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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.

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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.

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)

    ADS  Article  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)

    ADS  Article  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)

    ADS  Article  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)

    ADS  CAS  Article  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)

    ADS  Article  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)

    ADS  Article  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)

    ADS  Article  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)

    ADS  Article  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)

    ADS  Article  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)

    ADS  Article  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)

    ADS  Article  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)

    ADS  CAS  Article  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)

    ADS  Article  Google Scholar 

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

    ADS  Article  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)

    ADS  CAS  Article  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)

    ADS  Article  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)

    ADS  Article  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)

    ADS  Article  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)

    ADS  Article  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)

    ADS  CAS  Article  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)

    ADS  CAS  Article  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)

    ADS  Article  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)

    ADS  Article  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)

    ADS  CAS  Article  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)

    ADS  CAS  Article  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)

    ADS  CAS  Article  PubMed  Google Scholar 

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

    Book  Google Scholar 

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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.

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Correspondence to S. C. Singh.

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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)

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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

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