microscopic Properties and Processes in Minerals (eds Wright, K. & Catlow, R.) 539–559 (Kluwer Academic, Dordrecht, 1999)

    Book  Google Scholar 

  18. Simpson, F. Intensity and direction of lattice preferred orientation of olivine: are electrical and seismic anisotropies of the Australian mantle reconcilable? Earth Planet. Sci. Lett. 203, 535–547 (2002)

    Article  ADS  CAS  Google Scholar 

  19. Huang, X., Xu, Y. & Karato, S. Water content in the transition zone from electrical conductivity of wadsleyite and ringwoodite. Nature 434, 746–749 (2005)

    Article  ADS  CAS  Google Scholar 

  20. Hier-Mujander, S., Anderson, I. M. & Kohlstedt, D. L. Influence of protons on Fe-Mg interdiffusion in olivine. J. Geophys. Res. 110, B02202, doi:10.1029/2004JB003292 (2005)

    ADS  Google Scholar 

  21. Hammond, W. C. & Humphreys, E. D. Upper mantle seismic wave velocity: Effects of realistic partial melt geometries. J. Geophys. Res. 105(B5), 10975–10986, doi:10.1029/2000JB900041 (2000)

    Article  ADS  Google Scholar 

  22. Hammond, W. C. & Humphreys, E. D. Upper mantle seismic wave attenuation: Effects of realistic partial melt distribution. J. Geophys. Res. 105(B5), 10987–11000, doi:10.1029/2000JB900042 (2000)

    Article  ADS  Google Scholar 

  23. Faul, U. H., Fitz Gerald, J. D. & Jackson, I. Shear wave attenuation and dispersion in melt-bearing olivine polycrystals: 2. Microstructural interpretation and seismological implications. J. Geophys. Res. 109, B06202, doi:10.1029/2003JB002407 (2004)

    Article  ADS  Google Scholar 

  24. Karato, S. Mapping water content in upper mantle. In Inside the Subduction Factory (ed. Eiler, J.) 135–152 (Geophys. Monogr. Ser. 138, American Geophysical Union, Washington DC, 2003)

    Chapter  Google Scholar 

  25. Karato, S. Effects of water on seismic-wave velocities in the upper-mantle. Proc. Jpn. Acad. Ser. B. 71, 61–66 (1995)

    Article  Google Scholar 

  26. Aubaud, C., Hauri, E. H. & Hirschmann, M. H. Water partition coefficients between nominally anhydrous minerals and basaltic melts. Geophys. Res. Lett.(in the press)

  27. Lizarralde, D., Chave, A. D., Hirth, G. & Schultz, A. Northeastern Pacific mantle conductivity profile from long-period magnetotelluric sounding using Hawaii-to-California submarine cable data. J. Geophys. Res. 100, 17837–17854 (1995)

    Article  ADS  Google Scholar 

  28. Gaherty, J., Jordan, T. H. & Gee, L. S. Seismic structure of the upper mantle in a central Pacific corridor. J. Geophys. Res. 101, 22291–22309 (1996)

    Article  ADS  Google Scholar 

Download references

Acknowledgements

We thank S. Karato for comments. We are also grateful to S. Hier-Mujander and D. Kohlstedt for discussions. US participation in the MELT experiment and subsequent analysis was funded by NSF grants through the Marine Geology and Geophysics Program, Ocean Sciences Division.

Author information

Authors and Affiliations

  1. Department of Geology and Geophysics,

    Rob. L. Evans & Greg Hirth

  2. Department of Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, 02543, USA

    Alan Chave

  3. Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 2-15, Natsushima, Yokosuka, Kanagawa, 237-0061, Japan

    Kiyoshi Baba

  4. Department of Geology, Brown University, USA

    Don Forsyth

  5. GSY-USA, Inc., PMB#643, 2261 Market Street, California, 94114, San Francisco, USA

    Randall Mackie

Authors
  1. Rob. L. Evans
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Greg Hirth
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Kiyoshi Baba
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Don Forsyth
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Alan Chave
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Randall Mackie
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Rob. L. Evans.

Ethics declarations

Competing interests

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

Supplementary information

Supplementary Notes

Test of isotropy of Upper 60km. (DOC 30 kb)

Supplemental Figure S1

Cross sections of conductivity through the region 70–350km east of the SEPR in the MELT area. (PDF 3002 kb)

Rights and permissions

Reprints and permissions

About this article

Cite this article

Evans, R., Hirth, G., Baba, K. et al. Geophysical evidence from the MELT area for compositional controls on oceanic plates. Nature 437, 249–252 (2005). https://doi.org/10.1038/nature04014

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature04014

This article is cited by

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.

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing