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:

Seismic reflection images of the Moho underlying melt sills at the East Pacific Rise

Abstract

The determination of melt distribution in the crust and the nature of the crust–mantle boundary (the ‘Moho’) is fundamental to the understanding of crustal accretion processes at oceanic spreading centres. Upper-crustal magma chambers have been imaged beneath fast- and intermediate-spreading centres1,2,3,4 but it has been difficult to image structures beneath these magma sills. Using three-dimensional seismic reflection images, here we report the presence of Moho reflections beneath a crustal magma chamber at the 9° 03′ N overlapping spreading centre, East Pacific Rise. Our observations highlight the formation of the Moho at zero-aged crust. Over a distance of less than 7 km along the ridge crest, a rapid increase in two-way travel time of seismic waves between the magma chamber and Moho reflections is observed, which we suggest is due to a melt anomaly in the lower crust. The amplitude versus offset variation of reflections from the magma chamber shows a coincident region of higher melt fraction overlying this anomalous region, supporting the conclusion of additional melt at depth.

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

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

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

Figure 1: Three-dimensional seismic survey area and images of melt sills.
Figure 2: Three-dimensional view of reflection images of the Moho and melt sill.
Figure 3: Two-way reflection times of Moho and amplitude versus offset for melt sill.

Similar content being viewed by others

References

  1. Detrick, R. S. et al. Multi-channel seismic imaging of a crustal magma chamber along the East Pacific Rise. Nature 326, 35–41 (1987)

    Article  ADS  Google Scholar 

  2. Mutter, J. C. et al. Magma distribution across ridge axis discontinuities on the East Pacific Rise (8°40′ to 9°50′ North) from multi-channel seismic images. Nature 336, 156–158 (1988)

    Article  ADS  Google Scholar 

  3. Collier, J. & Sinha, M. C. Seismic images of a magma chamber beneath the Lau basin back-arc spreading centre. Nature 346, 646–648 (1990)

    Article  ADS  Google Scholar 

  4. Kent, G. M. et al. Evidence from three-dimensional reflectivity images for enhanced melt supply beneath mid-ocean-ridge discontinuities. Nature 406, 614–618 (2000)

    Article  ADS  CAS  PubMed  Google Scholar 

  5. Kent, G. M., Harding, A. J. & Orcutt, J. A. Distribution of magma beneath the East Pacific Rise between the Clipperton Transform and the 9° 17′ N Deval from forward modelling of common depth point data. J. Geophys. Res. 98, 13945–13969 (1993)

    Article  ADS  Google Scholar 

  6. Singh, S. C., Collier, J. S., Kent, G. M., Harding, A. J. & Orcutt, J. A. Seismic evidence for a hydrothermal layer above the solid roof of axial magma chamber at the southern East Pacific Rise. Geology 27, 219–222 (1999)

    Article  ADS  Google Scholar 

  7. Harding, A. J. et al. The structure of young oceanic crust at 13° N on the East Pacific Rise from expanding spread profiles. J. Geophys. Res. 94, 12163–12196 (1989)

    Article  ADS  Google Scholar 

  8. Vera, E. E. et al. The structure of 0 to 0.2 m.y. old oceanic crust at 9° N on the East Pacific Rise from expanding spread profiles. J. Geophys. Res. 95, 15529–15556 (1990)

    Article  ADS  Google Scholar 

  9. Toomey, D. R., Purdy, G. M., Solomon, S. C. & Wilcock, W. S. D. The three-dimensional seismic velocity structure of the East Pacific Rise near latitude 9°30′ N. Nature 347, 639–645 (1990)

    Article  ADS  Google Scholar 

  10. Dunn, R. A., Toomey, D. R. & Solomon, S. C. Three-dimensional seismic structure and physical properties of the crust and shallow mantle beneath the East Pacific Rise at 9°30′ N. J. Geophys. Res. 105, 23537–23555 (2000)

    Article  ADS  Google Scholar 

  11. Wilcock, W. S. et al. Seismic attenuation structure of the East Pacific Rise near 9° 30′ N. J. Geophys. Res. 100, 24147–24165 (1995)

    Article  ADS  Google Scholar 

  12. Dunn, R. A. & Toomey, D. R. Seismological evidence for three-dimensional melt migration beneath the East Pacific Rise. Nature 388, 259–262 (1997)

    Article  ADS  CAS  Google Scholar 

  13. Crawford, W. C., Webb, S. C. & Hilderbrand, J. A. Constraints on melt in the lower crust and Moho at the East Pacific Rise, 9°48′ N, using seafloor compliance measurements. J. Geophys. Res. 104, 2923–2939 (1999)

    Article  ADS  Google Scholar 

  14. Garmany, J. Accumulations of melt at the base of young oceanic crust. Nature 340, 628–632 (1989)

    Article  ADS  Google Scholar 

  15. Singh, S. C., Kent, G. M., Collier, J. S., Harding, A. J. & Orcutt, J. A. Melt to mush variations in crustal magma properties along the ridge crest at the southern East Pacific Rise. Nature 394, 874–878 (1998)

    Article  ADS  CAS  Google Scholar 

  16. Carbotte, S. & Macdonald, K. C. Evolution of ridge segments and discontinuities from SeaMARC II and three-dimensional magnetic studies. J. Geophys. Res. 97, 6959–6982 (1992)

