Continuous Mantle Melt Supply Beneath an Overlapping Spreading Center on the East Pacific Rise

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Science  09 Mar 2001:
Vol. 291, Issue 5510, pp. 1955-1958
DOI: 10.1126/science.1057683

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Tomographic images of upper mantle velocity structure beneath an overlapping spreading center (OSC) on the East Pacific Rise indicate that this ridge axis discontinuity is underlain by a continuous region of low P-wave velocities. The anomalous structure can be explained by an approximately 16-kilometer-wide region of high temperatures and melt fractions of a few percent by volume. Our results show that OSCs are not necessarily associated with a discontinuity in melt supply and that both OSC limbs are supplied with melt from a mantle source located beneath the OSC. We conclude that tectonic segmentation of the ridge by OSCs is not the direct result of magmatic segmentation at mantle depths.

  • * To whom correspondence should be addressed at Brown University. E-mail: Robert_Allen_Dunn{at}

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