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Evidence from three-dimensional seismic reflectivity images for enhanced melt supply beneath mid-ocean -ridge discontinuities

Nature volume 406, pages 614–618 (2000)Cite this article

Abstract

Quantifying the melt distribution and crustal structure across ridge-axis discontinuities is essential for understanding the relationship between magmatic, tectonic and petrologic segmentation of mid-ocean-ridge spreading centres. The geometry and continuity of magma bodies beneath features such as overlapping spreading centres can strongly influence the composition of erupted lavas1 and may give insight into the underlying pattern of mantle flow. Here we present three-dimensional images of seismic reflectivity beneath a mid-ocean ridge to investigate the nature of melt distribution across a ridge-axis discontinuity. Reflectivity slices through the 9° 03′ N overlapping spreading centre on East Pacific Rise suggest that it has a robust magma supply, with melt bodies underlying both limbs and ponding of melt beneath large areas of the overlap basin. The geometry of melt distribution beneath this offset is inconsistent with large-scale, crustal redistribution of melt away from centres of upwelling2,3. The complex distribution of melt seems instead to be caused by a combination of vertical melt transport from the underlying mantle and subsequent focusing of melt beneath a magma freezing boundary in the mid-crust.

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Figure 1: Sea-floor bathymetry and nomenclature for the ARAD seismic experiment.
Figure 2: In-line seismic reflectivity slices through the western and eastern limbs of the 9° 03′ N overlapping spreading centre.
Figure 3: Cross-line seismic reflectivity slices through the western and eastern limbs of the 9° 03′ N overlapping spreading centre.
Figure 4: Three-dimensional visualization of magma chamber structure.

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Acknowledgements

We thank the officers and crew of the RV Maurice Ewing for around-the-clock help during the 47-day-long cruise; H. Avendonk, D. Boschi, A. Cherrett, A. Greer, P. Henkart, C. Hollinshead, S. Hussenoeder, T. Owen and P. Zimmer for assistance with instrumentation and watch-standing duties during the experiment; and R. Detrick and D. Toomey for comments that significantly improved this Letter. Data-processing software was provided by Paradigm Geophysical, Houston, Texas. Focus 3-D was used for the three-dimensional binning, stacking and migration of the multichannel seismic data. Data presentation of the three-dimensional volume was facilitated through visualization modules within Focus 3-D and VoxelGeo. The ARAD seismic experiment is an international collaborative project between investigators at the Scripps Institution of Oceanography and the University of Cambridge, with financial support from the RIDGE program/National Science Foundation (USA), British Institutions Reflection Profiling Syndicate (BIRPS), and the Natural Environment Research Council (UK). Additional matching funds for computer visualization and data storage were provided by the Scripps Institution of Oceanography and the Cecil H. and Ida M. Green Foundation for Earth Sciences.

Author information

Author notes

  1. S. C. Singh & S. Bazin

    Present address: Laboratoire de Sismologie, Institut de Physique du Globe de Paris, 75252, Paris, Cedex 05, France

  2. M. C. Sinha

    Present address: School of Ocean and Earth Science, University of Southampton, Southampton, SO14 3ZH, UK

Authors and Affiliations

  1. Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics, University of California, San Diego, La Jolla, 92093, California, USA

    G. M. Kent, A. J. Harding, J. A. Orcutt & S. Bazin

  2. British Institutions Reflection Profiling Syndicate (BIRPS),

    S. C. Singh & R. W. Hobbs

  3. Department of Earth Sciences, Bullard Laboratories, University of Cambridge, Cambridge, CB3 0EZ, UK

    S. C. Singh, M. C. Sinha, P. J. Barton, R. S. White, C. H. Tong & J. W. Pye

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Correspondence to G. M. Kent.

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Kent, G., Singh, S., Harding, A. et al. Evidence from three-dimensional seismic reflectivity images for enhanced melt supply beneath mid-ocean -ridge discontinuities. Nature 406, 614–618 (2000). https://doi.org/10.1038/35020543

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