    Article  ADS  Google Scholar 

  17. Barth, G. A. & Mutter, J. C. Variability in oceanic crustal thickness and structure: Multichannel seismic reflection results from the northern East Pacific Rise. J. Geophys. Res. 101, 17951–17975 (1996)

    Article  ADS  Google Scholar 

  18. Canales, J.-P. et al. Segment-scale variations in the crustal structure of 150–300 kyr old fast spreading oceanic crust (East Pacific Rise, 8 15 N–10 5 N) from wide-angle seismic refraction profiles. Geophys. J. Int. 152, 766–794 (2003)

    Article  ADS  Google Scholar 

  19. Taylor, M. A. & Singh, S. C. Composition and microstructure of magma bodies from effective medium theory. Geophys. J. Int. 149, 15–21 (2002)

    Article  ADS  Google Scholar 

  20. Bazin, S. et al. A three-dimensional study of axial low velocity region beneath the 9°03′ overlapping spreading center. Geophys. Res. Lett. 30, 11-1–4, doi:10.1029/2002GL015137 (2003)

    Article  Google Scholar 

  21. Dunn, R. A., Toomey, D. R., Detrick, R. S. & Wilcock, W. S. D. Continuous mantle melt supply beneath an overlapping spreading center on the East Pacific Rise. Science 291, 1955–1958 (2001)

    Article  ADS  CAS  PubMed  Google Scholar 

  22. Crawford, W. C. & Webb, S. C. Variations in the distribution of magma in the lower crust and the Moho beneath a fast spreading mid-ocean ridge. Earth Planet. Sci. Lett. 203, 117–130 (2002)

    Article  ADS  CAS  Google Scholar 

  23. Wright, D., Haymon, R. M. & Fornari, D. J. Crustal fissuring and its relationship to magmatic and hydrothermal processes on the East Pacific Rise crest (9°12′ to 54′ N). J. Geophys. Res. 100, 6097–6120 (1995)

    Article  ADS  Google Scholar 

  24. Haymon, R. M. et al. Hydrothermal vent distribution along the East Pacific Rise crest (9°9′–54′ N) and its relationship to magmatic and tectonic processes on fast-spreading mid-ocean ridges. Earth Planet. Sci. Lett. 104, 513–534 (1991)

    Article  ADS  Google Scholar 

  25. Boudier, F., Nicolas, A. & Idefonse, B. Magma chambers in the Oman Ophiolite; fed from the top and bottom. Earth Planet. Sci. Lett. 144, 239–250 (1996)

    Article  ADS  CAS  Google Scholar 

  26. Kelemen, P. B., Koga, K. & Shimizu, N. Geochemistry of gabbro sills in the crust-mantle transition zone of the Oman Ophiolite; implications for the origin of the oceanic lower crust. Earth Planet. Sci. Lett. 146, 475–488 (1997)

    Article  ADS  CAS  Google Scholar 

  27. Nicolas, A. Structure of Ophiolites and Dynamics of Oceanic Lithosphere (Kluwer, Amsterdam, 1989)

    Book  Google Scholar 

  28. Maclennan, J. A., Hulme, T. & Singh, S. C. Thermal models of oceanic crustal accretion: Linking geophysical, geological and petrological observations. Geophys. Geochem. Geosyst. 5, doi:10.1029/2003GC000605 (2003)

  29. Carbotte, S. M., Small, C. & Donnelly, K. The influence of ridge migration on the magmatic segmentation of mid-ocean ridges. Nature 429, 743–746 (2004)

    Article  ADS  CAS  PubMed  Google Scholar 

  30. Yilmaz, O. Seismic Data Analysis (Society of Exploration Geophysicists, Tulsa, 2001)

    Book  Google Scholar 

Download references

Acknowledgements

The 3D seismic reflection data were acquired onboard RV Maurice Ewing, processed by Robertson Research Ltd, and interpreted using the 3D VoxelGeo software of Paradigm Geophysical. The ARAD seismic experiment was an international collaborative project between investigators from the University of Cambridge and Scripps Institution of Oceanography and was funded by the UK Natural Environment Research Council, British Institutions Reflection Profiling Syndicate, and the United States National Science Foundation. This is a Department of Earth Sciences (Cambridge) contribution and an Institut de Physique du Globe de Paris contribution.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to S. C. Singh.

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 Figure 1

Two-dimensional seismic sections through the 3D cube. Seismic sections along cross-line distance of 2.25 km (a) and in-line distance of 14.55 km (b). Moho reflections are clearly observed beneath the western limb of the OSC, beneath the OSC basin and beneath the AMC. On the eastern limb a continuous AMC reflection is observed at about 4500 ms two-way travel time (b). The two-way travel time between the AMC reflection and the Moho reflection increases from 1.30 sec in the south to 2.0 sec in the north. (PDF 1823 kb)

Supplementary Figure 2

Three-dimensional view of reflection images of Moho and melt sill. (a) Colour version of Figure 2 without any interpretation and (b) black and white version of Figure 2 without any interpretation. See Figure caption of Figure 2 for detailed description. (PDF 3060 kb)

Rights and permissions

Reprints and permissions

About this article

Cite this article

Singh, S., Harding, A., Kent, G. et al. Seismic reflection images of the Moho underlying melt sills at the East Pacific Rise. Nature 442, 287–290 (2006). https://doi.org/10.1038/nature04939

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature04939

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

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