Continuous Mantle Melt Supply Beneath an Overlapping Spreading Center on the East Pacific Rise
Robert A. Dunn,12*
Douglas R. Toomey,1
Robert S. Detrick,3
William S. D. Wilcock4
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.
1 Department of Geological Sciences, University
of Oregon, Eugene, OR 97403-1272, USA.
2 Department
of Geological Sciences, Brown University, Providence, RI 02912-1846,
USA.
3 Department of Geology and Geophysics, Woods
Hole Oceanographic Institute, Woods Hole, MA 02543, USA.
4 School of Oceanography, University of Washington,
Seattle, WA 98195-7940, USA.
*
To whom correspondence should be addressed at Brown University.
E-mail: Robert_Allen_Dunn{at}brown.edu
